EPA/600/R-15/176
                                                             ERASC-015F
                                                             October 2015
DETERMINATION OF THE BIOLOGICALLY RELEVANT SAMPLING DEPTH
  FOR TERRESTRIAL AND AQUATIC ECOLOGICAL RISK ASSESSMENTS
                    Ecological Risk Assessment Support Center
                   National Center for Environmental Assessment
                       Office of Research and Development
                      U.S. Environmental Protection Agency
                               Cincinnati, OH

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                                        NOTICE

       This document has been subjected to the Agency's peer and administrative review and
has been approved for publication as an EPA document. Mention of trade names or commercial
products does not constitute endorsement or recommendation for use.
Cover art on left-hand side is an adaptation of illustrations in two Soil Quality Information
Sheets published by the USD A, Natural Resources Conservation Service in May 2001: 1)
Rangeland Sheet 6, Rangeland Soil Quality—Organic Matter, and 2) Rangeland Sheet 8,
Rangeland Soil Quality—Soil Biota.

Cover art on right-hand side is an adaptation of an illustration from Life in the Chesapeake Bay,
by Alice Jane Lippson and Robert L.  Lippson, published by Johns Hopkins University Press,
2715 North Charles Street, Baltimore, MD 21218.
Preferred Citation:
U.S. EPA (U.S. Environmental Protection Agency). 2015. Determination of the Biologically Relevant Sampling
Depth for Terrestrial and Aquatic Ecological Risk Assessments. National Center for Environmental Assessment,
Ecological Risk Assessment Support Center, Cincinnati, OH. EPA/600/R-15/176.
                                            11

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                         TABLE OF CONTENTS
LIST OF TABLES	iv
LIST OF FIGURES	iv
LIST OF ABBREVIATIONS	v
AUTHORS, CONTRIBUTORS, AND REVIEWERS	vi
EXECUTIVE SUMMARY	1

l.PART 1. TERRESTRIAL BIOTIC ZONE	3
     1.1. INTRODUCTION	4
     1.2. METHODS	4
           1.2.1. DATA EXTRACTION	4
           1.2.2. STATISTICAL ANALYSIS	5
     1.3. RESULTS AND DISCUS SIGN	6
           1.3.1. META-ANALYSIS RESULTS	6
           1.3.2. RECOMMENDATION OF SAMPLING DEPTH	7
     1.4. REFERENCES	8

2. PART 2. AQUATIC BIOTIC ZONE	16
     2.1. INTRODUCTION	17
     2.2. BENTHIC ORGANISMS AND THEIR ENVIRONMENT	18
     2.3. BENTHIC HABITAT TYPES	19
          2.3.1. LOTIC VERSUS LENTIC ENVIRONMENTS	20
          2.3.2. HYPORHEIC ZONE	20
     2.4. METHODS	21
     2.5. RESULTS—BENTHIC BIOTIC ZONE: ABUNDANCE AND BIOMASS	22
     2.6. DISCUSSION	23
     2.7. RECOMMENDATION	24
     2.8. REFERENCES	25

APPENDIX	68
                                 in

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                                  LIST OF TABLES
1.      Summary of Data Used in Meta-analysis	12

2.      Parameter Estimates and 95% Lower and Upper Confidence Intervals51 (LCL and
       UCL, Respectively) for the Nonlinear Function (See Equation 1) Fit to
       Standardized Data for Both Forests and Grassland Environment Types	13

3.      Examples of Deep-Burrowing and/or Feeding Benthos	46

4.      Data Sources and Information (Realms/Ecoregions after Spalding et al., 2007
       [marine] and Abell et al., 2008 [freshwater]) used to Determine 80th Percentile of
       Benthic Abundance (see Figure 3) and Benthic Biomass (see Figure 4) Depth
       Distributions	57

5.      Biologically Relevant Sediment Depths—Biotic Zones—for Decisions Related to
       Ecological Assessment or Remediation	65
                                 LIST OF FIGURES
1.     Nonlinear (see Equation 1) Relationships Between Standardized (mean = 0;
      SD = 1) Biological Metrics and Their Midpoint Sampling Depths for Forests and
      Grasslands	14

