United States Office of Water EPA 822-R-96-004
Environmental Protection 4304 July 1996
Agency
National Nutrient
Assessment Workshop
Proceedings
December 4-6, 1995
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National Nutrient Assessment Workshop Proceedings
National Nutrient Assessment Workshop
December 4-6,1995
Washington,, B.C.
Introduction
Nutrient overenrichment is one of the leading causes of water quality problems in the United
States. The National Water Quality Inventory 1994 Report to Congress Executive Summary
cites nutrients (nitrogen and phosphorus) as one of the leading causes of water quality
impairment in our Nation's rivers, lakes, and estuaries. While nutrients are essential to the
health of aquatic ecosystems, excessive nutrient loadings can result in the growth of aquatic
weeds and algae, leading to oxygen depletion, increased fish and macroinvertebrate mortality,
and other water quality and habitat impairments.
Over the years, the Environmental Protection Agency's Office of Water has issued a number
of technical guidance documents and supported the development of water quality simulation
models and load estimating models to assess the impacts of urban, rural, and mixed land use
activities on receiving waters. In addition, some States currently have water quality standards
that incorporate criteria, primarily narrative, aimed at controlling problems associated with
overenrichment. However, in order for State and local agencies to better understand and
manage nutrient impacts to surface waters, additional work is required.
EPA established a Nutrient Task Force in July 1993 to gather existing data on nutrient
problems and currently available tools. The Task Force recommended that EPA provide
additional assistance to States in developing and implementing appropriate nutrient endpoints,
assessment methodologies, and models. The first step in carrying out the recommendations of
the Task Force was a nutrient assessment workshop, which was held in Washington, DC, on
December 4-6, 1995. The workshop was organized around plenary and breakout group
discussions on four major waterbody types: estuarine and coastal waters; lakes,
impoundments/reservoirs, and ponds; rivers and streams; and wetlands. Issue papers
describing the state-of-the science, gaps, and user needs in terms of nutrient assessment tools
and methodologies for each waterbody type were developed and used as foundations for group
discussion.
The primary goals of the workshop were to:
• Identify the full range of potential nutrient overenrichment endpoints, including early
warning indicators, assessment methodologies, and models available for application to
various types of waterbodies,
• Identify what gaps exist in providing a fall range of simple to complex nutrient
overenrichment endpoints assessment methodologies, and models for a wide range of
management applications.
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National Nutrient Assessment Workshop .— Proceedings
• Evaluate the existing and potential nutrient overenrichment endpoints, assessment
methodologies, and models in terms of the state-of-the-science supporting their
applications, date input requirements, and relative ease of transferabUity/application to
various types of waterbodies and geographically diverse areas.
• Evaluate and begin to prioritize specific user needs for nutrient overemichment
endpoints, assessment methodologies, models to address nutrient problems in various
waterbody types and in geographically diverse areas.
• Examine ways to apply nutrient assessment tools across various waterbody types,
geographical areas, and ecoregions.
Recognizing the long history EPA and its partners have had in addressing nutrient
overemichment impacts on aquatic ecosystems, we view this workshop and the subsequent
development of an Agency strategy as a turning point in our commitment to support
development of the tools necessary to set clear, quantifiable endpoints for addressing nutrient
overenrichment problems. Without definable endpoints - whether they are comprehensive
narrative descriptions, site- or regional-specific numerical criteria, or correlative relationships
defining water quality objectives - and the supporting assessment tools applicable at the
watershed and individual waterbody level, it is difficult to design and implement effective
management actions that are tailored to stem the increasing nutrient overenrichment of the
nation's surface waters.
Through development and implementation of a national strategy, it is our hope that we can
better support the development, validation, and implementation of the tools State and local
natural resource managers require to address nutrient overenrichment problems in surface
waters.
Robert H. Waylafid m Tudor Davies
Director Director
Office of Wetlands, Oceans and Watersheds Office of Science and Technology
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Executive Summary
The National Nutrient Assessment Workshop was held with the purpose of asking for expert
recommendations on the components of a national strategy addressing nutrient overenrichment
issues. There were approximately fifty participants in attendance, representing a diversity of
organizations and geographic regions (a list of the participants is attached at the end of these
proceedings).
The participants met over the course of two and a half days to discuss pertinent
eutrophication issues and potential nutrient assessment and management tools. Each expert
participated in one of four groups that were organized by waterbody (i.e., Estuaries and
Coastal Waters; Lakes and Reservoirs; Rivers and Streams; and Wetlands) and these groups
discussed their specific waterbodies during breakout sessions held on the first two days of the
workshop. Breakout groups reconvened at several points during the workshop to report to the
plenary session on the results of their discussions.
Many tools and measurement endpoints were deemed useful by each of the waterbody
breakout groups. Some waterbodies were better understood than others in this regard. For
example, measurement parameters for lakes are well known and the interactions between
these parameters and resulting eutrophication are generally understood. Because of this, the
lakes and reservoirs breakout group, which was dealing with a well-developed historical
database, was able to rate the various measurement parameters in terms of their usefulness; in
some cases the group was able to assign quantitative thresholds for each parameter. For
wetlands, on the other hand, the breakout group was limited by a very small historical
database and therefore was restricted to identifying potential measurement parameters and
assigning qualitative judgements to each of the parameters. The wetlands group was also
handicapped by the high variability encountered in wetland types.
Some of the general recommendations arising from the workshop were:
• A set of national standards is not a realistic goal and it would be more appropriate to set
nutrient standards on an ecoregional or watershed basis.
• Organizations, states, and societies should be involved in further discussions of nutrient
assessment and implementation issues, as well as development of the national nutrient
overenrichment assessment strategy.
« Cultural eutrophication should be recognized as a public health threat. The two examples
that were mentioned were 1) nutrient overenrichment can stimulate harmful and toxic algal
species that directly affect the safety of seafood products and 2) drinking water treated
from eutrophic lakes and reservoirs can be contaminated with harmful byproducts of the
disinfection process (e.g., trihalomethanes).
• Land use should be included as a separate early warning indicator.
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National Nutrient Assessment Workshop Proceedings
• EPA should provide simple, user-friendly, desktop-based software models, where available,
to state and local governments to aid them in waferbody decision making.
• While many models can be recommended for specific waterbody types and sites (e.g.,
lakes), more research is needed on investigating models for rivers and streams (especially
periphyton dominated systems), estuaries, and wetlands.
« The use of "reference sites" to develop baseline data for comparisons to potentially
impacted areas is recommended, especially for wetlands where information is scarce.
Some of the waterbody specific conclusions/recommendations arising from the workshop
were:
Lakes and Reservoirs
Conclusions/Recommendations
• National nutrient criteria must be narrative based and quantitatively implemented on a
local/regional basis. This is because public opinion of (and in fact) good water quality
varies by geographic region.
• There is a need to develop standardized protocols for several of the monitoring techniques
currently used in the field (e.g., total phosphorus, total chlorophyll concentration, Secchi
depth). These and other secondary indicators should be described in a technical guidance
manual for use by all states.
* Land use change around lakes and reservoirs is one of the most telling early warning
indicators of water quality trends. It was said, "A lake is a product of its watershed."
• Develop desk-top software for States to use for lakes and reservoirs individually to help
assess the data they gather.
« Use professional societies such as the North American Lake Management Society, as well
as EPA Regional meetings with the States and Tribes, to promote nutrient criteria and
management for lakes and reservoirs
Endpoints
• Total phosphorus, total nitrogen, total chlorophyll, Secchi depth and dissolved oxygen are
good endpoints to consider as indicators of trophic status of lakes and reservoirs.
• If we use chlorophyll as a parameter, total chlorophyll is arguably the best way to measure
(as opposed to chlorophyll a or b).
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• Secchi disk is a good, simple tool to use on lakes and reservoirs, recognizing that its use is
limited where water visibility is blocked by suspended inorganic sediment or the water has
obscuring color such as is naturally found in bog lakes.
» The best indicators are (in chronological order of response):
Early warning indicators: Land use changes
Sensitive in-lake indicators: Total phosphorus, total chlorphyll, Secchi depth,
total nitrogen
Lake status indicators: Total organic carbon, dissolved oxygen, total
suspended solids, turbidity, biological (fish, algae,
zooplankton, macrophytes)
Modeling
* Simple and effective "desktop" models currently exist at the State level that incorporate the
following parameters: dissolved oxygen, total phosphorus, Secchi depth, total chlorophyll,
and total nitrogen.
* A trend promoted by some modelers is to use carbon as a replacement parameter for
chlorophyll.
Information Needs/Next steps
« We need to better define the relationship between management policies and loading.
• We need to better understand the relationship between nutrient loading and the macrophyte
response.
• We need additional simple, accurate desktop models that distinguish between lakes and
reservoirs, as well as geographic and temperate differences.
• We need a better understanding of the effect that suspended solids have on nutrient release.
Rivers and Streams
Conclusions/Recommendations
• National nutrient criteria, whether numeric or narrative, must be ecoregion specific,
because of natural variabilities across waterbody types.
• National guidance should encourage States to adopt a nutrient control strategy, which
includes the following minimum set of endpoints: total nitrogen, total phosphorous, Secchi
denth dissolved nxvpp.n and soluble reartive nhosnhnrnus
memoes me ronowing minimum set or enapoinis: rcnai nu
depth, dissolved oxygen, and soluble reactive phosphorous.
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Proceedings
States should include land use as a separate early warning indicator (i.e., if development is
proposed in a watershed, an environmental impact study should be done to assess the
potential impact of such development on the surrounding waterbody).
Minimizing the turbulence by constructing channels in the waterbody would help in
reducing the rapid nutrient movement from one segment of the waterbody to another.
Shading the streams or canopy restoration can minimize eutrophication.
Biological control - Managers should consider introducing biomass eating organisms (e.g.,
cadis fly larva (Dicosmoecus gilvipes)), which efficiently remove both periphytic diatoms
and filamentous algae from rock substrata.
Endpoints
Plankton dominated systems
• Algal Biomass
• pH
« Dissolved Oxygen (DO)
• Chlorophyll
* Biointegrity (macroinvertebrate index)
• Total Nitrogen vs. Total Phosphorous
• Transparency (Secchi disk)
• Temperature
• Total suspended solid, Variable
suspended solid ratio
Modeling
Periphyton dominated systems
• Algal Biomass
* PH
• Dissolved Oxygen (DO)
• Chlorophyll
• Biointegrity (macroinvertebrate index)
• Dissolved inorganic nitrogen (DIN) vs.
Soluble reactive phosphorous
• Transparency (Black disk)
• Temperature
• Total suspended solid, Variable
suspended solid ratio
Desktop models that are easily transferred across waterbodies and use the following
parameters should be encouraged: total phosphorus, total nitrogen, total chlorophyll,
dissolved oxygen, temperature and light attenuation instrumentations (i.e., Secchi disk and
black disk).
Adding temperature simulation to WASPS is recommended. WASPS is widely used in
both water quality assessment and toxic modeling. The model considers comprehensive
dissolved oxygen and algal processes, but does not include the carbon and silica cycles or
full sediment diagenesis. In addition, the model's use is limited because it does not
account for temperature.
Periphyton should be added as a parameter incorporated within QUAL2E and HSPF.
QUAL2E and HSPF are one-dimensional models that capture the longitudinal transport
(steady-state flow) which dominate in most rivers and streams. QUAL2E and HSPF both
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consider advection and dispersion. Adding periphyton to these models will allow for
simulation of periphyton biomass in the riverine system.
• Introduce load/response relationship (plankton dominated system) and concentration/
response (periphyton dominated system), in order to pinpoint with high degree of accuracy
where loading reduction can be targeted.
• Other models of note are those used in combination with other techniques in the state of
Montana to set nutrient loading targets for Clark Fork River.
Information Needs/Next steps
• Use of community metrics as early warning indicator.
• EPA should conduct a comprehensive literature search to determine what work has already
been done on nutrient-related issues in rivers and streams.
• Need to synthesize information on the relative sensitivity of different riverine types to
nutrient enrichment and use this information to investigate regressional relationships.
• EPA should publish a national technical guidance document summarizing the Agency's
position on methodology information in assessing and controlling nutrients.
• EPA should set up a nationwide database for storing state of the science information on
nutrient overenrichment endpoints and modeling techniques to serve as a resource center
for water quality managers at state and local levels.
• Involve organizations such as American Society of Limnologist and Oceanographers
(ASLO), American Water Resources Association (AWRA), North American Benthological
Society (NABS) etc., in the development and implementation of the national nutrient
strategy.
« Investigate pH and DO amplitude.
* Investigate the role of fluvial geomorphology as a factor in controlling algal growth.
« Field research should be conducted on Cladophora, and diatom growth requirements.
Estuarine and Coastal Waters
Conclusions and Recommendations
• Coral Reefs - EPA should support research on the relationship between specific nutrient
concentrations and algal coverage and coral reef die-off.
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• Seagrass Dominated Systems - Tools for assessing nutrient enrichment impacts on seagrass
population exist and have been field tested. EPA should help in the transfer of these tools
and insights for assessing nutrient enrichment impacts to waterbody specific seagrass
habitats in estuarine and coastal management programs.
* Plankton Dominated Systems - Quantitative relationships have been established between
nutrient loading and chlorophyll a (primary productivity) and nutrient loading and
dissolved oxygen. EPA should assist research into the use of Vollenweider type methods
in developing nutrient response relationships for plankton dominated systems.
* Nuisance Algal Blooms/Brown Tide Blooms - The relationship between nutrient loadings
and nuisance algal blooms (e.g., brown tide) is not well established outside of laboratory
settings. EPA should support a comprehensive synthesis of correlative/experimental
evidence for toxic algal blooms response to nutrient enrichment.
» Macroalgae Dominated Systems - Only a qualitative relationship exists for relating nutrient
loadings to macroalgal cover. EPA should build on the existing information on the
relationship between nutrient loading and macroalgal cover.
Information Needs/Next Steps
* Coral reefs - Need to further study the relationship between nutrient concentrations and
algal coverage and coral reef die-off.
» Seagrass - Need to confirm that tools for assessing nutrient enrichment impacts from
Chesapeake Bay and Tampa Bay are appropriate for use across other waterbodies (i.e.,
identify any limitations of tools).
» Plankton - Need to develop nutrient/response relationships for plankton dominated systems
using Vollenweider type relationships (i.e., phosphorus loading to hypolimnetic dissolved
oxygen concentration regressions)
* Nuisance algae - Need to establish the relationship between nutrient loadings and nuisance
algal blooms such as brown tide in field settings (i.e., ground truth this research).
• Macroalgae - Need to compile nutrient loading data for: seagrass, macroalgae, and
phytoplankton. In addition, confirm the different community responses and pull out
thresholds relating to these community shifts. Also, quantify the macroalgae influence on
dissolved oxygen, dissolved organic carbon, and lower trophic levels.
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Wetlands
Conclusions/Recommendations
• There needs to be an accepted national wetlands classification system similar to the
hydrogeomorphic classification system developed by the Army Corps of Engineers.
• A nutrient database including baseline data according to wetlands types/regions needs to be
developed.
• Field experimentation should be conducted to determine nutrient limitation to wetland type
and to isolate the effects of nutrients from other variables, such as hydrology, climate, and
natural variability.
• Need to integrate parameter data collection with wetland indicators, or possibly other EPA
wetlands programs.
• Need to improve upon molecular biology techniques (e.g., stress proteins in plants).
• Currently, standards for wetlands are primarily narrative since it has been difficult to apply
certain numeric criteria to wetlands (e.g., dissolved oxygen is hard to standardize because
wetlands can be dry at times),
« Variability is important to consider in wetlands, especially in extreme flow and rainfall
events.
Endpoints
• A "Secchi disk" for wetlands could be feldspar (silicon dioxide) which shows accumulation
within a wetland over time. The rate of accumulation can be related to changes in
productivity.
• Most important indicators (short- and long- term) of nutrient impact are: bioavailable
nitrogen and phosphorous in sediments, soils, water, and vegetation; hydrology; and loads.
However, for most of these parameters there is no baseline data available with which to
compare collected data.
• For immediate assessment, recommended endpoints are: bioavailable nitrogen and
phosphorous in soils and water; plant species composition; plant species richness; plant
species structure; plant indicator species (vascular and non-vascular); soil oxygen demand.
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Modeling
• Very few models exist for wetlands. There is a model under development for the
Everglades which considers water budget, flow fields, vegetation and biology. It has a
spatial scale which is important in assessing wetlands.
« Other models of note are those done for the Des Plaines wetlands and Odum Creek
(Florida). However, these lack spatial scale.
• Landscape models can be used but are more coarse in their ability to predict impacts.
Grids can be very large (1 km by 1 km).
• Some members felt that numeric models may not be useful in predicting changes in
wetlands. Rather, more simple (i.e., heuristic) models may be more helpful in
understanding nutrient-related responses within wetlands.
Information Needs/Next steps
• EPA should develop a nationwide database for natural wetlands similar to that currently
available for constructed wetlands. The database should include a wetland type and
statistical characteristics that apply to each wetland type. A national database could be
used to compare the measurement parameters of assessed (impacted) wetlands to an
established set of reference conditions.
• EPA should conduct a comprehensive literature search to determine what work has already
been done on nutrient-related issues in wetlands.
• Organizations such as the State Association of Wetland Managers, Society of wetland
scientists, and private organizations (e.g., Ducks Unlimited) should be involved in the
development and implementation of the national nutrient strategy.
« Need to synthesize information on the relative sensitivity of different wetland types to
nutrient enrichment and use this information to investigate regressional relationships.
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Day One Plenary Session
Summary
I. Welcome and Participant Introduction
The National Nutrient Assessment Workshop opened with Rich Batiuk, U.S. EPA Chesapeake
Bay Program Office, who welcomed all of the participants and thanked them for attending.
Participants then introduced themselves and described their area of expertise as it related to
the workshop objectives. Rich noted that the workshop had succeeded in convening
representatives from a diversity of organizations, interests, and geographic areas to focus on a
set of issues of regional and national importance.
Rich then presented a brief synopsis of events leading up to and the purpose behind the
workshop. He informed the group that the workshop grew out of a recommendation of the
EPA Office of Science and Technology Nutrient Task Force draft report released December
30, 1994 and stressed that EPA and its partners are attempting to re-engage nutrient
overenrichment issues and to identify and address the relevant technical and implementation
issues. He stressed the importance of identifying endpoints and selecting assessment tools for
use at the individual waterbody and watershed scales. He pointed out that the workshop
should serve as a unique opportunity to pool the experience that is available in the scientific
and resource management communities in helping set the short and long-term priorities for a
national nutrient overenrichment assessment strategy.
II. Introductory Remarks
Tudor Davies, Director, U.S. EPA Office of Science and Technology
Tudor Davies emphasized that eutrophication continues to be a problem faced by many States
and municipalities. He challenged the workshop participants to ask whether or not there are
alternative ways to assess the nature and extent of nutrient enrichment problems and he
reminded them that their discussions should take into account implementation, as well as
technical and scientific issues. Tudor concluded his remarks by assuring the participants that
EPA is taking this issue very seriously and will use the results of the workshop as it prepares
its national strategy.
Bob Way land, Director, U.S. EPA Office of Wetlands, Oceans, and Watersheds
Bob Wayland spoke about confronting the nutrient overenrichment issue from a management
perspective. He mentioned the growing public awareness of eutrophication problems through
programs such as the Clean Lakes Program, the Chesapeake Bay Program, and the National
Estuaries Program. He stressed that a national nutrient strategy needs to have clear
management objectives and recognize concerns of dischargers, especially nonpoint sources,
about affordability. Bob expressed his hope that the workshop could serve to facilitate
technology transfer and communication among parties from all of the different communities
represented.
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III. Past, Present, and Future Perspectives on the Assessment and Management of
Nutrient Overenrichment Needs1
Robert Thomann, Manhattan College
Robert Thomann presented his perspective on the historical issues associated with the
assessment and management of nutrient overenrichment. He divided the past seventy years
into two periods: the Observational Descriptive period that began in the late 1920s and the
Predictive Management period that began circa 1965. He characterized the Observational
Descriptive period as a time when general observations were being made about nutrient
enrichment issues, but little was understood concerning the cause and effect relationships
between loadings and eutrophication.
The Predictive Management period, on the other hand, was characterized as a time when
researchers attempted to relate the basic science that was available to practical management
goals. The period from 1970 to 1980 saw a rapid expansion in the spatial detail and number
of variables included in nutrient models. This progress slowed somewhat during the period
from 1980 to 1990 (characterized as the "Dry Years") as many persons came to feel that the
problem of eutrophication had been solved—the National Eutrophication Program came to an
end and attention was diverted to chemical contaminants and acid rain. Interest began to
grow again during the late 1980s, however, as the public began to realize that nutrient
overenrichment could have far-reaching effects. By this time dynamic modeling had become
much more advanced, with more variables being included in each model and key inputs being
internalized into the model framework. This development was facilitated by the evolution in
computer technology and a reduction in computer costs.
Bob concluded his remarks by outlining the requirements of a successful nutrient management
program. He pointed out the need for a credible framework to support quantitative decision
making that takes into account what level of improvement to expect, a time frame for this
improvement, and a cost/benefit analysis, if possible. He also stressed that this framework
should incorporate the perspectives of nutrient dischargers, the scientific community, and the
general public.
Mimi Dannel, U.S. EPA Office of Wetlands, Oceans, and Watersheds
Mimi Dannel explained where EPA Headquarters and its regional offices are today in terms
of addressing the eutrophication issue. EPA is aware that there is a need for management of
excessive nutrient loadings, especially as evidenced by national and State findings
summarized in Clean Water Act section 305(b) reports (National Water Quality Inventory)
and section 303(d) lists (identifying water quality limited waters). EPA currently encourages
consideration of nutrient enrichment issues in State's implementing watershed protection
approaches, community-based environmental protection approaches, and in potential
Summaries of the overheads used during these presentations are attached at the end of the proceedings.
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National Nutrient Asxessntent Workshop ——— Proceedings
opportunities for pollutant trading. Mimi told the participants that she hoped they develop a
list of endpoints and assessment methodologies for each of the waterbodies, as well as a core
set of models to be used for "routine" application across the different waterbody categories.
She indicated that the focus should be on models that already exist and how they could be
enhanced and simplified. She also indicated that participants need to critically look at the
number of input parameters and how they are measured. Finally, she explained that there is a
need to be able to demonstrate the costs of model application versus the cost of controls to
avoid focusing on the tool more than the resource.
Steve Heiskary, Minnesota Pollution Control Agency
Steve Heiskary presented workshop participants with the nutrient control approach currently
used in Minnesota as an example of how a state could address nutrient issues on a regional
basis. He explained that most of the lakes in Minnesota are located in four main ecoregions
and that phosphorus criteria have been established in each ecoregion based on user
expectations and regional variations in attainable lake trophic status. This approach has been
aided by the selection of "reference" (minimally impacted) lakes within each ecoregion that
were chosen based on expert recommendations and input from citizen monitoring groups.
Steve also explained how Minnesota implemented the lake user survey approach (developed
in Vermont) to gauge the public's expectations of lake quality for each of the different
ecoregions.
Steve mentioned that several other states have been doing progressive work in this area (e.g.,
Vermont with the user surveys, Oregon with a nuisance phytoplankton approach, and North
Carolina with a nutrient sensitive approach). He ended his presentation by explaining that
Minnesota uses its criteria to prioritize and target nutrient reduction projects, to develop water
quality management plans, to serve as an educational tool, and to guide enforcement
decisions.
IV. Purpose and Goals of the Workshop
After the introductory presentations, Rich Batiuk presented the workshop participants with the
purpose and goals of the workshop and issued specific challenges to each of the breakout
groups. Emphasis was placed on coming up with a practical strategy that encompasses local
nutrient overenrichment assessment and implementation issues. The participants then
separated into their assigned groups for the day one breakout sessions.
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Breakout Group Discussion Questions
Lakes, and Reservoirs
Nutrient Enrichment Assessment Endpoints
• What are the currently available, ready to use, and most promising nutrient enrichment
endpoints for application to lakes, impoundments, and ponds?
« Are there any early warning indicators of onset of nutrient enrichment conditions?
« How readily applicable are these endpoints at the regional, state, and local watershed and
waterbody assessment scales? What are their advantages/disadvantages? Can they be
applied to a wide range of waterbodies or are they geographically limited in their
application?
* What is the balance that should be achieved between endpoints with a loading/response
condition focus vs. endpoints with more of a user perception-based focus? Are they
mutually exclusive or can they be married together in some form?
* Are there different sets of endpoints that apply only to large lakes vs. impoundments vs.
small lakes and ponds? What are they?
* What gaps exist in this current array of endpoints that are necessary for regional/state/local
watershed/waterbody-based assessment of nutrient enrichment status and, ultimately,
management? What is the relative priority that should be given to the
development/calibration/validation of new endpoints?
* Are some of the endpoints (or the science behind them) applicable to other non-
lake/impoundment/pond waterbodies?
Dissolved Oxygen
* Are the existing EPA freshwater criteria sufficiently protective enough and/or
comprehensive enough for full application to the entire range of lake, reservoir, and pond
ecosystems?
Light Penetration/Nutrient Criteria
• Does the current state of the science support derivation of light attention criteria for lakes,
impoundments, and ponds? What about nutrient, suspended solids, and chlorophyll a water
quality criteria?
• Should EPA be actively promoting regional-based development and adoption of such
criteria for the protection of lake and reservoir habitats?
Models
• What are the most appropriate models that should be highlighted within the national
strategy? What are their relative advantages and disadvantages in terms of direct
application, data calibration requirements, and amount of training/expertise necessary to
allow effective use by regional, state, and local management agencies?
• How well do the identified models perform in relation to the preliminary list of endpoints
that are concurrently being discussed at the workshop?
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• Is there a good match between the available endpoints and the available load-response
models?
• Which models and assessment tools are most likely to be used by local water quality
managers in support of reaching the identified endpoints for each waterbody type?
• How can existing models be enhanced or what types of new models need to be developed
to improve modelling capability and broaden use of models in assessment of nutrient
enrichment?
• Are the existing "state of the science" lake and reservoir models currently being developed
for and applied in large lakes and reservoirs at a point whereby simplified versions of the
models can be extracted and used by smaller, less wealthy lake restoration and protection
programs with the same basic management oriented results? If not, what steps need to be
taken to get to that point?
• What about the same questions directed towards watershed models that feed inputs into
lake/reservoir water quality models?
Issue Paper
• Are there obvious gaps in the lakes and reservoirs issue paper's coverage of the major
literature that should be filled prior to publication as an EPA report and in the peer
reviewed literature?
* Are there obvious gaps in the modeling issue paper's coverage of the major literature
addressing lakes and reservoirs that should be filled prior to publication as an EPA report
and in the peer reviewed literature?
Rivers and Streams
Nutrient Enrichment Assessment Endpoints
• What are the currently available, ready to use, and most promising nutrient enrichment
endpoints for application to rivers and streams?
• Are there any early warning indicators of onset of nutrient enrichment conditions?
• How readily applicable are these endpoints at the regional, state, and local watershed and
waterbody assessment scales? What are their advantages/disadvantages? Can they be
applied to a wide range of waterbodies or are they geographically limited in their
application?
* Are there different set of endpoints that apply only to large rivers vs. small streams? fast
flowing vs. slow flowing rivers?
* What gaps exist in this current array of endpoints that are necessary for regional/state/local
watershed/waterbody based assessment of nutrient enrichment status and, ultimately,
management? What is the relative priority that should be given to the
development/calibration/validation of new endpoints?
• Are some of the endpoints (or the science behind them) applicable to other non-riverine
waterbodies?
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Dissolved Oxygen
• Are the existing EPA freshwater criteria sufficiently protective enough and/or
comprehensive enough for full application to the entire range of river and stream
ecosystems?
Light Penetration/Nutrient Criteria
• Does the current state of the science support derivation of light attention criteria for rivers
and stream? What about nutrient, suspended solids, and chlorophyll a water quality
criteria? Are these really appropriate for these riverine systems (with the possible
exception of slow flowing rivers and streams with longer retention times)?
« Should EPA be actively promoting regional-based development and adoption of such
criteria?
Models
« What are the most appropriate models that should be highlighted within the national
strategy? What are their relative advantages and disadvantages in terms of direct
application, data calibration requirements, and amount of training/expertise necessary to
allow effective use by regional, state, and local management agencies?
• How well do the identified models perform in relation to the preliminary list of endpoints
that are concurrently being discussed at the workshop?
• Which models and assessment tools are most likely to be used by local water quality
managers in support of reaching the identified endpoints for each waterbody type?
» How can existing models be enhanced or what types of new models need to be developed
to improve modelling capability and broaden use of models in assessment of nutrient
enrichment?
* Are the existing "state of the science" models currently being developed for and applied in
rivers and streams at a point whereby simplified versions of the models can be extracted
and used by smaller, less wealthy river/stream restoration and protection programs with the
same basic management oriented results? If not, what steps need to be taken to get to that
point?
Issue Paper
* Are there obvious gaps in the rivers and streams issue paper's coverage of the major
literature that should be filled prior to publication as an EPA report and in the peer
reviewed literature?
• Are there obvious gaps in the modeling issue paper's coverage of the major literature
addressing rivers and streams that should be filled prior to publication as an EPA report
and in the peer reviewed literature?
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Wetlands
Nutrient Enrichment Assessment Endpoints
• Are there any available endpoints useful for assessing the relative impact of nutrient
enrichment on wetland ecosystems?
* Are there any early warning indicators for nutrient enrichment conditions within wetlands?
Models
• Are there any models available for simulating/assessing the relative impact of nutrient
enrichment on wetland ecosystems?
• What are the most appropriate wetlands models that should be highlighted within the
national strategy? What are their relative advantages and disadvantages in terms of direct
application, data calibration requirements, and amount of training/expertise necessary to
allow effective use by regional, state, and local management agencies?
• How well do the identified models perform in relation to the preliminary list of endpoints
that are concurrently being discussed at the workshop?
* Which models and assessment tools are most likely to be used by local water quality
managers in support of reaching the identified endpoints for each waterbody type?
• How can existing models be enhanced or what types of new models need to be developed
to improve modeling capability and broaden use of models in assessment of nutrient
enrichment?
Issue Paper
• Are there obvious gaps in the wetlands issue paper's coverage of the major literature that
should be filled prior to publication as an EPA report and in the peer reviewed literature?
* Are there obvious gaps in the modeling issue paper's coverage of the major literature
addressing wetlands that should be filled prior to publication as an EPA report and in the
peer reviewed literature?
Estuaries and Coastal Waters
Nutrient Enrichment Assessment Endpoints
• What are the currently available, ready to use, and most promising nutrient enrichment
endpoints for application to estuarine and coastal waterbodies?
• Are there any early warning indicators of onset of nutrient enrichment conditions?
• How readily applicable are these endpoints at the regional, state, and local watershed and
waterbody assessment scales? What are their advantages/disadvantages? Can they be
applied to a wide range of waterbodies or are they geographically limited in their
application?
• What gaps exist in this current array of endpoints that are necessary for regional/state/local
watershed/waterbody based assessment of nutrient enrichment status and, ultimately,
management? What is the relative priority that should be given to the
development/calibration/validation of new endpoints?
* Are some of the endpoints (or the science behind them) applicable to other non-
estuarine/coastal waterbodies?
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Dissolved Oxygen
• Building on the estuarine/marine dissolved oxygen criteria document under preparation for
northeast (Cape Cod to Cape Hatteras) coast, should EPA support development of the low
dissolved oxygen effects databases necessary to publish estuarine/marine dissolved oxygen
criteria for the southeast Atlantic (Cape Fear to Key West), Gulf, and Pacific coasts?
• What about development of the data sets necessary to extend the northeast criteria along
the coastline north of Cape Cod up into the Gulf of Maine?
Light Penetration/Nutrient Criteria
• Does the current state of the science support derivation of light attention criteria for
protection of submerged aquatic vegetation (seagrasses) along the U.S. coastlines? What
about nutrient, suspended solids, and chlorophyll a water quality criteria based on
protecting submerged aquatic vegetation?
• Should EPA be actively promoting regional-based development and adoption of such
criteria for the protection of shallow water habitats?
Models
• What are the most critical nutrient enrichment related issues that the existing models have
yet to be designed, calibrated, and/or applied to address?
• What are the most appropriate models that should be highlighted within the national
strategy? What are their relative advantages and disadvantages in terms of direct
application, data calibration requirements, and amount of training/expertise necessary to
allow effective use by regional, state, and local management agencies?
* How well do the identified models perform in relation to the preliminary list of endpoints
that are concurrently being discussed at the workshop?
• Are the existing "state of the science" estuarine/coastal models currently being developed
for and applied in Chesapeake Bay, Long Island Sound and other larger estuaries at a point
whereby simplified versions of the models can be extracted and used by smaller, less
wealthy estuarine and coastal protection programs with the same basic management
oriented results?
• If not, what steps need to be taken to get to that point?
• Which models and assessment tools are most likely to be used by local water quality
managers in support of reaching the identified endpoints for each waterbody type?
• How can existing models be enhanced or what types of new models need to be developed
to improve modelling capability and broaden use of models in assessment of nutrient
enrichment?
• What about the same questions directed towards watershed models that feed inputs into
estuarine/coastal water quality models?
Issue Paper
* Are there obvious gaps in the estuarine/coastal issue paper's coverage of the major
literature that should be filled prior to publication as an EPA report and in the peer
reviewed literature?
