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2.0 Florida's Watershed Management Approach
The Florida Department of Environmental Protection (FDEP) is responsible for preserving and
maintaining the quality of Florida's waters, essential natural resources for aquatic life and recreation, and
uses for public consumption, industry, and agriculture. This is a challenging task due to damage caused
by past practices, increasing demands placed on the water resources by rapid growth, and the various
entities responsible for regulating different activities that may impact water quality. To address this
challenge, and to recognize the need for defensible, science-based water quality assessments in support
of full implementation of the Clean Water Act, FDEP has designed a statewide, watershed-based
approach to water resource management.
Under the watershed management approach, Florida's water resources are managed on the basis of
natural boundaries such as river basins and bay systems, rather than political or regulatory boundaries
(Figure 2-1). Each of the states six districts are divided into five basin groups to facilitate
implementation. The process also focuses on collaboration with local citizens to determine goals and
priorities.
The approach is implemented using a five-year cyclical management process with emphasis being placed
on public involvement in decision-making. Instead of focusing only on individual sources of pollution,
water resources are assessed from a basin-wide perspective that considers the cumulative effects of
human activities. The approach is not new, nor does it compete with or replace existing programs. Rather
than relying on single solutions to address aquatic resource issues, it is intended to improve the health of
surface water and ground water resources by strengthening coordination among activities such as
monitoring, stormwater management, wastewater treatment, wetland restoration, land acquisition, and
public involvement.
FDEP's Division of Water Resource Management is developing this more comprehensive approach to
protecting Florida water quality involving basin-wide assessments and the application of a full range of
regulatory and non-regulatory strategies to reduce pollution. The Total Maximum Daily Load (TMDL) is
the heart of this approach, and the watershed management approach is the framework for implementing
TMDLs.
Section 3 03 (d) of the Clean Water Act (CWA) requires states to submit li sts of surface waters that do
not meet applicable water quality standards (impaired waters) after implementation of technology-based
effluent limitations, and establish TMDLs for these waters on a prioritized schedule. TMDLs establish the
maximum amount of a pollutant that a water body can assimilate without causing exceedances of water
quality standards. As such, development of TMDLs is an important step toward restoring our waters to
their designated uses. Chapter 99-223, Laws of Florida, also known as the "Florida Watershed
Restoration Act", sets forth the process by which the 303 (d) list is refined through more detailed water
quality assessments. It also establishes the means for adopting TMDLs, allocating pollutant loadings
among contributing sources, and implementing pollution reduction strategies.
Implementation of TMDLs refers to any combination of regulatory, non-regulatory, or incentive-based
actions that attain the necessary reduction in pollutant loading. Non-regulatory or incentive-based actions
7
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Central
. • ;- J v ••-.'..,•;...•.,
• -:.t*y
E?
Southeast
Gittup 5
OEP disiiid hxndarv
County Una
Figure 2-1 Florida DEP's basin delineation for their watershed management approach
using natural boundaries.
may include development and implementation of Best Management Practices (BMPs), pollution
prevention activities, and habitat preservation or restoration. Regulatory actions may include issuance or
revision of wastewater, stormwater, or other permits to include permit conditions consistent with the
TMDL. These permit conditions may be numeric effluent limitations or, for technology-based programs,
requirements to use a combination of structural and non-structural BMPs needed to achieve the
necessary pollutant load reduction.
Each of the state's six districts is divided into five basin groups. Each individual basin cycle will take five
years to complete, and the cycle within that basin will be repeated every five years. For the Pensacola
Bay watershed, the first phase was initiated in the fall of 2003.
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• Phase 1: Watershed Evaluation. The Department will conduct preliminary evaluations of the status
of the quality of surface water and ground water. This information will be used to generate a planning list
of potentially impaired waters for which TMDLs may be needed. At the end of Phase 1, a Basin Status
Report will be produced and a strategic monitoring plan will be developed.
• Phase 2: Strategic Monitoring. Monitoring will be conducted to help establish whether waters are, in
fact, impaired and to collect the data needed to calibrate and verify models for TMDL development. At
the end of the second phase, an assessment report will be produced. This report will contain an updated
and more thorough assessment of water quality, associated biological resources, and current restoration
plans and proj ects. Waters that are verified as being impaired will be placed on a basin-specific list of
impaired waters that will be adopted by the Department through a Secretarial Order. This verified list will
be submitted to the U. S. Environmental Protection Agency (EPA) as the state's Section 303(d) list of
impaired waters for the basin.
• Phase 3: Developing and Adopting TMDLs. TMDLs for priority impaired waters in the watershed
will be developed and adopted by rule. Due to fiscal and technical limitations, TMDLs cannot be
developed for all listed waters during a single watershed management cycle, therefore waterbodies will
be prioritized using the criteria in the Identification of Impaired Surface Waters Rule, Section 62-303,
Florida Administrative Code. This rule provides a new scientific approach, with quality assurance and
data sufficiency requirements, for identifying and prioritizing impaired surface waters in Florida. The
Department evaluates whether waters meet their designated uses, which include aquatic life, primary
contact and recreation, fish and shellfish consumption use support, and drinking water. Waters verified as
not meeting any one (or more) of their designated uses will be listed on the state's 303(d) list.
• Phase 4: Developing Watershed Management Plans. A watershed management plan will be
developed, including TMDL implementation plans specifying how pollutant loadings from point and
nonpoint sources will be allocated and reduced. The plans will include regulatory and nonregulatory (i.e.,
voluntary), structural and nonstructural improvements. The involvement of affected stakeholders in this
phase will be especially critical.