2.     Illustration of the Average Biologically Relevant Sampling Depth	15

3.     Mean 80th Percentile of Benthic Abundance Depth Distribution (+ Maximum 80th
      Percentile) in Various Habitats	66

4.     Mean 80th Percentile of Benthic Biomass Depth Distribution (+ Maximum 80th
      Percentile) in Various Habitats	67
                                          IV

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                            LIST OF ABBREVIATIONS
ANOVA     analysis of variance
Eh           redox potential
EPA         U.S. Environmental Protection Agency
ERA         ecological risk assessment
ERAF        Ecological Risk Assessment Forum
ERASC      Ecological Risk Assessment Support Center
IT           intertidal
LCL         lower confidence limit
NCEA       National Center for Environmental Assessment
NOAA       National Oceanographic and Atmospheric Administration
NRCS        Natural Resources Conservation Service
ORD         Office of Research and Development
PLFA        phospholipid fatty acids
SD           standard deviation
ST           subtidal
UCL         upper confidence limit
USDA       U.S. Department of Agriculture

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                  AUTHORS, CONTRIBUTORS, AND REVIEWERS
AUTHORS
Michael Kravitz
U.S. Environmental Protection Agency
Office of Research and Development
National Center for Environmental Assessment
Cincinnati, OH 45268

Richard H. Anderson1
U.S. Environmental Protection Agency
Office of Research and Development
National Center for Environmental Assessment
Cincinnati, OH 45268
REVIEWERS

Roman P. Lanno
Ohio State University
Columbus, OH

Roberto J. Llanso
Versar, Inc.
Columbia, MD

Michael J. Paul
Tetra Tech, Inc.
Research Triangle Park, NC
                              ACKNOWLEDGMENTS
       This research was supported in part by an appointment to the Research Participation
Program at the U.S. Environmental Protection Agency (EPA) National Center for Environmental
Assessment (NCEA) administered by the Oak Ridge Institute for Science and Education through
an interagency agreement between the U.S. Department of Energy and EPA. The first draft of
this document was internally (within EPA) reviewed by Michael Griffith (EPA Office of
Research and Development, National Center for Environmental).
1 Permanent Address: Air Force Center for Engineering and the Environment (AFCEE), Technical Support Division,
San Antonio, TX.
                                          VI

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            AUTHORS, CONTRIBUTORS AND REVIEWERS (continued)
Assessment [ORD/NCEA]) and Mark Sprenger (EPA Emergency Response Team Region 2).
David Farrar of EPA/ORD/NCEA provided useful comments on the manuscript. Amy Prues,
Dan Heing and other members of ECFlex, an EPA contractor, provided technical support under
contract EP-C-06-088. Programmatic review was conducted by Katie Matta (EPA Region 3) and
Marc Greenberg (EPA Emergency Response Team Region 2), both Trichairs of EPA's
Ecological Risk Assessment Forum.  This document was externally peer reviewed under contract
to Versar Inc., 6850 Versar Center, Springfield, VA 22151 (contract EP-C-07-025).
                                        vn

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                               EXECUTIVE SUMMARY