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• Are there obvious gaps in the modeling issue paper's coverage of the major literature
which address estuarine and coastal systems that should be filled prior to publication as an
EPA report and in the peer reviewed literature?
Watersheds
Nutrient Enrichment Assessment Endpoints
• What is/what should be the relationship between nutrient enrichment endpoints for
watersheds themselves vs. endpoints addressing watersheds as contributors to downstream
waterbodies? Is there an inherent conflict here?
Models
• What are the most appropriate watershed models that should be highlighted within the
national strategy? What are their relative advantages and disadvantages in terms of direct
application, data calibration requirements, and amount of training/expertise necessary to
allow effective use by regional, state, and local management agencies?
• How well do the identified models perform in relation to the preliminary list of endpoints
that are concurrently being discussed at the workshop?
• Which models and assessment tools are most likely to be used by local water quality
managers in support of reaching the identified endpoints for each waterbody type?
• How can existing models be enhanced or what types of new models need to be developed
to improve modelling capability and broaden use of models in assessment of nutrient
enrichment?
Issue Papers
• Are there obvious gaps in the four issue papers* coverage of the major literature addressing
watershed models that should be filled prior to publication as an EPA report and in the
peer reviewed literature?
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Day Two Plenary Session
Summary of Reports from Breakout Groups and Discussion
Workshop participants reconvened on the morning of the second day to report on the results
of their breakout group discussions. The following is a summary of what each of the
facilitators had to say concerning their respective day one breakout group sessions,
I. Lakes and Reservoirs Summary
The breakout group began its discussion by outlining what it hoped to accomplish during the
course of the workshop. It was agreed that the group would be making recommendations to
EPA on the utility of using various parameters to assess waterbody status and to use as early
warning indicators2 of lake and reservoir nutrient overenrichment. The breakout group also
agreed that they would be providing general recommendations on issues that would need to
be addressed in a national nutrient assessment strategy, including the capabilities and
limitations of existing modeling tools for lakes and reservoirs.
To organize the discussion, the group divided an initial list of parameters into three
categories. The group realized that these categories could be differentiated in a number of
ways (e.g., proactive parameters vs. reactive parameters; thermodynamic parameters vs.
species succession/community structure parameters; parameters that are well understood vs.
less well-understood parameters.) Eventually the group decided to separate the parameters
into the following subsets:
Chemical/Biomass Parameters
• Land Use/Loading • Nitrogen Concentration * Secchi Depth
• Phosphorus Concentration • Chlorophyll • Dissolved Oxygen
Community Structure Parameters
• Algal Community • Macrophytes • Zooplankton
• Macroinvertebrate Structure • Fish
Secondary Parameters
* Total Suspended Solids « Total Organic Carbon
The group began to evaluate each of these parameters based on the following evaluation
criteria:
How Measured What quantitative units are used to measure the parameter?
An early warning indicator was defined as "a change from a baseline condition within a region and
classification of the water resource and watershed which is sufficiently rapid to initiate increased monitoring or
management before degradation (unacceptable change) takes place."
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Value
Scientific Validity
Practicality
Cost
What advantages does using the parameter provide to the resource
manager relative to using other parameters?
Are there well-accepted (i.e., within the scientific community),
reproducible measurement techniques available for measuring the
parameter?
Is this a parameter that the states can realistically use given time,
personnel, and resource constraints?
What is the cost of collecting and using this parameter?
Public Understanding Is this a parameter that the public understands and will support?
Modeling Capability/ Is the relationship between loading and subsequent response well-
Load-Response understood? Can the parameter be modeled given existing tools or
easy-to-develop tools?
In general, the group was able to reach consensus on a rating3 for each of the evaluation
criteria for each of the parameters. The results of their discussion are summarized in the
tables below. Blank spaces in the "Rating" column indicate that either no consensus was
reached or no formal designation was specified.
Land Use/Loadings
How Measured
Value
Scientific Validity
Cost
Practicality
Public Understanding
Modeling Capability/ Load-
Response
Rating
High
High
Variable
High
Medium
to High
High
Notes
Loadings are measured based on the existing understanding
between certain types of land use and related loadings.
Aggregated loadings allow you to get to one number for all of
the sources within a watershed
Some states have adequate land use data while others are still in
the process of gathering it.
Public does not intuitively understand the relevance of loading,
but is capable of learning (as evidenced by 40% reduced
loading target for Chesapeake Bay).
'A high rating typically meant that the group felt the parameter performed well in terms of the evaluation
criteria (e.g., a high rating for Scientific Validity means the parameter is well-accepted within the scientific
community whereas a low rating means that it is not). The one exception was the cost criteria, in which case a
low rating is preferable to a high rating.
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Phosphorus
Units of Measurement
(Total P)
Value
Scientific Validity
Cost
Practicality
Public Understanding
Modeling Capability/ Load-
Response
Rating
High
Medium
to High
Low
High
Medium
to High
Notes
Total phosphorus should be used because it is a more
comprehensive measurement.
Phosphorus is the start of all productivity. Total phosphorus
also has the potential for being a "one shot" measurement
because other variables can usually be related to it.
Scientific validity is high for lakes (especially for certain tvpes
of lakes); not as well established for reservoirs.
Already measured as a component of most monitoring
programs. Springtime phosphorus can be especially cheap
because it only needs to be collected once.
The meaning behind phosphorus concentrations has to be
translated for the public, but interested citizens are aware of
their significance.
Modeling capability is especially good for temperate and glacial
lakes.
Nitrogen
Units of Measurement
(Total N)
Value
Scientific Validity
Cost
Practicality
Public Understanding
Modeling Capability/ Load-
Response
Rating
Medium
Low
Medium
Low
Notes
Nitrogen used to get N:P ratio; some systems are nitrogen
limited.
Nitrogen interactions have not been as extensively studied as
phosphorus because there is less motivation to do so for lakes
and reservoirs.
Cost of sampling is similar to that for phosphorus.
Not as practical as phosphorus because fewer lakes and
reservoirs are nitrogen limited. EPA needs to promote a
standard methodology for sampling.
Public is less aware of significance of nitrogen (as compared to
phosphorus); they tend to be lumped together as "nutrients".
More sophisticated models for predicting impact of nitrogen
concentrations need to be developed; load-response relationship
not worked out as well as for phosphorus because of the
number of variables in the nitrogen cycle (e.g., nitrogen
fixation).
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Chlorophyll
Units of measurement
(mg/l)
Value
Scientific Validity
Cost
Practicality
Public Understanding
Modeling Capability/ Load-
Response
Rating
High
High
Low
Medium
Medium
Variable
Notes
The group differed on the utility of using total chlorophyll vs.
chlorophyll a. One problem with chlorophyll a is that
measurements taken prior to 1982 can't be compared to later
values because the measurement method has changed. The
group suggested that EPA make a definitive statement on a
standardized methodology.
Chlorophyll is the best biomass surrogate and is the first
biomass response to phosphorus. Chlorophyll is also the most
interpretable parameter, but has high temporal and spatial
variability.
Chlorophyll is less predictable than phosphorus and is not as
good for trend detection because of its high variability.
Sampling cost similar to phosphorus, although collection costs
are higher.
Samples need to be taken many times per year and over the
course of several years to detect trends. The group
recommended the sampling regime spreadsheet distributed by
the North American Lake Management Society as guidance.
Measurement may be linked to subjective measures of user
perceptions.
Chlorophyll concentrations can be modeled, but need to have
phosphorus concentrations to do so.
Secchi Depth
Units of Measurement
(depth)
Value
Scientific Validity
Cost
Practicality
Public Understanding
Modeling Capability/ Load-
Response
Rating
High
Variable
Low
High
High
Notes
Seems like a simple process, but the group recommended that
EPA establish a consistent methods and material protocol.
Secchi depth measurements have low temporal variance
(especially compared to chlorophyll), but high silt content can
distort the use of the readings for nutrient impact (i.e., may be
a non-nutrient enrichment related problem).
Depends upon what it is used for — low validity if used for
chlorophyll surrogate, but high if used to estimate
transparency and total phosphorus.
Measurement may be linked to subjective measures of user
perceptions.
Not a straight line relationship because it is difficult to
distinguish Secchi depth changes once in the low visibility
range. There is also a problem with natural variability when
trying to detect trends: only a few models break transparency
down into total suspended solids, color, etc.
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Dissolved Oxygen*
Units of Measurement
(mg/I)
Value
Scientific Validity
Cost
Practicality
Public Understanding
Modeling Capability/ Load-
Response
Rating
Variable
Low
High
High
High
Notes
Measurement generally accepted as end of summer dissolved
oxygen in hypolimnion; could also be areal hypolimnetic
oxygen depletion (AHOD) or oxygen depletion rate or days of
anoxia or when the lake went anoxic.
Four problems: 1) there is considerable spatial and temporal
variability associated with dissolved oxygen readings; 2)
southeastern reservoirs display rapid changes between anoxia
and oxia during withdrawal cycles; 3) some investigators now
want to measure CO2 accumulation rate as a negative oxygen
value (i.e., a reducing environment); 4) affected by non-
nutrient-related factors such as temperature and morphology.
Has cross lake validity and provides information on aquatic life
use support.
Fairly cheap once equipment is available; have to measure at
least four times per year.
There is a high degree of public understanding because low
dissolved oxygen levels are related to fish kills.
Can be modeled at least as well as the other parameters.
*Discussion restricted to lakes that stratify.
After discussing the chemical/biomass parameters, the group talked about whether or not total
suspended solids or total organic carbon should be included as potential nutrient assessment
endpoints. They eventually agreed that both parameters provide additional information
beyond that provided by the previously mentioned parameters and decided to add them as
"secondary parameters". The point was made that carbon might prove helpful because it is
related to a host of other waterbody problems that affect and are affected by eutrophication.
It was also during this discussion that the importance of emphasizing eutrophication as a
public health concern first arose. In particular, the participants noted the hazards associated
with consuming drinking water containing potentially carcinogenic disinfection by-products,
such as trihalomethanes. (Trihalornethanes can be produced as a by-product of the
disinfection process used in plants that take their water from eutrophic lakes or reservoirs.)
The group agreed that this public health issue needs to be emphasized by EPA and others to
gain public support for a national nutrient strategy.
Several questions were posed to the lakes breakout group by members of the plenary session.
These included whether or not the group had addressed the cross-cutting issue of assessing
and managing large lakes vs. small lakes and whether or not the group had evaluated how
well the different species of phosphorus would serve as endpoints (as opposed to total
phosphorus). The lakes group stated that these were two issues they intended to address in
the next breakout session.
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II. Rivers and Streams Summary
Introductions/Agenda
The rivers and streams breakout group began with participant introductions and a discussion
of the agenda. The participants briefly discussed the morning plenary session and agreed that
a reiteration of the breakout group's goals and objectives would not be necessary. Some of
the participants suggested using the issue paper as a springboard for the discussion. While
this suggestion was not adopted, participants agreed that during the course of the workgroup
session attention should be given to identifying and filling in the information gaps in the issue
paper.
The main issue addressed in the discussion of the agenda was whether or not the group
should pursue a process versus an endpoint specific approach to addressing the problem of
nutrient loading. Participants emphasized the importance of recognizing local and regional
differences among rivers and streams. There was an acknowledgement that it would be very
difficult to develop specific endpoints that could be applied to all river and stream systems.
As a result, the group agreed to focus on developing a better understanding of the nutrient
loading process in an effort to provide recommendations on appropriate indicators.
Moving from their agreement to emphasize process, the group began to discuss some of the
basic biological factors associated with the nutrient loading. There was a consensus that
understanding nutrient loading impacts on streams and rivers was different from
understanding nutrient loading impacts on lakes. The relationship between algae growth and
nutrient loading is relatively linear in lakes while in streams the relationship is more complex.
In a more dynamic stream or river ecosystem, low levels of soluble nutrients can produce
both small and large volumes of biomass.
Factors Contributing To Nutrient Growth
Participants agreed that given this complexity, more information was needed to improve our
understanding of the various relationships and factors associated with algae growth in streams
and rivers. As a result, the group felt it would be an important first step to list some of the
known factors other than nutrient loading that contribute to algae growth. Some of the
factors mentioned by the participants included:
• Extended low flow periods
• Grazers, fish
• Stream morphology
• Scouring flow threshold - "tumbling rocks" disrupts colonization (in periphyton dominated
systems).
Emerging from this discussion was an awareness that nutrients may not always be the main
contributor to algal growth. In fact, one participant noted that this might indicate a mis-
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focusing of traditional management efforts by primarily regulating nutrient loading and not
adequately addressing the other contributing factors.
As a result of this discussion, participants reconfirmed their commitment to a process oriented
approach. The group agreed that it would be useful to categorize the different types of
streams and rivers. Participants felt that this would facilitate the identification of some basic
endpoints as well as a better understanding of the nutrient loading process.
River and Stream Categorization and Endpoint Identification
To effectively categorize rivers and streams and identify endpoints, the group began by listing
some of the major factors that should be considered in a stream/river categorization.
Participants identified the following factors:
• Regime/climate • Stream order/drainage area
* Substratum (eroding vs. deposition • Regulated vs. unregulated
• Land use • Local geology
• Canopy cover/riparian vegetation • Flow
• Volume of wetted channel/bankfill • Morphology
From this brief discussion of factors, the group initially reached the conclusion that a basic
way to categorize the different types of streams and rivers was to distinguish between low
gradient and high gradient streams. The participants, however, soon discarded this distinction
and agreed that a more appropriate characterization would be between plankton dominated
and periphyton dominated streams.
Following the basic categorization, the group was then able to move on to identifying
endpoints. Essentially, for both plankton dominated and periphyton dominated streams the
participants identified factors that they felt were meaningful in terms of managing and
understanding these systems. Participants did not focus their discussion on specific numbers
or measurements for the endpoints. Table 1 on the following page lists the basic endpoints
that were identified for each system. Potential endpoints that were specifically not
recommended for both systems included nitrogen:phosphorus ratios and the algal growth test.
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Table 1. Potential Endpoints for Plankton and Periphyton Dominated Systems.
Plankton Dominated
Periphyton Dominated
Algal biomass
pH (maximum and diel)
Dissolved Oxygen (minimum and diel)
Transparency (Secchi depth)
Biointegrity (macroinvertebrate index,
community composition)
Total suspended solids, volatile suspended solids,
ratios
Dissolved organic material
Autotrophic Index (AFDW/CNa)
Total nitrogen
Total phosphorus
Ratios of summer/winter nutrient concentrations
Ratios of dissolved/total nutrient concentrations
Aesthetics (foam, scum)
Algal biomass (mg/m2, percent coverage)
pH (maximum and diel)
Dissolved Oxygen (minimum and diel)
Transparency (Black disk)
Biointegrity (macroinvertebrate index,
community composition)
Total suspended solids, volatile suspended solids,
ratios
Dissolved organic material
Autotrophic Index (AFDW/cht a)
Total nitrogen, dissolved inorganic nitrogen
Total phosphorus, soluble reactive
phosphorus
Ratios of summer/winter nutrient concentrations
Ratios of dissolved/total nutrient concentrations
Aesthetics (foam, scum)
Process Diagrams
Following the identification of endpoints, the discussion moved to how the different endpoints
and factors that influence algae growth interrelate and connect. Group members decided to
construct flow diagrams to facilitate the understanding of the eutrophication process in both
plankton and periphyton dominated systems. The figures on the next page are the process
diagrams that were created by the participants. Both of the diagrams take a "nutrient centric"
view of the process. The interrelationships among the other contributing factors to algae and
periphyton growth were not discussed in detail.
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Figure 1. Plankton Dominated Systems.
Proceedings
Figure 2. Periphyton Dominated Systems.
AESTHETICS
TRANSPARENCY
FISH
BIOINTEGRITY
FACTORS
flow regime
channel
characteristics
velocity
j travel time
i light availability
j temperature
I mass transport of
nutrients
turbulence
toxictty
organic carbon
inputs
NUTRIENTS
TN,TP
AESTHETICS
TRANSPARENCY
FISH
BIOINTEGRITY
FACTORS
*flow regime
channel
characteristics
'velocity,
turbulence
travel time
*TSS, scouring,
high flow, bed
transport
•grazing
light availability
temperature
mass transport of
nutrients
toxicity, other
growth limiters
fine sediment
organic carbon
inputs
NUTRIENTS
DN,SRP
TN, TP
* specific factors that set periphyton dominated systems apart
from plankton dominated svstems
The day's discussion concluded with the group highlighting the key differences between the
plankton dominated and periphyton dominated systems. Participants identified four specific
factors that set periphyton dominated systems apart from plankton dominated systems: the
flow regime, velocity, total suspended solids/scouring/high flow/bed transport, and grazing.
The group emphasized that these factors all contribute to the one major characteristic that
distinguishes these two systems. The major differentiating characteristic is that nutrients will
saturate the biomass at a much lower level in the periphyton dominated system than they will
in the plankton dominated system.
To help illustrate this difference, participants constructed the graphs in Figure 3. The graphs
show the relationship between nutrient concentrations and biomass saturation in both plankton
dominated and periphyton systems. Note that the graphs only serve to illustrate a concept.
The graphs are not drawn to scale and they have not been constructed from actual data, but
are based on the combined experience of the discussion group. The numbers begin to
approximate the typically observed thresholds based on limited field studies.
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Figure 3. Relationships between nutrient concentrations and biomass saturation in both
plankton and periphyton dominated systems.
"300
I
Plankton Dominated Lakes &
Maybe Plankton Dominated Rivers1
-500
Total Phosphorus |ug/L)
1000 h
Periphyton Dominated Rivers1
s a.
10 Soluble Reactive Phosphorus (wg/L)
50 Dissolved Inorganic Nitrogen
i: Light Travel Time, Grazing
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III. Wetlands
To begin the morning session, the wetlands breakout group discussed the definition and use of
the term 'endpoint'. When a variable is chosen and a threshold determined, that threshold
value or range can become an endpoint. Based on current operational definition, a "standard"
only differs from an endpoint in that it has a legal connotation. However, there are different
types of endpoints, such as measurement and assessment endpoints. Because the terminology
can lend to confusion, the group agreed to use the term 'measurement parameters'. Once the
appropriate list of parameters for measuring change's in wetlands can be determined, then
assignment of them as endpoints or standards can be later determined.
Currently, the standards for wetlands in the United States are primarily narrative criteria
developed by states, as it is has been difficult to apply certain numeric criteria to wetlands.
For example, dissolved oxygen is hard to standardize, because a wetland can be dry and have
zero dissolved oxygen. Enforcement and setting of permit limits are based on fixed numbers,
but for wetlands, the limits might be based on concentrations related to flow or even load-
based measures.
The breakout group recognized that literature synthesized and analyzed for the issue paper
tended to vary on the issue of wetland nutrient sensitivity. Variability is important to
consider in wetlands, especially in flow, rainfall, and extreme events. Examples were sought
where some measurement number has been set for wetlands and used as a goal for
management efforts. One example from the Everglades was described where phosphorus was
selected as a focus, but other factors such as seasonal and natural variability were also
considered important. Other potential parameters include:
Nitrogen species concentration
Phosphorus species concentration
Nitrogen:phosphorus ratio
Dissolved oxygen concentration
Another issue that was raised was whether the initial list of potential parameters included
measures which are important to wetlands. The group agreed that the national nutrient
assessment strategy should be looking for some measurement that will indicate whether a
wetland is impacted, on its way to being impacted, or if there is another factor that drives the
system from the outside. These measurements may need to be normalized (for example,
changes by season). Sediment also needs to be considered, because nutrients are related to
sediment loading in wetlands. Change of community structure is also measurable and shows
the effect of eutrophication in wetlands. It is necessary to understand the natural history of
the system to see if the structure, species composition, etc. are natural or anthropogenic. One
suggestion was to detect nutrient-related changes in wetlands through the use of reference or
control sites.
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The group agreed to attempt to identify measurement parameters, and emphasized that there is
a need to identify early warning signals, signals that may clue managers and scientists into
what may occur 10 years later. The following tasks of the breakout group were identified:
1) Create a list of parameters which measure and improve our understanding of nutrient-
related impacts to wetlands.
2) Rank the parameters in importance or organize them for wetlands in a national strategy,
3) Decide how to implement assessment.
4) Create a list of available models, if any, for use in nutrient assessment of wetlands.
The following two approaches were discussed on how to best address these tasks:
• Identify parameters first and then discuss application in various wetland types
• Identify wetland type first and then discuss what parameters are appropriate for
specific types.
The workgroup expressed concern that it might not be able to agree on definitions of
wetlands, and therefore, would like to avoid discussing wetland types initially. Given the
potentially long list of wetland types, and potentially involved discussion around the type of
wetland classification system to use, the group agreed to first examine a hypothetical wetland
system and make a list of measurement parameters, emphasizing parameters that potentially
apply to as many wetlands as possible. Thus, discussion centered around processes in
wetlands as a first step followed by discussion of their application to wetlands types.
The group acknowledged other important questions to consider, but also recognized the time
limitations and the need to develop specific measurement parameters for wetlands. Some of
the other issues/questions to consider included:
• Eutrophication needs to be defined according to whether it is natural or human-
induced.
• At what point is eutrophication in a wetlands system considered a "bad" thing? (For
example, too many cattails in the Everglades—what causes these to spread and is that
"natural". First we need to decide what's good and what's bad).
• Decisions need to be made on whether the system should be controlled or allowed to
follow the change (even if it is human-induced).
Another suggestion was made by the breakout group that here should be an EPA database for
natural wetlands (like that currently available for constructed wetlands). The database should
include a wetland type and statistics that apply to each type. Figure 1 illustrates how a
national database could be used to compare the measurement parameters of assessed wetlands
to an established set of reference conditions. Wetland conditions found to lie outside of the
normal range would indicate impacted conditions.
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Figure 4. Hypothetical example of how a national database of reference wetlands
could be used in assessment of nutrient impacts. Dashed lines represent a
hypothetical confidence interval around a given reference set. Type A, B, C,
and D refer to different wetland types. Driving functions and response
variables can be single or multiple variables.
Ecosystem response
variableorindex
Community metabolism
Enzyme activity
SoiJ accretion rate
Sediment oxygen demand
Nutrient retention
Species indices
iliyil
. type A
••
'•V..
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\>t\
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Ecosystem driving functions
Areal nutrient load index (average and variable)
Area! hydrologic load index (average and variable)
Retention time index (average and variable)
Altitude
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National Nutrient Assessment Workshop ——-—: Proceedings
The group next discussed the relationship between wetland processes and wetland indicators
as one potential way to use indicators to assess wetlands. Parameters measuring wetland
processes can be organized by:
* water quality
• soil
* hydrology
* biota
* processes
Important nutrient processes in wetlands were listed as follows:
Carbon
• respiration (microbes)
• aerobic (water, litter, soil)
• anaerobic (soil)
- sulfate reduction
- methanogenesis
• plant uptake
Nitrogen
• mineralization
• nitrification/denitrification (includes nitrate reduction)
• biological nitrogen fixation
• plant uptake
Phosphorus
• mineralization
* plant uptake
• soil adsorption
Traditional water quality parameters can also affect or be affected by nutrients and should not
be overlooked (e.g., those parameters typically used for assessment of lakes, rivers, and
streams). Surface water chemistry (pH, temperature, and cations) should be reviewed as
potential parameters. Another issue discussed was groundwater chemistry. Both surface and
groundwater quality should. Groundwater interactions and influence on wetlands depend on
the type of wetland, but where applicable, groundwater chemistry should be considered.
Additional Issues
Important issues also discussed during the course of parameter identification included the
following:
Which nutrients are limiting in a given wetland? This is the critical indicator, and a
function of other variables, such as wetland type, water source, latitude, seasonality, time of
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National Nutrient Assessment Workshop - •— — Proceedings
sampling and other factors. Many of the selected parameters may be irrelevant unless
sensitivity of the wetland's response to nutrient enrichment is known. For example, Spartina
sp. salt marshes may exist at either low or high phosphorous or nitrogen concentrations, and
loading rates may make no difference to salt marsh response sensitivity. Some bogs cannot
tolerate certain nitrogen and phosphorus variations.
Signal to noise ratio was also discussed as an issue of importance for some of the chemical
parameters. Multiple samples would be required to understand the variability observed during
sampling within a particular wetland. For wetland assessment, one suggestion was discussed
to place Feldspar (silicon dioxide) in a variety of wetlands, marking the area where deposited
(e.g., with a global positioning system), and then monitoring for 5 to 10 years. This would be
an inexpensive methodology and would show any sediment/organic accretion.
Finally, information gaps identified during the course of the first day's discussion included
stress indicators in plant physiology and rnicrobial community structure.
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National Nutrient Assessment Workshop _ _ _ ___ _ procee^ni,s
IV. Estuaries and Coastal Waters
The estuaries and coastal waters breakout group approached its review of the current status of
nutrient enrichment assessment from three different perspectives: understanding causal
relationships between nutrient enrichment and estuarine/coastal waters use impairments;
evaluating the quantitative or qualitative nature of relationships between nutrient loadings and
system responses; and identification of existing nutrient enrichment assessment tools and
necessary next steps organized by several dominant estuarine/coastal communities. The group
concluded that there is a real need to develop additional confidence in a select number of key
empirical (hopefully causal) relationships, but that the goal of quantitative and predictive
relationships for measurement "endpoints" is simply out of reach for most of the usual list of
indicative measurements. In response to this, the group chose to identify use impairments
{responses) and then to seek an approach to constructing empirical relationships between these
and probable (generally accepted) causal agents directly or indirectly linked to nutrient
loadings.
Use Impairments
The first round of breakout group discussion yielded the following listing of nutrient
overenrichment related use impairments for estuarine and coastal waters:
Beaches
* Toxic and nontoxic algal blooms
• Aesthetics
• Sea Lice (Florida)
Shellfish beds
* Toxic algal blooms (both human and shellfish health concerns; habitat concerns)
• Nontoxic algal blooms (e.g., brown tides — habitat concerns)
Aquatic habitat
• Seagrass losses (due to both loss of light penetration to leaf surfaces and direct toxic
effects from exposure to elevated nitrate in the leaf zone)
* Organic fouling on settling surfaces
• Benthic community impairments (low dissolved oxygen; direct toxic effects through
exposure to elevated sediment ammonia, organic carbon concentrations)
• Fish community impairments (low dissolved oxygen, loss of prey, loss of habitat,
increased disease prevalence)
• Coral reef dieoffs
• Presence of nuisance species (excessive macrophytes; species shifts)
• Aesthetics (odors, discoloration of the waters)
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Nutrient Loading/System Response Relationships
Breakout group members posed three questions to characterize the relative certainty of how
well we understand the relationships between nutrient loading and responses of
estuarine/coastal systems:
• What do we know quantitatively with regard to nutrient loading-system response?
• What do we know qualitatively with regard to nutrient loading-system response?
• Where do we think there may be a relationship, but we can't quantify or quality the
relationship?
Examples of the quantitative relationships included: nutrient loading/chlorophyll a and
primary production relationships, nutrient loading/dissolved oxygen relationship, and nutrient
loading/seagrass production relationships. Two examples were given for qualitative
relationships: nutrient loading/fish yields and nutrient loading/macroalgae.
System-based Tools and Needs
The breakout group next discussed nutrient assessment issues within the context of specific
types of coastal systems. The first round of breakout sessions concluded with a discussion of
coral reef systems.
Coral reef systems
Tools
• Regression relationship of the percent algal cover vs. nutrient concentration to provide the
threshold concentrations at which the coral reefs become degraded (e.g., 1 um dissolved
inorganic nitrogen, 0.1 urn soluble reactive phosphorus from research by LaPointe and
colleagues),
• Regression relationship of coral coverage by algae vs. nutrient loadings.
Next Steps
« Fund a team of investigators to conduct a critical synthesis of the studies supporting these
relationships, publish the results, and get scientific/management community buy-in.
« Support synthesis of existing work and support further studies necessary to quantify the
relationship between coral reef community fish diversity, algal cover, and nutrient loading.
• Develop and publish case study examples to provide for straightforward illustrations of the
above relationships for the public.
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Day Three Plenary Session
Summary of Reports from Breakout Groups and Discussion
On the afternoon of the second day, workshop participants addressed cross-cutting issues
within their breakout groups. The focus during these discussions was on how appropriate
tools can be applied to accomplish nutrient management goals, the transferability of various
tools across waterbody types and geographically and ecologically diverse areas, and the
prioritization of user needs.
Workshop participants then met on the morning of the third day to summarize the results of
their second round of breakout group discussions. Each breakout group facilitator reported on
the recommendations made by their respective breakout group and answered questions posed
to the group by other members of the workshop. Important "next steps" and organizations to
involve in the process were also identified during this period.
I. Lakes and Reservoirs
The lakes and reservoirs breakout group began its second round of discussion by reviewing
several of the objectives of the workshop. They agreed that one component of the national
nutrient assessment strategy should be to provide a guidance document to the states regarding
the importance of controlling nutrient overenrichment. The guidance document should also
identify the best available assessment and control tools. The group also acknowledged that an
assumption throughout their discussion was that any type of guidance should be based on a
regional approach due to climatological differences between regions as well as variable user
perceptions between regions. The ecoregion approach used by Minnesota was brought up as
an example of how this could be done. The importance of including land use changes as
early warning indicators was stressed.
The next step that the group took was to evaluate the community/ecological structure
parameters. A general discussion was held concerning the difference between these types of
parameters and the chemical/biomass parameters. It was agreed that the biological/
community structure indicators cannot be modeled as well as the chemical/biomass
parameters. This is partially due to the fact that there are numerous factors (other than
nutrients) that can affect them. The point was also made that biological indicators can be
measured in a number of ways—tolerance, intolerance, functional groups, health conditions,
diversity (dominance), numbers, threshold effects, and indicator species. It was also
suggested that although the public may be most concerned with biological indicators, they are
the most difficult to predict. The issues raised in connection with each of the individual
community/ecological structure parameters are summarized in the tables which follow.
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National Nutrient Assessment Workshop
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Algal Community
Units of Measurement
(several ways to measure)
Value
Scientific Validity
Cost
Practicality
Public Understanding
Modeling Capability/ Load-
Response
Rating
High
Promising
High
Variable
Notes
Algal community could be measured as concentration or taxa
composition; need an accepted, cost-effective measurement
technique.
Value would be very high with an appropriate, accepted
parameter; contains information on the state of the system.
Need more rapid assessment techniques.
Usefulness is hindered by lack of adequate state databases
(i.e., need a background to compare to).
Group was shown graph displaying the relationship between
trophic state index and fish abundance (based on study done
by Bruce Wilson, Minnesota Pollution Control Agency).
Combination of Biological
Indicators*
Units of Measurement
(many ways to measure)
Value
Scientific Validity
Cost
Practicality
Public Understanding
Modeling Capability/ Load-
Response
Rating
High
Variable
Medium
to High
High
Low
Notes
Biological indicators can be measured in a number of ways —
tolerance, intolerance, functional groups, health conditions,
diversity (dominance), numbers, threshold effects, and indicator
species.
Highly visible indicators of lake biota; however, do not serve as
early warning indicators and are not phosphorus specific (i.e.,
are influenced by a number of factors besides phosphorus.)
Validity depends upon how indicators are used (i.e., good for
evaluating consequences, not as good for providing information
on trophic state).
Individual samples cost a lot, but need to sample less often and
take fewer samples.
Complements other information; basically addresses whether or
not species is there, its abundance, and the size of organisms.
We do not have accepted predictive capabilities for all of these
types of endpoints; ones that are available should be used with
caution.
* To facilitate the discussion, the group addressed zooplankton, benthos, and fish measurements together.
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Macrophytes
Units ot" Measurement
(many ways to measure)
Value
Scientific Validity
Cost
Practicality
Public Understanding
Modeling Capability/ Load-
Response
Rating
High
High
Variable
High
High
Low
Notes
Biomass of macrophytes can be measured as grams dry
weight/nr or grams phosphorus/gram carbon; extent can be
measured as areal coverage. Issue of light deprivation and
effect on macrophyte growth was raised.
The public can readily understand the significance of dense
weedmats impeding boat traffic and swimming.
Limited by our inability to predict whether a system will be
plankton or macrophyte dominated (depends on depth of lake,
springtime conditions, substrate, etc.).
General Recommendations
1) Any nutrient strategy should be promoted and developed on a regional basis.
The breakout group agreed that a national nutrient assessment strategy could only be
done if individual regions—both EPA regions and ecoregions within states—were
given the flexibility to adopt their own nutrient endpoints (i.e., no single national
number should be promulgated by EPA). The regional approach is necessary because
of the different types of waterbodies that exist across different climates and the fact
that user perceptions of acceptable water quality also differ. Minnesota's ecoregion
approach was referred to as an example.
2) The benefits of addressing nutrient overenrichment should be recognized as a public
health benefit.
To gain public support, the impact of nutrient overenrichment on public health needs
to be stressed. An important example is the effect nutrient enrichment can have on
drinking water supplies (e.g., trihalomethanes and toxic algal blooms).
Specific Tools
1) EPA should publish a national technical guidance document summarizing the Agency's
position on (and recommended methods for) nutrient assessment and control.
This document would serve to eliminate the ad hoc approach that currently exists from
one state to another and would motivate certain states to become more proactive. The
publication of such a document would also signal that addressing nutrients is a
national priority.
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2) States should include land use as a separate early warning indicator (e.g., if development
is proposed in a watershed, some type of analysis should be done concerning potential
impacts on the waterbody.)