• Phase 5: Implementing Watershed Management Plans. Implementation of the activities specified
in the watershed management plan will begin. The watershed management approach is an iterative
process. One of its key components is that the effectiveness of management activities (TMDL
implementation) will be monitored in successive cycles. Monitoring conducted in Phase 2 of subsequent
cycles will be targeted at evaluating whether water quality obj ectives are being met and whether
individual waters remain impaired. The Department also will trackthe implementation of scheduled
restoration activities, to ensure continued progress towards meeting the TMDLs.
This approach is intended to protect and enhance the ecological structure, function, and integrity of
Florida's water by promoting the management of entire natural systems and addressing the cumulative
effects of human activities on a watershed basis. The approach provides a framework for setting
priorities and focusing the Department's resources on protecting and restoring water quality, and aims to
increase cooperation among federal, state, regional, and local interests. Emphasizing public involvement,
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the approach encourages stewardship by all Floridians to preserve water resources for future generations.
The watershed approach i s intended to speed up proj ects by focusing funding and other resources on
priority water quality problems, strengthening public support, establishing agreements, and funding multi-
agency proj ects. It avoids duplication by building on existing assessments and restoration activities and
promotes cooperative monitoring programs. It encourages accountability for achieving water quality
improvements through improved monitoring and by establishing TMDLs.
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3.0 Study Design
Aprobabilistic survey design was developed by EPA's Environmental Monitoring and Assessment Program
(EMAP) and used in the Pensacola Bay Monitoring Study to estimate ecological status and trends. EMAP
was developed in response to the Clean Water Act to advance the science of natural resource monitoring at
regional and national scales. Under the Clean Water Act, states and tribes are responsible for reporting on
the condition of all their waters. EMAP's surveys use a statistical, scientifically-defensible approach to
assess the condition of the nation's waters (Summers et al 1995). The use of a probabilistic survey design
to sample the Pensacola Bay System provided a statistically rigorous approach for assessing the ecological
condition by insuring unbiased (random), spatially distributed sampling sites. The sampling design generated
for this study consisted of 38 sites (Fig. 3-1), sampled quarterly over a five-year period from 1995 -2000.
The thirty-eight (3 8) stations were established within the PB S, each equally weighted in their probability of
inclusion, using geographical information systems software. The total sampling area assessed for the PB S
was about 296 km2, with each station representing 7.7 km2. Each station was randomly located within a
7.7 km2 hexagon (Fig. 3.2). A grid of these hexagons was overlaid upon the PBS at a density to provide
the correct sample size.
Figure 3-1 Image of the Pensacola Bay System showing sampling station locations.
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Figure 3-2 Hexagonal grid overlaid onto the Pensacola Bay System with each hexagon
representing 7.7 km2. Circles show the locations of sampling stations.
12
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4.0 Water Quality
Water quality assessments use a set of hydrographic, chemical and biological indicators. Water quality
data presented for the Pensacola Bay System include a mixture of hydrographic (salinity, pH, temperature,
dissolved oxygen, and light penetration), chemical (nutrients), and biological (benthic community and
chlorophyll) measurements.
4.1 Stratification
The distribution of salinity in estuarine systems is modified by freshwater input, tidal forces, and circulation
patterns. The water column becomes stratified when lower density freshwater floats atop denser seawater.
Stratification can limit the exchange of nutrients and dissolved oxygen across the pycnocline, (the boundary
between fresh and salt water). Although estuarine organisms typically are adapted to wide salinity ranges,
benthic communities may be altered when altered salinity persists for extended periods. Salinity in the PB S
averages 17.5 ppt annually. Surface and bottom salinities are useful for estimating the degree of
stratification in an estuary. The Pensacola Bay System is a river dominated system where freshwater flows
over saltwater and becomes mixed (Fig. 4-1). When rainfall within the watershed is low, the amount of
freshwater entering the system decreases causing decreased stratification throughout the estuary. High
freshwater inflows tend to increase stratification. An index of stratification was calculated based upon the
difference between the surface and bottom salinities. Differences less than 2 ppt indicates low stratification
2-10 ppt partially mixed, and > 10 ppt highly stratified. Based on this index, 36% of the Pensacola Bay
system was highly stratified (Fig. 4-2), with 11% was well mixed, and 53% was partially mixed.
Seasonally the PB S shows a higher degree of stratification in winter and summer when compared to the
same stations sampled in spring and fall (Fig. 4-3).
4.2 Temperature
Water temperature in the PBS ranged from 8.0 to 33.7 °C with a mean value of 22.2 °C. Differences in
bottom and surface temperatures exist in the deepest portions of the bay year-round. When seasonal
temperatures begin to drop, the surface waters cool and tend to sink causing vertical mixing or "turnovers"
of the water column. As the winter months approach, the water cools and water column temperature
becomes more uniform. Point source thermal discharges can elevate water temperatures locally and
decrease oxygen concentrations. State of Florida permit guidelines for thermal discharge state that the
temperature of receiving coastal waters shall not exceed 92° F (33.3° C) in summer months and ambient
temperatures shall not be elevated more than 2° F (1.1° C). For the remainder of the year, the
temperature must not exceed 90° F (32.2° C) and shall not be elevated more than 4° F (2.2° C) above
ambient water temperature.
4.3 pH
The pH in estuarine systems is usually stable due to the buffering capacity of seawater. Measurable
changes in pH may occur during in periods of heavy rain, increased river flow, algal blooms, and high
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Winter
Summer
Spring
Fall
Figure 4-1 Seasonal surface salinity concentrations of the Pensacola Bay system.
oxygen demand. When pH values drop below 6.0 for extended periods ammonium can accumulate in
the water column due to a decrease in nitrification process (Schindler 1991). The pH of the Pensacola
Bay System ranges between 4.1-9.1 with a mean of 7.8. State of Florida surface water criteria
designate a general acceptable pH range of 6.5-8.5. Many organisms are sensitive to pH changes,
particularly algal species. Seawater pH may inhibit or enhance the growth rates of phytoplankton
species by affecting the availability of nutrients and trace metals. In coastal environments, seawater pH
may limit phytoplankton blooms (Hinga 2002). Water column pH also affects the solubility and
speciation of contaminants.