       Ecological risk assessors are frequently faced with the challenge of defining the
biologically active zone, or "biotic zone," in soils and sediments during the design and
interpretation of soil and sediment sampling programs.  Knowledge of the biotic zone is
necessary when evaluating sediment/soil concentrations, calculating risks to ecological receptors,
and attempting to delineate the relevant depth for remediation at sites where an action is needed.
As current practice with regards to determining the biotic zone is quite varied, EPA's Ecological
Risk Assessment Forum (ERAF) submitted a request to Office of Research and Development
(ORD)'s Ecological Risk Assessment Support Center (ERASC) to develop a scientifically
defensible definition for the depth of the biotic zone in soils and sediments (see Appendix). In
response to the ERAF request, the present document attempts to provide defensible
approximations for what the depth of the biotic zone is within certain environments.  Actual
sampling depths may be modified by the assessor based on the purpose of the assessment. The
primary audience for this document is Superfund staff and contractors, and ecological risk
assessors, though general ecologists should find the information useful as well. The methods
used in this study differ somewhat between Part 1 (Terrestrial Biotic Zone) and Part  2 (Aquatic
Biotic Zone). In Part 1, biological activity was quantified in forests and grasslands as a function
of depth across selected metrics. In Part 2, the biotic zone(s) in various habitats was based on the
80th percentile of abundance or biomass depth distributions. Part 1 has also been summarized in
Anderson etal., (2010).
       Part 1 (Terrestrial Biotic Zone) of this study uses a meta-analysis approach to quantify
the zone  of highest biological activity for soil-dwelling ecological receptors commonly utilized
in ecological risk assessments (ERAs). Endpoints evaluated include: invertebrate density,
microbial biomass carbon (C), microbial density, mycelium production, root biomass, root
production and total phospholipid fatty acids (PLFA). Results suggest sampling strategies
should be adaptive allowing for variable depths. If constant depths are utilized, our  results
suggest that samples should be collected to a depth of approximately 25-30 cm.
       Part 2 (Aquatic Biotic Zone) explores data from a wide realm of habitat types in an
attempt to develop habitat-specific practical default values for the depth of the biotic zone, where
most organism-substrate interactions occur.  We recommend that the depth of the biotic zone be
based upon the 80th percentile of abundance or biomass depth distributions. The biotic zone,
based on benthic abundance, in most estuarine and tidal freshwater environments is 10 or 15 cm.
Exceptions are oligohaline and polyhaline mud (5 cm) and oligohaline sand (5 cm).  In marine
muds (both coastal and offshore), the biotic zone is 15 cm.  In other marine substrates it is 10 cm
(marine coastal mixed and marine offshore sand) or 5 cm (marine coastal sand). In lentic

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environments, the biotic zone is 15 cm. The biotic zone tends to be deeper when biomass is
taken into account.  The biotic zone in lotic systems varies from 15 to 35 cm depending upon
water/habitat type.  In areas populated by a high density of deep dwelling organisms such as the
examples provided, the biotic zone may be somewhat deeper than our recommended values.

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1. PART 1. TERRESTRIAL BIOTIC ZONE

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                                 1.1.  INTRODUCTION

       Risk assessors are frequently faced with the challenge of defining the biologically
relevant sampling depth or "biotic zone" in soils and sediments during the design and
interpretation of ecological studies. This may have important implications when evaluating
ecological risk and/or designing a remediation scenario. For example, contamination occurring
in layers deeper than the zone where most organisms live or feed may not be relevant to
assessing ecological risk. In essence, spatial and vertical co-occurrence of soil contamination
and ecological receptors need to be considered to estimate risks. While methodologies have
been proposed that focus on optimizing the spatial scale of sampling efforts (Hathaway et al.,
2008; Taylor and Ramsey, 2005), sampling depths for ERAs are usually dictated by the vertical
distribution of soil contamination (Singh et al., 2008) or default to a generic value.  These
approaches may not adequately reflect site-specific exposures to soil biota.  The default sampling
depth for estimating exposure of plants, as well as earthworms, to contaminants  has been
reported as the top 30 cm (Suter, 2007); the top 12 cm has also been recommended as a default
sampling depth for estimating exposure of plants to metals (U.S. EPA, 2005). The purpose of
this study is to use a meta-analysis of ecological literature  to quantify the zone of highest
biological activity for soil-dwelling ecological receptors, and to determine whether or not a
default value for the biologically relevant (soil) sampling depth can be supported.

                                    1.2.  METHODS

1.2.1. DATA EXTRACTION
       Nonagricultural literature was searched using the Academic Search Complete database.
Journal articles were limited to primarily 2000 through 2009. An exception was made in the
case of a recent summary paper that cites earlier studies (Briones et al., 2007). There were no
restrictions on publication sources so long as they were peer-reviewed.  The database was
searched with iterative combinations of (1) the keyword "soil" (2) keywords to locate studies
containing appropriate biological metrics and (3) keywords to locate studies examining the
metrics at stratified depths.  Literature searches were restricted to soil invertebrate, plant, and
microbial endpoints.  Specifically, endpoints evaluated include: invertebrate density, microbial
biomass carbon (C), microbial density, mycelium production, root biomass, root production and
total PLFA.  Studies were further restricted to those with data extractable from a table or a
readable graph, reporting the depth for the top and bottom of each sample observation.
       A categorical variable that refers to the dominant matrix vegetation at each site was
defined and referred to as the "environment type" (e.g., forest, grassland, desert, shrubland, etc.)