The group realized that this was an obvious point, but wanted to explicitly mention
land use change as the most important early warning indicator of nutrient enrichment.
3) In addition, within the national guidance document, states should be encouraged to adopt a
nutrient control strategy adopting at least the following set of parameters: secchi depth,
dissolved oxygen, total phosphorus, and total chlorophyll).
The group felt that this "short list" of parameters needed to be included in any state
nutrient control program because of their scientific validity, cost, and modeling
capability advantages in support of lake assessment.
4) EPA should provide simple, user-friendly, desktop-based software models to state and
local governments to aid them in waterbody management decision making.
This recommendation was strongly endorsed by the members of the breakout group.
They noted that advances in computer technology make this easier than ever to
accomplish and identified several existing models that could serve as starting points
(e.g., BATHTUB, Reckhow-Simpson technique). The group stressed that state
personnel should be included in the design team developing such models and that the
models should correlate to the recommendations outlined in the guidance document
(i.e., include the same parameters and be based on land-use information as well as in-
lake processes).
Gaps that Need to Be Addressed
I) The relationship between management practices and resulting load reductions is not well
understood.
The fact that waterbody managers do not understand how much load reduction will be
provided by various control practices seriously limits their ability to restore
waterbodies to desired conditions. It also limits their ability to argue that the benefits
of their proposed actions outweigh the costs.
2) The relationship between nutrient loading and macrophyte growth is not well understood.
The group realized that macrophytes can be a useful parameter, but that currently there
is a lack of information on the relationship between nutrient loading and macrophyte
growth.
3) Simple models for addressing reservoirs and impoundments are not at the same level as
lake models.
Although impoundment and reservoir models exists, the group did not feel that they
are as well-developed as some of the lake models. The group realized that this was
due to the fact that impoundments and reservoirs are more complicated systems that
are more difficult to model.
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4) The impact of sediment loadings on nutrient enrichment is not well understood.
The group felt that the lack of information on the relationship between sediment
loading and related nutrient enrichment is a gap that needs to be filled with more
research.
Questions and Next Steps
Several questions were posed to the lakes and reservoirs breakout group by other workshop
participants. One participant wanted to know whether or not the group had addressed the
issue of using paniculate phosphorus versus soluble phosphorus as an endpoint. The group
answered that they had for the most part only discussed total phosphorus because it is a good
indicator in lakes and because of its cost-effectiveness. The group acknowledged the
usefulness of measuring the different phosphorus species. Other questions that were asked
concerned such issues as: how nutrient controls can lead to curbs on development, the
difficulty involved with determining incremental changes in lake water quality, and how
nutrient issues should be addressed in the reauthorization of the Clean Water Act.
After addressing these questions, the workshop participants identified several "next steps" that
should be undertaken in regard to nutrient issues for lakes and reservoirs.
• EPA should raise the level of priority placed on nutrients in Clean Water section 319 and
section 314 programs and within the regional offices.
• Other federal agencies need to be involved in this process (e.g., Corp of Engineers,
Bureau of Reclamation, U.S. Geological Survey).
• The North American Lake Management Society (NALMS) could serve as a forum for the
development and regional/state implementation of a national nutrient strategy specific to
lakes and reservoirs.
For questions and comments regarding the lakes and reservoirs breakout group discussions,
please contact either of the following facilitators:
George Gibson Bob Carlson
U.S. EPA (4304) Dept. of Biological Sciences
Office of Science and Technology Kent State University
401 M Street, SW Kent, Ohio 44242
Washington, DC 20460 (216) 672-3849
(202) 260-7580 rcarlson@Phoenix.kent.edu
gihson.george @ epamail. epa. gov
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II. Rivers and Streams Summary
Session Review
The rivers and streams breakout group began the session by reviewing some of their
conclusions from the previous day. The first topic of discussion concerned the list of
potential endpoints for plankton dominated and periphyton dominated systems. The group
consensus was that additional endpoints should be added to both lists. The participants
considered these additional endpoints to be more of a wish list. The group recognized that
the data for these endpoints might be technically difficult to obtain and the cost associated
with such acquisition could be prohibitive. However, there was a recognition that, if possible,
these are the types of things that really should be considered. Table 2 lists the additional
endpoints that the group agreed should be added to the periphyton and plankton dominated
lists.
Table 2. Additional Endpoints for Plankton and Periphyton Dominated Systems.
Plankton Dominated
Benthic community metabolism
Sediment composition
• organics
size fraction
nutrients
profile
sediment fluxes, O2, nutrients
Secondary production
meiofauna, macroinvertebrates, fish
Dissolved oxygen amplitude
Production/respiration
Periphyton Dominated
Benthic community metabolism
riffle/pool
Sediment composition
• organics
• size fraction
• nutrients
• profile
sediment fluxes, O,, nutrients
Secondary production
• meiofauna, macroinvertebrates, fish
Dissolved oxygen amplitude
Production/respiration
The discussion then moved to a review of the plankton and periphyton dominated flow
diagrams and graphs. In terms of the flow diagrams, the group was generally satisfied with
the diagrams and only made a few additions. In particular, the group agreed that the
following factors should be added.
* Organic carbon and toxicity were added to both lists as a factors affecting algae and
periphyton growth. The group felt that it was very important to consider the impact of
organic carbon inputs in addition to looking at phosphorus and nitrogen loading.
• Total suspended solids, and other growth limiters were added as influential factors to the
periphyton dominated system diagram. The group noted that total suspended solids is a
factor that is unique to periphyton dominated streams.
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In reviewing both the periphyton and plankton dominated graphs, the participants noted the
following changes.
• Plankton river graph - participants noted that it was assumed that the plankton dominated
rivers would behave like lakes. It was agreed that the graph should indicate some of the
factors limiting algae growth such as light, travel time, and grazing. In addition, the
group agreed that total phosphorus would only extend to approximately 500
• Periphyton river graph - participants felt that both nitrogen and phosphorus concentrations
should be considered. As a result, the group agreed to add nitrogen at 50 jjg/1 as a
suggested threshold to the Y-axis.
Modeling
The next issue discussed by the group was the role of modeling in understanding and
assessing nutrient loading. The group viewed modeling as a way to explain the
interrelationships between nutrient loading and the other factors affecting biomass growth. It
was recognized that an improved understanding of these factors would help managers control
the system. The group was in consensus that based on the current state of our scientific
knowledge, biomass growth could not accurately be predicted in periphyton dominated
streams and rivers. The group pointed out that our knowledge of the periphyton dominated
systems is especially poor. Participants suggested that the national strategy needs to give high
priority to support research and development of process oriented models to improve our level
of understanding in this area.
The group then moved into a discussion of some of the know instances or "case studies"
where models have been used. Participants focused on how the state of Montana used
modeling with a combination of other techniques in setting nutrient load targets for the Clark
Fork River. Information from reference reaches, artificial stream experiments, and simplified
modeling, were used to define the appropriate nutrient levels or in-stream targets. The targets
developed for the Clark Fork River are as follows:
* 6 ug/L soluble reactive phosphorus • 30 ug/L dissolved inorganic nitrogen
• 300 ug/L total nitrogen * 20 ug/L total phosphorus
• Biomass 100 mg chlorophyll a/m2 mean, 150 mg/m2 max
A mass balance nutrient model was then used for the load allocation process to ensure that in-
stream targets will be met. It was noted that at the present time only point sources are being
considered, but future consideration will be given to nonpoint sources.
The next issue that the group addressed in their discussion of modeling centered on the
current state of modeling as it relates to nutrient assessment. The discussion focused on
identifying the existing models, characterizing their complexity, and identifying the degree to
which these models help explain the processes in both plankton and periphyton dominated
systems. Figure 5 is a product from this discussion. It provides information on the current
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state of receiving water modeling for plankton and periphyton dominated systems across a
range of modeling complexity.
Figure 5. Receiving Water Modeling.
Plankton
Load/response
relationships
QUAL2E
WASPS
CEQUAL-RIV1,
W2
HSPF
Periphyton
Concentration/
response
relationships
9
Research needs
C'
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Table 3. Research Needs Identified by the Rivers and Streams Breakout Group
Chlorophyll measurements (periphyton)
- sampling methods
Cladophora, diatom growth requirements
- field research
Stream bank riparian zone and denitrification
Literature search on stream models
(especially periphyton systems)
Investigate dissolved oxygen & pH amplitude
Investigate community metrics to
characterize rivers for nutrient effects
- ecoregions
- which metrics are most sensitive
- literature search on indicator taxa
- is biointegrity sensitive as an early
warning tool?
Role of fluvial geomorphology as a
factor in controlling algae development
Whole stream enrichment studies
Nutrient Loading and Use Impairment
The next major issue addressed by the group concerned the level at which biomass and
chlorophyll a concentrations begin to impair beneficial uses of rivers and streams (i.e.
recreation or aesthetics). The group felt that an understanding of this relationship was
important in establishing any kind of criteria or endpoints. The participants felt, however, that
a set of national standards was not realistic and that it would be more appropriate on a
ecoregional basis.
The discussion of use impairment led to an acknowledgement by the group that in
establishing any type of nutrient standards for rivers and streams the maintenance of the
designated use is of prime importance. As a result, they felt it would be helpful to develop a
flow chart to assist in the evaluation of the control/management options that could be adopted
based on the use characterization of a waterbody. The participants acknowledged that critical
to this process was the idea that although the relationship between nutrient loading and
periphyte abundance might not be fully understood, we can work from our general
understanding of the relationship between nutrient loading and biomass growth. Figure 6 is
the flow chart that was developed by the workgroup.
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Figure 6, Use Characterization and Management Options.
River/Stream Lse
Have biomass levels led to use imparement?
Restore
|
Assess DO.
biomass, algae
Relate Nutrients to Biomass
Evaluate nutrient load/
concentration as a viable control
option
Nutrient
Control Mixed
Program Control Controls
Determine nutrient reduction needs
to restore uses
Biological/chemical indicators
Check downstream protection
needs
Protect
Early Warning
Monitoring
Anti- Degradation
Models, GIS
Loading Analysis
(new development issues)
Other Management Measures
The next issue addressed by the group concerned the identification of management options,
other than nutrient controls, that could be implemented to maintain designated uses of streams
and rivers. Group members recognized the need for these additional measures based upon our
understanding of systems and that the implementation of nutrient control may not be
sufficient to restore systems. A mixed or alternative control policy may be required,
especially in periphyton dominated systems where nutrients are limiting only at very low
concentrations. Table 4 contains a list of the other protection measures that were identified
by the group.
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Table 4, Other Protection Measures Identified by the Rivers and Streams Breakout
Group
Shade the stream
Riparian zone management
Grazer habitat
Sediment and erosion control
Biological controls
Cattle management
Channel type - restoration
Hydrology, hydraulics:
- stormwater management
- stream regulation
- flow management (scouring, freezing,
minimum flow)
Short Term Needs and Tasks
The group concluded the breakout session with a discussion of what needed to be done in the
short term to both improve our understanding of the eutrophication process and to enhance
modeling efforts. The group agreed that at the present time there is not enough information to
develop a complete guidance document. Group members noted, however, that an important
first step should be to update the issue paper and provide states with the available information
in an ongoing process. Information on available tools, measures, and case studies could assist
in the development of nutrient control and reduction plans in the near future. The group
recommended that the experts reconvene in approximately 3 years to discuss their progress.
Table 5 is a list of the short term needs and tasks that should be undertaken to update the
issue paper and to improve the science.
Table 5. Short Term Tasks and Needs Identified by the Rivers and Streams Breakout
Group
Literature searches on key areas
- stream modeling techniques
- community metrics
- designated use and biomass relationships (public survey techniques)
Modeling
- add temperature simulation to the WASPS model
- add periphyton to the QUAL2E, WASPS, and HSPF models
- carbon-based simulations
- model maintenance and support
- sensitivity analysis studies
- sample applications
- land use connections in watershed-scale models
- improved nitrogen-phosphorus cycling on different land uses (septic, forest systems)
Investigate seasonal relationships between nutrients
and biomass across streams
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Questions and Next Steps
Several questions were asked of the rivers and streams breakout group during the plenary
presentation. The workshop participants were especially interested in discussing the use of
biological indicators as nutrient assessment endpoints. Several of the participants felt that
because previous research in this area had proven unsuccessful, it should not be recommended
as a top EPA priority. Other members of the workshop argued that biological indicators are
extremely valuable since they can be easily monitored and reflect waterbody changes that the
public is most concerned with (i.e., loss of species). One recurring issue was the degree to
which biological indicators can be used to determine the cause of a systemic change, as
opposed to only detecting change itself.
Other points that were raised during this discussion included: the need to scale endpoints in
rivers and streams (e.g., by unit substrate or depth of system); the fact that the proportion of
periphyton vs. plankton dominated systems is changing (due to increased development in
suburban areas); and the need to prioritize the recommended list of endpoints so that EPA can
specify a minimum level of effort that is expected of the states.
The next steps that were identified by the workshop participants were:
• Involve other organizations/societies (e.g., North American Benthological Society,
American Society of Limnology and Oceanography, American Society of Civil Engineers,
American Geophysicists Union, and American Water Resources Association) and have
them sponsor special sessions devoted to nutrient issues related to rivers and streams at
their upcoming meetings.
. Need to move forward on the causal linkages observed in stream community metrics.
• Need to tap into volunteer monitoring groups as an important resource and constituency.
For questions and comments regarding the rivers and streams breakout group discussions,
please contact either of the following facilitators:
Patrick Ogbebor Gene Welch
U.S. EPA (4304) Dept. of Civil Engineering
Office of Science and Technology University of Washington
401 M. St., SW Seattle, WA 98195
(202) 260-6322 (206) 543-2632
ogbehor.patrick@eparnaiLepa.gov ebwelch@ii.washington.edu
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III. Wetlands
On the second day, the breakout group continued with parameter identification under the five
general categories.
Water Quality
Parameters added to the 'water quality' category were conductivity, dissolved organic carbon,
and conservative tracers (e.g., uranium). Each of the categories was discussed and clarified as
to whether it related to biological or other aspects. The issue of variability was also
discussed. It was noted that the signal to noise ratio is a function of sampling frequency.
Timing of sampling is also an important factor to consider. One point was that measures
could be direct or indirect indicators. A direct indicator would be an actual measurement of a
nutrient; an indirect indicator would be the response of vegetation to a nutrient
overenrichment. A question that was raised was: how is a response measured without having
a database with which to compare the samples? In order to measure a parameter, we need to
understand what is being impacted.
Hydrology
Parameters that were added were surface water inflow/outflow (input/output), water source,
and hydroperiod. Residence time will be an extremely variable measurement parameter.
Wetland area to catchment area ratio is also important. All this background information is
necessary to understand the processes potentially affecting wetlands.
The group agreed to present the following recommendations to the plenary session:
* There is a need for a nationwide database that characterizes wetlands as pristine or
impacted. This would be similar to EPA's constructed wetlands database. It was
suggested that tables be developed through a comprehensive literature search showing
what work has already been done on nutrient-related issues in wetlands. This information
could serve as the initial foundation for a wetlands database, or could be added to a
wetlands database.
• The breakout group reorganized the list of parameters into five categories and discussed
each parameter's relevance to monitoring.
• A short-term strategy for addressing nutrient overenrichment issues in wetlands is needed
be current wetlands managers; a long-term strategy incorporating ongoing research is also
critical.
* The Army Corps of Engineers is working on implementing the Hydrogeomorphic Wetland
Classification system; the goal is to cover 80 percent of all wetlands, including the
collection of a lot of variables on these wetlands. One issue is who will host and
maintain the data. Can states access these reference data sets? Can states add parameters
that are important? Impacts and functionality of wetlands are a part of this project. The
scope could potentially be broadened so that it can apply to other management issues,
such as nutrients.
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• The 'Secchi Disk' of wetlands could be Feldspar (silicon dioxide) to show accumulation
within wetlands over time as an indication of whether there has been a change in
productivity. Feldspar does not react with other chemicals in the soil.
Is water quality sampling for wetlands included in STORET? No one in the group could
initially answer this question. However, subsequent investigation found that some limited
information is available on wetlands in STORET. In particular, Michigan and Florida have
sampling stations in wetlands, but Michigan includes fish tissue data only. Florida has
sampling information on wetlands, including nutrient concentrations (see Figure 7).
Figure 7. Distribution of sampling stations in the USEPA STORET database that are
wetlands. The figure emphasizes the sparse national distribution on wetlands data.
In the afternoon session it was discussed whether there may be a better way to classify
wetlands for understanding of nutrient impacts (i.e., other than Cowardin, et al., 1979). The
hydrogeomorphic classification approach has three major themes - water source,
hydrodynamics, physiographic setting (includes: slope, soils, watershed). The classification
system looks at the primary source of change.
There was further discussion on whether there is a set of indicators that can potentially extend
across all wetlands. The breakout group decided that the most productive course should be to
list all the relevant indicators and highlight the most important indicators. Bioavailable
nitrogen and phosphorus in sediments, soils, water, vegetation, hydrology, and loads are the
indicators that are useful in a diagnostic study. These indicators should provide some
indication of nutrient impacts. One concern is that there is no baseline data available with
which to compare the collected data. Reference sites need to be chosen and baseline data
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determined. This can become the long-term database. From the baseline data, another
wetland can be analyzed and the data could support determining if the wetland is impacted or
not impacted. Because of the variability in wetland systems, the parameters cannot be
prioritized or ranked. The group also cannot rank them as the "best" indicators to use.
Thus, long and short-term issues were simplified as follows:
Long-term — » setting up a reference baseline database
Short-term — » using a reference site next to the impacted site
Parameters for use in a short term strategy (independent of wetland type) include the
following:
• Bioavailable nitrogen and phosphorus in soils and water
• Plant species composition
* Plant species richness
• Plant species structure (including recruitment)
* Plant indicator species - vascular and non vascular species
• Soil oxygen demand (indicator of microbial respiration)
Volunteer monitors would be able to measure everything on the short-term list. A suggestion
was made to create several central analyzing facilities that volunteer programs could send
samples to for standardized analysis. These labs would serve as the QA/QC centers to ensure
a standardized sample analysis.
The long-term list of measurement parameters is included in Table 6. It was suggested that a
recommendation to EPA would be to continue literature searches, especially for long-term
studies.
Models
There is a model under development for understanding how wetlands function in the
Everglades. Water budget, flow fields, vegetation, and biology are considered. This has been
calibrated against data sets. There are some other models on the Des Plaines wetlands and
Odum Creek (Florida) but they do not have as large a spatial scale as the Everglades model
does. Spatial scale is an important aspect in assessing wetlands. Landscape models can
address a broader spatial scale, but are much coarser in their ability to predict impacts. For
example, each grid is 1 km by 1 km, so there is not as much detail. These types of models
have shown some promise in South Florida. Additional literature searches on wetland models
may identify other modeling approaches or applications.
The group did not address modeling efforts that compute/predict nutrient loadings to wetlands
(i.e., transport models successfully used for other water bodies), and these may have
important roles in helping to manage loading-related impacts to wetlands.
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Proceedings
Table 6. Measurement Parameters Identified by Wetland Breakout Group
SURFACE WATER QUALITY
Total Kjeldhal nitrogen
*Ammonia
Nitrate
Soluble reactive phosphorus
Total phosphorus
Total suspended solids
Chlorophyll a
Nitrogen:phosphorus ratio
Nutrient limitation
Dissolved oxygen
PH
Temperature
Conductivity
Dissolved organic carbon
Conservative tracer
BIOTA
*Nitrogen
* Phosphorus
* Nitrogen: phosphorus ratio
Nutrient uptake
*Changes in species composition
Vegetative structure
Plant species diversity/richness
Maeroinvertebratc species diversity/richness
Indicator species
Net primary productivity
Recruitment
Leaf area/solar transmittance (remote sensing
change detection)
HYDROLOGY
Wetland area
Depth
Transpiration
Precipitation
Residence time
Groundwater flow
Surface water inflow/outflow
Hydroperiod
Parameters marked with an asterisk (*) are "early indicators".
Parameters in bold type are parameters that are specific to one category.
SOILS
Total Kjeldhal nitrogen
Ammonia
Nitrate
Total phosphorus
Nttrogen:phosphorus ratio
*Soil oxygen demand
Sand/silt/clay fraction
Redox potential/pH
Organic accretion
Sediment accretion
Microbial biomass
Enzyme activity
Bioavailable nutrients
PROCESSES
Carbon
microbial respiration
Aerobic
Water column
Litter
Soil
Anaerobic
Soil
Sulfate reduction
Methanogenesis
Plant uptake
*Nitrogen
Mineralization
Nitrification/denitrification
Biological nitrogen fixation
Plant uptake
* Phosphorus
Mineralization
Plant uptake
Adsorption capacity
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Some members expressed concern that there is a gap in the availability of well-accepted
wetland models, but other members argued that numeric models may not be useful in
predicting changes within wetlands. Rather, more simple (i.e. heuristic) models may be more
helpful in understanding nutrient-related responses within wetlands.
In closing the session, the breakout group identified several information gaps in understanding
nutrient-related impacts to wetlands. Based on these discussions, the breakout group
submitted a series of recommendations at the closing plenary session.
1) There needs to be an accepted national wetland classification system similar to the
hydrogeomorphic classification system developed by the U.S. Army Corp of Engineers.
2) A comprehensive literature review needs to be undertaken with the purpose of parameter
and data extraction to create "threshold" table(s).
3) A nutrient database including baseline data according to wetlands types/regions needs to
be developed (long-term benefit).
4) Field experimentation should be conducted to determine nutrient limitation by wetland
type and to isolate the effects of nutrients from other variables, such as hydrology,
climate, events, and natural variability.
5) Integrate parameter data collection with wetland indicators, or possibly other EPA
wetlands program(s).
6) Volunteer monitoring needs to be encouraged, as well as the development of state
capability of monitoring.
7) Need to improve upon molecular biology techniques e.g., stress proteins in plants.
8) There needs to be further development of remote sensing techniques.
Questions and Next Steps
Workshop participants had several questions for the wetlands group. They wanted to know
whether or not there are any existing relationships for certain types of wetlands that could be
used to develop nutrient assessment and management tools. The wetlands group responded
by pointing out that this research area is in its infancy compared to work that has already
been done for the other waterbody types. Workshop participants also inquired about how the
hypothetical wetlands database would be organized and what information it would provide to
resource managers.
The next steps that were identified were:
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• Involve organizations such as the State Association of Wetlands Managers, Society of
Wetlands Scientists, and private organizations (e.g., Ducks Unlimited) in the development
and implementation of the wetlands component of the national nutrient assessment
strategy.
• Need to synthesize the results from the workshop with a proposal for how to proceed
from here.
• Need to better articulate the level of concern about nutrient overenrichment of natural
wetlands and communicate to policymakers and the public.
» Need to synthesize information on the relative sensitivity of different wetlands types to
nutrient enrichment and use this information to investigate regressional relationships.
For questions and comments regarding the wetlands breakout group discussions, please
contact:
Bob Cantilli Kristen Martin
U.S. EPA (4304) U.S. EPA (4503F)
Office of Science and Technology Office of Wetlands, Oceans and Watersheds
401 M. St., SW 401 M. St. SW
Washington, DC 20460 Washington, DC 20460
(202) 260-5546 (202) 260-7108
cantilli.robert@epamail.epa.gov martin.kristen@epamail.epa.gov
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IV. Estuaries and Coastal Waters
Over the course of the workshop, several major themes and recommendations emerged from
the group's detailed discussions. Perhaps the most pervading challenge in establishing tools
and standards for assessment and management of nutrient inputs to aquatic systems is the fact
that large, real variability exists in physical and biological structure and processes among all
systems. This variability means that a given input results in a different response. While
science may agree qualitatively about the expected response, quantitative prediction is rarely
if ever possible with acceptable confidence limits. In addition, regional differences exist in
human/societal expectations so that what condition is "acceptable" is also not uniform. Taken
together, these perspectives suggest that arbitrarily defined standards of general applicability
may be untenable, and strongly call for a different approach.
Most of the group's effort was initially directed toward what metrics seem meaningful,
rigorous, and yet practically useful in the assessment of effects. The group set aside for the
moment the issue of subjective definition of standards of what is acceptable or unacceptable
as a basis for regulation. However these standards are defined, they must be based on
acceptable measures of dose response.
Faced with this, the estuaries work group approached a consensus that the only practical
initial approach is to construct empirical relationships between indicator responses and
probable driving variables. This is essentially the approach taken by Vollenweider in
documenting responses of lakes to phosphorus loading. Some examples of these empirical
relationships are clearly significant statistically, but they display large variability, even for
comparable estuaries. For only plankton-based systems, for example, chlorophyll stocks show
a 10-fold range in response for similar inputs of total nitrogen. For other types of systems,
however, such relationships have not been adequately explored. It is recommended that
significant effort be devoted to a careful gathering of available information for a variety of
systems, and an incisive analysis of relationships. It must be emphasized that this is not a
menial task. Care and insight are necessary to evaluate each published study to assure
appropriate comparisons are made.
A benefit of this approach is that the power of the method will increase with time. As more
information becomes available, three significant areas of progress in the empirical approach
may be anticipated. First, separate relationships may be developed for different types of
systems, effectively stratifying the variance among more similar groups of sites (e.g. micro-
vs. macrotidal). The group separated benthic, seagrass, and plankton based systems with this
rationale. Second, schemes for parameterizing multiple factors may be developed within
which tighter relationships may be possible (e.g., Vollenweider's parameter normalized
phosphorus input to freshwater turnover time). Third, as time series of data for an increasing
number of cases become available, tighter relationships will emerge, more strongly suggesting
site specific predictive relationships.
In some cases, natural year-to-year variability may define the dose-response quite accurately
for a given system. This empirical approach guarantees a number of benefits. With time, the
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archive of systems for which diagnostic dose-response measurements are available will
increase. Thus the use of empirical relationships has immediate value, but is also perfect
stimulus for adaptive management using the more predictive relationships that will emerge
with time.
Seagrass Dominated Systems
Tools
• Areal survey of seagrasses (aerial photography/mapping/digitization; ground surveys via
transects) to document distribution, abundance, and depth penetration of seagrass beds.
• Simple to complex nutrient loading models of the surrounding watershed and water
quality models for simulating chlorophyll a concentrations over the seagrass beds.
• Methodologies for partitioning out the various water column light attenuators (e.g.,
chlorophyll a, inorganic suspended solids, color) to determine the relative contribution due
to nutrient enrichment:
- Multiple regressions of various fractions of total suspended solids, color, chlorophyll
a, etc. using multi-wavelength spectral methods
- Literature values of specific extinction coefficient (chlorophyll a)
- Light transmission models (e.g., Gallegos 1994)
• The 20% incident light requirement that holds up across a range of seagrass species
(recognizing one has to consider both water column and leaf surface attenuation due to
epiphytes at the site/waterbody specific level).
• Field tested protocols for designing, conducting, and analyzing results from water quality
monitoring along seagrass gradients (depth penetration, vegetated to non-vegetated, and
water quality gradients).
« Field tested protocols for assessing relationships between seagrass depth penetration vs.
light attenuation coefficient to determine waterbody specific light requirements.
• Host of field tested/possible early warning indicators of pending seagrass declines:
- C:N:P ratios in above- and below-ground tissue, blade width, Hsat, quantum
irradience, leaf chlorophyll a, chlorophyll a to b ratios, stable isotope.
Next Steps
• Sort out the light requirements over different regional habitats of the dominant seagrass
species from the existing wealth of literature.
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* Determine, synthesize and publish thresholds for nutrient concentrations, light penetration,
total suspended solids, chlorophyll a, etc. under different environmental conditions (e.g.,
temperature) based on the current and soon to be published literature.
• Through a workshop/working group, develop an approach which will enable states and
estuarine/coastal management programs with minimal to no existing SAV survey data (but
with historical or ongoing seagrass declines) to set: 1) light and nutrient thresholds, 2)
depth penetration restoration goals, 3) distribution restoration goals, 4) and seagrass
resource restoration based nutrient reduction goals for the surrounding watershed.
• Assemble a series of teams of experts to actively assist these states and estuarine/coastal
management programs in the design and conduct of the necessary studies and data
interpretations.
• Publish a full accounting of the approaches taken in Chesapeake Bay and Florida for
using seagrasses to set nutrient reduction targets in a form for ready application to other
semi-tropical to temperate systems.
• Pull from the literature simplified versions of the land use mosaic/nutrient loadings
relationships.
• Devote greater effort to modeling in seagrass restoration given actual or predicted water
quality changes based on the reproductive biology of the waterbody's species.
• Identify species-appropriate early warning indicators, synthesize the literature supporting
field validation/case study verification of the utility of these indicators, and work to build
these indicators into ongoing and planned seagrass monitoring programs to build up the
requisite data base.
Plankton Dominated Systems
Tools
• A range of empirical relationships and more limited set of models connecting nutrient
loadings and "top-down" trophic influences interacting to control phytoplankton
production.
• Techniques for separating photopigments into chlorophyll a and other diagnostic pigments
(chlorophylls and carotenoids) with analysis by HPLC and C,4 incorporation. These
techniques can provide insight into the composition and growth rates of the algae in order
to predict algae composition in response to nutrient enrichment,
• Field tested techniques and instrumentation necessary to establish monitoring stations to
define a dissolved oxygen fluctuation signature for a system.
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• Techniques for general source discrimination using N,5 and C,4 stable isotopes,
• Satellite/aerial imagery and interpretation techniques to display chlorophyll a and other
diagnostic pigment patterns with much greater spatial resolution and estimate surficial
primary productivity.
• In-depth information about the sometimes-complex life cycles of some species.
• Scanning and transmission electron microscopy to aid in identification of picoplankton
(e.g., brown tide organisms) and other phytoplankton componenets (e.g., small
dinoflagellates).
• Mesocosms for studying species succession and community- or ecosystem-level response
to nutrient inputs.
• Molecular probes for rapid, reliable species detection, identification and enumeration.
Next Steps
• Need to further examine the role of silica relative to nitrogen and phosphorus (silica
depletion in phytoplankton blooms).
• Need to take the short list of key questions that keep coming up again and again in these
types of workshop but never get resolved and bring together a group drawn from key
parts of the community (Estuarine Research Federation, American Society of Limnology
and Oceanography, Benthic Society, NOAA, EPA, and others) to synthesize the existing
information and come to a conclusion.
« Need to develop more comprehensive dissolved oxygen tolerance/effects thresholds for
systems beyond Virginian Province (Cape Cod to Cape Hatteras) supporting waterbody
specific determination of dissolved oxygen criteria.
• Need to tackle the question of what amount of dissolved oxygen fluctuations are due to
natural vs. anthropogenic causes.
« Need technological refinements in the areas of bioindicators and sensors of nutrient
enrichment. Specifically, there is a need for indicators capable of reflecting natural
community responses.
• Need an equivalent set of relationships for plankton dominated systems for nutrient
loadings to chlorophyll a response (estuarine version of the Vollenweider relationships).
• Continue to unravel the complex life cycles of some abundant algal taxa, and to determine
nutritional controls on stage dominance.
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• Further examine the role of changing N:P ratios on shifts in phytoplankton dominance
from desirable to undesirable species, and the role of silica in these species shifts,
Nuisance Algal Blooms
Harmful Nontoxic Algal Blooms
Tools
• A range of empirical relationships connecting nutrient loading with species growth and
abundance.
• Techniques for separating photopigments into chlorophyll a and other diagnostic pigments
(chlorophylls and carotenoids) with analysis by HPLC and C14 incorporation. These
techniques can provide insight into the composition and growth rates of the algae in order
to predict algae composition in response to nutrient enrichment.
• Field tested techniques and instrumentation necessary to establish monitoring stations to
define a dissolved oxygen fluctuation signature for a system.
• Techniques for general source discrimination using N,5 and C,4 stable isotopes.
* Satellite/aerial imagery and interpretation techniques to display chlorophyll a and other
diagnostic pigment patterns with much greater spatial resolution and estimate surficial
primary productivity.
• In-depth information about the sometimes-complex life cycles of some species.
• Scanning and transmission electron microscopy to aid in identification of picoplankion
(e.g., brown tide organisms) and other phytoplankton componenets (e.g., small
dinoflagellates).
• Mesocosms for studying species succession and community- or ecosystem-level response
to nutrient inputs.
« Molecular probes for rapid, reliable species detection, identification and enumeration.
Next Steps
• Need to further examine the role of silica relative to nitrogen and phosphorus (silica
depletion in phytoplankton blooms),
« Initiate long term monitoring to collect data to provide the basis for correlating brown tide
blooms with nutrient enrichment.
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• Test laboratory based findings in controlled field experimentation.
• Support a more comprehensive synthesis of correlative/experimental evidence for brown
tide blooms responses to nutrient enrichment.
• Continue to unravel the life cycles of harmful nontoxic algal taxa, and to determine
nutritional controls on stage dominance.
* Continue to develop/improve molecular probes to detect, identify and enumerate harmful
algal species.
• Continue to develop isotopic methods to trace the source of nutrients to harmful algal
bloom species and to determine relative importance of natural versus anthropogenic
nutrient inputs in stimulating their growth.
• Improve remote-sensing algorithms for detecting harmful algal blooms and the water
masses with which they are associated.
• Establish long-term monitoring programs for both bloom-forming (e.g., brown tide
species) and low-abundance harmful species (e.g., "needle" forming diatoms such as
Chaetoceros concavicornis), in order to document major trends and linkages to cultural
eutrophication.