4.4 Light
The amount of sunlight that penetrates the water column i s important to primary productivity. Algae and
submerged aquatic vegetation (SAV) require sufficient light for photosynthesis. The amount of light
penetrating the water column is influenced by colored dissolved organic matter (CDOM) concentrations
and total suspended solids including self shading algal biomass. Some estuarine systems are naturally
turbid, especially shallow, river dominated systems. The upper portions of the Pensacola Bay System,
e.g. Blackwater Bay, are characterized by darkened water due to high CDOM content. Water color,
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Highly Stratified
36%
Vertically Mixed
11%
Partially Mixed
53%
Figure 4-2 Percentages of the Pensacola Bay System exhibiting the different
stratification regimes.
however, is not itself an indication of poor water quality. Water quality as a function of water clarity is
generally evaluated based on elevated concentrations of chlorophyll and suspended solids.
The PB S historically has supported S AV. The loss of S AV throughout the system has been attributed to
poor water quality and may be linked to water clarity. Because the system is shallow, light often reaches
the bottom. When the water becomes more turbid, the amount of light reaching the bottom decreases.
When less than 10% of the ambient light is observed at a depth of 1 meter, water clarity is considered
poor (USEPA1999). This value is based on the system's ability to support SAV and takes into
consideration the natural conditions contributing to light attenuation (CDOM). When light is not limited,
and there are excess supplies of nutrients, the conditions are optimal for phytoplankton growth. When
phytoplankton become dense, light is absorbed and SAV may suffer due to insufficient light. This
situation may cause a shift in the plant community from SAV to phytoplankton. Increases in algal
biomass can eventually lead to oxygen problems.
Based on the 10% light guideline at 1 meter, poor water clarity was observed in < 10% of the system in
summer. The extent of the poor water clarity varied with season (Fig. 4-4), occurring to a greater extent
in the summer months. Areas of poor water clarity generally occurred near the river mouths.
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Spring
Summer
13%
29%
47%
58%
Vertically Mixed
Fall
Partially Mixed
18%
16%
66%
5%
D Highly Stratified
Winter
5%
42%
Figure 4-3 Seasonal variation in the different stratification regimes for the Pensacola
Bay System.
4.5 Chlorophyll a
The chlorophyll a concentration in the water column of the PBS was used as an estimate of the biomass
of phytoplankton present. Alarge amount of phytoplankton or "bloom" may indicate the presence of
excess nutrients, reduce the amount of light penetrating to SAV, and cause hypoxia when the bloom dies
and begins to decompose. If the amount of chlorophyll a exceeds a criterion, the waters are judged to
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Winter
Summer
Spring
Fall
Figure 4-4 Seasonal % light transmission to a depth of 1.0 meter in the Pensacola
Bay system.
be degraded or impaired. The State of Florida considers an estuarine water body to be impaired if the
mean concentration of chlorophyll a is greater than 11 ug/L for a calendar year. For our data we assigned
a poor rating to sites where the chlorophyll a concentration was greater than 20 //g/L; fair was a
concentration from 5-20 //g/L; and good was less than 5 //g/L. Approximately 55 % of PBS was rated
as having concentrations of chlorophyll a in the good range, while 45% rated as fair, and none of the area
was rated poor.
4.6 Dissolved Oxygen
Oxygen dissolved in the water is required by most aquatic species. Dissolved oxygen is an excellent
indicator of overall water quality. Dissolved oxygen may be depleted due to the decay of organic matter
by bacteria or animal respiration. This depletion is mostly observed in near-bottom waters during warm
summer months, where respiration consumes more oxygen than is replenished. When oxygen is depleted
to a level that begins to stress aquatic organisms, it is referred to as hypoxia. Hypoxia, or the more severe
17
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condition, anoxia (no oxygen), may contribute to the death of aquatic organisms that cannot escape, or
cause behavioral changes which make species more vulnerable to predation.
Organic matter is delivered via sewage discharges, stormwater runoff, and rivers draining into the PBS.
In addition, excess nutrients can stimulate algal growth. The algae die and are subsequently decomposed,
contributing to oxygen depletion. Estuarine fish and invertebrates can become chronically stressed if
dissolved oxygen concentrations remain below 5.0 mg/L. In addition to the threat to aquatic life, nutrient
concentrations are also affected. Under hypoxic conditions, ammonia and phosphorus contained in
bottom sediments are released. These nutrients are then available for algal uptake and may fuel more
primary production, continuing the cycle. For the protection of aquatic life, the State of Florida has
established dissolved oxygen criteria for marine waters to average no less than 5.0 mg/L in a 24-hour
period and to never be less than 4.0 mg/1 in a single reading. Some estuarine waters are naturally more
susceptible to dissolved oxygen problems due to poor mixing; however, anthropogenic inputs of nutrients
and organic matter usually exacerbate the condition.
The PBS experiences low dissolved oxygen during the summer months (Fig. 4-5). The extent of poor
oxygen conditions using a conservative criterion of, < 2.0 mg/L, increases as temperatures and
stratification increase. Seasonal averages of dissolved oxygen indicate no occurrences of poor dissolved
oxygen in winter, but poor conditions in approximately 24% of the PB S area are present in summer.