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and was extracted via site descriptions in the articles.  However, sufficient data (n> 10) only
existed for forests and grasslands. Consequently, only data from forests and grasslands were
included in the analyses and are summarized in Table 1, which includes the biological metric,
environment type, and number of depth intervals for each study. Admittedly, grouping sites into
categories defined by generalized classes of vegetation is an oversimplification of the complexity
of natural  systems. However, we default to broad scale patterns in ecological organization
necessary  for meta-analyses of biological processes using studies with highly variable
environment conditions (Levin, 2005).
       An additional categorical variable that refers to the climate at each study site was also
determined and included in analyses. Climate type was determined in a Geographic Information
System. First, the geographic locations of study sites were extracted via site descriptions in the
articles. Each site was then mapped with the Koppen-Geiger climate classification data (Kottek
et al., 2006) and assigned a climate type based on its placement on the map.  The broadest
Koppen-Geiger categories (e.g., tropical humid [equatorial], dry [arid], mild mid-latitude [warm
temperate], severe mid-latitude [snow], and polar) were used.

1.2.2. STATISTICAL ANALYSIS
       Primary objectives of data analyses were to quantify biological activity as a function of
depth for the selected metrics.  To facilitate these objectives, paired data were necessary.
Consequently, the midpoint of each depth interval was calculated to relate to the corresponding
metric value reported from that particular depth interval.  Relationships between midpoint depths
and biological metric values were subsequently evaluated.
       Relationships were evaluated collectively across metrics. However, it was first necessary
to scale observations. First, all data within a metric were converted to a standard unit. Standard
units were determined as the unit that was most frequently reported within a metric.
Subsequently, all data within a metric were standardized to a standard normal variable
(mean = 0, standard deviation [SD] = 1) across depths, environment types, and climates because
each metric produced values with unique units or a completely different range of values for the
same unit.  Standard normal variables are simply computed by subtracting off the mean and
dividing by the standard deviation.  The idea being that data from similar depths would produce
similar standardized metric values (i.e., z scores) that fall reasonably close to one another on the
standard normal probability distribution allowing observations to be evaluated for depth,
environment type, and climate effects across metrics.
       Trends between standardized metric values and midpoint depths followed an exponential
decay pattern. Consequently, nonlinear regression with an exponential decay function was used

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to model relationships.  Because standardized metric values contained both positive and negative
values, a three parameter exponential decay function was utilized of the form:

                                                                                  (Eq. i)

where y is standardized metric value, A is thej/-intercept, B is a slope parameter, and C is a scale
parameter necessary because metric values contained both negative and positive values.
       Preliminary analyses indicated that significantly (a = 0.05) different trends occurred
between grasslands and forests as determined by contrasting residual sums of squares for full
(both forests and grasslands) and nested reduced (forests and grasslands separately) models (see
Equation 1). Consequently, Equation 1 was fitted to data from forests and grasslands separately.
Unique parameters were estimated for each environment type. Climate effects were
subsequently evaluated by testing the residuals from Equation 1 for differences across climate
types within each vegetation class by analysis of variance (ANOVA). Nonlinear regression was
performed using PROC NLIN and ANOVA was performed using PROC GLM in SAS
Version 9.2 for Windows.

                           1.3. RESULTS AND DISCUSSION

       Common soil-dwelling receptor groups evaluated during ERAs consist of plants and
invertebrates (U.S. EPA, 2005). Microbial endpoints can be impacted by environmental
contaminants (Giller et al., 1998), but they are often considered too variable to provide utility as
a basis for chemical-specific soil screening levels (U.S. EPA, 2005). However, abundance of
microbial communities is tightly coupled with the quality (i.e., carbon:nitrogen ratio) of
substrates and  regulates essential nutrient (e.g., nitrogen) availability in soils (Friedel and Gabel,
2001).  Thus, microbial endpoints affect other higher order endpoints through feedback loops
and were considered essential to our objectives.