• Identify nontoxic harmful algal bloom species that can serve as "indicators" of different
types or conditions of eutrophication. Develop these species as indices of ecosystem
"stress."
• Determine nutrient uptake characteristics and requirements for key nontoxic harmful algal
bloom species, allowing for the sensitivity of many harmful species to mixing conditions
and enclosure effects.
• Determine the interactions of both inorganic and organic nutrient sources in stimulating
nontoxic harmful algal bloom species.
• Develop physicological indicators of nutrient limitation in nontoxic harmful algal bloom
species to assess their nutrient status under both natural and nutrient enriched conditions,
and including consideration of both nutrient supplies and supply ratios.
Toxic Algal Blooms
Tools
« A range of empirical relationships connecting nutrient loading with species growth and
abundance.
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National Nutrient Assessment Workshop - ——— — — , Proceedings
• Techniques for separating photopigments into chlorophyll a and other diagnostic pigments
(chlorophylls and carotenoids) with analysis by HPLC and CI4 incorporation. These
techniques can provide insight into the composition and growth rates of the algae in order
to predict algae composition in response to nutrient enrichment.
« Field tested techniques and instrumentation necessary to establish monitoring stations to
define a dissolved oxygen fluctuation signature for a system.
• Techniques for general source discrimination using N,5 and C,4 stable isotopes.
« Satellite/aerial imagery and interpretation techniques to display chlorophyll a and other
diagnostic pigment patterns with much greater spatial resolution and estimate surficial
primary productivity.
• In-depth information about the sometimes-complex life cycles of some species.
• Scanning and transmission electron microscopy to aid in identification of picoplankton
(e.g., brown tide organisms) and other phytoplankton cornponenets (e.g., small
dinoflagellates).
• Mesocosms for studying species succession and community- or ecosystem-level response
to nutrient inputs.
• Molecular probes for rapid, reliable species detection, identification and enumeration.
Next Steps
• Initiate long term local and regional monitoring to collect data to provide the basis for
correlating toxic algal blooms with nutrient enrichment.
• Test laboratory based findings with controlled field experimentation.
• Utilize bioindicators (molecular, immunological) of linkage between nutrient enrichment
and toxic/harmful characteristics of algal blooms.
• Support a more comprehensive synthesis of correlative/experimental evidence for toxic
algal blooms responses to nutrient enrichment.
• Assessment of effects of other variables on nutrient contribution to nuisance tide
generation.
• Examine linkage between newly-recognized and growing local/regional sources of
nutrients and bloom dynamics in estuarine and coastal waters (i.e., atmospheric deposition
and groundwater).
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• Need to further examine the role of silica relative to nitrogen and phosphorus (silica
depletion in phytoplankton blooms).
• Techniques for separating photopigments into chlorophyll a and other diagnostic pigments
(chlorophylls and carotenoids) with analysis by HPLC and C14 incorporation. These
techniques can provide insight into the composition and growth rates of the algae in order
to predict algae composition in response to nutrient enrichment.
• Initiate long term monitoring to collect data to provide the basis for correlating brown tide
blooms with nutrient enrichment.
• Test laboratory based findings in controlled field experimentation.
« Support a more comprehensive synthesis of correlative/experimental evidence for brown
tide blooms responses to nutrient enrichment.
« Continue to unravel the life cycles of harmful toxic algal taxa, and to determine
nutritional controls on stage dominance and toxin production.
* Continue to develop/improve molecular probes to detect, identify and enumerate harmful
algal species, and to detect/quantify toxins.
• Continue to identify and characterize toxin bioaccumulation impacts through food webs.
• Establish research efforts to determine chronic sublethal impacts of toxic algal species on
life history stages of dominant herbivores and predators (e.g., shellfish and finfish), and
the influence of nutrient overenrichment in exacerbating these impacts.
• Continue to develop isotopic methods to trace the source of nutrients to harmful algal
bloom species and to determine relative importance of natural versus anthropogenic
nutrient inputs in stimulating their growth.
• Improve remote-sensing algorithms for detecting harmful algal blooms and the water
masses with which they are associated.
• Establish long-term monitoring programs for both bloom-forming (e.g., brown tide
species) and low-abundance harmful species (e.g., "needle" forming diatoms such as
Chaetoceros concavicornis), in order to document major trends and linkages to cultural
eutrophication.
• Identify nontoxic harmful algal bloom species that can serve as "indicators" of different
types or conditions of eutrophication. Develop these species as indices of ecosystem
"stress."
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• Determine nutrient uptake characteristics and requirements for key nontoxic harmful algal
bloom species, allowing for the sensitivity of many harmful species to mixing conditions
and enclosure effects.
• Determine the interactions of both inorganic and organic nutrient sources in stimulating
toxic harmful algal bloom species.
• Develop physieological indicators of nutrient limitation in toxic harmful algal bloom
species to assess their nutrient status under both natural and nutrient enriched conditions,
and including consideration of both nutrient supplies and supply ratios.
Macroalgae Dominated Systems
Tools
• NI5 signature connecting wastewater effluent with macroalgae.
Next Steps
• Compile the various seagrass/macroalgae/phytoplankton/nutrient loadings data sets (e.g.,
Florida Bay, Tampa Bay, MERL, Waquiot Bay, MA, Great Bay, NH) and further confirm
the paradigm shift and pull out the thresholds relating to these community shifts.
• Quantify the relationship between fish diversity, macroalgal cover, and nutrient loading.
• Quantify the macroalgae influence on dissolved oxygen concentrations, dissolved organic
carbon concentrations, and lower trophic levels.
Questions
There were several questions and issues raised at the conclusion of the estuaries and coastal
waters plenary session presentation. One participant recommended that endpoints be used
cautiously until the basic science underlying these types systems is more well understood; he
was concerned about making too many decisions based solely on empirical relationships.
Other participants emphasized the importance (as well as the difficulty) of determining
accurate land use loading estimates and recommended that biologists and engineers work
together to confront this technical gap. Other comments that were voiced included: taking a
linked management/science approach and keeping in mind the significance of spatial and
temporal scales in regard to the nutrient overenrichment issue.
For questions and comments regarding the estuaries and coastal waters breakout group
discussions, please contact either of the following facilitators:
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Rich Batiuk Jim Kremer
U.S. EPA Chesapeake Bay Program Professor of Marine Sciences
410 Severn Avenue Suite 109 University of Connecticut
Annapolis, MD 21403 Avery Point Campus
(410) 267-5731 2084 Shennecosset Road
batiuk.richard@epamail.epa.gov Groton, CT 06340-6097
(860) 445-3407
V. Workshop Wrap-up4
The workshop concluded with Rich Batiuk outlining EPA's plans for carrying the nutrient
overenrichment issue forward. These plans include distributing the draft proceedings to
workshop participants along with revised versions of the issue papers for review and
comment. A draft national Nutrient Assessment Strategy will be drafted based on input from
the workshop and presented to EPA Program Offices, EPA Regional Offices, ORD
laboratories, federal agencies, states, and professional societies in the spring of 1996 for
review and comment. A draft final strategy may then be submitted to the Science Advisory
Board in the summer of 1996 and a final EPA strategy will be published in the fall of 1996.
4Siimmaries of the overheads used during the workshop wrap-up are included at the end of the
proceedings.
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Appendix
Agenda
List of Workshop Participants
Participant Addresses
Summary of Overheads
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•— Proceedings
National Nutrient Assessment Workshop Agenda
December 4-6, 1995
Washington, D.C.
December 4
Theme: Waterbody Type-based Endpoints,
Assessment Methodologies & Models
Plenary Session
8:30 am - 9:00 am
9:00 am - 9:15 am
9:15 am - 9:30 am
9:30 am - 10:30 am
10:30 am - 11:00 am
Registration (1st Floor Meeting Room)
Welcome, Purpose & Goals of the Workshop, Introductions
(Rich Batiuk, EPA Chesapeake Bay Program Office)
Introductory Remarks
(Tudor Davies, Director, Office of Science and Technology, and Robert
Way land, Director, Office of Wetlands, Oceans, and Watersheds)
Past, Present, and Future Perspectives on the Assessment and Management
of Nutrient Overenrichment Needs
(Robert Thomann, Manhattan College; Mimi Dannel US EPA HQ (invited);
and Steve Heiskary, Minnesota Pollution Control Agency)
Purpose & Goals of the Workshop; Purpose of Breakout Groups and Charge
to Breakout Groups
(Rich Batiuk, EPA Chesapeake Bay Program Office)
Concurrent Breakout Groups - Waterbody Type-based Issues
11:00 am - 12:00 pm Breakout Groups (Organization & Planning)
For the morning and afternoon sessions, there will be 4 concurrent breakout
groups, organized according to waterbody type: estuaries and coastal waters;
lakes, impoundments, ponds; rivers and streams; and wetlands.
Each breakout group will have a facilitator, a synthesizer, and a recorder.
Each breakout group will be asked to discuss and come to consensus on a
number of issues and questions. Specific questions and background
materials will be provided in advance of the workshop to enable participants
to prepare for workshop discussions.
12:00 pm - 1:00 pm LUNCH (on your own)
Concurrent Breakout Groups - Waterbody Type-based Issues
1:00 pm - 5:30 pm Continuation of Breakout Groups
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National Nutrient Assessment Workshop __ _ _ .— . procee(fa
December 5 Theme: Cross-cutting Issues - Integration of
Tools Across Waterbody Types and
Geographical Areas
Concurrent Breakout Groups - Waterbody Type-based Issues
8:30 am - 10:30 am Continuation and Closure of Breakout Group Discussions
10:30 am - 10:45 am BREAK
Plenary Session
10:45 am - 11:45 am Brief Synthesis Reports from Breakout Groups & Discussion
11:45 am - 12:00 pm Purpose of Afternoon Breakout Group Discussions and Charge to Breakout
Groups
12:00 pm - 1:00 pm LUNCH (on your own)
Concurrent Breakout Groups • Cross-Cutting Issues
1:00 pm- 5:30 pm Breakout Groups
Workshop participants will return to their breakout groups to discuss and
come to consensus on a new set of issues and questions directed toward
cross-cutting issues. The focus of these breakout groups will be on how
appropriate tools can be applied to accomplish nutrient management goals
and the transferability of various tools across waterbody types and
geographically and ecologically diverse areas. Participants will also be
asked to begin to identify and prioritize user needs and the steps needed to
address these needs.
Breakout groups will again have a facilitator, a synthesizer, and a recorder.
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National Nutrient Assessment Workshop
December 6
Theme:
——— — Proceedings
Strategy for Development & Validation
of Needed Nutrient Assessment Tools
(Bringing Everything Together)
Plenary Session
8:30 am- 10:00 am
10:00 am - 12:00 pm
12:00 pm - 12:30 pm
12:30 pm
Reports from Breakout Groups & Discussion
Synthesis - Developing a Strategy
As a group, participants will identify and prioritize the available tools for
addressing nutrient overenrichment that should be promoted and refined. In
addition, we will try to identify and rank new tool development needs.
Participants will be asked to discuss and evaluate a straw EPA strategy and
create a "to do list" for EPA . Finally, the group will begin to brainstorm
potential roles and responsibilities of other state, regional, federal, and
academic nutrient assessment partners within the context of a larger national
strategy framework.
Wrap-up & Next Steps
(Rich Batiuk, EPA Chesapeake Bay Program Office)
ADJOURN
Note: Following the workshop, EPA will produce a meeting summary, including revised versions of
the issue papers used at the workshop, and a draft of EPA '$ strategy document. This will be
provided to all workshop participants for review and comment.
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National Nutrient Assessment Workshop — — proceedings
National Nutrient Assessment Workshop—List of
Participants by Breakout Group
Estuaries and Coastal Waters
Rich Batiuk, U.S. EPA, Chesapeake Bay Program Office
Suzanne Bricker, NOAA Office of Resources Conservation and Assessment
Tom Brosnan, NY City Harbor Monitoring Program
JoAnn Burkholder, North Carolina State University
Dominic DiToro, HydroQual Inc.
Ken Dunton, University of Texas Marine Sciences Institute
Alan Hais, U.S. EPA, Office of Science and Technology
Joe Hall, U.S. EPA, Office of Wetlands, Oceans, and Watersheds
Michael Kemp, University of Maryland
Jim Kremer, University of Connecticut
Brian LaPointe, Harbor Branch Oceanographic Institute
Virginia Lee, University of Rhode Island
George Loeb, U.S. EPA, Office of Wetlands, Oceans, and Watersheds
Chris Madden, University of Maryland
Wayne Magley, Florida Department of Environmental Regulation
Hassan Mirsajadi, Delaware Department of Natural Resources & Environmental Control
Scott Nixon, University of Rhode Island
Cynthia Nolt, U.S. EPA, Office of Science and Technology
Hans Paerl, University of North Carolina
Ruth Swanek, North Carolina Department of Environment, Health & Natural Resources
David Tomasko, Sarasota Bay National Estuary
Ivan Valiela, Boston University Marine Program
Steve Weisberg, Senior Scientist, VERSAR, Inc.
Lakes, Reservoirs, and Ponds
Robert Carlson, Kent State University
Steve Chapra, University of Colorado
Jeroen Gerritsen, Tetra Tech, Inc.
George Gibson, U.S. EPA, Office of Science and Technology
Steve Heiskary, Minnesota Pollution Control Agency
Dianne Reid, North Carolina Division of Environmental Management
Joel Salter, U.S. EPA, Office of Science and Technology
Eric Smeltzer, Vermont Department of Environmental Quality
Robert Thomann, Manhattan College
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National Nutrient Assessment Workshop —— —• ———— Proceedings
Riverg=and Streams
Dennis Anderson, Colorado Department of Public Health and Environment
Dan Butler, Oklahoma Conservation Commission
Mimi Dannel, U.S. EPA, Office of Wetlands, Oceans, and Watersheds
Gary Ingman, Montana Water Quality Division
Russ Kinerson, U.S. EPA, Office of Science and Technology
Jerry LaVeck, U.S. EPA, Office of Science and Technology
Lewis Linker, U.S. EPA, Chesapeake Bay Program Office
Winston Lung, Univerity of Virginia
Dennis Newbold, Stroud Water Research Center
Patrick Ogbebor, U.S. EPA, Office of Science and Technology
Greg Searle, Wisconsin Department of Natural Resources
Leslie Shoemaker, Tetra Tech, Inc.
Amy Sosin, U.S. EPA, Office of Wetlands, Oceans, and Watersheds
Sam Stribling, Tetra Tech, Inc.
Gene Welch, University of Washington
Wetlands
Darryl Brown, U.S. EPA, Office of Wetlands, Oceans, and Watersheds
Bob Cantilli, U.S. EPA, Office of Science and Technology
Tom Fontaine, South Florida Water Management District
Andy Hooten, Tetra Tech, Inc.
Kristen Martin, U.S. EPA, Office of Wetlands, Oceans, and Watersheds
Jarnes Morris, University of South Carolina
Ramesh Reddy, University of Florida
Doreen Robb, U.S. EPA, Office of Wetlands, Oceans, and Watersheds
William Sipple, U.S. EPA, Office of Wetlands, Oceans, and Watersheds
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National Nutrient Assessment Workshop —
Proceedings
Participant Addresses
Dennis Anderson
Colorado Department of Public Health and Environment
WQ Control Division
4300 Cherry Creek Drive South
Denver, CO 80222-1530
(303) 692-2000
Tom Brosnan
DEP - Bureau of Clean Water
Marine Sciences Section
New York City Harbor Monitoring Program
Room 213
Wards Island, NY 10035
(212)860-9378
Joann Burkholder
Department of Botany
Box 7162
North Carolina State
Raleigh, NC 27645
(919)515-2726
joannj>urkholder@ncsu. edu
Robert Carlson
Department of Biological Sciences
Kent State University
Kent, OH 44242
(216)672-3849
rcarlson@Phoenix. kent. edu
Rich Batiuk
US EPA
Chesapeake Bay Program Office
410 Severn Avenue, Suite 109
Annapolis, MD 21403
(410)267-5731
batiuk, richard@epatnaiL epa.gov
Suzanne Bricker
NOAA ORCA1 SSMC4
Office of Resources Conservation and Assessment
1305 East-West Highway
Silver Spring, MD 20910
(301) 713-3000, ext. 200
Sbricker@seamail. nos. noaa. gov
Dan Butler
Oklahoma Conservation Commission
1000 West Wilshire Boulevard
Suite 123
Oklahoma City, OK 73116
(405) 858-2006
Bob Cantilli
US EPA (4304)
Office of Science and Technology
401 M St., SW
Washington, DC 20460
cantilli. robert©epamail, epa. gov
Steve Chapra
University of Colorado
College of Engineering and Applied Science
Campus Box 428
Boulder, CO 80309-0428
(303) 492-7573
Dominic DiToro
HydroQual Inc.
1 Lethbridge Plaza
Mahwah, NJ 07430
(201) 529-5151
dditoro@hydroqual. com
Ken Dunton
University of Texas
Marine Science Institute
Box 1267
Port Aransas, TX 78373
(512)749-6744
dunton©utmsi. zo. utexas. edu
Tom Fontaine
South Florida Water Management District
3301 Gun Club Rd
West Palm Beach, FL 33416
(407) 686-6551
tom.fontaine@sjwmd. gov
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National Nutrient Assessment Workshop —
Proceedings
Charles Gal legos
Smithsonian Environmental Research Center
P.O. Box 28
Edgewater, MD21037
(410) 798-4424
Gallegos®SERC. SI. edu
Jeroen Gerritsen
Tetra Tech, Inc.
10045 Red Run Blvd.
Suite 110
Owings Mills, MD 21117
(410) 356-8993
George Gibson
US EPA (4304)
Office of Science and Technology
401 M St., SW
Washington, DC 20460
(202) 260-7580
gibson. george@epamail, epa, gov
Steve Heiskary
Minnesota Pollution Control Agency
520 Lafayette Road
St. Paul, MN55155
(612)296-7217
Steven. heiskary@pca. state, mn. us
Michael Kemp
University of Maryland-CEES
Horn Point Environmental Laboratory
P.O. Box 775
Cambridge, MD 21613
(410)221-8436
Alan Hais
US EPA (4304)
Office of Science and Technology
401 M St., SW
Washington, DC 20460
(202) 260-1306
ha is. alan@epamail. epa. gov
Gary Ingman
Water Quality Division
Montana Department of Environmental Quality
1520 E. 6th Avenue
PO Box 200901
Helena, MT 59620-0901
(406) 444-5320
Russ Kinerson
US EPA (4304)
Office of Science and Technology
401 M St., SW
Washington, DC 20460
(202) 260-1330
kinerson. russell@epama.il, epa. gov
Jim Kremer
Professor of Marine Sciences
University of Connecticut
Avery Point Campus
2084 Shennecosset Road
Groton, CT 06340-6097
(860) 445-3407
Brian LaPointe
Harbor Branch Oceanographic Institute
2190 Ivess Isle Road #6
Palm Beach, FL 33480
(305) 872-2247
lapointe@gate.net
Jerry LaVeck
US EPA (4304)
Office of Science and Technology
401 M St., SW Washington, DC 20460
(202) 260-7771
laveck.jerry@epamail, epa.gov
Virginia Lee
University of Rhode Island
Bay Campus
Marine Resources Building
Narragansett, RI 02882
(401) 792-6224
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National Nutrient Assessment Workshop —
Proceedings
Lewis Linker
U.S. EPA Chesapeake Bay Program Office
410 Severn Avenue
Annapolis, MD 21403
(410) 267-5741
linker. lewis®epamail. epa. gov
Winston Lung
Department of Civil Engineering
Univerity of Virginia
Thornton Hall D209
Charlottesville, VA 22903
(804) 924-3722
wl@virginia. edu
Wayne Magley
Florida Department of Environmental Regulation
Twin Towers
2600 Blair Stone Rd
Tallahassee, FL 32399-2400
(904) 488-0780
Hassan Mirsajadi
Delaware Dept. of Natural Resources
and Environmental Control
89 Kings Highway
PO Box 1401
Dover, DE 19903
(302) 739-4590
George Loeb
US EPA (4305F)
Office of Wetlands, Oceans, and Watersheds
401 M St., SW
Washington, DC 20460
(202) 260-0670
loeb, george@epamail. epa. gov
Chris Madden
University of Maryland-CEES
Horn Point Environmental Laboratory
PO Box 775
Cambridge, MD 21613
(410)221-8436
madden@hpel. umd. edu
Kristen Martin
US EPA(4503F)
Office of Wetlands, Oceans, and Watersheds
401 M St., SW
Washington, DC 20460
(202) 260-7108
martin. kristen@epamail. epa.gov
James T. Morris
Department of Biological Sciences
University of South Carolina
Columbia, SC 29208
(803) 777-3948
morris®ds. biol. sc. edu
Dennis Newbold
Philadelphia Academy of Natural Sciences
Stroud Water Research Center
512 Spencer Rd. Avondale, PA 19311
(610) 268-2153, ext 227
Newbold@say. acnatsq. org
Scott Nixon
University of Rhode Island
Sea Grant College
South Ferry Road
Narragansett, RI 02882
(401) 792-6800
Cynthia Nolt
US EPA (4304)
Office of Science and Technology
401 M St., SW
Washington, DC 20460
(202) 2604940
nolt. cynthia@epamaU. epa. gov
Patrick Ogbebor
US EPA (4304)
Office of Science and Technology
401 M St., SW
Washington, DC 20460
(202) 260-6322
ogbebor.patrick@epamail. epa. gov
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National Nutrient Assessment Workshop
Proceedings
Hans Paer!
University of North Carolina
Institute of Marine Sciences
3431 Arendell St
Morehead City, NC 28557-3209
(919) 726-6841
hpaerl@email. unc. edu
Ramesh Reddy
University of Florida
Soil and Water Science Department
Gainesville, FL 32611
(904) 392-8462
Dianne Reid
North Carolina Division of Environmental Management
P.O. Box 27687
Raleigh, NC 27611-7687
(919) 733-5083, ext. 568
dianner@dem. ehnr. state, nc. us
Joel S alter
US EPA (4304)
Office of Science and Technology
401 M St., SW
Washington, DC 20460
(202) 260-8484
salter.joel@epamail, epa, gov
Greg Searle
Wisconsin Department of Natural Resources
PO Box 7921
Madison, WI 53707-7921
(608) 267-7644
searlg@dnr, state, wi. us
Leslie Shoemaker
Tetra Tech, Inc.
10306 Eaton Place, Suite 340
Fairfax, VA 22030
(703) 385-6000
ltshoemy@planetcom. com
Eric Smeltzer
Vermont Department of Environmental Quality
Water Quality Division
103 South Main Street
Waterbury, VT 05671
(802) 241-3770
Amy Sosin
US EPA (4305F)
Office of Wetlands, Oceans, and Watersheds
401 M St., SW
Washington, DC 20460
(202) 260-7058
sos in. amy@epamail. epa.gov
James Stribling
Tetra Tech, Inc.
10045 Red Run Blvd.
Suite 110
Owings Mills, MD21117
(410) 356-8993
Ruth Swanek
NC Division of Environmental Management
P.O. Box 29535
Raleigh, NC 27626-0535
(919) 733-5083
ruth@dem. ehnr. state, nc. us
Robert Thomann
Manhattan College
Department of Environmental Engineering and Science
Manhattan College Parkway
Riverdale, NY 10471
(718)920-0100, ext. 947
David Tomasko
Sarasota Bay National Estuary
1990 Ken Thompson Parkway
Sarasota, FL 34236
(813) 483-5970
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National Nutrient Assessment Workshop — . Proceedings
Ivan Valiela Steve Weisber
Boston University Marine Program VERSAR
Marine Biological Laboratory 9200 Rumsey Road
Woods Hole, MA 02543 Columbia, MD 21045
(508) 289-7515 (410) 268-6844
weisbergste@ver$ar. com
Eugene Welch
Department of Civil Engineering
University of Washington
Seattle, WA 98195
(206) 543-2632
ebwelch@u. Washington. edu
Acknowledged contributor to the estuaries
and coastal waters section of the
proceedings:
Don Anderson
Department of Biology
Woods Hole Oceanographic Institution
Woods Hole, MA 02543
(508) 457-2000, ext. 2351
danderson@whoi. edu
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National Nutrient Assessment Workshop ——; — _____ ___ _ Proceedings
Summary of Overheads Used in Day One Plenary Session
Robert Thomann, Manhattan College
I. Nutrient assessment & management—A long history: two periods
A. Observational Descriptive (Beginning c. 1930)
B. Predictive Management (Beginning c. 1965)
II. Observational descriptive period (c. 1930)
A. Juday, Birge, Hutchinson, Sawyer, Mortimer, Kethem
B. Known: Adverse Effects of High Loading: Estuaries, Lakes, Rivers
C. Known: Limiting Nutrient Concentration IN 30: IP 10 ug/L
D, Known: Nutrient Loadings; Point (Sewage), Non-Point (Farms, Urban, Atmospheric)
E. NOT KNOWN: How to Relate Loading to Water Body Response
III. Predictive management period (c. 1965)
A. Critical Loading Models for Lakes
1. Vollenweider:
a. Feb. 16 & 17th, 1966, Paris. OECD request: Gather the eutrophication literature, but
with the hope that "...the report would have a 'practical' bias and not be too
'scientific'"
B. First Model to Relate Nutrient Loading to Lake Trophic Status
1, Assumptions:
a. Steady State, Completely Mixed Lake
b. Total Phosphorus: Measure of Trophic Status
2. Allow. TP Load = (0.01)*(10+H/det t)
C. Regression Models
D. Dynamic Interactive Models: All Waters
1. Di Toro (1970)
a, San Joaquin River: Effect of Nutrient Loads & flow Diversions on Sacramento-San
Joaquin Delta
- Single Volume, Time Variable, CSMP/1130
E. 1970 - 1980 Rapid Expansion: Spatial Detail, State Variables
1. Great Lakes: U.S. & Canadian Phosphorus Agreement; Lake Ontario, Lake Huron,
Saginaw Bay
2. Lake Erie: First Inclusion of Sediment Model for Hypolimnetic DO
3. Coastal Waters: Delta, Potomac Estuary
IV. The "Dry Years"
A. 1980-1990
I. A General Hiatus in National Focus on Eutrophication
a. National Eutrophication Program ends
b. "The Problem's over." Phosphorus controls in place
c. Toxics, Acid Rain
B. Exceptions: Algal bloom in Potomac; Low DO in Chesapeake & LI Sound
B. 1985 - 1990 Renewal Begins
I. Focus on Coastal Waters, National Estuary Program
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National Nutrient Assessment Workshop —————•— • — Proceedings
2. Nitrogen Reductions: Significant Cost
3, Questions More Complex: Point vs. Non-Point Control
V. Results
A, Predictive Models are Robust: They travel well from water body to water body
B. Some Post Auditing: Predictions Generally Successful
C. Some "Failures": Potomac Estuary 198 3 bloom (sediment phosphorus release);
Sacramento San Joaquin 1977 "non-bloom" (benthic filter feeders)
VI. So what?
A. Has productive management been productive?
VII. YES: An Effective Nutrient Management Program Needs:
A. Credible framework for quantitative decision making.
1. What level of improvement to expect
2. When will level be achieved
3. Cost/Benefit analysis if possible
B. Support of
1. Nutrient Dischargers
2. Scientific Community
3. General Public
C. Framework for Quantitative Understanding of Nutrient Response
1. Reduce Surprises
2. Understand surprises that do occur
VIII. Conclusions
A. We benefit now from 70 years of observation, prediction, and successful management -
Can't stop now.
B. Essential that quantitative predictive frameworks be incorporated in nutrient management
programs.
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National Nutrient Assessment Workshop — ——— Proceedings
Mimi Dannet, U.S. EPA, Office of Wetlands, Oceans, and Watersheds
I. Is there a need for nutrient management?
A. 1994 305 (b) Report to Congress
1. Third leading cause of impairments to rivers and streams
2. Top cause of impairment for lakes
3. Top cause of impairments for estuaries
B. 303(d) Lists
I. Among the top three causes of impairments for listed waters
II. How does nutrient management mesh with current initiatives?
A. Watershed Protection Approach
B. Community-based Environmental Protection
C. Trading
III. Endpoints and Assessment Methodologies
A. How can the endpoint be tied back to exisiting State water quality standards?
B. How responsive is the endpoint to improved nutrient control?
C. Can the endpoint response be predicted?
D. Is the endpoint appropriate for volunteer monitoring?
IV. Models
A. Focus on a core set of models for "routine" applications
B. Avoid developing new models if possible
1. Enhance existing models
a. Enhancement can mean simplification
b. Need improved periphyton and macrophyte capabilities
C. When evaluating a model, consider:
I, Number of input parameters
2. How input parameters are determined
3. Comparability of model compexity with probable controls
4. Cost of model application vs. cost of controls
D. Watch out for "Home Improvement" Syndrome
I. Keep the focus on the resource, not the tool
V. Models - General Needs
A. Training and Technical Support
B. Guidance Needs
\. Model-specific guidance
a. Input parameter determination
- Monitoring design for measured parameters
- Estimation techniques for other inputs
b. Input parameter estimation for projection models
2, Case studies
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National Nutrient Assessment Workshop — p ,.
Steve Heiskary, Minnesota Pollution Control Agency
I. Minnesota's Approach to Lake Water Quality Criteria Development
A. Steve Heiskary, Minnesota Pollution Control Agency
II. Northern Lakes and Forests
A. Land Use - Forest Dominant
1. Forest 75%
2. Water and March 11%
3. Pasture and Open 7%
4. Cultivated 5%
5. Urban 2%
B. Soils - Sand and Silt
C. Lakes - 5,500 Over 10 Acres (46%)
1. Maximum Depth Typically 20-55 Feet
2. Surface Area Typically 100-550 Acres
III. North-Central Hardwood Forests
A. Land Use - No Single Dominant Type
1. Forest 16%
2. Water and March 8%
3. Pasture and Open 20%
4, Cultivated 50%
5. Urban 5%
B. Soils - Sand and Silt
C. Lakes - 4,765 Over 10 Acres (40%)
1. Maximum Depth Typically 20-55 Feet
2, Surface Area Typically 150-650 Acres
IV. Western Corn Belt Plains
A. Land Use - Agriculture Dominant
I. Forest 3%
2. Water and March 2%
3. Pasture and Open 10%
4. Cultivated 83%
5. Urban 2%
B. Soils - Silt
C. Lakes - 577 Over 10 Acres (5%)
1. Maximum Depth Typically 7-16 Feet
2. Surface Area Typically 350-850 Acres
V. Northern Glaciated Plains
A. Land Use - Agriculture Dominant
1. Forest <1%
2. Water and March 3%
3. Pasture and Open 11%
4, Cultivated 84%
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National Nutrient Assessment Workshop
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5. Urban 1%
B. Soils - Silt
C. Lakes - 855 Over 10 Acres (7%)
I. Maximum Depth Typically 7-13 Feet
2. Surface Area Typically 350-850 Acres
VI. Phosphorus Criteria for Minnesota Lakes - Factors Considered
A. Impacts on Lake Condition
1. Chlorophyll-a
2. Transparency
3. Hypolimnetic Dissolved Oxygen
B. Impacts on Lake Uses
\, Aesthetics
2. Recreation
3. Fisheries (Most Sensitive Uses)
C. Regional Factors
VII. Most Sensitive Lake Uses by Ecoregion and Corresponding Phosphorus Criteria
ECOREGION
Northern Lakes and Forests
North-Central Hardwood
Forests
Western Corn Belt Plains
Northern Glaciated Plains
MOST SENSITIVE USES
Drinking Water Supply
Cold Water Fishery
Primary Contact Recreation and
Aesthetics (Full Support)
Drinking Water Supply
Primary Contact Recreation and
Aesthetics (Full Support)
Drinking Water Supply
Primary Contact Recreation and
Aesthetics (Full Support)
(Partial Support)
Primary Contact Recreation and
Aesthetics (Partial Support)
P CRITERIA
(Mg/l)
15
15
30
30
40
40
40
90
90
VIII. Western Corn Belt and Northern Glaciated Plains
A. Management Considerations
1. Maintain Current Tropic Status
2. Focus on Lakes <90 ppi: 1' (25th Percentile)
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National Nutrient Assessment Workshop
3. Realistic Goals Needed for Restoration
B, Phosphorus Goals
I. Swimmabie - Full Support: <40 ppb
- Partial Support: <90 ppb
r D(KufP Frequency of Severe Nuisance Blooms , 25% of Summer)
C. Problems
1. Shallow Lakes
2. High Percent Agricultural Land Use -»High P Export
3. Limited Flushing (High Evaporation)
IX. Uses and Application of Criteria
A. Prioritizing and Selecting Projects
B. Developing Water Quality Management Plans
C. Educating (Goal Setting)
D. Guide Enforcement Decisions
E. Guide Interpretations of Nondegradation
X. Approaches for Standards Criteria Development
Proceedings
State/Entity
British Columbia
ME
OR
NC
VA
TVA
IJC
Approach
User Survey - Trophic Characterization & User
Perception
Ecoregion - Reference Lakes, User Perception,
Most Sensitive Uses
Water Use - Trophic Characterization & Fish
Requirements
• •——
Nondegradation - Determine Acceptable
Increase in P, Categorize for Protection
Nuisance Phytopiankton - Characterization
Average Chl-a. Considers Thermal Stratification
Nutrient Sensitive - Chl-a Criteria for Warm
and Cold Water Fisheries, Exceedance Leads to
Study
Nutrient-Enriched - Designation Considers chl-
a, DO Fluctuation, and TP
Biological - Index of Biotic Integrity to ID
Communities Out of BaIance~»Management
Priority
-.ake-Specific Detailed Analysis of Biota,
"hemicai and Loading->Loading Goals,
Jasinwide Phus
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National Nutrient Assessment Workshop ~ Proceedings
XI. Conclusions .
A. Eutrophication Standards Should Be Developed to Protect Lakes and Reservoirs From
the Negative Impacts of Cultural Eutrophication.