Approximately 1% of area sampled exhibited low dissolved oxygen in spring and fall. Evaluating the
causes of hypoxia in the system requires careful consideration in terms of ecosystem management due to
multiple factors. Naturally occurring conditions such as stratification and temperature increases can be
significant in modifying oxygen concentrations. Factors related to primary productivity can be evaluated
by examining the dissolved nutrient, chlorophyll a, and organic carbon concentrations.
4.7 Dissolved Inorganic Nutrients
Nutrients delivered to estuarine and coastal systems support biological productivity. Sources of
anthropogenic nitrogen and phosphorus include applied fertilizers (urban runoff and agricultural runoff),
livestock waste, and atmospheric deposition from fossil fuel combustion (Table 1). Nutrients are
regenerated internally during decomposition and other microbial processes.
Excessive levels of nutrients can cause intense biological productivity that leads to hypoxia. The process
of nitrification is significantly reduced under anoxic conditions, preventing an important process that can
return fixed nitrogen to atmospheric nitrogen (N2). Biologically available nitrogen (NO3, NO2, NH4,
DON) promotes phytoplankton, blooms. Certain nitrogen species, such as ammonia, can be toxic to
aquatic life. Phosphorus limitation for the growth of phytoplankton has been observed in portions of the
PBS (Murrell et al, 2002). In this situation nitrogen is in excess and it is the amount of phosphorus
entering the system that limits the productivity.
Because of the impact of nutrients on primary productivity they are maj or factors of concern in the
development of limits allowed to be discharged into the PB S. Development of these regulatory limits is
crucial for the protection of biological integrity of estuarine systems. Concentrations of dissolved
nutrients in the surface water are indicators of the amount available for primary productivity. Although no
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Winter
Summer
Spring
Fall
s
CL
Ranges
<2
2-4
>4
Figure 4-5 Seasonal bottom dissolved oxygen concentrations (ppm) of the
Pensacola Bay system.
criteria are established for nutrient concentrations in estuarine surface waters for the State of Florida, an
EPA recommended guideline for estuarine waters isa 10:1 ratioof nitrogen to phosphorus. Nitrogen and
phosphorus concentrations are highest in the bayous of the PB S. These areas are typically poorly flushed
and are the receiving waters for a large amount of urban runoff. The upper portions of Escambia Bay,
closest to the river, tend to be higher in nitrogen and phosphorus, and are diluted by seawater (nutrient
poor) or removed by algal uptake, as the water moves through the system. Nutrient concentrations
observed in the surface waters of the PBS are rarely in excess of 0.1 mg/LN and 0.05 mg/LP The
hydrodynamics of the system, which provide a flushing time for the entire system of 21-34 days, may be
very important in controlling the nutrients in the system, thereby limiting the development and frequency of
algal blooms.
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39%
Factors Affecting Water Quality
100
CO
to
Phosphorus Nitrogen
Water
Clarity
Dissolved
Oxygen
Chi a
Figure 4-6 Percentages of the Pensacola Bay System exhibiting good, fair, or poor water
quality based on a calculated index.
4.8 Water Quality Index
The water quality index that was developed for this report was based on five variables each averaged
across seasons: water clarity, dissolved oxygen, chlorophyll a, nitrogen, and phosphorus. Each of the
variables was assigned a rating of good, fair, or poor. The ratings were then combined to rank each of
the sites. With this ranking, the areal extent of the ratings could be assessed. Based on this approach,
39% of the area of the PBS had good water quality, with 61% having fair water quality, and 0% having
poor (Fig. 4-6). Phosphorus, chlorophyll a concentrations, and reduced water clarity were the major
contributors to the fair ranking.
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5.0 Sediment Quality
Pensacola Bay System sediments are composed mainly of materials which originate up the rivers that
have been washed downstream. Sediment transport throughout the system is dependent upon sediment
grain size and the river flow. Finer sediments, such as silt and clay can be transported throughout, while
the coarser sands tend to settle closer to the river mouths. Pensacola and Escambia Bay sediments are
composed mostly of sand, whereas those from East and Blackwater Bays are mainly clay. Pensacola
Bay sediments were assessed in many ways, based on total organic carbon content, chemical
contaminant concentrations, andbenthic condition.
5.1 Silt /Clay
The silt/clay fraction of sediment is defined as that portion which is less than 63 //m in diameter. If 80%
of a sample of sediment is classified as being silt/clay, it is described as mud, and if < 20% of a sample of
sediment is classified as silt/clay, it is described as sand. There are also a number of descriptions for the
mixtures of the two types. The maj ority of the sediments in the Pensacola Bay System fall between the
two types and are >20%, but <80% silt/clay (Fig. 5-1). The majority of the mud is located along the
delta of the Escambia River or in the bayous of Pensacola Bay.
5.2 Total Organic Carbon
Total organic carbon (TOC) is a measure of how much organic matter occurs in sediments. Runoff and
sewage outfalls may contribute to higher organic content. Carbon content in sediments may be elevated
following algal blooms, rain events, and sewage spills. Decomposition of organic material contributes to
oxygen consumption. In combination with benthic invertebrate community analyses, organic carbon
content can be useful in sediment quality assessment. Total organic carbon content usually correlates
positively with the percentage of silt/clay in the sediments.
Hyland et al. (2000) found that extreme concentrations of TOC can have adverse effects on benthic
communities. TOC levels below 0.05% and above 3.0% were related to decreased benthic abundance
and biomass. No total organic carbon concentrations measured in the PB S fell into the lower end, but
approximately 40% of the area had sediment TOC concentrations in excess of 3.0%. For sediment
quality >5% TOC is considered poor and <2% TOC is considered good. Approximately 5% of the area
within the PB S had TOC concentrations greater than 5.0%. According to the Surface Waters
Improvement and Management Program Report (NWFWMD, 1991), the Pensacola Bay had the
second highest organic carbon content (after Mobile Bay) among Gulf of Mexico estuaries.
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0 2.5 5 10,...
^K—MK_—^^^^^^^^B Miles
Ranges
Mud
Muddy Sand
; Sand
Locator Map
USGS/NWRC 2003-5-0114
Figure 5-1 The extent and locations of different sediment types in the PBS.
5.3 Contaminants
Sediment contaminants (metals, pesticides, PCBs andPAHs) can adversely affect estuarine organisms.
The biological effects of contaminants vary, ranging from acute toxicity to sublethal effects such as
reduced reproductive capability. Industrial and municipal discharges all contribute to urban and
agricultural runoff, accidental spills, and atmospheric deposition. Few regulatory criteria are established
for sediment contaminants, making it difficult to evaluate the levels present in the PBS. Guidelines
developed by NOAA (Long and Morgan 1990, Long et al. 1995) provide benchmarks for determining
contaminant levels that may have negative affects on estuarine organisms. The effects range low (ERL)
is defined as the concentration of a contaminant that may result in biological effects 10% of the time.
The effects range medium (ERM) is the concentration at which a contaminant may have an biological
effect 50% of the time. These guidelines are based on literature surveyed and are considered
experimental.
The Ecological Condition of Gulf of Mexico Estuaries (USEPA1999), reported that areas of Pensacola
Bay had severely contaminated sediments, with as many as 40 chemicals at concentrations greater than
the ERL guideline. These areas were located primarily in the bayous and in the mainstem of Pensacola
Bay. A station in Bayou Texar had sediment with concentrations of mercury, total DDT, and zinc that
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were greater than the ERM guidance. Sediment from stations in both Bayou Texar and Bayou Grande
exceeded the ERL guidance values for all 7 metals listed, with the station in Bayou Grande also exceeding
the ERM value for zinc.
The bayous are small, poorly flushed, partially enclosed bodies of water. Particle retention times are
longer, therefore sediment contaminants may accumulate resulting in higher concentrations than sediments
in the open bay. Additionally, the bayous are more susceptible to human use activities. The higher
sediment contaminant concentrations may reflect all of these factors.
Contaminants accumulated in the sediment may be available for uptake by benthic organisms.
Contaminants may be acutely toxic (kill relatively quickly) to the organism or bio-accumulate (concentrate
in the body tissue). This accumulation can be magnified upwards through the food chain as other
organisms feed on these contaminated ones. This magnified concentration may eventually become toxic
to the upper level consumers. The toxicity of several of the sediments in Pensacola Bay was tested using
standard testing protocols with representative marine organisms. Only sediments collected from Bayou
Texar and Bayou Grande exhibited toxicity towards estuarine amphipods and crustaceans (Lewis et al.
60°/c
32%
• Good
DFair
DPoor
Factors Affecting Sediment Quality
TOO
ERL
ERM
Figure 5-2 Percentages of the Pensacola Bay System exhibiting good, fair, poor
sediment quality based on a calculated index.
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2001). The results of these acute toxicity tests correlate well with the results of the chemical analyses of
bayou sediments exceeding the ERM and ERL guidance values.
5.4 Sediment Index
Based on a cumulative score from three indicators, TOC, concentrations above ERL, and concentrations
above ERM, approximately 8% of the Pensacola Bay System has poor sediment quality (Fig. 5-2).
5.5 Beninic Index
Engle and Summers (1998) used Pensacola Bay to examine the causes of benthic condition. Correlating
the quantity and diversity of organisms living in the sediments with levels of contaminants and the physical
characteristics of the sediment Engle (1998) estimated the overall health of the benthic population. The
benthic index that was created identified 12 of the 40 sites sampled as degraded (Fig. 5-3). These data
were collected from 18 sites in 1996 and were primarily located in the main stem of Pensacola Bay and in
the bayous. In development of the benthic index, Engle and Summers (1998) determined that
concentrations of lead, silver, and the number of contaminants with concentrations greater than the ERL
guidance were the most important parameters distinguishing degraded and undegraded sites.
13%
58%
13%
16%
DGood
DFair
DPoor
D Missing
Figure 5-3 Percentages of the Pensacola Bay System exhibiting good, fair, poor quality
of benthos based on a calculated index.
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6.0 Land Use and Habitat
The PB S, contained within the Escambia River watershed, is influenced by a variety of land use practices.
Forested areas in the upper reaches of the tributaries are the dominant land cover in the Escambia River
watershed (Fig. 6-1) Residential and commercial land use increase with increasing proximity to the PB S.
Emergent woody wetlands comprise approximately 8% of the land area surrounding the Pensacola Bay
System. Wetlands serve as natural filters, improving surface water quality by processing residential,
agricultural and industrial wastes, trapping sediments and removing nutrients, while protecting coastal areas
from storm and wave damage.
In addition to the buffering capacity, wetland and estuarine areas provide essential habitat for fish, shellfish,
migratory birds and other wildlife. Tidal marshes are critical habitats for juvenile shrimp, blue crabs and
some species of gamefish, for example, spotted seatrout. The quality and coverage of wetland habitat has
been linked to the harvest of commercially important species such as shrimp (Boesch and Turner 1984).
Wetland loss in Gulf of Mexico estuaries was high historically, but the rate of wetland loss has slowed
significantly. Drainage and development of wetlands for commercial and residential use are the maj or
cause of wetland loss in the state of Florida (Duke and Kruczynski 1992).
During the period from 1979-1996, the PBS showed a net loss of wetland habitat of approximately 809
hectares, about 7% (Fig. 6-2). Not all of the wetland losses in the Gulf of Mexico are due to coastal
development. Sea-level rise, coastal subsidence, and interference with normal erosion and deposition
processes also contribute. The greatest contribution to wetland loss was attributed to the conversion of
wetlands to uplands; only about 10% of the loss was conversion of wetlands to open water. Recognition
of the ecological and economical importance of wetlands during the last decade has spurred the
restoration and protection of these critical habitat areas.