B. Because Federal Criteria or Guidance is Lacking, State EutrophicationControl Programs
May Continue to Be Discreationary in Their Approach.
C. Eutrophication Standards Should Be Developed by the States and Should Be Tailored
to Local/Regional Conditions and User Expectations.
D Lake Monitoring is an Essential Part of Eutrophication Standards Application.
E Eutrophication Criteria and Standards Can Serve a Vareity of Purposes. Primary
Purpose Is to Assist Lake Managers in the Protection and Improvement of Lake Water
Quality.
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National Nutrient Assessment Workshop — Proceedings
Summary of Overheads Used During Workshop Wrap-up
Day Three Plenary Session Discussion Questions
• Taking into account work that has already been completed in the area of nutrient
enrichment assessment, what are the priority nutrient assessment tools EPA should
high-light within its national strategy for development, validation, and implementation?
• Of these high priority nutrient assessment tools, which ones have the added benefit of
being applicable across waterbodies and/or different geographical areas?
• What should be the relative timing for development, validation, and field testing these
high-priority assessment tools?
• What organizations-state, federal, local, consulting, academic, nonprofit, etc.--and which
key individuals should be involved in the development, validation, and implementation of
these high-priority assessment tools?
• What opportunities are there to leverage ongoing or planned work in the short (1-3 years)
and long (3-10 years) timeframes?
• What national and regional programmatic shifts should be encouraged and fostered?
• How feasible are these recommendations taking into consideration the realities of resources
and capabilities?
• How do we keep the momentum for getting nutrient enrichment assessment back on the
national, regional, state, and local watershed management agendas? What existing
networks should we tap into to get the word out and leverage the necessary resources (both
people and dollars)?
National Nutrient Assessment Strategy: Next Steps
* Preliminary draft strategy (based on the workshop) and draft workshop proceedings
distributed to workshop participants with a request for review (December)
• Revised versions of the issue papers distributed to relevant breakout group members with
request for review (January)
• Final workshop proceedings summary published (end of January)
* Final issue papers published (end of February)
* Draft strategy ready for presentation to senior EPA managers (February)
• Presentation of draft strategy to EPA Program Offices, EPA Regional Offices, ORD
Laboratories, federal agencies, states, professional societies (February - May)
• Draft final strategy for Science Advisory Board review (May)
• Science Advisory Board review (Summer 1996)
• Publication of subsets of the issue papers in peer reviewed literature (Fall 1996)
• Final EPA Strategy (Fall 1996)
• Continued work with other federal agencies, states, professional societies on a more
encompassing strategy—similar substance, more definitive commitments to take
responsibility for specific actions, policy changes, resource allocations, etc. (Summer/Fall
1996)
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National Nutrient Assessment Strategy: An Overview of
Available Endpoints and Assessment Tools
Introduction
Nutrient overenrichment continues to be one of the leading causes of water quality
impairment in the United States. The National Water Quality Inventory 1994
Report to Congress cites nutrients (nitrogen and phosphorus) as one of the leading
causes of water quality impairment in our nation's rivers, lakes, and estuaries.
Although nutrients are essential to the health of aquatic ecosystems, excessive
nutrient loadings can result in the growth of aquatic weeds and algae, leading to
oxygen depletion, increased fish and rnacroinvertebrate mortality, and other water
quality and habitat impairments.
Over the years, the Environmental Protection Agency's Office of Water has issued
a number of technical guidance documents and supported the development of water
quality simulation models and load estimating models to assess the impacts of
urban, rural, and mixed land use activities on receiving waters. In addition, some
states currently have water quality standards that incorporate criteria, primarily
narrative, aimed at controlling problems associated with overenrichment. However,
for state and local agencies to better understand and manage nutrient impacts to
surface waters, additional work is required.
EPA established a Nutrient Task Force in July 1993 to gather existing data on
nutrient problems and currently available tools. The Task Force recommended that
EPA provide additional assistance to states in developing and implementing
appropriate nutrient endpoints, assessment methodologies, and models. The first
step in carrying out the recommendations of the Task Force was a nutrient
assessment workshop, which was held in Washington, D.C., on December 4-6,
1995. The workshop was organized around discussions on four major waterbody
types: estuarine and coastal waters; lakes, impoundments/reservoirs, and ponds;
rivers and streams; and wetlands. Working papers describing the state of the
science, gaps, and user needs in terms of nutrient assessment tools and
methodologies for each waterbody type were developed and used as foundations
for group discussion.
These issue papers have since been revised and condensed into this one document
by incorporating the discussions that were held at the workshop and reviewing
additional literature suggested by workshop participants. This condensed paper is
intended to represent a brief yet comprehensive overview of the nutrient
overenrichment endpoints, assessment methodologies, and modeling tools that have
been or could be used in assessing nutrient overenrichment. It should be viewed
Introduction
-------
as a working document that provides an initial synthesis of the available literature,
not as an attempt to address all of the detailed issues associated with managing
nutrient overenrichment.
This introductory section includes a discussion of issues that overlap across the
four waterbody types. These overlapping issues include defining the term
endpoint, outlining characteristics of effective endpoints, and reviewing simulation
loading models that can be applied across multiple types of waterbodies. The
following papers then address specific endpoints and models that can be used for
each of the four waterbody types.
Defining Endpoints
Key to the development of a national nutrient assessment strategy will be
identifying endpoints that can be used at an ecosystem or regional level to describe
nutrient enrichment conditions. In the context of this paper, the term endpoint is
used broadly to encompass any type of target set for nutrient protection. As a
simple example, Minnesota has adopted a phosphorus endpoint of 30 ug/L for
drinking water supply lakes in its North Central Hardwood Forests ecoregion. The
endpoint 30 ug/L therefore separates an "impacted" lake from a "nonimpacted"
lake. Because natural conditions, like trophic state, actually represent a continuum
of conditions, endpoints are only artificially exacting. Yet they serve a necessary
role in management activities because crossing an endpoint typically yields
consequences. Once endpoints have been established, actual or predicted
measurements can be compared to them and conclusions drawn about the status of
nutrient enrichment.
Although water quality endpoints are similar, they are not the same as water
quality standards, and the two terms should not be confused. Water quality
standards consist of a designated use for a waterbody (such as for swimming,
fishing, or protection of aquatic life), as well as either numeric or narrative criteria
to protect that use (e.g., a minimum dissolved oxygen concentration of 5 mg/L)
(USEPA, 1994). Similarly, nutrient endpoints are used to determine whether a
waterbody has become eutrophied to the point that certain uses are impaired. The
key distinction is that water quality standards have a legal and regulatory
connotation because of their inclusion in state or federal regulations, whereas
endpoints do not necessarily have a regulatory connotation.
Using Endpoints
The selection of universal nutrient endpoints is complicated by the fact that given
nutrient concentrations can cause different effects in different aquatic systems
(Ingman, 1992). Many states approach this problem by using narrative criteria to
An Overview of" Available Endpoints and Assessment Tools
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address the effects of overenrichment (e.g., nutrients should be kept at
concentrations that prevent nuisance growths of aquatic plants). A primary
advantage of having quantitative nutrient overenrichment endpoints in place would
be that violations would prompt and focus management action and remedies could
be instituted when available (NALMS, 1992). Quantitative endpoints would allow
water resource managers to determine the status of their waterbody and would also
provide the justification for taking steps toward improving the resource. For
example, if a certain river segment were violating a soluble reactive phosphorus
endpoint of 6 ug/L, the regulatory agency would be obligated to initiate some type
of management action. This could be as simple as checking to make sure the local
wastewater treatment plant is in compliance with its permit or it could be as far-
reaching as developing a total maximum daily load (TMDL) that targets point and
nonpoint source phosphorus controls.
Given the wide variability in the types of waterbodies that can be affected by
nutrient overenrichment, in addition to the climatological differences that might
affect waters in different areas, it is generally accepted that endpoints should be
regional in nature as opposed to nationwide (Heiskary and Wilson, 1989; NALMS,
1992; Porcella, 1989). This reflects the fact that some waters will not be able to
reach the same level of quality as others and also acknowledges that different parts
of the country have different uses. In some cases, nutrient endpoints might even
need to be site-specific or developed within the context of a total maximum daily
load. In general, a balance should be struck between choosing endpoints that
reflect specific ecoregion conditions and choosing those which allow practical
implementation.
Endpoints can also be used to identify incremental changes as a waterbody moves
toward eutrophication-related degradation, thus affording water quality managers
the opportunity to take actions that might prevent a system from degrading to a
point where beneficial uses are affected. An example of this would be a nutrient
concentration endpoint that signals that a lake is approaching the point where
plankton blooms and surface scums have historically been a problem. This "early
warning" function can be especially beneficial in high-profile, nondegraded
systems where the costs of nutrient overenrichment might be especially high.
Quantitative endpoints can be used as indices to determine waterbody status at a
point in time, as well as status over a number of years. This use may be important
in biennial Clean Water Act section 305(b) reporting, in identifying which lakes,
rivers, estuaries, and other waterbodies should be prioritized for restoration, and in
evaluating the success of existing programs and watershed management plans.
Endpoints can provide focus for watershed management activities and can serve an
important role in communicating waterbody goals to the public. A Secchi depth
endpoint of 3 feet, for example, directly reflects something that is valued by the
public and is more easily understood than a goal of having "no undesirable or
Introduction 3
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nuisance aquatic life." Since waterbody users will often be called on to voluntarily
alter their actions in an attempt to improve the resource, it is important that they
understand and support the reasons for doing so. Endpoints can play a key role in
this capacity. Additionally, endpoints can play a role in communicating to the
public what level of quality can be reasonably expected of a resource given
background conditions (Heiskary, 1989).
Characteristics of Effective Endpoints
Effective nutrient overenrichment endpoints should accurately reflect the water
quality that is desired in the waterbody. They should be directly related to the
designated beneficial uses of the water and should be strict enough to keep a
comfortable margin of safety between actual conditions and conditions that have
been determined to impair use (whether those uses are swimming, boating, fishing,
drinking water supply, or others) (NALMS, 1992). Borrowing from concepts
applied in lakes and reservoirs, a number of authors have suggested that impaired
use conditions can be estimated by surveying users to determine at what levels
they feel their enjoyment of a waterbody is diminished (Heiskary and Wilson,
1989; Heiskary, 1989; Smeltzer and Heiskary, 1990). Survey results can be
correlated with simultaneous water quality measurements to establish endpoints at
the border between acceptable and unacceptable conditions. If 90 percent of those
surveyed agree that their aesthetic enjoyment of a lake is impaired at chlorophyll a
concentrations exceeding 30 ug/L, this value represents a possible biomass
endpoint. The survey approach recognizes that the overall water quality of a
waterbody is highly subjective and is best determined by the end user.
Nutrient enrichment endpoints should also be linked in some manner to potential
management options. In other words, endpoints should provide managers with
some understanding of the nutrient load reductions that will be necessary to correct
violations. Most likely this will involve the use of water quality models that can
predict water quality parameters based on existing and potential nutrient loads, as
well as other model inputs (such as streamflow, residence time, and temperature).
A final consideration in selecting endpoints is the cost associated with monitoring.
Water quality parameters that can be measured easily and accurately will obviously
be superior to those which require more time and resources to obtain. Issues to
keep in mind in this regard include how often the measurements must be taken,
who (e.g., experts vs. volunteers) can take the measurements, and the cost of
monitoring equipment and laboratory analysis.
An Overview of Available Endpoints and Assessment Tools
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Watershed Loading Models
Simulation models have been and will continue to be integral components of water
quality planning and pollution control activities, including evaluating the degree of
nutrient overenrichment. They serve an essential role in assessing and predicting
nutrient overenrichment effects and in evaluating management alternatives. Model
selection criteria should include factors such as prediction uncertainty, cost of
calibration and testing, meaningful endpoints, appropriate spatial and temporal
detail, and simplicity in application and understanding.
Most simulation models can be classified according to whether they focus on
pollutant export (loading models) or waterbody response (receiving water models).
Because the focus of loading models is on the surrounding watershed and not the
waterbody itself, these types of models can be applied to estimate loadings to
multiple types of waterbodies A summary of loadings models is therefore
presented here, while a discussion of receiving water models specific to the various
waterbody types is included in the individual waterbody sections. Information on
these models has been summarized from the revised Compendium of Tools for
Watershed Assessment and TMDL Development (USEPA, in review).
Loading models are used to predict key factors such as flow, nutrient type,
concentration, and load delivered to the selected receiving waterbody. Models
vary in their capabilities to simulate these processes. For discussion purposes,
loading models are divided into categories based on their complexity, operation,
time step, and simulation technique. They can be grouped into three
categories—simple methods, mid-range models, and detailed models (USEPA,
1992). The three categories of models and types of available models in each
category are discussed below.
Simple Loading Methods
The major advantage of simple methods is that they can provide a rapid means of
identifying critical loading areas with minimal effort and data requirements.
Simple methods are compilations of expert judgment and empirical relationships
between physiographic characteristics of the watershed and pollutant export. They
can often be applied by using a spreadsheet program or hand-held calculator.
Simple methods are often used when data limitations and budget and time
constraints preclude the use of complex models. They are used to diagnose
nonpoint source pollution problems where limited information is available. Default
values provided for these methods are derived from empirical relationships that are
evaluated based on regional or site-specific data.
Simple methods provide only rough estimates of sediment and pollutant loadings
and have very limited predictive capability. The empiricism contained in the
Watershed Loading Models 5
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models limits their transferability to regions other than those for which they were
developed. Because they often neglect seasonal variability, simple methods might
not be adequate to model water quality problems for which loadings of shorter
duration are important. They might be sufficient for modeling nutrient loadings to
and eutrophication of long-residence-time waterbodies (e.g., lakes, reservoirs).
Summaries of the simple methods' capabilities, model components, and input and
output data are provided below.
EPA Screening Procedures. The EPA Screening Procedures, developed by the
EPA Environmental Research Laboratory in Athens, Georgia, (McElroy et al.,
1976; Mills, 1985) include methodologies to calculate nutrient loads from point
and nonpoint sources, including atmospheric deposition, for preliminary assessment
of water quality. The procedures consist of loading functions and simple empirical
expressions relating nonpoint pollutant loads to other readily available parameters.
Data required generally include information on land use/land cover, management
practices, soils, and topography. An advantage of this approach is the possibility
of using readily available data as default values when site-specific information is
lacking. Application of these procedures requires minimum personnel training and
practically no calibration. However, application to large complex watersheds
should be limited to preplanning activities.
The Simple Method. The Simple Method is an empirical approach developed for
estimating pollutant export from urban development sites in the Washington, D.C.,
area (Schueler, 1987). It is used at the site-planning level to predict pollutant
loadings under a variety of development scenarios. Its application is limited to
small drainage areas of less than a square mile. Pollutant concentrations of
phosphorus, nitrogen, chemical oxygen demand, biological oxygen demand
(BOD), and metals are calculated from flow-weighted concentration values for new
suburban areas, older urban areas, central business districts, hardwood forests, and
urban highways. The method relies on the National Urban Runoff Program
(NURP) data for default values (USEPA, 1983). A graphical relationship is used
to determine the event mean sediment concentration based on readily available
information. This method is not coded into a computer program but can be easily
implemented with a hand-held calculator.
USGS Regression Approach. The regression approach developed by USGS
researchers is based on a statistical description of historic records of storm runoff
responses on a watershed level (Tasker and Driver, 1988). This method may be
used for rough preliminary calculations of annual pollutant loads when data and
time are limiting. Input data include drainage area, percent imperviousness, mean
annual rainfall, general land use pattern, and mean minimum monthly temperature.
Application of this method provides storm-mean pollutant loads and corresponding
confidence intervals. The use of this method as a planning tool at a regional or
watershed level might require preliminary calibration and verification with
additional, more recent monitoring data.
An Overview of Available Endpoints and Assessment Tools
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Simplified Pollutant Yield Approach (SLOSS-PHOSPH). This method uses two
simplified loading algorithms to evaluate soil erosion, sedimentation, and
phosphorus transport from distributed watershed areas. The SLOSS algorithm
provides estimates of sediment yield, whereas the PHOSPH algorithm uses a
loading function to evaluate the amount of sediment-bound phosphorus.
Application to watershed and subwatershed levels was developed by Tim et al.
(1991) based on an integrated approach coupling these algorithms with the Virginia
Geographical Information System (VirGIS). The approach was applied to the
Nomini Creek Watershed, Westmoreland County, Virginia, to target critical areas
of nonpoint source pollution at the subwatershed level (USEPA, 1992c). In this
application, analysis was limited to phosphorus loading; however, other pollutants
for which input data or default values are available can be modeled in a similar
fashion. The approach requires full-scale GIS capability and trained personnel.
Watershed. Watershed is a spreadsheet model developed at the University of
Wisconsin to calculate phosphorus loading from point sources, combined sewer
overflows (CSOs), septic tanks, rural croplands, and other urban and rural sources.
The Watershed program can be used to evaluate the trade-offs between control of
point and nonpoint sources (Walker et al, 1989). It uses an annual time step to
calculate total nutrient loads and to evaluate the cost-effectiveness of pollution
control practices in term of cost per unit load reduction. The program uses a
series of worksheets to summarize watershed characteristics and to estimate
pollutant loadings for uncontrolled and controlled conditions. Because of the
simple formulation describing the various pollutant loading processes, the model
can be applied using available default values with minimum calibration effort.
The Federal Highway Administration (FHWA) Model. The FHWA's Office of
Engineering and Highway Operations has developed a simple statistical spreadsheet
procedure to estimate pollutant loading (including nutrients) and impacts to streams
and lakes that receive highway stormwater runoff (Federal Highway
Administration, 1990). The procedure uses several worksheets to tabulate site
characteristics and other input parameters, as well as to calculate runoff volumes,
pollutant loads, and the magnitude and frequency of occurrence of instream
pollutant concentrations. The FHWA model uses a set of default values for
pollutant event-mean concentrations that depend on traffic volume and the rural or
urban setting of the highway's pathway. The Federal Highway Administration
uses this method to identify and quantify the constituents of highway runoff and
their potential effects on receiving waters and to identify areas that might require
controls.
Watershed Management Model (WMM). The Watershed Management Model
was developed for the Florida Department of Environmental Regulation for
watershed management planning and estimation of watershed pollutant loads
(Camp, Dresser, and McKee, 1992). Nitrogen and phosphorus from point and
nonpoint sources can be estimated. The model is implemented in the Lotus 1-2-3
Watershed Loading Models 7
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spreadsheet environment and can thus calculate standard statistics and produce
plots and bar charts of results. The model includes computational components for
stream and lake water quality analysis using simple transport and transformation
formulations based on travel time. The WMM has been applied to several
watershed management projects including the development of a master plan for
Jacksonville, Florida, and the Part II estimation of watershed loadings for the
NPDES permitting process. It has also been applied in Norfolk County, Virginia;
to a Watershed Management Plan for North Carolina; to a wasteload allocation
study for Lake Tohopekaliga, near Orlando, Florida; and for water quality planning
in Austin, Texas (Pantalion et al., 1995).
Mid-range Loading Models
Mid-range models attempt a compromise between the empiricism of the simple
methods and the complexity of detailed mechanistic models. The advantage of
mid-range watershed-scale models is that they evaluate nutrient sources and
impacts over broad geographic scales and therefore can assist in defining target
areas for mitigation programs on a watershed basis. Several mid-range models are
designed to interface with geographic information systems, which greatly facilitate
parameter estimation (e.g., AGNPS). Greater reliance on site-specific data gives
mid-range models a relatively broad range of regional applicability. However, the
use of simplifying assumptions can limit the accuracy of their predictions to within
about an order of magnitude (Dillaha, 1992) and can restrict their analysis to
relative comparisons.
Unlike the simple methods, which are restricted to predictions of annual or storm
loads, mid-range tools can be used to assess the seasonal or inter-annual variability
of nonpoint source pollutant loadings and to assess long-term water quality trends.
Also, they can be used to address land use patterns and landscape configurations in
actual watersheds. In addition, they typically require some site-specific data and
calibration. Some mid-range models simplify the description of transport processes
while emphasizing possible reductions available with controls; others simplify the
description of control options and emphasize changes in concentrations as
pollutants move through the watershed.
It should be noted that neither the simple nor the mid-range models consider
degradation and transformation processes, and few incorporate adequate
representation of pollutant transport within and from the watershed. Although their
applications might be limited to relative comparisons, however, they can often
provide water quality managers with useful information for watershed-scale
planning level decisions.
Stormwater Intercept and Treatment Evaluation Model for Analysis and
Planning (SITEMAP). SITEMAP, previously distributed under the name
NPSMAP, is a dynamic simulation program that predicts daily runoff, nutrient
An Overview of Available Endpoints and Assessment Tools
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loadings, infiltration, soil moisture, evapotranspiration, and drainage to
groundwater. (Omicron Associates, 1990). The model can be used to evaluate
user-specified alternative control strategies, and it simulates stream segment load
capacities (LCs) in an attempt to develop point source wasteload allocations
(WLAs) and nonpoint source load allocations (LAs). Probability distributions for
runoff and nutrient loadings can be calculated by the model based on either single-
event or continuous simulations. The model can be applied in urban, agricultural
or complex watershed simulations. Although this model requires a minimum
calibration effort, it requires moderate effort to prepare input data files. The
current version of the program considers only nutrient loading; sediment and other
pollutants are not yet incorporated into the program. The model is easily interfaced
with GIS (ARC/INFO) to facilitate preparation of land use files. Two examples of
where SITEMAP has been applied as a component of a full watershed model are
the Tualatin River basin for the Oregon Department of Environmental Quality, and
the Fairview Creek watershed for the Metropolitan Service District in Portland,
Oregon.
Generalized Watershed Loading Functions (GWLF) Model. The GWLF model
was developed at Cornell University to assess the point and nonpoint loadings of
nitrogen and phosphorus from urban and agricultural watersheds, including septic
systems, and to evaluate the effectiveness of certain land use management practices
(Haith et al., 1992). One advantage of this model is that it was written with the
express purpose of requiring no calibration, making extensive use of default
parameters. The GWLF model includes rainfall/runoff and erosion and sediment
generation components, as well as total and dissolved nitrogen and phosphorus
loadings. The GWLF model uses daily time steps and allows analysis of annual
and seasonal time series. The model also uses simple transport routing, based on
the delivery ratio concept. In addition, simulation results can be used to identify
and rank pollution sources and evaluate basinwide management programs and land
use changes. The most recent update of the model incorporates a septic (on-site
wastewater disposal) system component. The model also includes several reporting
and graphical representations of simulation output to aid in interpretation of the
results. This model was successfully tested on a medium-size watershed in New
York (Haith and Shoemaker, 1987). A version of the model with an enhanced user
interface and linkages to national databases, WSM (Watershed Screening Model),
has recently become available and is distributed with EPA-OWOW's Watershed
Screening and Targeting Tool (WSTT).
Urban Catchment Model (P8-UCM). The P8-UCM program was developed for
the Narragansett Bay Project to simulate the generation and transport of stormwater
runoff pollutants in small urban catchments and to assess impacts of development
on water quality, with minimum site-specific data. It includes several routines for
evaluating the expected removal efficiency for particular site plans, selecting or
siting best management practices (BMPs) necessary to achieve a specified level of
pollutant removal, and comparing the relative changes in pollutant loads as a
Watershed Loading Models 9
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watershed develops (Palmstrom and Walker, 1990). Default input parameters can
be derived from NURP data and are available as a function of land use, land
cover, and soil properties. However, without calibration, the use of model results
should be limited to relative comparisons. Spreadsheet-like menus and on-line
help documentation make extensive user interface possible. On-screen graphical
representations of output are developed for a better interpretation of simulation
results. The model also includes components for performing monthly or
cumulative frequency distributions for flows and pollutant loadings.
Automated Q-ILLUDAS (AUTO-QI). AUTO-QI is a watershed model
developed by the Illinois State Water Survey to perform continuous simulations of
stormwater runoff from pervious and impervious urban lands (Terstriep et al.,
1990). It also allows the examination of storm events or storm sequence impacts
on receiving water. Critical events are also identified by the model. However,
hourly weather input data are required. Several pollutants, including nutrients,
chemical oxygen demand, metals, and bacteria, can be analyzed simultaneously.
This model also includes a component to evaluate the relative effectiveness of best
management practices. An updated version of AUTO-QI, with an improved user
interface and linkage to a geographic information system (ARC/INFO on PRIME
computer), has been completed by the Illinois State Water Survey. This interface
is provided to generate the necessary input files related to land use, soils, and
control measures. AUTO-QI was verified on the Boneyard Creek in Champaign,
Illinois, and applied to the Calumet and Little Rivers to determine annual pollutant
loadings.
Agricultural Nonpoint Source Pollution Model (AGNPS). Developed by the
U.S. Department of Agriculture's (USDA) Agricultural Research Service, AGNPS
addresses concerns related to the potential impacts of point and nonpoint source
pollution on water quality (Young et al., 1989). It was designed to quantitatively
estimate pollution loads from agricultural watersheds and to assess the relative
effects of alternative management programs. The model simulates surface water
runoff, as well as nutrient and sediment constituents associated with agricultural
nonpoint sources and point sources. It also accounts for point sources like
treatment plants, and stream bank or gully erosion. The available version of
AGNPS is event-based; however, a continuous version is under development
(Needham and Young, 1993). The AGNPS grid system allows the model to be
connected to other software such as geographic information systems (GIS) and
digital elevation models (DEM). This connectivity can facilitate the development
of a number of the model's input parameters. Two new terrain-enhanced versions
of the model— AGNPS-C, a contour-based version, and AGNPS-G, a grid-based
version—have been developed to generate the grid network and the required
topographic parameters (Panuska et al., 1991). Vieux and Needham (1993) describe
a GIS-based analysis of the sensitivity of AGNPS predictions to grid-cell size.
Engel et al. (1993) present GRASS-based tools to assist with the preparation of
model inputs and visualization and analysis of model results. Tim and Jolly (1994)
10 An Overview of Available Endpoints and Assessment Tools
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used AGNPS with ARC/INFO to evaluate the effectiveness of several alternative
management strategies in reducing sediment pollution in a 417-ha watershed in
southern Iowa. The model also includes enhanced graphical representations of
input and output information.
Detailed Loading Models
Detailed models best represent the current understanding of watershed processes
affecting pollution generation. If properly applied and calibrated, detailed models
can provide relatively accurate predictions of variable flows and water quality at
numerous points within a watershed. The additional precision they provide,
however, comes at the expense of considerable time and resource expenditure.
Detailed models incorporate the manner in which watershed processes change over
time in a continuous fashion rather than relying on simplified terms for rates of
change (Addiscott and Wagenet, 1985). They tend to require rate parameters for
flow velocities and nutrient accumulation, settling, and decay instead of capacity
terms. The length of time steps is variable and depends on the stability of
numerical solutions as well as the response time for the system (Nix, 1991).
Algorithms in detailed models more closely simulate the physical processes of
infiltration, runoff, pollutant accumulation, instream effects, and
groundwater/surface water interaction. The input and output of detailed models
also have greater spatial and temporal resolution. Moreover, the manner in which
physical characteristics and processes differ over space is incorporated within the
governing equations (Nix, 1991). Linkage to biological modeling is possible
because of the comprehensive nature of continuous simulation models. In addition,
detailed hydrologic simulations can be used to design potential control actions.
Detailed models use small time steps to allow for continuous and storm event
simulations. However, input data file preparation and calibration require
professional training and adequate resources. Some of these models (e.g.,
STORM, SWMM, ANSWERS) were developed not only to support planning-level
evaluations but also to provide design criteria for pollution control practices. If
appropriately applied, state-of-the-art models like HSPF and SWMM can provide
accurate estimations of pollutant loads and the expected impacts on water quality.
New interfaces developed for HSPF and SWMM, and links with GISs, can
facilitate the use of complex models for environmental decision-making. However,
their added accuracy might not always justify the amount of effort and resources
they require. Application of such detailed models is more cost-effective when used
to address complex situations or objectives.
Storage, Treatment, Overflow Runoff Model (STORM). STORM is a U.S.
Army Corps of Engineers (COE) model developed for continuous simulation of
runoff quantity and quality, including sediments and several conservative
pollutants. STORM has been widely used for planning and evaluation of the trade-
Watershed Loading Models 11
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off between treatment and storage control options for CSOs and was primarily
designed for modeling stormwater runoff from urban areas. It requires relatively
moderate to high calibration and input data, STORM was initially developed for
mainframe computer usage; however, several versions have been adapted by
various individual consultants for use on microcomputers. The model has been
applied recently to water quality planning in the City of Austin, Texas (Pantalion
et at., 1995).
Areal Nonpoint Source Watershed Environment Response Simulation Model
(ANSWERS). ANSWERS is a comprehensive model developed at the University
of Georgia to evaluate the effects of land use, management schemes, and
conservation practices or structures on the quantity and quality of water from both
agricultural and nonagricultural watersheds (Beasley, 1986). The distributed
structure of this model allows for a better analysis of the spatial as well as
temporal variability of pollution sources and loads. It was initially developed on a
storm event basis to enhance the physical description of erosion and sediment
transport processes. Data file preparation for the ANSWERS program is rather
complex and requires mainframe capabilities, especially when dealing with large
watersheds. The output routines are quite flexible; results may be obtained in
several tabular and graphical forms. The program has been used to evaluate
management practices for agricultural watersheds and construction sites in Indiana.
It has been combined with extensive monitoring programs to evaluate the relative
importance of point and nonpoint source contributions to Saginaw Bay. This
application involved the computation of unit area loadings under different land use
scenarios for evaluation of the trade-offs between LAs and WLAs. Recent model
revisions include improvements to the nutrient transport and transformation
subroutines (Dillaha et al., 1988). Bouraoui et al. (1993) describe the development
of a continuous version of the model.
Multi-event urban runoff quality model (DR3M-QUAL). DR3M is a watershed
model for routing storm runoff through a branched system of pipes and/or natural
channels using rainfall as input. The model provides detailed simulation of storm-
runoff periods selected by the user and a daily soil-moisture accounting between
storms. Kinematic wave theory is used for routing flows over contributing
overland-flow areas and through the channel network. Storm hydrographs may be
saved for input to DR3M-QUAL, which simulates the quality of surface runoff
from urban watersheds. The model simulates impervious areas, pervious area, and
precipitation contributions to runoff quality, as well as the effects of street
sweeping and/or detention storage. Variations of runoff quality are simulated for
user-specified storm-runoff periods. Between these storms, a daily accounting of
the accumulation and washoff of water-quality constituents on effective impervious
areas is maintained. Input to the model includes the storm hydrographs, usually
from DR3M. The program has been extensively reviewed within the USGS and
applied to several urban modeling studies (Brabets, 1986; Lindner-Lunsford and
Ellis, 1987; Guay, 1990).
12 An Overview of Available Endpoints and Assessment Tools
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Simulation for Water Resources in Rural Basins - Water Quality
(SWRRBWQ). The SWRRBWQ model was adapted from the field-scale
CREAMS model by USDA to simulate hydrologic, sedimentation, nutrient, and
pesticide movement in large, complex rural watersheds (Arnold et al., 1989),
SWRRBWQ uses a daily time step to evaluate the effect of management decisions
on water, sediment yields, and pollutant loadings. The model is useful for
estimation of the order of magnitude of pollutant loadings from relatively small
watersheds or watersheds with fairly uniform properties. Input requirements are
relatively high, and experienced personnel are required for successful simulations
SWRRBWQ was used by the National Oceanic and Atmospheric Administration
(NOAA) to evaluate pollutant loadings to coastal estuaries and embayments as part
of its national Coastal Pollution Discharge Inventory. The model has been run for
all major estuaries on the east coast, west coast, and Gulf coast for a wide range of
pollutants (Donigian and Huber, 1991). Although SWRRBWQ is no longer under
active development, the technology is being incorporated into the Soil and Water
Assessment Tool (SWAT) as part of the Hydrologic Unit Model for the United
States (HUMUS) project at Temple, Texas (Arnold et al., 1993; Srinivasan and
Arnold, 1994). EPA's Office of Science and Technology (OST) has recently
developed a Microsoft Windows-based interface for SWRRBWQ to allow
convenient access to temperature, precipitation, and soil data files.
Storm Water Management Mode! (SWMM). SWMM is a comprehensive
watershed-scale model developed by EPA (Huber and Dickinson, 1988). It was
initially developed to address urban stormwater and assist in storm-event analysis
and derivation of design criteria for structural control of urban stormwater
pollution, but it was later upgraded to allow continuous simulation and application
to complex watersheds and land uses. SWMM can be used to model several types
of pollutants provided that input data are available. Recent versions of the model
can be used for either continuous or storm event simulation with user-specified
variable time steps. The model is relatively data-intensive and requires special
effort for validation and calibration. Its application in detailed studies of complex
watersheds might require a team effort and highly trained personnel. In addition to
developing comprehensive watershed-scale planning, typical uses of SWMM
include predicting combined sewer overflows, assessing the effectiveness of BMPs,
providing input to short-time-increment dynamic receiving water quality models,
and interpreting receiving water quality monitoring data (Donigian and Huber,
1991). EPA's Office of Science and Technology distributes a Microsoft Windows
interface for SWMM that makes the model more accessible. A postprocessor
allows tabular and graphical display of model results and has a special section to
help in model calibration.
The Hydrological Simulation Program - FORTRAN (HSPF). HSPF is a
comprehensive package developed by EPA for simulating water quantity and
quality for a wide range of organic and inorganic pollutants from agricultural
watersheds (Bicknell et al., 1993). The model uses continuous simulations of
Watershed Loading Models 13
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water balance and pollutant generation, transformation, and transport. Time series
of the runoff flow rate, sediment yield, and user-specified pollutant concentrations
can be generated at any point in the watershed. The model also includes instream
quality components for nutrient fate and transport, biochemical oxygen demand
(BOD), dissolved oxygen (DO), pH, phytoplankton, zooplankton, and benthic
algae. Statistical features are incorporated into the model to allow for frequency-
duration analysis of specific output parameters. Data requirements for HSPF are
extensive, and calibration and verification are recommended. The program is
maintained on IBM microcomputers and DEC/VAX systems. Because of its
comprehensive nature, the HSPF model requires highly trained personnel. It is
recommended that its application to real case studies be carried out as a team
effort. The model has been extensively used for both screening-level and detailed
analyses. The Chesapeake Bay Program is using HSPF to model total watershed
contributions of flow, sediment, nutrients, and associated constituents to the tidal
region of the Bay (Donigian et al., 1990; Donigian and Patwardhan, 1992). Moore
et al. (1992) describe an application to model BMP effects on a Tennessee
watershed. Scheckenberger and Kennedy (1994) discuss how HSPF can be used in
subwatershed planning. Ball et al. (1993) describe an application of HSPF in
Australia. Lumb et al. (1990) describe an interactive program for data
management and analyses that can be effectively used with HS and Lumb and
Kittle (1993) present an expert system that can be used for calibration and
application of HSPF.
14 An Overview of Available Endpoints and Assessment Tools
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Lakes and Reservoirs
Lakes and reservoirs are among the water resources identified as part of EPA's
National Nutrient Assessment Strategy. They are especially vulnerable to the
effects of nutrient overenrichment because of their long residence time.
Eutrophication in lakes and reservoirs can manifest itself in many ways, including
as plankton surface scums, excessive macrophyte growths, seasonal blue-green
algal blooms, and decreased dissolved oxygen concentrations. Treated drinking
water taken from eutrophic lakes and reservoirs can also potentially be
contaminated with disinfection by-products such as trihalomethanes, posing a threat
to human health. Through the biennial National Water Quality Inventory Report to
Congress, state officials consistently identify nutrients as the cause of more lake
and reservoir impairments than any other single pollutant (USEPA, 1992, 1994a).
In some respects, the body of science regarding the causes and effects of
eutrophication in lakes and reservoirs is more mature than it is for other
waterbodies. A great deal of research has been conducted in this area dating back
to the work of Vollenweider in the mid- to late-1960s, and the linkage between
nutrient loading and the eutrophication of lakes and reservoirs has been strongly
established in the literature (e.g., Vollenweider, 1968; Hutchinson, 1973; Wetzel,
1983). Many lake and reservoir managers have taken advantage of this by
applying the existing base of knowledge to the management of their individual
lakes. Nevertheless, there is no widely accepted approach to managing nutrient
overenrichment and many communities continue to suffer the ill effects of human-
induced eutrophication.
The relationship between nutrient loading and eutrophication is complicated by a
variety of physical, chemical, and biological factors that make each lake, reservoir,
and watershed unique. In some waterbodies, for example, increased sedimentation
(and corresponding loss of volume) of nutrient-rich soils and partially decomposed
plant material is an important part of the eutrophication process (Cooke and
Carlson, 1989). Internal loading of nutrients from the sediment may also drive
biological production cycles in many lakes (e.g., Cooke et al., 1993; van der Molen
and Boers, 1994), and the growth of nuisance vegetation may often be controlled
by factors such as the amount of available light, grazing populations, or water
temperature. Resource managers must keep all of these factors in mind as they
attempt to formulate a strategy to address nutrient overenrichment.
State of the Science—Endpoints
A review of the available literature suggests that a number of water quality
parameters have been used to characterize the nutrient enrichment of lakes and
reservoirs. In some instances these parameters have been used on a statewide
Lakes and Reservoirs 15
-------
basis; in other instances they have been specifically designed for individual lakes.
Still other parameters have simply been proposed in the literature.
Carlson (1984) points out the importance of distinguishing between causal factor
parameters (e.g., phosphorus) and biological response parameters (e.g., algal
biomass). Endpoints of both types of factors have been used to evaluate, classify,
and set standards for lakes and reservoirs. Other parameters include hypolimnetic
oxygen depletion rate and odor and taste indicators. Presented below are short
descriptions of these parameters.
Causal Factor Parameters
Total Phosphorus. Perhaps the most common current nutrient enrichment
endpoint in lakes and reservoirs is total phosphorus concentration. Total
phosphorus standards have been used to address eutrophication in the Great Lakes,
Lake Champlain, Lake Okeechobee, and a number of smaller watersheds (NALMS,
1992; Smeltzer, 1992; Goldstein and Ritter, 1993; Heiskary and Walker, 1988).
These standards are typically based on summer ambient levels and can range
anywhere from 7 to 200 pg/L (MWCG, 1982). The use of spring total phosphorus
has also been shown to be an effective early warning predictor of summer algal
levels (Jones et al., 1979) and might prove to be a highly cost-effective endpoint.
Several studies have shown it to be an effective predictor of summer mean and
summer maximum chlorophyll a in both temperate and subarctic lakes (Ostrofsky
and Rigler, 1987).
Phosphorus has been commonly used as an enrichment endpoint because of its
direct correlation with the associated negative effects of eutrophication. It is most
often the limiting nutrient that controls the growth of nuisance algae and
macrophytes and can therefore be used to predict their growth. Phosphorus is also
relatively inexpensive to monitor and is already incorporated into most monitoring
programs. Most simulation models incorporate phosphorus concentrations either as
an input variable or as part of model output.
One concern with using total phosphorus as an endpoint is that the nutrient itself is
not what hinders water use (Walker, 1979). There are those who would argue that
only use-related parameters (such as algal biomass or fish kills) should serve as
endpoints. Another concern arises in situations where the limiting nutrient is
unclear or might change by season. A phosphorus endpoint in a nitrogen limited
lake, for instance, would be a misdirected goal.
Total Nitrogen Concentration. Several states reported using total nitrogen
concentration as a eutrophication-based water quality standard in 1987 (NALMS,
1988). However, since freshwater systems are more often phosphorus, rather than
nitrogen-limited, relatively little attention has been focused on using this parameter
as a eutrophication endpoint. This is reflected by that fact that it has not been as
16 An Overview of Available Endpoints and Assessment Tools
-------
extensively studied as has phosphorus and by the lack of sophisticated models that
adequately account for its effect on the eutrophication process. Nitrogen might be
an appropriate endpoint only for those highly productive lakes and reservoirs that
are moving toward nitrogen limitation.
Nkrogen:Phosphorus Ratio. For those lakes and reservoirs which might be
approaching nitrogen limitation, the nitrogen-to-phosphorus ratio, both of loadings
and of standing concentrations, can provide important insight regarding which
nutrient should be controlled. Nitrogen and phosphorus are taken up by algae in
an approximately constant ratio of 16 atoms of nitrogen per 1 atom of phosphorus,
or 7.2:1 by weight. The practical range around this number is 10-20 (Chiaudani
and Vighi, 1974; Boynton et ah, 1995; Thomann and Mueller, 1987). Waters with
relative concentrations, then, of <10:1 nitrogen to phosphorus might have
insufficient nitrogen for algal uptake relative to the available phosphorus. Nitrogen
availability limits plant growth in these situations. When nitrogen:phosphorus is
>20, the converse may be true: phosphorus becomes the limiting nutrient for plant
production. An assessment of potential limitation at intermediate values is
problematic. Complicating factors involve other limitations (e.g., light), the
presence of nitrogen-fixing algae, and the availability of the forms of nitrogen and
phosphorus present. Bioassays have been used to assess nutrient limitation; for
fresh waters, a standardized test has been developed.
Biological Response Parameters
Although macrophytes play a dominant role in many lakes and reservoirs, algal
biomass in the open water is traditionally the parameter used to characterize
nutrient enrichment. Due to the difficulty in analyzing biomass, limnologists have
turned to two popular biomass surrogates, chlorophyll a concentration and Secchi
disk depth.
Chlorophyll a. Chlorophyll a is the dominant pigment in algal cells and is fairly
easy to measure. Even though chlorophyll concentration varies from species to
species and fluctuates according to light intensity, it still remains a valuable
surrogate for algal biomass (Carlson, 1980; Watson, et al., 1992). Several states
have adopted chlorophyll a concentrations as standards for lake quality. Oregon
has set an endpoint of 10 ug/L for natural lakes that thermally stratify and 15 ug/L
for natural lakes that do not thermally stratify (NALMS, 1992). Similarly, North
Carolina uses a standard of 40 ug/L for warm waters and 15 ug/L for cold waters
(NALMS, 1992). On the regional level, Raschke (1994) has proposed a mean
growing season limit of 15 ug/L for water supply impoundments in the
southeastern United States and a value of 25 ug/L for waterbodies primarily used
for other purposes (e.g., viewing pleasure, safe swimming, fishing, boating).
Lakes and Reservoirs 17
-------
Chlorophyll a is desirable as an endpoint because it closely reflects use impairment
(often it is the impairment) and because it can usually be closely correlated to
loading conditions. Both seasonal mean and instantaneous maximum
concentrations can be used to determine violations, and most monitoring programs
already include measurements for chlorophyll.
Chlorophyll might not be an appropriate endpoint in instances where use
impairment is more closely related to excessive macrophyte or attached algae
growth. There also might be instances where the relationship between nutrient
concentrations and chforphyll response is highly variable and difficult to predict.
Laws and Chalup (1990), for example, have shown that the correlation between
growth rate and chlorophyll axarbon is positive under nutrient-limited conditions
and negative under nutrient-saturated (light-limited) conditions. This might
complicate the ability to make management decisions based on targeted chlorophyll
concentrations. Other potential drawbacks associated with using chlorophyll
include the lack of a standardized testing methodology and its high spatial and
temporal variability.
Secchi Depth. Due to its simplicity and low cost, Secchi depth is the most widely
used surrogate for estimating algal biomass and, subsequently, trophic state
(Michaud, 1991). It is, however, a much more indirect measure and subject to
interferences from a variety of sources. Secchi depth has been shown to be highly
correlated to chlorophyll a concentrations (Rast and Lee, 1978) and is a
particularly important measure because water clarity is easily perceived by the
public (Thomann and Mueller, .1977). However, lake and reservoir managers must
still be able to relate desired Secchi depths with nutrient loads. Secchi depth
might be a reliable indicator of the trophic state of a waterbody provided that
water clarity is primarily dependent on algal biomass (i.e., the amounts of
inorganic turbidity and color present in the water column are low).
Six states reported using Secchi depth as a eutrophication-based water quality
standard in 1988 (NALMS, 1988), and Raschke (1993) reports on using a mean
growing season Secchi depth endpoint of >1.5 meters for water supply
impoundments in the southeastern Piedmont. For impoundments used for fishing
and swimming, >1 meter is considered acceptable. Secchi depth was also
included as one of the parameters to be used in the surface waters component of
the Environmental Monitoring and Assessment Program (EMAP) (Whittier and
Paulsen, 1992).
Other biological response factors that have potential for use as water quality
endpoints include the following:
Macrophyte Coverage or Density. Newbry et al. (1981) recommend using percent
macrophyte coverage as a potential nutrient enrichment endpoint. Specifically, the
endpoint would be the percentage of the waterbody having a depth of 2 meters or
18 An Overview of Available Endpoints and Assessment Tools
-------
less that is impaired by macrophyte growth during peak recreation use. Other
researchers have suggested a similar approach, but a somewhat deeper cutoff point
(Porcella et al., 1980). This potential endpoint might be particularly appropriate
for those shallow lakes and reservoirs where users are aware of and sensitive to
changes in the abundance and distribution of macrophytes (e.g., the southeastern
United States). One confounding issue related to macrophyte density is the
positive relationship between increasing water clarity and the extent of macrophyte
beds (Quinn, 1991). A limitation involved with using macrophyte measurements
as endpoints is the difficulty involved with predicting whether a system will be
dominated by macrophytes or plankton.
Fish Yields/Quality. Lee and Jones (1991) discuss the effects of eutrophication on
fisheries and also introduce an approach for estimating the fish yield that can be
associated with changing phosphorus loadings. Fish yields were also included as
indicators in the surface waters component of the Environmental Monitoring and
Assessment Program (Whittier and Paulsen, 1992). This endpoint is obviously
attractive for lakes or reservoirs where fishing is a primary use.
Biological Indicators. A number of states have used biological indicators in
setting stream and river standards, although it does not appear that any have
developed indices specifically designed for lakes or reservoirs (Hughes et al.,
1992). Proposed biological indicators have attempted to incorporate information
on fish, benthic invertebrates, zooplankton assemblages, algae, macrophytes, etc.
An advantage of using biological indicators is that they are not as subject to
temporal variability as are chemical pollutants (NALMS, 1992). However, a
disadvantage associated with biological indicators is that they might reflect
impairments not necessarily caused by cultural eutrophication (i.e., they are better
at indicating change itself than they are at providing information on the cause of
change (Hughes et al., 1992).
Sedimentary Diatom Assemblages. The emerging field of paleolimnology has
shown that sedimentary diatom assemblages can be used to determine baseline
trophic conditions and natural variability in lakes and reservoirs (Dixit et al.,
1992). In addition to providing information on historical conditions, these algal
microfossils can also be used to detect water quality trends occurring during more
recent years; they could therefore serve as potential early warning indicators of
eutrophication. Sedimentary diatom assemblages were one of the parameters
measured as part of the Northeast Lakes Pilot of the Environmental Monitoring
and Assessment Program (Larsen et al., 1991; Hughes et al., 1992).
Other Factors
Dissolved Oxygen Concentration. Dissolved oxygen concentration could be used
as a eutrophication endpoint in waterbodies where a primary concern is support of
aquatic life. It could be measured as end of summer concentration in the
Lakes and Reservoirs 19
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hypolimnion, the date at which a lake or reservoir becomes anoxic, or the length of
time a system is anoxic. Problems associated with using dissolved oxygen as an
endpoint are related to the high spatial and temporal variability in its measurement
and the fact that some reservoirs (especially southeastern ones) can display rapid
changes between anoxia and oxia.
Others. Other water quality parameters that have at times been mentioned as
potential eutrophication endpoints include extent of submerged aquatic vegetation
(USEPA, 1994b), odor and taste indicators (Hughes and Paulsen, 1990; Seligman
et al., 1992), and treatment plant chlorine demand (Lee et al., I995a). These
potential endpoints might prove to be most appropriate where they relate to
specific considerations in individual lakes and reservoirs. They might be less
applicable across state or ecoregion boundaries than the endpoints discussed
previously.
State of the Science—Models
A discussion of the issues involved with assessing nutrient overenrichment in lakes
and reservoirs would be incomplete without addressing the use of water quality
models. As mentioned in the introduction to the issue papers, numerous watershed
loading models are available for the assessment of nutrient overenrichment, many
of which can be applied across multiple waterbody types. A summary is provided
here of some of the receiving water models that are especially useful for predicting
and assessing the eutrophication process in lakes and reservoirs. These summaries
were prepared based on information from the revised Compendium of Tools for
Watershed Assessment and TMDL Development (USEPA, in review). References
pertaining to each of these models are listed in a separate section at the end of this
paper.
EUTROMOD. EUTROMOD is a spreadsheet-based watershed and lake modeling
procedure developed for eutrophication management, with an emphasis on
uncertainty analysis. The model estimates nutrient loading, various trophic state
parameters, and trihalomethane concentration using data on land use, pollutant
concentrations, and lake characteristics. The model was developed using empirical
data from the USEPA's national eutrophication survey, with trophic state models
utilized to relate phosphorus and nitrogen loading to in-Iake nutrient
concentrations. The phosphorus and nitrogen concentrations were then related to
maximum chlorophyll level, Secchi depth, dominant algal species, hypolimnetic
dissolved oxygen status, and trihalomethane concentration. EUTROMOD allows
for uncertainty analysis by considering the error in regression equations employed,
and utilizing an annual mean precipitation and coefficient of variation to account
for hydrologic variability. EUTROMOD is limited in its application because it is
designed for watersheds in the Southeast and because it provides only predictions
20 An Overview of Available Endpoints and Assessment Tools
-------
of growing season averages. EUTROMOD is distributed by the North American
Lake Management Society (NALMS).
PHOSMOD. PHOSMOD uses a modeling framework described by Chapra and
Canale (1991) for assessing the impact of phosphorus loading on stratified lakes.
A total phosphorus budget for the water layer is developed with inputs from
external loading, recycling from the sediments, and considering losses due to
flushing and settling. The sediment-to-water recycling is dependent on the levels
of sediment total phosphorus and hypoiimnetic oxygen, with the concentration of
the latter estimated with a semi-empirical model. PHOSMOD can be used to make
daily or seasonal analyses and was developed to assess long-term dynamic trends;
output includes tabular and graphical output of lake total phosphorus, percentage of
total phosphorus in sediment, hypoiimnetic dissolved oxygen concentrations, and
days of anoxia. It also is distributed by NALMS.
BATHTUB. BATHTUB applies a series of empirical eutrophication models to
morphologically complex lakes and reservoirs. The program performs steady-state
water and nutrient balance calculations in a spatially segmented hydraulic network
that accounts for advective and diffusive transport, and nutrient sedimentation.
Eutrophication-related water quality conditions (total phosphorus, total nitrogen,
chlorophyll a, transparency, and hypoiimnetic oxygen depletion) are predicted
using empirical relationships derived from assessment of reservoir data (Walker,
1985; 1986). Applications of BATHTUB are limited to steady-state evaluation of
relationships between nutrient-loading, transparency and hydrology, and
eutrophication responses. BATHTUB has been cited as an effective tool for lake
and reservoir water quality assessment and management, particularly where data
are limited (Ernst et al., 1994).
WASPS. WASPS is a general-purpose modeling system for assessing the fate and
transport of conventional and toxic pollutants in surface waterbodies. Its EUTRO5
submodel is designed to address eutrophication processes and has been used in a
wide range of regulatory and water quality management applications. The model
may be applied to most waterbodies in one, two, or three dimensions and can be
used to predict time-varying concentrations of water quality constituents. It might
have some limited applications in lakes due to a lack of internal temperature
simulation. The model reports a set of parameters, including dissolved oxygen
concentration, carbonaceous biochemical oxygen demand (BOD), ultimate BOD,
phytoplankton, carbon, chlorophyll a, total nitrogen, total inorganic nitrogen,
ammonia, nitrate, organic nitrogen, total inorganic nitrogen, organic phosphorus,
and inorganic phosphorus. Although zooplankton dynamics are not simulated in
EUTRO5, their effect can be described by user-specified forcing functions.
CE-QUAL-W2. CE-QUAL-W2 is a two-dimensional, longitudinal/vertical water
quality model that can be applied to most waterbody types. It includes both a
hydrodynamic component (dealing with circulation, transport, and deposition) and
Lakes and Reservoirs 21
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a water quality component. The hydrodynamic and water quality routines are
directly coupled, although the water quality routines can be updated less frequently
than the hydrodynamic time step to reduce the computational burden in complex
systems. Water quality constituents that can be modeled include algae, dissolved
oxygen, ammonia-nitrogen, nitrate-nitrogen, phosphorus, total inorganic carbon,
and pH.
Several limitations are associated with using CE-QUAL-W2 to model nutrient
overenrichment in lakes and reservoirs. Because the model assumes lateral
homogeneity, it is best suited for relatively long and narrow waterbodies that
exhibit strong longitudinal and vertical water quality gradients. It might be
inappropriate for large waterbodies. The model also has only one algal
compartment, and algal succession, zooplankton, and macrophytes cannot be
modeled.
CE-QUAL-ICM. CE-QUAL-ICM incorporates detailed algorithms for water
quality kinetics and can be applied to most waterbodies in one, two, or three
dimensions. Interactions among input variables are described in 80 partial
differential equations that employ more than 40 parameters (Cerco and Cole,
1993). Model outputs include temperature; inorganic suspended solids; diatoms;
blue-green algae (and other phytoplankton); dissolved, labile and refractory
components of particulate organic carbon; organic nitrogen; organic phosphorus;
ammonium; nitrate and nitrite; total phosphate; and dissolved oxygen. Although
the model has full capabilities to simulate state-of-the-art water quality kinetics, it
is potentially limited by available data for calibration and verification. In addition,
the model might require significant technical expertise in aquatic biology and
chemistry to be used appropriately.
22 An Overview of Available Endpoints and Assessment Tools
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Rivers and Streams
The beneficial uses supported by the Nation's rivers and streams continue to be
threatened by the damaging effects of nutrient overenrichment. Nitrogen and
phosphorus loadings originating from wastewater treatment plants, agricultural
fields, industrial discharges and other sources are contributing to excessive plant
growths in rivers and streams of all sizes and in all regions. These plant growths
can clog water intake pipes, use up precious dissolved oxygen when they decay,
and interfere with fishing and other recreational uses. As an indication of the
extent of this problem, the most recent National Water Quality Inventory Report to
Congress stated that nutrients were the second leading cause of impairment in
assessed rivers and streams, behind only siltation (USEPA, 1994a). State officials
reported that nutrients had negatively impacted 37 percent of all the assessed river
and stream miles in the country.
Although the damaging effects of nutrient overenrichment have been recognized
for some time, many states and local communities continue to struggle with
developing an effective strategy for addressing the issue. Rivers and streams are
complicated systems, and it is difficult to accurately assess the nature of nutrient
loadings as well as their impact on the growth of nuisance vegetation. Managers
are also handicapped by their need to consider the role rivers and streams play as
conduits through which nutrients are carried into and impact other waterbodies,
such as lakes, reservoirs, and estuaries.
Background
In rivers and streams, eutrophication can result from an increase in the supply of
inorganic nutrients such as nitrates, ammonia, and soluble reactive phosphorus.
For the purposes of this paper, the focus will be on nutrient overenrichment that
occurs as a consequence of human activity and results in the impairment of river
and stream beneficial uses (e.g., fishing, swimming, and drinking water supply).
To better understand the linkage between nutrient loading and impaired uses, one
must first realize there are various types of rivers and streams that can be affected
by eutrophication.
Rivers and streams represent a diverse set of waterbody systems, ranging from the
deep, slow-flowing lower Mississippi to the cascading, coldwater mountain streams
of the Rockies. A number of different concepts have been used to describe this
diversity (Johnson et al., 1995). For example, the river-continuum concept
specifies that rivers and streams can be categorized according to stream order. A
first-order stream has no tributaries, whereas a second-order stream is formed when
two first order streams join. When two second-order streams meet, they form a
third-order stream and so on (Johnson et al., 1995). Within this concept, stream
orders of first to third are considered small streams, fourth to sixth are considered
Rivers and Streams 23
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medium-sized rivers, and those greater than sixth order are considered large rivers.
The significance of the stream order concept is that the structure and function of
small stream biotic communities are very much different from those of large rivers
(Johnson et al., 1995). For example, in small forest streams the existence of a
canopy reduces the amount of light available for photosynthesis. This means that
the primary energy source is likely to be terrestrial leaf litter and the dominant
invertebrate species will be shredders and collectors. Conversely, there is typically
more light available in mid-size rivers; the main energy source is autochthonous
production1, and the dominant invertebrate groups are grazers that feed by scraping
algae and microbes off rocks (Johnson et al., 1995). These grazers can have a
profound impact on whether nutrient-enriched benthic algae will grow to nuisance
levels (Walton et al., 1995).
In addition to the continuum concept, rivers and streams can be described
according to their flow characteristics. A high-gradient stream is one that is
located along relatively steep slopes, displays relatively high velocities, and is
more likely to have rapids, Whitewater, and similar features; low-gradient streams,
on the other hand, follow more gradual terrain and therefore have slower currents
and longer residence times. The distinct physical conditions that exist in these two
types of systems have a significant impact on eutrophication conditions. For
example, research has shown that the growth of benthic algae can be highly
dependent on stream current velocity (Horner et al., 1990; Welch, 1989; see
discussion below).
Another way to distinguish different types of rivers and streams, and the one that
is perhaps of most significance for the purposes of this paper, is by their dominant
plant types. Plankton-dominated systems are those with large populations of
freely floating microscopic plants such as diatoms, blue-green algae, and flagellates
(Quinn, 1991). Periphyton (or benthic algae)-dominated systems, on the other
hand, are impaired by plants that grow attached to the streambed or on solid
objects like logs. One of the most common groups of benthic algae are the
filamentous greens, such as Cladophora. The nuisance effects of both plankton
and periphyton are described in Tables 1 and 2 (adapted from Quinn, 1991).
The processes governing the growth of nuisance plants (especially periphyton) in
rivers and streams are not nearly as straightforward as they are for other
waterbodies. In lakes, for example, the biomass of plankton per unit volume of
water is proportional to the initial mass of limiting nutrient per unit volume (Welch
et al., 1989). This relationship, which has been shown in the laboratory and
'Autochthonous production refers to production originating in the river itself (as opposed to being from
terrestrial sources),
24 An Overview of Available Endpoints and Assessment Tools
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Table 1. Potential nuisance effects of excessive phytoplankton growth with possible
nutrient enrichment endpoints (from Quinn, 1991).
Water Uses
Water Supply
Aesthetic appeal
Recreation
Aquaculture
Ecosystem Protection
Nuisance Effects
• Taste and odor problems
* Production of toxins (e.g., by blue-green algae)
• Blockage of intake screens and filters
* Disruption of ffocculation and chlorination processes in
water treatment plants.
• Reduced clarity and altered color
* Surface scums (including "red tides") and floating mats
• Boating, swimming, water skiing and other water-based
recreation restricted or degraded.
• Fish kills (via toxicity)
• Shellfish contamination resulting in human poisoning
* Diurnal fluctuations in pH and dissolved oxygen that can
stress or eliminate sensitive species
• Oxygen depletion in bottom water through decay of organic
material eliminates sensitive species and releases sediment
phosphorus
• Reduced light penetration may cause macrophyte decline
Possible
Endpoints
• Odor and taste
indicators
• Cost of
treatment
* Secchi depth
* Secchi depth
• Chlorophyll a
• Fish advisories
• pH
• Dissolved
oxygen
• Secchi depth
Table 2. Potential nuisance effects of excessive periphyton growth (from Quinn, 1991).
Water Uses
Water Supply
Aesthetic appeal
Recreation
Ecosystem Protection
Nuisance Effects
• Blockage of intake screens and filters
• Reduced clarity and altered color due to sloughed material
• Floating mats
* Strandings on river margins during flow recessions cause
odor
• Swimming and other water based recreation restricted or
degraded due to aesthetic degradation
* Slippery bed makes wading dangerous
• Sloughed material fouls fisher' lines and nets
• Dense algal mats restrict invertebrates preferred as food by
sports fish
• Diurnal fluctuations in pH and dissolved oxygen that can
stress or eliminate sensitive species
• Dense mats covering the bed reduce intergravel flow and
habitat quality for benthtc invertebrates and fish spawning
Possible
Endpoints
• Cost of
treatment
• Black disk.
* Biomass
• Odor indicators
• Biomass
• Black disk
• pH
* Dissolved
oxygen
* Biomass
Rivers and Streams
25
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frequently observed in the field (e.g., VoIIenweider, 1968; Lee et al., 1995) makes
the selection of nutrient endpoints for lakes and other lentic systems somewhat
clear (i.e., a certain algal biomass is expected given a certain nutrient
concentration). Such a linear relationship between ambient nutrient concentrations
and periphyton biomass has not been observed in rivers and streams (Jones et al.,
1984) and may not exist (Welch, 1994). A number of factors other than nutrient
concentration govern periphyton biomass growth in rivers and streams, and the
quantitative relationship between nutrient supplies and algal biomass in lotic
systems has not yet been well characterized (Dodds and Smith, 1995). Nutrients
receive the most attention only because the other factors are nearly impossible to
control (Ingman, 1992).
One of the most important factors controlling periphyton growth in rivers and
streams is velocity. Horner et al. (1990) and others have shown in laboratory
streams that biomass growth is positively related to stream velocity in the range of
0 to 60 cm/s (after which increases in velocity decrease biomass growth by
increasing erosion due to abrasion by suspended sediments.) Researchers believe
that higher stream velocities enhance algal growth "by reducing the thickness of
the ... nutrient-depleted laminar boundary layer adjacent to the growing surface"
(Dodds and Smith, 1995).
As mentioned previously, grazing pressure might also play a significant, non-
nutrient-dependent role in periphyton growth. Grazing by aquatic insects has been
shown to affect periphyton populations by decreasing biomass, affecting primary
productivity, and changing the taxonomic composition and community structure
(Walton et al., 1995). Other important factors that affect nuisance plant growth
include frequency of scouring floods, quantity of suspended sediment, degree of
shading, and types of substrata (Quinn, 1991). Water resource managers must
recognize that the eutrophication process in rivers and streams is governed by the
interactions between all of these various factors. They make the adoption of an
effective, comprehensive nutrient enrichment strategy for rivers a complex process.
State of the Science—Endpoints
Selecting Endpoints
A review of the available literature suggests that there are several examples of
rivers and streams with different nutrient enrichment endpoints already in place.
These are described below along with other water quality parameters that could
serve as endpoints in certain situations. The complete list of endpoints identified
by participants in the National Nutrient Assessment Workshop is shown in the
Table 3.
26 An Overview of Available Endpoints and Assessment Tools
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Table 3. Potential Endpoints for Plankton- and Periphyton- Dominated Systems.
Plankton Dominated
Algal biomass
pH (maximum and diel)
Dissolved Oxygen (minimum and diel)
Transparency (Secchi depth)
Biointegrity (macroinvertebrate index,
community composition)
Total suspended solids, volatile suspended solids,
ratios
Dissolved organic material
Autotrophic Index (AFDW/CNa)
Total nitrogen
Total phosphorus
Ratios of summer/winter nutrient concentrations
Ratios of dissolved/total nutrient concentrations
Aesthetics (foam, scum)
Periphyton Dominated
Algal biomass (mg/nr, percent coverage)
pH (maximum and diel)
Dissolved Oxygen (minimum and diel)
Transparency (Black disk)
Biointegrity (macroinvertebrate index,
community composition)
Total suspended solids, volatile suspended solids,
ratios
Dissolved organic material
Autotrophic Index (AFDW/chl a)
Total nitrogen, dissolved inorganic nitrogen
Total phosphorus, soluble reactive
phosphorus
Ratios of summer/winter nutrient concentrations
Ratios of dissolved/total nutrient concentrations
Aesthetics (foam, scum)
Periphyton Biomass. Perhaps the most obvious example of an endpoint for
periphyton-dominated rivers and streams would be periphyton biomass. Periphyton
biomass can be measured either qualitatively (e.g., no visible growths on hand-held
stones) or quantitatively (e.g., ash-free dry weight or milligrams of chlorophyll a
per square meter) (Quinn, 1991). The primary advantage of this measurement is
that it directly reflects the water quality characteristic that impairs use. In this way
biomass endpoints force managers to focus on all of the factors that contribute to
periphyton growth, instead of relying only on nutrient controls to provide relief.
(For example, repairing the canopy in a small river could potentially cause light to
become a limiting factor.) The primary disadvantage associated with using
periphyton biomass as an endpoint is the cost and difficulty associated with its
monitoring.
An example of the adoption of algal biomass as a target is in the Clark Fork River
in the states of Washington, Idaho, and Montana. The target is a mean value of
100 rng chlorophyll aim2 and a maximum value of 150 mg chlorophyll aim2.
These values were chosen based on a literature review performed to determine
what levels of algae interfere with beneficial water uses (Ingman, 1992), and they
resemble levels proposed by Horner et al. (1983) and Welch et al. (1988). The
targets have been adopted as part of the Clark Fork - Pend Oreille Basin
Management Plan (USEPA, 1993). A variety of actions have been planned to
achieve these targets, including instituting a basinwide phosphorus detergent ban
and making improvements at municipal wastewater treatment facilities.
Dissolved Oxygen Concentration. Dissolved oxygen concentrations are an ideal
endpoint where the primary beneficial use to be protected is support of aquatic life.
Rivers and Streams
27
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Such an endpoint could be stated as a minimum daily value or as an average value
over a certain period (e.g., weekly, monthly, or seasonally). The advantage of
using a daily minimum value is that this reflects what organisms (especially fish)
respond to. However, practical limitations involved with daily monitoring of
dissolved oxygen have often meant that the standard applies to a longer period of
time. The spatial variability associated with dissolved oxygen readings also makes
a longer monitoring period attractive. Current criteria for dissolved oxygen in
ambient fresh waters have been established primarily on the basis of lethal
conditions for freshwater fish (USEPA, 1986.) The criteria stipulate 30-day means
of 6.5 and 5.5 mg/L and an acute, one-day (instantaneous) minima of 4.0 mg/Land
3.0 mg/L for cold waters and warm waters, respectively.
pH. pH measurements might be another parameter that is useful in instances
where protection of aquatic life is of utmost importance. pH levels in gravel-
bottom rivers with large periphyton biomass can be as high as 10, severely
restricting the ability of stream organisms to function normally. A difficulty
associated with this parameter is that factors other than eulrophication might be
affecting water acidity. One advantage of using pH as an endpoint is that pH can
be inexpensively monitored by nontechnical personnel.