Seagrass, or S AV, play a vital role in sustaining the ecological functions of estuaries. Water quality and light
availability are key factors determining the health and distribution of S AV. Seagrasses provide food and
other habitat values, such as protection from predators, for many estuarine species. Blue crabs and
estuarine fishes, especially very young juveniles, are often found at much higher densities in SAVbeds than
in unvegetated habitats. Seagrasses act as filters and processors of nutrients and sediments, thereby
helping to stabilize estuarine ecosystems. Since SAV species are sensitive to changes in water quality, loss
of submerged vegetation within an estuary may be indicative of a decline in estuarine health.
SAV decline in the PB S, as documented by Olinger (1975), was significant in Escambia Bay from the
1940s through the early 1970s. By 1974, SAV beds in Escambia Bay were almost nonexistent (Rogers
andBisterfield 1995). A gap in survey datafor SAVbeds forthePBS existed until theearly 1990s. A
1992 USGS survey showed a significant improvement in the distribution of SAV in Escambia Bay (Fig 6-
3). The increase in SAV coverage has been attributed to reduced nutrient loadings, achieved through
improved wastewater treatment methods. Mapping and monitoring of SAV in the Pensacola Bay System
in 1998 showed continuing improvement in upper Escambia Bay. According to Lores and Specht (2001),
grassbeds in areas of the system characterized by lower salinities are recovering faster than those
associated with higher salinity. Coastal development is considered to be the major cause for the lack of
SAV recovery in higher salinity areas.
25
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28
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As with the abundance of SAVbeds, shellfish beds may be an indicator of the biological health of an
estuarine system. The Pensacola Bay system could be a very productive oyster harvest area based on
hydrographic data such as salinity and temperature regimes. Oyster landings for Escambia County
peaked in 1970 at approximately 63,502 kg (Collard 1991). Unfortunately, by 1971, over 90% of the
commercially harvestable oysters in Escambia Bay fell victim to the parasitic disease caused by
Perkinsus marinus, also known as Dermo. Lack of the hard substrate that larval oysters require for
settlement, due to removal of dredged material and the loss of living oyster reefs to disease, has
contributed to the decline. Although water quality has improved dramatically over the last two decades,
oyster populations within the system have been slow to recover. Suitable substrate may be a limiting
factor at present. Habitat restoration projects such as Project Greenshores are attempting to restore
oyster reef habitat (FLDEP 2001). These restoration attempts may provide vital information in re-
establishing oyster populations within the system.
In summary, the Pensacola Bay System suffered a period of maximum environmental degradation in the
late 1960s-early 1970s, apparent in the loss of SAV and oyster beds during that period. The
improvement of water quality and implementation of best land use practices, in conjunction with
protection of wetland areas, are vital steps in the restoring and protecting the ecological health of the
PBS.
29
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30
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7.0 Ecological Condition
In determining the current ecological condition of the PB S three indices were used: a water quality index, a
sediment quality index, and benthic condition index. The supplemental information for developing the
indices was presented in the appropriate sections. The three indicators were assigned a good, fair, and
poor rating. These ratings were each assigned numerical values which were then averaged in order to
create an overall score for the PBS. The use of indicators to describe coastal condition is still
experimental. In this report, condition rating is based on reference conditions to address change in
expectations for the indicators. The overall ecological condition for the PBS was assessed using a
straightforward combination of the indicator scores.
Water Quality
39%
61%
Sediment Quality
32%
60%
Benthic Condition
8%
Good
Fair
Poor
Missing
Ecological Condition
13%
58%
16%
16%
68%
Figure 7-1 Percentages of the Pensacola Bay system exhibiting the different levels
based on different indicator scores.
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For water quality, 30% ofthe PBS was in good condition, with61%fair (Fig. 7-1). The quality of the
sediment was more diverse, with 8% poor, 60% fair, and 32% good. For benthic organisms, 16% of
the area was poor, 13% fair, and 58% good, with 13% having missing values. When the results of these
analyses were combined to determine the ecological condition ofthe system it indicated that 16% was
poor, 68% was fair, and 16% was in good condition.
Results from these indices agree with the popular interpretation of current condition ofthe system.
Overall, the PB S could be described as being in fair to good condition. There are periods, usually in the
summer, when portions ofthe bottom ofthe system become hypoxic. The PBS can become stratified
and contain temporarily elevated populations of pathogens, all associated with rainfall events. Though it
is slow to flush, there were no highly elevated concentrations of contaminants in any ofthe sediments,
with the exception ofthe bayous which will be addressed in a following section. According to our
sediment index 92 % ofthe sediment is in good or fair condition, and the area of wetlands within the
system has increased. However, the area of SAV throughout the system is still declining.
32
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8.0 Bayous
8.1 Description
Three small tidal estuaries, Bayou Texar, Bayou Chico, and Bayou Grande, are located in the northwest
portion of PensacolaBay (Fig. 8-1). Each of these bayous is shallow and each receives runoff from areas
with different land uses. Because of these factors some of the responses reported for the PBS have really
been occurring in the bayous. Our study design did not supply enough data points to calculate indices and
perform separate assessments, but the bayous have been well characterized. The most recent data have
been summarized for this report.
Figure 8-1 Locations of Bayou Texar, Bayou Chico, and Bayou Grande.