Transparency. Transparency, as measured by Secchi depth, would be a very
effective nutrient overenrichment endpoint in those rivers and streams which are
plankton-dominated. Its advantages include its simplicity, low cost, and
acceptability (Michaud, 1991). Its chief disadvantage in terms of assessing nutrient
overenrichment is that it is only an indirect indicator of eutrophication. One
cannot tell strictly from Secchi readings whether a river is impaired by high algal
growths or by some other conditions, such as elevated levels of suspended
sediments or color. Transparency would not be an appropriate indicator in high-
gradient, periphyton-dominated systems.
Biointegrity/Macroinvertebrate Index. A number of states have used biological
indicators in setting stream and river standards (Hughes et al., 1992). The Ohio
EPA uses the index of biotic integrity (IBI), for example, to assess the aquatic life
in its rivers and streams (Hughes et al., 1992). Biological indicators are
advantageous in that they relate broadly to ecological condition, which is a primary
concern of the public. However, it may be difficult to use these indicators in
situations where a number of factors (in addition to nutrient enrichment) are
affecting biotic integrity.
Nitrogen. Nitrogen concentrations can serve as useful endpoints in those systems
where nitrogen is potentially the limiting factor. They can be measured as either
total nitrogen or dissolved inorganic nitrogen (nitrate, nitrite, and ammonia).
However, limiting concentrations in severely enriched waters might often be so
low as to preclude serving as practical targets. This might be especially true for
rivers affected by the filamentous green species Cladophora, which is able to
28 An Overview of Available Endpoints and Assessment Tools
-------
survive in relatively low nitrogen environments (Ingman, 1992). The lack of
understanding concerning the level of nuisance vegetative growth associated with
nitrogen concentrations may also pose a challenge to using this nutrient as an
endpoint. As mentioned above, other factors such as stream velocity, grazing
populations, and light availability are likely to play an important role in periphyton
growth.
Nevertheless, nitrogen concentration endpoints might still provide a variety of
useful purposes. Where the limiting concentration is known, for instance, it could
serve as the long-term goal of a nutrient management plan. Somewhat higher
values could then be adopted as intermediate goals. Nitrogen endpoints could also
be used to control the extent of nuisance growth, if not the total yield. Data
suggest, for example, that nutrient additions beyond the range of 40 to 100 jug/L
dissolved inorganic nitrogen will not the increase periphyton yield immediately
downstream of a discharge, but might increase the downstream extent of
periphyton proliferations (Quinn, 1991). A nitrogen endpoint that aims to limit the
distance downstream at which periphyton growth reaches nuisance levels could
therefore be instituted.
The nitrogen targets in the Clark Fork management plan mentioned earlier are 300
ug/L total nitrogen and 30 ug/L dissolved inorganic nitrogen (Ingman, 1992).
These levels were based on the nitrogen concentrations found in reaches of the
Clark Fork where algae are not a frequent problem.
Phosphorus. As with nitrogen, phosphorus endpoints (measured as either total
phosphorus or soluble reactive phosphorus) are not as easy to implement in rivers
and streams as they are in lakes and reservoirs. Again, limiting concentrations
might be so low as to be difficult to achieve and an adequate relationship between
phosphorus and algal growth might not be available. For the Spokane River,
Welch et al. (1989) report that biomass levels exceeding 200 mg chlorophyll aim2
can persist for more than 10 km downstream from a point source unless soluble
reactive phosphorus concentrations are held below 10 ug/L. Bothwell (1985, 1988)
reports that streams can be phosphorus-saturated at concentrations as low as < 1 to
4 ug/L.
Summer phosphorus targets in the Clark Fork River were set at 6 ug/L soluble
reactive phosphorus and 20 ug/L total phosphorus. These were based on ambient
levels in relatively unimpaired reaches of the river (Ingman, 1992).
Ratio of Dissolved to Total Nutrient Concentrations and Ratio of
Summer/Winter Nutrient Concentrations. In addition to using strict nutrient
concentrations as endpoints, another possible methodology is to base management
decisions on the ratios of either dissolved to total nutrients or summer to winter
concentrations. The nitrogen-to-phosphorus ratio, both of loadings and of standing
concentrations, can provide important insight regarding which nutrient should be
Rivers and Streams 29
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controlled. Nitrogen and phosphorus are taken up by algae in an approximately
constant ratio of 16 atoms of nitrogen per I atom of phosphorus, or 7.2:1 by
weight. The practical range around this number is 10 to 20 (Chiaudani and Vighi
1974; Boynton et al., 1995; Thomann and Mueller, 1987). Waters with relative
concentrations, then, of <10:1 nitrogen to phosphorus might have insufficient
nitrogen for algal uptake relative to the available phosphorus. Nitrogen availability
limits plant growth in these situations. When nitrogemphosphorus is >20, the
converse might be true: phosphorus becomes the limiting nutrient for plant
production. An assessment of potential limitation at intermediate values is
problematic. Complicating factors involve other limitations (e.g., light), the
presence of nitrogen-fixing algae, and the availability of the forms of nitrogen and
phosphorus present. Bioassays have been used to assess nutrient limitation; for
fresh waters, a standardized test has been developed.
Others. Numerous other water quality measurements could potentially serve as
nutrient overenrichment endpoints. Some of these might be appropriate for certain
regions or for specific rivers with unique considerations. Many of the following
measurements are not ideal overenrichment endpoints because they describe
conditions that might be unrelated to nutrient loading. They might best be used in
combination with some of the other measurements described previously.
• Total and volatile suspended solids concentrations
• Dissolved organic material
• Benthic community metabolism
• Sediment composition (organics, size fraction, nutrients, profile,
sediment fluxes)
• Secondary production (meiofauna, macroinvertebrates, fish)
• Production/respiration
• Aesthetics (foam, scum)
30 An Overview of Available Endpoints and Assessment Tools
-------
Plankton
Load/response
relationships
QUAL2E
WASPS
CEQUAL-RIV1,
W2
HSPF
Periphyton
Concentration/
response
relationships
9
Research needs <
'x
aj
0.
o
(J
£
ca
0
identified
Figure I. Models/assessment tools available for
plankton and periphyton dominated systems.
State of the Science—Receiving Water Models
Several widely available simulation models can be used to assess aspects of the
nutrient overenrichment process in rivers and streams (see Figure 1, for example).
Plankton-dominated systems can be well described by currently available models
that incorporate the dynamics of algal growth. Modeling of periphyton-dominant
systems is limited by our understanding of the growth processes. Because the
underlying chemical, physical, and biological processes are so complex, the
accuracy that can be attained from using these models varies. Nevertheless, the
ability to predict nutrient and dissolved oxygen concentrations, as well as algae and
macrophyte levels, is essential to the water quality management process. The
following summaries describe the state of the science regarding the available
models. The descriptions are based on information from the revised Compendium
of Tools for Watershed Assessment and TMDL Development (USEPA, in review).
QUAL2E. The Enhanced Stream Water Quality Model (QUAL2E), originally
developed in the early 1970s, is a one-dimensional water quality model that
assumes steady-state flow but allows simulation of diurnal variations in
temperature or algal photosynthesis and respiration (Brown and Barnwell, 1987.)
QUAL2E represents the stream as a system of reaches of variable length,' each of
which is subdivided into computational elements that have the same length in all
reaches. Withdrawals, branches, and tributaries can be incorporated into the
prototype representation of the stream system. The basic equation used in
QUAL2E is the one-dimensional advection-dispersion mass transport equation. An
implicit, backward difference scheme, averaged over time and space, is employed
Rivers and Streams
31
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to solve the equation. Water quality parameters simulated include conservative
substances, temperature, bacteria, biochemical oxygen demand, dissolved oxygen,
ammonia, nitrate, organic nitrogen, phosphate, organic phosphorus, and algae.
QUAL2E includes components that allow quick implementation of uncertainty
analysis using sensitivity analysis, first-order error analysis, or Monte Carlo
simulation. The model has been widely used for stream waste load allocations and
discharge permit determinations in the United States and other countries. Paschal
and Muller (1991) used QUAL2E to evaluate the effects of wastewater effluent on
the South Platte River from Chatfield reservoir through Denver, Colorado, and
Johnson and Mercer (1994) report a QUAL2E application to the Chicago waterway
and Upper Illinois River waterway to predict dissolved oxygen and other
constituents in the dissolved oxygen cycle in response to various water pollution
controls. EPA's Office of Science and Technology recently developed a Microsoft
Windows-based interface for QUAL2E that facilitates data input and output
evaluation.
WASPS. WASPS is a general-purpose modeling system for assessing the fate and
transport of conventional and toxic pollutants in surface waterbodies. Its EUTRO5
submodel is designed to address eutrophication processes and has been used in a
wide range of regulatory and water quality management applications. The model
may be applied to most waterbodies in one, two, or three dimensions and can be
used to predict time-varying concentrations of water quality constituents. The
model reports a set of parameters, including dissolved oxygen concentration,
carbonaceous biochemical oxygen demand (CBOD), ultimate BOD, phytoplankton
carbon and chlorophyll a, total nitrogen, total inorganic nitrogen, ammonia, nitrate,
organic nitrogen, total inorganic nitrogen, organic phosphorus, and inorganic
phosphorus. Although zooplankton dynamics are not simulated in EUTRO5, their
effect can be described by user-specified forcing functions. Lung and Larson
(1995) used EUTRO5 to evaluate phosphorus loading reduction scenarios for the
Upper Mississippi River and Lake Pepin, while Cockrum and Warwick (1994)
used WASP to characterize the impact of agricultural activities on instream water
quality in a periphyton-dominated stream. Stoddard et al. (1995) describe a fully
three-dimensional application of EUTRO5 in conjunction with the EFDC
hydrodynamic model to assess the effectiveness of options for the removal of total
nitrogen from a wastewater treatment plant.
CE-QUAL-RIV1. The Hydrodynamic and Water Quality Model for Streams (CE-
QUAL-RIV1) was developed to simulate transient water quality conditions
associated with the highly unsteady flows that can occur in regulated rivers. The
model has two submodels for hydrodynamics (RIV1H) and water quality (RIV1Q).
Output from the hydrodyanmic solution is used to drive the water quality model.
Water quality constituents modeled include temperature, dissolved oxygen,
carbonaceous biochemical oxygen demand, organic nitrogen, ammonia nitrogen,
nitrate nitrogen, and soluble reactive phosphorus. The effects of algae and
32 An Overview of Available Endpoints and Assessment Tools
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macrophytes can also be included as external forcing functions specified by the
user.
CE-QUAL-W2. CE-QUAL-W2 is a two-dimensional, longitudinal/vertical water
quality model that can be applied to most waterbodies (Cole and Buchak, 1994),
It includes both a hydrodynamic component and a water quality component. CE-
QUAL-W2 is best applied to stratified waterbodies like reservoirs and narrow
estuaries where large variations in lateral velocities and constituents do not occur.
It might not be appropriate for high-flow streams and rivers. The model simulates
the interaction of physical factors (such as flow and temperature), chemical factors
(such as nutrients), and algal interaction. The water quality and hydrodynamic
routines are directly coupled; however, the water quality routines can be updated
less frequently than the hydrodynamic time step thereby reducing the computation
burden for complex systems. A limitation associated with using CE-QUAL-W2 to
address nutrient overenrichment issues is that it has only one algal compartment
and algal succession, zooplankton, and macrophytes cannot be modeled.
CE-QUAL-ICM. CE-QUAL-ICM was developed as the integrated-compartment
eutrophication model component of the Chesapeake Bay model package (Cerco and
Cole, 1993). The model incorporates detailed algorithms for water quality kinetics.
Interactions among variables are described in 80 partial differential equations that
employ more than 140 parameters (Cerco and Cole, 1993). The state variables can
be categorized into a group and five cycles—the physical group, and the carbon,
nitrogen, phosphorus, silica, and dissolved oxygen cycles. An improved finite- '
difference formulation is used to solve the mass conservation equation for each
grid cell and for each state variable. Although the model has been designed for
application in Chesapeake Bay, it can be applied to other waterbodies. One
limitation is the difficulty associated with amassing an adequate amount of data for
calibration and verification. In addition, the model might require significant
technical expertise in aquatic biology and chemistry to be used appropriately.
Rivers and Streams 33
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Estuaries and Coastal Waters
During the National Nutrient Assessment Workshop, several major themes and
recommendations emerged from the detailed discussions of the estuaries and
coastal water group. Perhaps the most pervading challenge in establishing tools
and standards for assessment and management of nutrient inputs to aquatic systems
is the fact that large, real variability exists in physical and biological structure and
processes among all systems. This variability means that a given input might
result in different responses. While science might agree qualitatively about the
expected response, quantitative prediction is rarely if ever possible within
acceptable confidence limits. In addition, regional differences in the
human/societal expectations exist so that what condition is considered "acceptable"
is not uniform. Taken together, these perspectives suggest that arbitrarily defined
standards of general applicability might be untenable and strongly call for a
different approach.
Most of the group's effort was initially directed toward what metrics seem
meaningful, rigorous, and yet practically useful in the assessment of effects. The
group set aside for the moment the issue of subjective definition of standards of
what is acceptable or unacceptable as a basis for regulation. However these
standards are defined, they must be based on acceptable measures of dose
response.
Faced with this, the estuaries work group approached a consensus that the only
practical initial approach is to construct empirical relationships between indicator
responses and probable driving variables. This is essentially the approach taken by
Vollenweider in documenting responses of lakes to phosphorus loading. Some
examples of these empirical relationships are clearly significant statistically, but
they display large variability, even for comparable estuaries. For only
plankton-based systems, for example, chlorophyll stocks show a 10-fold range in
response for similar inputs of total nitrogen. For other types of systems, however,
such relationships have not been adequately explored. The group recommended
that significant effort be devoted to a careful gathering of available information for
a variety of systems, as well as an incisive analysis of relationships. It must be
emphasized that is not a menial task. Care and insight are necessary to evaluate
each published study to ensure appropriate comparisons are made.
A benefit of this approach is that the power of the method will increase with time.
As more information becomes available, three significant areas of progress in the
empirical approach can be anticipated. First, separate relationships might be
developed for different types of systems, effectively stratifying the variance among
more similar groups of sites (e.g., micro- vs. macrotidal). The group separated
coral reefs, seagrass, and plankton-based systems with this rationale. Second,
schemes for parameterizing multiple factors might be developed, within which
34 An Overview of Available Endpoints and Assessment Tools
-------
tighter relationships might be possible. For example, Vollenweider's parameter
normalized phosphorus input to freshwater turnover time. Third, as time series of
data for an increasing number of cases become available, tighter relationships will
emerge, more strongly suggesting site-specific predictive relationships.
In some cases, natural year-to-year variability might define the dose response quite
accurately for a given system. This empirical approach guarantees a number of
benefits. With time, the archive of systems for which diagnostic dose-response
measurements are available will increase. Thus, the use of empirical relationships
has immediate value, but is also a perfect stimulus for adaptive management using
the more predictive relationships that will emerge with time.
The following discussion identifies several measurement indices for which
empirical relationships can be determined in estuaries and coastal waters. It also
addresses several tools to assess and identify nutrient limitation and potential
indicators of historic trends.
State of the Science—Endpoints
Clarity. Clarity is a function of the quantity and spectral quality of light in the
aquatic environment. Nutrient enrichment affects clarity through the promotion of
phytoplankton growth and biornass accumulation. Phytoplankton of various groups
absorb and attenuate light in the water column (Kirk, 1983). They shade each other
and the bottom. At high biomass, conditions of low light selectively favor algal
species that are adapted to low light or have motility, morphological, and/or
buoyancy mechanisms that sustain them near the water surface. By preventing
sufficient light from reaching the bottom, they eliminate most benthic primary
production, leading to the demise of benthic algal and vascular plant populations.
Often these algae are not edible or easily grazed on by zooplankton and fish
planktivores, or they lead to gill-clogging in fish. The result is a shift in trophic
status toward a monocultural, algal-dominated system. The fate of this organic
carbon is microbial breakdown, with subsequent hypoxia/anoxia and organic
accumulation in the sediments.
However, clarity also has contributing factors that are not the result of nutrient
enrichment. These factors include colored dissolved organic matter, such as humic
and fulvic acids, which are the degradation products of organic matter from
terrestrial and aquatic plants and animals. In some regions, rivers deliver large
quantities of dissolved organic matter into estuarine and coastal waters. Dissolved
organic matter is a strong absorber of light in the blue region of the spectrum, near
the blue absorption peak of chlorophyll (Kirk, 1983). Of course, water itself is a
strong absorber in the red region of the spectrum. The light that penetrates waters
high in dissolved organic matter has a yellow quality and is of little use to plants
regardless of how much is present. Another factor in clarity not directly related to
Estuaries and Coastal Waters 35
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nutrient enrichment is the suspended inorganic load, which predominately scatters
light, again most strongly in the blue region of the spectrum (Kirk, 1983),
It is clear, then, that with respect to clarity and nutrient enrichment, only certain
measurement endpoints are applicable. Secchi disk depth, a quick, inexpensive, and
ubiquitous measure of light penetration, is indiscriminant with respect to the
factors affecting clarity. Also, Secchi disk determinations are subject to the
response of the human eye, which is more sensitive to light in the middle of the
visible spectrum, while plants absorb, and therefore require, light in the blue and
red regions of visible light. Therefore, although Secchi depth is directly a measure
of water clarity, it is not the optimal measure of light penetration pertinent to
photosynthesis. The diffuse downwelling light attenuation coefficient (Kd) for
photosynthetically active radiation (PAR) is an endpoint that can be related to
water quality parameters and is relevant for assessment of potential photosynthesis.
It also has the advantage of connecting traditional water quality monitoring and
modeling parameters with a key indicator of habitat quality for plant production,
especially for benthic flora. Measurements of Kd are made with quantum light
sensors. Supporting measurements should include water column chlorophyll a, total
suspended matter, and if warranted by the water body, color or dissolved organic
matter. Advancement of the science of near-shore aquatic optics should involve
spectral characteristics of light penetration and the optically active constituents in
estuarine and coastal waters (e.g., Gallegos, 1994; McPherson and Miller, 1987)
and the relationships between how light conditions are assessed and the natural
(temporal) signals and availability of light in the aquatic environment (Morris and
Tomasko, 1993; Miller and McPherson 1995).
Hypoxia/Anoxia. Dissolved oxygen concentration in natural waters is a function
of physical and chemical factors that determine solubility and the transport of
oxygen across the air-water interface, as well as the mixing of surface and deep
waters. Within a water mass, a mix of biological processes determine oxygen
concentration. Phytoplankton in surface waters and, given sufficient light
penetration, benthic algae and vascular plants produce oxygen via photosynthesis.
Plant, animal, and bacterial respiration consumes oxygen, as do bacterially
mediated transformations of nitrogen during nitrification (oxidizing ammonium to
nitrite and nitrate). Other bacterial processes leading to the reduction of sulfate and
carbon dioxide produce sulfide and methane, which react with and provide
additional demands on dissolved oxygen. Considering especially these biological
processes, nutrient enrichment is often signaled by excessive oxygen production in
surface waters, leading to supersaturation in some cases, and by hypoxia or anoxia
in deep waters when excessive plant production is consumed.
Thus, dissolved oxygen concentration is one of the major endpoints for assessment
of eutrophication in estuaries and coastal waters. Criteria for dissolved oxygen in
ambient (fresh) waters have been established, principally on the basis of lethal low
dissolved oxygen conditions for freshwater fish (USEPA 1986). The criteria
36 An Overview of Available Endpoints and Assessment Tools
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stipulate 30 day means of 6.5 and 5.5 mg/L and acute, ! day (instantaneous)
minima of 4.0 and 3.0 mg/L for cold water and warm water, respectively.
In coastal waters where natural variability is high, long-term records of dissolved
oxygen concentrations in both surface and bottom waters might be necessary for
the evaluation of nutrient enrichment effects (e.g., Justic et al., 1987). In estuarine
and coastal waters, hypoxia, generally where dissolved oxygen concentration drops
below 2.0 mg |-' (Harding et al. 1992), is apparent with alterations in the benthic
macrofaunal community, both in structure and loss of biomass (Smith and Dauer
1994; Schaffneret al., 1992).
Submerged Aquatic Vegetation (SAV) Losses. SAV is composed of flowering
vascular plants (angiosperms) that live completely underwater; a few species have
flowers that protrude through the surface (Hurley, 1990). SAV species are found
from freshwater to marine habitats. While several hundred SAV species are known
from freshwater and brackish habitats, the truly marine species number about 60
(den Hartog, 1970; Dennison et al., 1993). SAV species are relatively sensitive to
the available underwater light; they require approximately 20 percent of daily
incident light for their survival in comparison with other plants (ranging from
planktonic and benthic algae to forest floor dwellers), which require <1 percent of
daily incident light (Dennison et al., 1993; Kenworthy and Haunert, 1991).
In temperate, nutrient-enriched estuaries such as the Chesapeake Bay, this light
requirement restricts the maximum depth of occurrence to 1 to 2 meters (MLW).
Decadal scale changes in water transparency are reflected in the changes in the
historic distributions of SAV (Orth and Moore, 1983, 1986). Simulation analysis
driven by light attenuation coefficients from sites both with and without present
SAV beds also suggest sensitivity to available light as a determinant in the survival
and depth of occurrence of SAV (Wetzel and Meyers, 1994). Nutrient enrichment
represents a large factor in water transparency by supporting increased
phytoplankton biomass. It also enhances epiphytic growth on SAV leaf surfaces
themselves, further limiting the light available to SAV for photosynthesis (Neckles
et al., 1993). This later relationship, however, can be mitigated by extensive
grazing on epiphytes (Neckles et al., 1993).
SAV are an important source of habitat, providing refuge to juvenile fish and
shellfish and providing a food source for fish and waterfowl. Consequently, the
assessment of SAV provides a direct link between water quality (nutrients,
chlorophyll a, and suspended sediments) and ecologically and economically
important species. In addition, the use of SAV as an water quality endpoint is not
confounded by direct human uses, unlike similar assessments for fisheries stocks
(Dennison et al., 1993). Lastly, the sensitive relationship between SAV, water
transparency, and nutrients makes SAV a good indicator of habitat quality.
Estuaries and Coastal Waters 37
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The sensitive nature of SAV relative to available underwater light makes the
maximum depth of individual SAV beds an indicator of habitat quality.
Assessment criteria should be related to the species present or potentially able to
inhabit the site, with targets based on species-specific light requirements for
growth applied to the maximum depth observed for the species in pristine sites
similar to the region of interest. As a guide, a target of not less than 20 percent of
daily irradiance just below the water surface available at the bottom during the
growing season of the plant may be set. At a depth of 2.0 m, this would
correspond to a downwelling diffuse attenuation coefficient of -ln{0.20)/2.0 = 0.80
rrr1. Required knowledge includes key SAV species and their light compensation
points under local conditions, and the desired depth distribution, based on historic
data obtained prior to nutrient enrichment or data from a comparable location.
Geographic (areal) distribution, in concert with maximum depth of distribution,
defines the area of SAV habitat. The availability of this habitat is important for
fish, shellfish, and waterfowl. Monitoring, typically on a large scale with remote
imagery (aerial photography, satellite imagery), in combination with a GIS
database approach, can provide regional areal estimates and the basis for spatial
and temporal trend analysis. NOAA's C-CAP program is evaluating methods and
building a database of land (including submerged lands or estuaries) use and biotic
change using remote sensing techniques (Dobson et al., 1995).
Monospecific Algal Blooms and Trophic Alterations. Alterations in either the
primary production or the consumption of that production can change the state of a
waterbody. Nutrient enrichment can cause such changes. One such alteration is an
ultimate shift from diatom-dominant production, which is easily grazed on and
ultimately beneficial to desirable fish stocks, to other phytoplankton groups that are
less heavily grazed on. Additions of nitrogen and/or phosphorus lead to short-term
increases in diatom production, followed by depletion of dissolved silica (DSi) and
eventually, the replacement of diatoms with green and blue-green algae as DSi
concentrations fall into limiting ranges for diatom growth (Schelske and Stoermer,
1971, 1972). The implications of this for coastal and marine environments were
made clear by Officer and Ryther (Officer and Ryther, 1980, 1981): food webs and
fates of phytoplankton carbon are distinctly different depending on whether
primary production is dominated by diatoms or by other algae (including greens,
flagellates, and blue-greens). Enrichment-induced shifts from a diatom-based food
web lead to changes in food web structure, away from production of desirable fish
species toward the production of excessive, ungrazed algae, which sink and
promote bottom water hypoxia/anoxia. Recent reviews of the global implications of
alterations in the Si:N:P ratio, including increased potentials for toxic and nuisance
algal blooms, food web alterations, and changes in bottom water oxygen dynamics,
further suggest that coastal waters that once had excesses of silicon relative to
nitrogen and phosphorus are now approaching nutrient balance or are experiencing
seasonal silicon limitation (Justic et al., 1995; Conley et al., 1993). This suggests
that coastal areas dominated by direct river discharge will be subject to increasing
38 An Overview of Available Endpoints and Assessment Tools
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alterations in plankton composition, increased occurrences of nuisance algal
blooms, and subsequent changes in trophic structure.
Although not directly impacted by nutrient enrichment, suspension-feeding
populations, both benthic and planktonic, in some cases can exert a primary control
on algal populations and alter suspended particle concentrations. Losses of these
populations by harvesting (shellfish), disease, increases in suspended load,
enrichment-induced hypoxia, or shifts in algal populations represent positive
feedback on eutrophication effects. That is, a control of algal populations that
under other circumstances would counter the enrichment effect, fails, eliciting
greater negative impacts on the ecosystem. Furthermore, with respect to restoration
goals, in the absence of these "top-down" grazer controls, it may be more difficult
or take longe to restore a system using moderate nutrient load reductions.
Dissolved Concentration Potential. Similar to Vollenweider relationships for
lakes, Quinn and others (1989) have proposed the use of the dissolved
concentration potential (DCP) as an index of estuarine susceptibility to
eutrophication. In a comparison mode, the DCP uses a constant loading, L= 10,000
tons/year so that intrinsic physical differences (i.e., flushing ability) among
estuaries can be assessed. For evaluation of an individual estuary's status and
classification relative to the impact of its nutrient loadings, the actual loading value
is used for W.
DCP= (W / Qfw) (Vfw / Vtot)
where:
W = nutrient loading rate (kg d~'),
Vfw = volume of freshwater in the estuary (m"1),
Qfw = rate of freshwater inflow (m1 d~'), and
Vtol = total volume of estuary (m"1).
Annual averages are used for inflows and volumes (NOAA, 1985; Klein and
Orlando, 1989). Essentially, DCP is a loading factor weighted for total volume and
freshwater turnover. Orders of magnitude for potential enrichment impact have
been established: low (0.01-0.10 mg/L, med (0.1-1.0 mg/L), high (1.0-10 mg/L).
Limitations of this index are (1) it assumes conservative behavior of bioactive
nutrient elements; (2) the oceanic nutrient source is neglected; (3) it assumes a
vertically homogeneous estuarine water mass; (4) it ignores variability (seasonal,
aperiodic) in discharges; and (5) to be applicable, it requires a gradient in salinity
relative to the seawater source (e.g., DCP would be a poor predictor of
susceptibility in estuaries dominated by seawater inputs such as Cape Cod Bay).
NOAA's National Estuarine Inventory (NEI) has tabulated estimates of nitrogen
and phosphorus concentrations for given estuaries. Note that the estimates are
based on loadings and are subject to error resulting from the relative degree of
recycling within an estuary, which might be very high (Boynton et al., 1982; Kemp
Estuaries and Coastal Waters 39
-------
et al., 1982), Based on this and on observations of eutrophication impacts within
estuaries and the DCP, classifications of nutrient concentrations were developed:
Nitrogen: low (<0.1 mg/L), medium (0.1-1.0 mg /L), high (>I.O rng/L).
Phosphorus: low (<0.0i mg/L), medium (0.01-0.10 mg/L), high (>0.10
mg/L)
The utility of this classification scheme is problematic. The loadings from which
concentrations were estimated are based on total inputs, some portion of which
(particularly in the case of phosphorus) might not be available to plants because of
its chemical form. Further, estimates based on loadings might not reflect actual
concentrations because of the intensity of recycling within a particular estuary or
subestuary (Boynton et al., 1982). They also do not take into account the relative
recycling rates of nitrogen versus phosphorus or the denitrification potential, which
is a significant loss of nitrogen in estuarine systems (Seitzinger, 1988).
Nitrogen:Phosphorus Ratio. Another proposed indicator of potential enrichment
problems is the nitrogen-to-phosphorus ratio, both of loadings and of standing
concentrations. Nitrogen and phosphorus are taken up by algae in an approximately
constant ratio of 16 atoms of nitrogen per 1 atom of phosphorus, or 7.2:1 by
weight. The practical range around this number is 10-20 (Chiaudani and Vighi,
1974; Boynton et al, 1995; USEPA, 1985). Waters with relative concentrations,
then, of <10:1 nitrogen to phosphorus might have insufficient nitrogen for algal
uptake relative to the available phosphorus. Nitrogen availability limits plant
growth in these situations. When nitrogen:phosphorus is >20, the converse might
be true: phosphorus becomes the limiting nutrient for plant production. An
assessment of potential limitation at intermediate values is problematic.
Complicating factors involve other limitations (e.g., light), the presence of
nitrogen-fixing algae, and the availability of the forms of nitrogen and phosphorus
present. Bioassays have been used to assess nutrient limitation; for fresh waters, a
standardized test has been developed.
Biological Indicators. Detection of incipient change resulting from nutrient
enrichment relies on consistent and continuous monitoring programs. The natural
variability inherent in measurement endpoints from estuarine and coastal waters
makes the interpretation of trends difficult unless a sufficient multiyear record, i.e.,
10 years or more, is available, especially if biological variables are to be used as
indicators.
Benthic fauna biomass and composition, larval fish abundance, and algal and
zooplankton species composition are both affected by and may be good substitutes
for primary endpoints like dissolved oxygen and nutrient concentrations. The use
of these biological indicators as measurement endpoints provides a fundamental
link between water quality and habitat quality, as well as stated assessment
endpoint objectives, i.e., the maintenance of beneficial algal populations, a healthy
40 An Overview of Available Endpoints and Assessment Tools
-------
benthic fauna, and desired abundances of commercially or recreationally important
fish stocks, for restoration plans.
Tools to Assess and Identify Nutrient Limitation
Algal Growth Potential Test. The Algal Growth Potential Test (AGPT)
reviewed by Raschke and Schultz (1987), provides a means to assess and'identify
potential nutrient limitation and the potential impacts of increased concentrations of
a given nutrient on the resultant algal production. Bottle assays of Selenastrum
capriconutum, a freshwater alga, using various test waters (fresh waters only)
based on the premise that yield is proportional to the bioavailable nutrient in least
supply (Liebig's Law of the Minimum) can be used to define nutrient limitation.
The advantage of this test as a standard method is its simplicity and low cost.
Yields respond to bioavailable portions of total nitrogen and total phosphorus
pools. There is no need to assume which nutrient element is limiting, nor assume a
maximum potential growth rate. The test can give maximum potential growth rate
estimates and identify the limiting nutrient. The disadvantages are the questionable
applicability of a standard organism to site-specific, species-specific responses; i.e.,
the test does not consider the ecological or trophic relationships of native species "
and their grazers. There appears to be a need to establish relationship between the
test maximum allowable biomass of Selenastrum capriconutum and that for the
native suite of species present in the waterbody of interest.
Enzyme Assays, In estuarine and coastal waters, as well as in fresh waters,
enzyme assays have been used to assess phosphorus limitation. Vadstein et al.
(1988) and Vargo and Shaney (1985) have shown that phytoplankton alkaline
phosphatase (AP)2 activity might be related to phosphorus limitation. In addition,
bacterial AP as well as S'-nucleotidase (5PN), which cleaves the phosphate moiety
off nucleotides and other organic phosphorus sources, might be indicative of
phosphorus-limited systems or might increase the pool of bioavailable phosphorus
(Ammerman and Azam, 1991). Problems of spatial scale, in terms of relating this
activity to ambient concentrations of organic phosphorus, exist. It has been
suggested that recycling of organic phosphorus to inorganic phosphorus might be
tightly coupled to organic matter excretion within clusters of bacteria and
phytoplankton such that recycling appears to be independent of bulk concentrations
of either soluble reactive phosphorus or organic phosphorus (Ammerman and
Azam, 1991). Further use of such an assay requires more scientific investigation
and a larger database in relation to changes in nutrient enrichment status of a given
waterbody.
Alkaline phosphate is an enzyme present on the outer cell membrane that cleaves the phosphate group off
dissolved organic matter.
Estuaries and Coastal Waters 41
-------
Other elements, notably silica, have an impact on the production of specific algal
groups, i.e., diatoms. The impact of nutrient enrichment and environmental change
on the relative contribution of diatoms to total phytoplankton production and its
implications for trophic alterations are discussed above.