33
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8.2 Bayou Texar
Lewis (2001) characterized Bayou Texar as having a surface area of 1.4 km2 with a volume of 3 million
cubic meters (3 x 106 m3) and an average depth of 2 meters. It is described as a residential bayou with
recreational uses. It flushes at a higher rate than the other bayous, approximately 24% of its volume
daily. There are several factors acting upon Bayou Texar that can potentially impact it. There are
maintained lawns extending to the water's edge, it receives stormwater runoff from Carpenters Creek,
and it also receives groundwater from a superfund site. Bayou Texar designated use is for recreational
fishing and water sports.
Bayou Texar exhibits annual concentrations of nitrogen and phosphorus that are greater than the other
bayous and the PBS (Smith et. al. 2001). The elevated nutrients correlate with a high concentration of
chlorophyll a in the bayou. Concentrations of nitrogen have been observed to be four times greater than
those measured in the open bay system during the summer. Spring fertilizer application and increased
stormwater runoff may be driving the nitrogen concentrations. There have also been elevated levels of
fecal bacteria associated with the runoff events, causing closure of the bayou to recreational activities.
Surface waters in Bayou Texar exceed the State of Florida criteria for Class III waters for cadmium,
copper, and nickel (Table 8-1). Sediment concentrations of polycyclic aromatic hydrocarbons (PAHs),
DDTs, copper, lead, cadmium, and zinc exceed both the probable effects level (PEL) for the State of
Florida and ERL guidance value. Sediment concentrations of mercury in the upper bayou exceed the
ERM guidance values (Table 8-2).
TableS-l.Analyte
Maximum measured concentration in water (ug/L).
Values in bold exceed the FL criteria for Class III marine waters.
Cadmium
Chromium
Copper
Lead
Nickel
Zinc
Criteria
9.3
50
2.9
5.6
8.3
86
Bayou Texar Bayou Chico Bayou Grande
15.0
43.0
22.4
ND
33.0
22.3
13.7
36.5
18.7
ND
29.5
21.7
13.5
13.7
18.2
ND
16.7
22.6
ND= Below detection limit.
34
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8.3 Bayou Chico
Bayou Chico is the smallest of the three bayous with a surface area of 1.0 km2, volume of 2 million cubic
meters (2 x 106 m3), and an average depth of 2 meters. The land use surrounding Bayou Chico is split,
with the southern portion industrial and the northern portion residential. The industrial area consists of
marinas, dry docks, ship construction, barge operations, metals salvage, and a large chemical manufacturing
facility. Stormwater runoff has impacted the bayou to such an extent that the local government and citizen
groups have focused on efforts to control runoff through increased treatment and regulation. In addition to
the stormwater, Bayou Chico also receives the discharges from a large number of septic tank drain fields.
Seasonally, Bayou Chico had the highest concentrations of chlorophyll a (30 //g/L) in the summer, higher
than any of the other bayous, although the nitrogen and phosphorus levels never exceeded 0.15 mg/L. A
chlorophyll concentration of this level would classify Bayou Chico as impaired under the State of Florida
criteria, and rank poor using our index. Surface waters from the bayou exceeded the State of Florida
criteria for Class III waters for cadmium, copper, and nickel (Table 8-1). Sediment concentrations of
poly chlorinated biphenyls (PCBs), DDTs, copper, lead, and zinc exceeded the PEL and ERL values.
Concentrations of arsenic, cadmium, and mercury in the sediments also exceeded the ERL value (Table 8-
2).
Table 8-2.
Analyte Maximum measured concentration in sediment.
Metals (ug/g dry wt.), Organics (ng/g dry wt).
Values in bold exceed the ERL guidance (Long et al. 1995).
ERL Bayou Texar Bayou Chico Bayou Grande
Arsenic 8.2 1.1 11.7 7.9
Cadmium 1.2 2.9 1.9 4.8
Chromium 81 51.7 56.8 178.1
Copper 34 237.8 206.9 38.1
Lead 46.7 155.5 147.5 128.9
Mercury 0.15 1165.2s 428.1 172.9
Nickel 20.9 17.4 20.4 14.2
Zinc 150 1069.6 979.9 199.2
Total DDT 1.6 29.3 80.5 17.2
Total PAHs 4020 4475.2 - 179.1
Total PCBs 22.7 22.9 99.7 70.2
* Value exceeds the ERM guidance (Long et. al.)
35
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8.4 Bayou Grande
Bayou Grande is approximately four times larger than the other two bayous, with a surface area of 4.3
km2, a volume of 10 million cubic meters(l x 107m3), and an average depth of 3 meters. Land use
around the bayou is mixed; residential on the northern side, with a military installation (Naval Air Station
Pensacola) to the south. Both areas contribute to the stormwater runoff into Bayou Grande, and the
residential side has a large number of septic tank drain fields. Naval Air Station Pensacola has a marina,
a golf course, aircraft runway, and areas of dense woods adj acent to the bayou. In addition, NAS
Pensacola also has restoration sites or areas that have been identified as requiring contamination
assessment and soil remediation. The bayou is utilized for both recreational fisheries and watersports.
The chlorophyll and nutrient concentrations in Bayou Grande are similar to those measured in the open
bay system. The only exception was that chlorophyll a was elevated (12 //g/L) in the summer compared
to the open bay (6 //g/L). The surface waters in Bayou Grande contained concentrations of cadmium,
copper, and nickel that exceeded the State of Florida criteria for Class III waters (Table 8-1).
Sediments from the bayou exceeded the PEL and ERL for cadmium, chromium, lead, and DDTs. The
ERL was also exceeded for PCBs, copper, mercury, and zinc (Table 8-2).