Indicators of Historic Trends
Patterns observed in monitoring programs in estuaries, coastal waters, and their
tributaries might be biased by the relatively brief period of coverage. Changes that
might or might not be attributed to nutrient enrichment because of their ambiguity
need to be placed into a context that extends back prior to the intense coastal
development of the 20th century and, if possible, prior to the intense agricultural
development of the 19th century. Such long-term records of biotic and physical
conditions within estuarine and coastal waters place nutrient enrichment processes
in context with natural long term trends and meterological cycles, which might be
biasing our present view of the situation. Historical records are also useful for
calibrating simulation models prior to the simulation of nutrient enrichment effects
and testing management scenarios for nutrient reduction (Chapra, 1977).
In a review of historic trends in Chesapeake Bay nutrients, D'Elia suggests that a
time series of data should encompass 10 cycles in order to distinguish cyclical
patterns from long-term trends; for a 6-year climatic rainfall cycle, a 60-year
nutrient loading record would be required (D'Elia, 1982). Though few, there are
nutrient, suspended sediment and oxygen records that extend over many decades
through the 20th century and can at least lend weight to the fact that nutrient
enrichment in coastal waters has exerted real impacts on a global scale (Heinle et
al., 1980; Justic et al., 1987; Walsh et a!., 1981; Turner and Rabalais, 1991).
Additional perspective, extending our view centuries into the past, can be obtained
from the sediment record. Paleoecological indicators have been analyzed for a
2,500-year history in Chesapeake Bay (Cooper and Brush, 1993). These indicators
include pollen, diatom assemblages, total organic carbon, nitrogen, sulfur, and the
degree of pyritization. Pollen and charcoal can be used to date
deforestation/agricultural events and natural fires/early industrial activity,
respectively (Brush, 1989). Preserved frustules (silicious, species-specific cell
walls) of diatoms can be used to indicate loss of diversity and shifts in the centric-
to-pennate ratio (c:p). Centric diatom forms are cylindrical and typify planktonic
species, whereas pennate forms are oblate and typify benthic species. Increased
predominance of centric forms indicates shifts from benthic to pelagic primary
production as would accompany increased nutrient loading and turbidity (Cooper
and Brush, 1993). In Chesapeake Bay, there is a dramatic increase in organic
carbon and in sulfur deposition since the mid 1700s, continuing to the present
(Cooper and Brush, 1991, 1993). Similarly, the degree of pyritization, which is the
ratio of pyritic iron to pyritic iron plus acid-soluble iron, which varies with the
oxygen content of bottom waters during deposition (Raiswell et al, 1988), has also
42 An Overview of Available Endpoints and Assessment Tools
-------
increased in the last two centuries of coastal habitation (Cooper and Brush 1991
1993). Since there is no natural signal during this time frame that can compare
with the increase in human activity, the historic record presents a strong case for
the impacts that humans can have on the coastal environment.
The value of these long-term records is that they corroborate long model runs prior
to management scenario testing. Additionally, and perhaps most importantly they
do show a discernible human signal in the environmental record which puts'a
magnitude on the impacts.
State of the Science—Models
A discussion of the issues associated with assessing nutrient overenrichment in
lakes and reservoirs would be incomplete without addressing the use of water
quality models. As mentioned in the introduction to the issue papers, numerous
watershed loading models are available for the assessment of nutrient
overenrichment, many of which can be applied across multiple waterbody types
A summary is provided here of some of the receiving water models that are
especially useful for predicting and assessing the eutrophication process in lakes
and reservoirs. These summaries were prepared based on information from the
revised Compendium of Tools for Watershed Assessment and TMDL Development
(USEPA, in review). References pertaining to each of these models are listed in a
separate section at the end of this document.
WASPS. WASPS is a general-purpose modeling system for assessing the fate and
transport of conventional and toxic pollutants in surface waterbodies. Its EUTRO5
submodel is designed to address eutrophication processes and has been used in a
wide range of regulatory and water quality management applications. The model
can be applied to most waterbodies in one, two, or three dimensions and can be
used to predict time-varying concentrations of water quality constituents. The
model reports a set of parameters, including dissolved oxygen concentration,
carbonaceous biochemical oxygen demand (CBOD), ultimate BOD, phytoplankton
carbon and chlorophyll a, total nitrogen, total inorganic nitrogen, ammonia, nitrate,
organic nitrogen, total inorganic nitrogen, organic phosphorus, and inorganic
phosphorus. Although zooplankton dynamics are not simulated in EUTRO5, their
effect can be described by user-specified forcing functions. Stoddard et al. 0995)
describe a fully three-dimensional application of EUTRO5 in conjunction with the
EFDC hydrodynamic model to assess the effectiveness options for the removal of
total nitrogen from a wastewater treatment plan.
Tidal Prism Model (TPM). TPM was originally developed as a tool for water
quality management of small coastal basins (Kuo and Nei!son,1988). Physical
transport processes are simulated in terms of the concept of tidal flushing. The
numerical solution scheme implemented for solving the tidal flushing equations is
Estuaries and Coastal Waters 43
-------
well suited to application in small coastal basins, including those with a high
degree of branching. The model allows consideration of shallow embayments
connected to the primary branches in the basin. The basic assumptions in the
model are that the tide rises and falls simultaneously throughout the waterbody and
that the system is in hydrodynamic equilibrium. Kinetic formulations in TPM are
similar to those in CE-QUAL-ICM (Cerco and Cole, 1993), and 23 state variables,
including total active metal, fecal coliform bacteria, and temperature, can be
simulated. TPM includes a sediment submodel, also based on the sediment
process model in CE-QUAL-ICM, that considers the depositional flux of
paniculate organic matter, its diagenesis, and the resulting sediment flux. TPM
has been applied to a number of tidal creeks and coastal embayments in Virginia
(Kuo and Neilson, 1988).
CE-QUAL-ICM. CE-QUAL-ICM was developed as the integrated-compartment
eutrophication model component of the Chesapeake Bay model package (Cerco and
Cole, 1993). The model incorporates detailed algorithms for water quality kinetics.
Interactions among variables are described in 80 partial differential equations that
employ more than 140 parameters (Cerco and Cole, 1993). The state variables can
be categorized into a group and five cycles—the physical group, and the carbon,
nitrogen, phosphorus, silica, and dissolved oxygen cycles. An improved finite-
difference formulation is used to solve the mass conservation equation for each
grid cell and for each state variable. Although the model has been designed for
application in Chesapeake Bay, it may be applied to other waterbodies. One
limitation is the difficulty of amassing an adequate amount of data for calibration
and verification. In addition, the model might require significant technical
expertise in aquatic biology and chemistry to be used appropriately.
44 An Overview of Available Enclpoints and Assessment Tools
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Wetlands
Wetlands are consistently cited for their value in the control of nonpoint source
(NFS) pollution through water storage, flood attenuation, and water quality
enhancement through uptake and processing of nutrients, sediments, and toxic
chemicals (see Olson, 1993). Texts have been written on the design, construction,
and use of wetlands specifically for treatment of waste water and enhancement of '
water quality (Hammer, 1989; Moshiri, 1993). Because the purifying capacity of
wetlands is so often identified as fundamental in their value to society, the
question might arise: "Is wetland eutrophication a national problem?" 'After all
wetlands are most often the first line of defense in protecting receiving waters '
from the effects of pollution such as excessive nutrients.
Many authors indicate that potential impacts to natural wetlands from nutrient
enrichment and pollutant overloads are of significant concern to researchers and
resource managers (Olson, 1993; Walbridge, 1993; van der Valk and Jolly 1992-
Bowden et al., 1991; Landers and Knuth, 1991; Hammer, 1989; Johnston *1989-'
Cooper and Gilliam., 1987; Kadlec, 1983). However, scientific understanding of
wetlands, wetland management, and even wetland classification schemes is still
evolving, and synthesizing common information about such variable ecosystems on
a nationwide scale remains an onerous task (see Nixon and Lee, 1986, Knight,
1992). As examples, researchers such as Brinson (1993) Adamus et al. (1987);
and Kent et al. (1992) discuss classification and monitoring strategies for wetlands
and others, such as Howard-Williams (1985) and Johnston (1991) discuss nutrient'
dynamics in various wetlands. However, in the literature reviewed, no examples of
a standardized strategy to assess or manage nutrient overenrichment in the interest
of wetland "health" were found.
The purpose of this working document is to stimulate thought and discussion
regarding how to assess and manage nutrient overenrichment in wetlands. The
literature reviewed and cited does not reflect a comprehensive examination of
relevant research in wetlands, but has been selected to highlight particular issues.
This discussion restricts the definition of "wetlands" to those lands which are
transitional between terrestrial and aquatic systems (for example, shallow,
vegetated tidal and nontidal wetland communities, either separate from or adjacent
to stream, river, lake, and coastal waterbodies). Benthic wetland communities,
such as submerged aquatic vegetation located within streams or rivers, or seagrass
beds in nearshore coastal environs, have been implicitly excluded because they are
part of receiving waters addressed in other sections of this overview.
Wetlands 45
-------
Background
Nationally, natural wetlands continue to experience reduction in abundance and
distribution. Approximately half of the wetlands in the continental United States
have been lost since colonial settlement (Prayer et al., 1983). Although wetland
modification has slowed significantly since the 1950s, wetland losses from
dredging, filling and land development have continued. National policy instituting
a "no net loss" of wetlands was adopted in the mid-1980s in an attempt to reverse
the negative trend.
In July 1990 the USEPA developed national guidance for wetland water quality
standards to be established during fiscal years 1991-1993. The guidance was
developed to ensure that provisions of the Clean Water Act (CWA) applied to
other surface waters were also applied to wetlands. States were required to include
wetlands in their definition of "State Waters," as well as to adopt narrative and
numeric criteria and antidegradation policies for wetland protection (USEPA,
1990). Constructed wetlands, for the specific purpose of wastewater treatment, are
excluded from protection; however, the knowledge gained from the processes
within these wetlands might contribute to developing endpoints or standards
elsewhere. Currently, the standards for wetlands are primarily narrative criteria
developed by states, because it has been difficult to apply certain numeric criteria
to wetlands. For example, dissolved oxygen is hard to standardize because a
wetland can be dry and have zero dissolved oxygen. Enforcement and setting of
permit limits are based on fixed numbers, but for wetlands the limits might be
based on concentrations related to flow or perhaps load-based measures.
On June 10-11, 1991, EPA sponsored a workshop to define scientific and policy
issues concerning wetland quality and nonpoint source (NPS) pollution, and to
evaluate the role of created and natural wetlands in control of rural NPS pollution
(Olson, 1993). General findings of the workshop identified several key points.
Since eutrophication can be considered a subset of NPS pollution, the following
findings and issues provide a basis for further consideration in development of a
national nutrient assessment strategy:
Natural wetlands should not be used as wastewater treatment systems. In most
cases, natural wetlands are considered waters of the United States and thus are
entitled to protection under the CWA. Natural wetlands, while providing NPS
pollution control service, should not have NPS pollutants intentionally diverted into
them. Furthermore, natural wetlands that may be in threat of significant
community changes should be protected from NPS sources through the use of
BMPs or vegetated buffer strips. Several researchers echo this concern. Hammer
(1989) and van der Valk and Jolly (1992) also recommend that natural wetlands be
avoided when trying to address excessive nutrient loadings. Natural wetlands are
not particularly effective as nutrient sinks, but clearly perform a valuable function
in attenuating diffuse runoff (Howard-Williams, 1985). Johnston (1991) identified
46 An Overview of Available Endpoints and Assessment Tools
-------
wetlands designed for pollutant filtration as having a much greater assimilative
capacity and range compared to natural wetlands.
Wetlands must be part of an integral landscape approach to NPS control.
Created, restored or natural wetlands can contribute to this strategy, but must be
sited appropriately, so they are not overloaded. Attempts have been made in
developing guidelines for certain aspects of wetlands as pollutant filters, including
wetland siting within a watershed or landscape unit. However, certain technical
issues, such as fate and effects of contaminants and development of design and site
selection criteria, are in need of resolution before siting and using restored
wetlands for NFS pollution control (van der Valk and JoHy, 1992).
Knowledge of technical issues is uneven. This point was also made by Nixon and
Lee (1986). Having performed an extensive review of wetlands and water quality,
they state that information on wetlands nationwide is unevenly distributed, and
there is a need to learn a great deal more about wetland processes and functions
before the scientific community can generalize the overall role of wetlands in
water quality. Current knowledge of nutrient dynamics (and other parameters)
varies by wetland type and region. These factors are important considerations
since they might indicate that a regional or ecoregional strategy might be more
effective for nutrient assessment than a single, national strategy.
Technical and scientific issues will not be as difficult to resolve compared to social
and economic ones, largely because administrative boundaries rarely coincide with
the logical management units of watersheds. This issue is particularly challenging
for environmental managers in developing cooperative agreements with other
administrations sharing the same watershed(s). The changes observed in wetlands
from nutrient enrichment are likely to be more subtle and over a longer term
compared to receiving waters, such as lakes and reservoirs. Public use values for
receiving waters, such as drinking water, fishing, and swimming, have been well
developed for most areas. Conversely, social, and in particular, economic use
values might not be as well developed or expressed for specific wetlands in some
regions. In general, large uncertainties remain in the economic evaluation of
wetlands (Costanza et al., 1989).
For this discussion, additional policy issues/questions to consider include the
following:
• Eutrophication needs to be defined according to whether it is natural or
human-induced.
• At what point is eutrophication in a wetland system considered a "bad" thing,
and what standards will be used for comparison?
• Decisions and value judgments are needed to determine whether a given system
should be controlled or allowed to follow the change (even if that change is
human-induced).
Wetlands 47
-------
State of the Science—Endpoints
Knowledge of wetlands has increased significantly over the last 20 years. The
scientific literature describes studies of nutrient dynamics, uptake capacity of soils
and wetland types, examples of using wetlands to ameliorate nutrients from
agricultural or nonpoint source pollution, and discussions of wetland values (for
example, Gilliam, 1994; Detenbeck et a!., 1993; Phillips et al., 1993; Baker, 1992;
Knight, 1992; Masscheleyn et al., 1992; Mitsch et al., 1991; Costanza et al., 1989;
German, 1989; Kuenzler, 1989; Reddy et al., 1989; Kemp et al., 1985; Rhodes et
al., 1985; Johnston et al., 1984). A common finding in much of the literature
reviewed is that natural wetlands have many dynamic variables. For nutrients,
various input sources, such as surface, atmosphere, runoff, and groundwater make
it difficult to generalize about their effect on wetland quality (Johnston, 1991;
Leibowitz and Brown, 1990; Nixon and Lee, 1986).
The use of restored or constructed wetlands specifically for nutrient retention (i.e.,
sewage treatment) and water quality enhancement has been extensively studied and
has emerged as a discipline within wetland science (see Moshiri, 1993; Mitsch,
1992b; Hammer, 1989). Consequently, findings from work with engineered
wetlands are likely to be useful in determining some measurement parameters and
appropriate endpoints. However, compared to many natural wetlands, constructed
wetlands are often much less diverse in biological and physical characteristics,
compared to many natural wetlands.
A potentially important consideration in assessing nutrient conditions in wetlands
on a broad scale, such as a watershed or ecoregional level, might involve revisiting
wetland classification with nutrient dynamics in mind. The Cowardin et al. (1979)
hierarchical system of wetland classification is based largely on plant species
composition. Although this classification has been useful for inventorying
wetlands nationally, uptake by plants is only one pathway for nutrients.
Alternatively, Brinson (1993) developed a wetland classification system that
grouped characteristics more by hydrogeomorphic processes. Figure 2 depicts
nutrient availability as a core factor with hydrologic energy and hydroperiod.
Biological attributes, such as wetland species composition, are then used to refine
wetland classification. Such a general classification approach might be useful in
organizing wetlands specifically for nutrient management.
48 An Overview of Available Endpoints and Assessment Tools
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CORE FACTORS
RIVERINE
.FRINGE
BASIN
Figure 2. Relationship of core hydrogeomorphic factors (note nutrient availability) to
charactnze various wetland types. Modified from Brinson (1993).
Nutrients in Wetlands
Nutrient retention and release kinetics are highly site-specific, and uptake
mechanisms and differ among wetland types, soils, water levels, seasons and other
parameters (Phillips et a]., 1993; Johnston, 1991; Kemp et al., 1985). Factors
contributing to variable nutrient uptake in wetlands include:
• Source. Wetlands can receive nutrients from agricultural, rural or urbanizing
environments, which deliver varying concentrations. Sources might be specific
points or a cumulative contribution from nonpoint sources, or both. Nutrients
are carried by inputs from streams, rivers, tidal exchanges, groundwater,
precipitation, or atmospheric deposition.
• Physical Factors. Latitude, climate, hydrology, and soil type are among the
physical attributes that affect wetland size, structure, and, consequently, nutrient
dynamics.
• Chemical Factors. pH, organic matter, substrate characteristics,
nitrification/denitrification, and reduction/oxidation potential all affect nutrient
cycling and availability.
• Biological Factors. Plant, animal, and microbial ecology all contribute to
nutrient dynamics-and pathways within wetlands. Aside from sediment often
serving as a sink for phosphorus, biological components serve as significant
nutrient storages and processors in wetlands. The availability of biological
processes depends greatly on source, physical, and chemical factors.
Several other authors have identified hydrology within wetlands as critical, but
understanding of nutrient dynamics is lacking (Gilliam, 1994; Brinson, 1993;
Johnston, 1991; Clausen and Johnson, 1990). The highly transient hydrology of
many wetlands makes evaluating long-term nutrient and sediment removal difficult.
However, in spite of the range of variables and currently unknown factors of
Wetlands
49
-------
nutrient dynamics in wetlands, some ecological consequences of eutrophication
have been identified and measured, Kadlec (1983) identified certain conditions
resulting from nutrient overenrichment through effluent discharge: the death and
uprooting of trees, exotic plant invasion, and presence of specific fungi and
bacteria. While nitrogen was consistently reduced over 8 years of study,
phosphorus eventually overloaded the system. Wetland recovery was documented
after cessation of the effluent discharge.
In detailed literature reviews, Johnston (1989) and Howard-Williams (1985)
identify several factors in which nutrient overenrichment likely affects wetland
quality:
• Changes in plant species composition. Eutrophication may alter plant species
dominance in a wetland, affecting factors such as long-term nutrient assimilative
capacity or foraging habits by wildlife. Changes in trophic status may favor
invasion by exotic plants, which might outcompete native species for space and
resources (see Kadlec, 1983). Also, changes in species composition might
ultimately affect a wetland's ability to take up other pollutants.
• Reduced photosynthesis. A reduction in photosynthesis is a reduction in
primary productivity and, consequently, nutrient uptake and processing.
• Interference with feeding and nutrition of aquatic plants and animals. In
shallow-water wetland systems with long residence times, eutrophic conditions
might cause phytoplankton and macroalgal blooms or development of epiphytes,
which might interfere with the growth and productivity of wetland plants and
microbes.
The majority of research specifically addressing nutrient dynamics in wetlands
measures concentrations and pathways of either nitrogen or phosphorus, and
deposition of sediment, litter, or other input. Specific techniques for measuring
nutrient flows or storage (e.g., soils, plants, detritus) in wetlands appear to be well
developed (see van der Valk et al., 1991; Johnston, 1991; Chambers et al., 1992).
However, no examples were found that specifically recommend limits or thresholds
of nutrients or sediment for a particular type of wetland.
Of the literature reviewed, Johnston (1991) comes closest in designing a table-type matrix to
consider a range of nutrient parameters affecting wetland quality (Table 4). Johnston's
review focused on wetland effects on the quality of surface water entering ecosystems
downstream, and not directly on wetland "health." Nevertheless, the approach to examining
the literature for various means and ranges of nutrients in wetlands is useful, and an updated
literature review targeted specifically for wetland quality could provide insight into
organization of wetlands by region or type.
50 An Overview of Available Endpoints and Assessment Tools
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Table 4. Matrix considering a range of nutrient parameters affecting wetland quality.
Wetlands Name
Reedy Cr. Wetland. 1979
Reedy Cr. Wetland. 1980
Reedy Cr. Wetland, 1981
Reedy Cr. Wetland. 1982
Reedy Cr. Wetland, 1983
Reedy Cr. Wetland, 1984
Reedy Cr Wetland, 1985
Thuja peatland, 1976
Thuja peatland, 1977
Thuja peatland, 1978
Thuja peatland, 1979
Thuja peatland, 1980
Thuja peatland, 1981
Thuja peailand, 1982
Thuja peatland, 1983
Fresh marsh, enriched
Water hyacinth marsh
Boggy Gut Wetland
Cattail march
Nevin Wetland
Mixed hardwood swamp
Cypress Dome
Cypress-Tupelo Swamp
Tupelo Swamp
Arithmetic Mean
Wetland
Type
Swamp
Swamp
Swamp
Swarnp
Swamp
Swamp
Swamp
Bog
Bog
Bog
Bog
Bog
Bog
Bog
Bog
Marsh
Marsh
Marsh
Marsh
Marsh
Swamp
Swamp
Swamp
Swamp
Enriched
with
Sewage
Sewage
Sewage
Sewage
Sewage
Sewage
Sewage
Sewage
Sewage
Sewage
Sewage
Sewage
Sewage
.
.
Sewage
Sewage
Sewage
Sewage
Hatchery
Sewage
Sewage
Drainage
Nutrients
Location
Orlando
Orlando
Orlando
Orlando
Orlando
Orlando
Orlando
Bellaire
Beliaire
Bellaire
Bellaire
Bellaire
Bellaire
Bellaire
Bellaire
Clennont
Gnsville.
H. Head
Bnllion
Madison
Wtdlwood
Gnsville.
Barataria
Tar River
St
FL
FL
FL
FL
FL
FL
FL
Ml
Ml
MI
Ml
MI
MI
MI
Ml
FL
FL
SC
Wl
WI
FL
FL
LA
NC
Total N
53.2
75.5
74.9
71.0
72.6
57.5
61.7
1.84
6.75
9.63
6.21
9.07
4.46
0.76
-
-
.
44.9
-
15.0
-
11. 1
3.8
-
10.34
71%
84%
95%
87%
77%
76%
77%
75%
80%
80%
77%
75%
81%
61%
-
-
-
83%
.
21%
74%
26%
-
64%
Tola! P
-19.4
-19.2
5.72
-11.6
-17.0
-2.7 1
-2.35
1.07
3.01
1.58
1.47
1.46
-0.33
-0.04
-0.03
37.1
7.7
12.1
4.8
0.11
0.79
10.4
1.69
25.1
-
-103%
-80%
23%
-52%
-171%
-30%
-28%
91%
88%
72%
64%
65%
-27%
-2%
-1%
98%
16%
62%
68%
7%
87%
92%
41%
57%
Wetlands
51
-------
Currently, the more common techniques for assessing nutrient conditions in
wetlands come from development of evaluation indicators of ecological stress and
design and engineering of wetlands for water quality enhancement. In particular,
Leibowitz and Brown (1990), Mitsch (I992b), Mendelssohn and McKee (1992),
and Kent et al. (1992) have identified indicators specifically for wetlands. The
techniques identified are designed to evaluate multiple stressors, but include
nutrients.
Measurement parameters to be considered for wetlands include the following:
Nitrogen Species Concentrations. Atnmonium-N, nitrite-N, and nitrate-N can all
be sampled using standardized collection and analytical methods. Sources of N are
the water column, wetland detritus, litter and peat, and standing stock of plant
biomass. A challenge in considering any nutrient concentration in the context of
developing endpoints is the uptake range and variability among wetlands.
Examples of the variability found in nitrogen uptake in wetlands include German
(1989), who found a 36 percent removal rate of N from an undeveloped Florida
wetland, and Rhodes et al. (1985), who documented a 99 percent removal
efficiency of riparian forests.
Phosphorous Species Concentrations. Total inorganic phosphorous and total
organic phosphorous. Sources are sediment, litter/detritus, microbes, and standing
stock biomass. Ranges of P concentrations and uptake are also large depending on
wetland type. As examples, Mitsch (I992a) found phosphorous retention capacity
of natural wetlands to be 4 to 10 percent efficient, compared to 63 to 96 percent in
constructed wetlands. Masscheleyn et al. (1992) compared phosphorous
assimilation and release of a bottomland hardwood swamp soil with that of a
freshwater marsh and found that the swamp forest soil displayed greater sorption
capability. Cooper and Gilliam (1987) estimated that 50 percent of P was removed
by runoff from agricultural fields in North Carolina. Chescheir et al. (1991) found
that small pumping events of agricultural drainage water into wetlands retained
substantial phosphorus concentrations, but that large events documented increased
phosphorus concentrations leaving the wetland.
Nitrogen:Phosphorus Ratio. The N:P ratio indicates relative concentration of N
and P and aids in determining nutrient availability or limitation within a system.
N:P ratios are used in assessing marine and aquatic systems. Given the variability
of nutrient limitation within various wetlands, the N:P ratio could be a useful
endpoint for comparing impacted wetlands to reference conditions.
Dissolved Oxygen Concentration. The dissolved oxygen (DO) concentration
could be used as a eutrophication indicator in wetlands with extended
hydroperiods.
52 An Overview of Available Endpoints and Assessment Tools
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Processes as Measurement Parameters
Hydrology and Hydroperiod. Hydrology within wetlands is a critical determinant
of wetland condition and nutrient dynamics, but more research is needed to
understand hydrological mechanisms in wetlands (Gilliam, 1994; Johnston, 1991;
Clausen and Johnson, 1990). The highly transient hydrology of'many wetlands '
makes evaluating long-term nutrient and sediment removal difficult. Clausen and
Johnson (1990) determined that lake-level hydrology significantly influenced the
fluctuation of nutrients and total suspended solids into and out of an adjacent
wetland. Dye tracer studies used to examine water velocity through a wetland
found rates to be highly variable; lower velocities resulted in greater residence time
and greater pollutant removal (Chescheir et al., 1991b). Phillips et al. (1993)
determined that the effect of forested wetlands on water quality depends largely on
hydrologic conditions. Also, changes in hydroperiod can have significant effects on
nutrient pathways and cycling rates, as well as plant species composition
(Leibowitz and Brown, 1990; Mitsch, 1992; Brinson, 1993).
Organic Matter and Sediment Accretion. Sediment accretion refers to the
accumulation of both mineral and organic matter in wetlands and provides a good
indication of trophic status (Leibowitz and Brown, 1990). Cooper and Gilliam
(1987) demonstrated that areas between field edges and perennial streams served as
sinks for sediment and phosphorus from the continual runoff deposition.
Nutrient Uptake and Mass Balance. Mass balance measures the difference
between nutrient input and output of a system and assigns the difference as uptake
by biologiccal, chemical, or physical processes. There are many examples of
measuring nutrient uptake in applied wetland research. Kemp et al. (1985)
conducted field and laboratory studies to determine decomposition rates and
nutrient flux in a Louisiana swamp forest. Twenty-six percent N and 40 percent P
were retained by the swamp, mainly from the settlement of paniculate matter, and
these percentages indicate that the swamp is a long-term sink for N and P via
burial of decomposed organic matter and denitrification. However, direct
measurement of nutrient cycling is difficult in systems that lack the clearly defined
input/output points necessary for mass balance equations or nutrient fluxes between
storage compartments (Leibowitz and Brown, 1990; Johnston, 1991). As a potential
assessment endpoint, Kent et al. (1992) present nutrient uptake and metabolism as
a component in a functional value index for monitoring wetlands. In combination
with other metrics of the index, net loss of N or P from a monitored wetland is
compared to reference wetland conditions.
Nitrification/Denitrification. Nitrification is a biological process by which
atmospheric N is fixed into inorganic N compounds available for biological
assimilation. Denitrification is a reverse process by which nitrate is chemically
converted into gas and dissipated into atmospheric N. Since many wetlands are
nitrogen-limited, this might be a critical measurement parameter to determine a
Wetlands 53
-------
wetland's capacity to handle nitrogen (Hansen et al, 1994), Reddy et al. (1989)
have successfully quantified nitrification-denitrification at the plant root-sediment
interface in wetland plants.
Biological/Ecological Parameters
Use of Indicator Species to Determine a Nutrient-related Condition. The
presence or absence of certain plants, animals, or microbes might be useful in
flagging a potentially changing wetland trophic condition. Often, invasive exotic
plants might serve as early indicators of elevated nutrient concentrations.
Abundance, Diversity and Species Composition. Wetland plants are reliable
indicators of stress, such as eutrophication, and hydrologic condition, and sampling
methods are well developed (Leibowitz and Brown, 1990). Marked changes in
species richness and composition of plants might indicate an accelerated change
resulting from nutrient enrichment. A change in successional status of a wetland
might be included as part of measuring changes in species richness. However,
plant community succession might occur in combination with other factors, such as
sedimentation and changes in hydrology or competition for space (Odum, 1971).
Peak Biomass or Net Primary Productivity. Overall net primary productivity of
a wetland can indicate "health" and a relative stage of succession (Mitsch, 1992).
Although nutrients often stimulate plant growth and production, this factor, used in
conjunction with plant species diversity, might indicate a change in trophic status
resulting from nutrient enrichment.
Leaf Area, Solar Transmittance and Greenness. Changes in characteristics of
wetland canopy plant species might also be an indicator of eutrophic conditions
(Leibowitz and Brown,, 1990). If positively correlated, then remote sensing
techniques might be useful in assessing large wetland areas. Nutrient flux has
been examined at the landscape level using remote sensing and GIS tools (Correll
et al., 1992).
Aquatic Microbial Community Structure. Microbial communities are linked to
nutrient cycling and litter decomposition (Leibowitz and Brown, 1990).
State of the Science—Wetland Monitoring and Assessment
Of the literature reviewed, several authors provide detailed discussions of
monitoring wetlands (Kent et al, 1992; Adamus, 1992; Leibowitz and Brown,
1990). Assessment of nutrients is generally included as a component in monitoring
programs, but is often combined with other metrics to assess general conditions.
Consequently, the focus is often qualitative and therefore lacks the precision
needed to clearly assess nutrient impacts. Landers and Knuth (1991) found that
54 An Overview of Available Endpoints and Assessment Tools
-------
wetland monitoring to determine the impact of nutrients on lakes in LJSEPA
Region 5 was lacking. Nixon and Lee (1986) recommend that a combination of
carefully selected field studies, with establishment of microcosm studies, serve as
the basis for monitoring and increased understanding of wetland functions.
Various approaches to field monitoring were identified by:
• Geographic region
• Wetland type
• Accessibility and ease of study (for cost-effectiveness)
• Size and visibility (enlisting public interest and support)
• Availability of supporting information (building on previous research)
The use of reference wetlands or conditions is an important consideration in
assessing impacts. Establishing a series of reference wetlands to serve as a
database within a region would allow comparison for a range of parameters (Figure
3). For example, a parameter (such as nutrient load) for wetlands undergoing
assessment could be compared to those reference conditions having a "normal"
range. Assessed wetlands falling outside the normal range may be considered
impaired for that specific parameter.
Within EPA, the STORET database has some limited information on wetlands. In
particular, Michigan and Florida have wetland sampling stations, but Michigan
contains fish tissue data only. Florida has sampling information on wetlands,
including nutrient concentrations (Figure 4). However, the distribution of sampling
stations emphasizes the uneven spatial coverage on a national scale.
Wetlands 55
-------
Figure 3. Hypothetical example of how a national or regional database of
reference wetlands could be used to assess nutrient impacts. "Wetland Type 1, 2,
3 & 4" refers to different hypothetical wetland classifications that display a range
of "normal" characteristics for a given parameter. The parallel lines bordering the
wetland types represent hypothetical confidence intervals for a "normal" response.
Driving functions (X axis) and response variables (Y axis) can represent single or
multiple variables. Assessed wetlands for a given variable falling outside a
"normal" range would indicate a potentially impaired condition.
56
An Overview of Available Endpoints and Assessment Tools
-------
Figure 4. Distribution of sampling stations in the USEPA STORET database that are
wetlands. The figure emphasizes the sparse national distribution of wetlands data.
Models that compute or predict nutrient loadings to wetlands (transport models for
groundwater or surface water flow) are well developed and have been reasonably
successful. Assessment of inputs/loadings using a variety of loading models (such
as SWMM and HSPF) can be used to predict nutrient and sediment loads to
wetlands. Loadings can also be estimated from local monitoring studies. As a
general class, models that are capable of predicting wetland responses to nutrient
loads are not well developed. However, some traditional water quality models,
such as CEQUAL-W2, and WASPS, have been used for evaluating wetlands and
hydrodynamic models, such as EFDC, are being applied to wetlands in Florida to
assess hydrologic response (Hamrick, Virginia Institute of Marine Science,
personal communication).
Summary
Because of the high degree of variability between and within wetlands, it is
possible that a regional strategy for wetlands is a more prudent course than a
detailed national strategys. Additionally, it is clear that more research is needed to
understand the specific mechanisms that affect wetland quality. These research
needs include the following:
• Additional monitoring and improved documentation of the effects of
nutrient overenrichment on various wetland types. This may involve (1)
synthesis and organization of wetland research to determine whether
certain parameters have sufficient data for developing assessment
Wetlands 57
-------
endpoints for various wetland types, and (2) development of a regional
or national database for wetland reference conditions.
Specific assessment methods for process-based parameters, such as
nutrient fluxes between storages in wetlands.
Improved modeling techniques for predicting nutrient uptake and
dynamics and the responses of wetlands to these processes.
58 An Overview of Available Endpoints and Assessment Tools
-------
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