8.5 Summary
All three bayous, Texar, Chico, and Grande, had concentrations of the same contaminants present in the
water and in the sediment. Each bayou had 8 compounds exceed of the ERL guidance values for
sediment and 3 exceedances of the State of Florida criteria for Class III waters. Bayou Grande
exhibited the lowest concentrations of contaminants in both the water and sediment compared to the
other 2 bayous. Bayou Chico ranked next, followed by Bayou Texar with highest concentrations of
contaminants. The absence of similar concentrations of contaminants found in the bay system outside
each of the bayous indicates that the material may not be easily transported. These contaminants may
be binding to the sediments and remaining in the bayous due to the low flushing and transport rates. The
bayous appear to be acting as sinks or catchment basins for a large amount of the stormwater runoff.
Because each bayou is somewhat isolated from the bay system, the effects of stormwater runoff are
contained and in some cases magnified, as indicated by algal blooms and closures due to bacterial levels.
36
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9.0 References
Boesch, D. E, andR. E. Turner. 1984. Dependence of Fishery Species on Salt Marshes: The Role of
Food and Refuge. Estuaries Vol. 7, No. 4A, 460 - 468.
Collard, S.B.: 1991, Surface water improvement and management plan (S.W.I.M.) Program. The
PensacolaBay System: Biological Trends and Current Status. Water Resources Special Report 91-3,
Northwest Florida Water Management District, Havana, Florida.
Duke, T.W., and W.L. Kruczyski, eds. 1992, Status and trends of emergent and submerged vegetated
habitats of the Gulf of Mexico, USA. Gulf of Mexico Program, U.S. Environmental Protection Agency,
John C. Stennis Center, MS. 161 pp.
Engle, V.E. and J.K. Summers 1988. Determining the causes of benthic condition. Environmental
Monitoring and Assessment 51: 3 81 -3 97.
FLDEP. 2001. Project GreenShores Summary. Northwest District, Florida Department of
Environmental Protection, Pensacola, Florida.
George, S.M. 1988. The sedimentology and mineralogy of the Pensacola Bay System. M.S. Thesis,
Univ. So. Mississippi, Hattiesburg, MS, 95 p.
Flinga, K.R. 2002. The Effects of pH on Marine Phytoplankton in coastal environments. Mar. Ecol.
Prog. Ser. 238:281-300
Hyland JL, Balthis WL, Hackney CT, Posey M. 2000. Sediment quality of North Carolina estuaries: an
integrative assessment of sediment contamination, toxicity, and condition of benthic fauna. Journal of
Aquatic Ecosystem Stress and Recovery 8(2): 107-24.
Lewis, M.A., J.C. Moore, L.R. Goodman, J.M. Patrick, R.S. Stanley, T.H. Roush, andR.L. Quarles
2001. The effects of urbanization on the chemical quality of three tidal bayous in the Gulf of Mexico.
Water, Air, and Soil Pollution 127: 65-91.
Long, E.R., D.D. MacDonald, Smith, S.L., and Calder, F.D.: 1995, Incidence of adverse biological
effects within ranges of chemical concentrations in marine and estuarine sediments. Environmental
Management 19(1): 81-97.
Long, E.R. and Morgan, L.G: 1990. The potential for biological effects of sediment-sorbed
contaminants tested in the National Status and Trends Program. NOAATechnical Memorandum NOS
OMA52. NOAA, Rockville, MD.
Lores,E. M. andD. T Specht. 2001. Drought-Induced Decline of Submerged Aquatic Vegetation in
EscambiaBay, Florida. GulfMex. Sci. 19(2): 161-164.
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Murrell, M. C., R. S. Stanley, E. M. Lores, G. T. DiDonato, L. M. Smith and D. A. Flemer. 2002.
Evidence That Phosphorus Limits Phytoplankton Growth in a Gulf of Mexico Estuary: Pensacola Bay,
FL, USA. Bull. Mar. Sci. 70(1): 155-167.
Pritchard,D.W. 1955. Estuarine circulation patterns. Proc. Am. Soc. Civil. Engin. 81:1.
Rogers, R.G, andBlisterfiels, F.T.: 1995. Loss of Submerged Aquatic Vegetation in the Pensacola Bay
System, 1949-1974. In: Proceedings ofthe Second Annual Conference on Restoration of Coastal
Vegetation in Florida. R.R. Lewis (ed.), pp. 35-51.
Schindler, D. W. 1991. Aquatic Ecosystems and Global Ecology in Fundamentals of Aquatic Ecology.
R.S. Barnes and K.H. Mann Eds. Blackwell Scientific Publications, Oxford. 118 p.
Smith, L. S., W.G Craven, J.M. Macauley, and J.K. Summers. 2001. Spatial and Temporal Variation in
Nutrient Concentrations and Phytoplankton in Three Northwest Florida Bayous. Estuarine Research
Federation Annual Meeting 2001.
Summers, J.K., J.F. Paul, and A. Robertson. 1995. Monitoring the Ecological conditions of Estuaries in
the United States. Toxicological and Environmental Chemistry 49,93.
SWIM. 1991. Surface Water Improvement and Management (S.W.I.M.) Program. The Pensacola Bay
System; Biological Trends and Current Status. Northwest Florida Water Management District. 181p.
SWIM. 1997. The Pensacola Bay system Surface Water Improvement and Management Plan. Program
Development Series 97-2. Northwest Florida Water Management District. 146p.
USEPA. 1999. Ecological Condition of Estuaries in the Gulf of Mexico. EPA620-R-98-004. U.S.
Environmental Protection Agency. Office of Research and Development, National Health and
Environmental Effects Research Laboratory, Gulf Ecology Division, Gulf Breeze, Florida.
USEPA 1975. Environmental and Recovery Studies of Escambia Bay and the Pensacola Bay System,
Florida. EPA-904/7-76-016. U.S. Environmental Protect on Agency. Region IV Survey and Analysis
Division.
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