1.3.1. META-ANALYSIS RESULTS
       Relationships between the standardized metric meta-data and their corresponding
midpoint sampling depths are presented in Figure 1. Three-parameter exponential decay
functions (see Equation 1) were fitted to meta-data for grassland and forests separately. Climate
was not significant (a = 0.05) and did not influence relationships. Parameter estimates and
approximate confidence intervals are presented in Table 2. Both models were highly significant
(p < 0.0001). Grasslands produced an exponential decay function with higher standard normal

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scores and a steeper slope indicating relatively higher values for each common metric (i.e.,
invertebrate density, mycelium production, and root biomass; see Table 1) and a faster rate of
decline. However, both functions resulted in an asymptotic plateau at roughly 27 cm (see
Figure 1).
       Grassland soils contain greater amounts of organic matter than forest soils because of
higher primary production rates at steady state with decomposition (Zak et al., 1994). In general,
matrix vegetation in grasslands consists of perennial herbaceous plants with high root densities
and receive relatively less precipitation (Saviozzi et al., 2001).  This greatly suppresses microbial
decomposition and allows for the accumulation of organic matter, which produces soils with
darker surface horizons relative to forest soils (NRCS, 2003). As a result, soil biota are usually
more productive in grasslands because they experience less carbon limitation (Zak et al., 1994),
which is consistent with Figure  1.

1.3.2. RECOMMENDATION OF SAMPLING DEPTH
       Soils are highly heterogeneous mixtures of inorganic and organic constituents. Complex,
multi-trophic assemblages of organisms comprise the soil biology and inextricably interact with
and feed back to the soil organic matter resulting in a zone  of interdependent biological
processes referred to as the rhizosphere.  Microorganisms are essential to the rhizosphere through
the development of stable organic compounds (i.e., humic substances) and the hierarchical
structure of soil aggregates (Kandeler et al., 2001).  Soil organic matter is responsible for giving
the rhizosphere its characteristic darker color, which in general  soil classification terms is
referred to as the A horizon (NRCS, 2003).  Soil organic matter provides a source of energy for
microbial respiration, which in turn regulates essential plant nutrients (Luxhoi et al., 2006).
Consequently, the A horizon, via the rhizosphere, provides the foundation to the food web for
soil ecosystems and should contain the vast majority of biological activity.
       Results from Figure 1 were compared to the average depth of soil horizons.  Accordingly,
a regional data set was obtained from the U.S. Department  of Agriculture (USDA) National
Resource Conservation Service  (NRCS) Cooperative Soil Survey Program. Depths of dominant
soil horizons (O, A, B, and C) were utilized, which were measured from 636 soil pedons (i.e., the
smallest volume of material that can be called "soil") from  around the conterminous United
States. The database is freely available and can be accessed online at
                                                   Only data from Alfisol (characteristic
forest soil) and Mollisol (characteristic grassland soil)  soil orders  (i.e., the highest level of USDA
classification) were evaluated (NRCS, 2003).
       Figure 2 illustrates the average biologically relevant sampling depth. Mean horizon
depths for both Mollisol and Alfisol soil orders are shown overlaid on the first derivatives of

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Figure 1. Mollisol and Alfisol soil orders are characterized with mean A horizons that extend to
19.3 and 20.2 cm, respectively. First derivatives from Figure 1 reach an approximate minimum,
on an absolute scale, at 27 cm, roughly consistent with the mean depth of A horizons, although
depths associated with derivative values are midpoints of a sampling interval.  However,
standard deviations for mean A horizon depths for Mollisol and Alfisol soil orders are 19.4 and
53.6, respectively,  suggesting the minimum (on an absolute scale) derivative value of 27 cm falls
within error limits  of the A horizon for both soil orders.  Thus, a definitive  conclusion of this
study is that A horizons, although not necessarily all inclusive, represent the average biologically
active zone, at least for the metrics evaluated. Hence, capturing the A horizon is paramount to
accurately evaluating potential exposure of environmental contaminants to  soil biota.
       Soil development is rarely uniform and processes such as erosion and deposition can
influence the vertical distribution of biological activity across landscapes.  Sampling strategies
where a constant depth is collected may not accurately reflect site-specific  exposures of
environmental contamination to the soil biota. Samples that  either fail to capture the extent of, or
exceed, the A horizon may not accurately represent contaminant exposure to soil biota, resulting
in inaccurate risk estimates. The depth of horizontal soil horizons can vary across the landscape
(Luxhoi et al., 2006), which may also confound ERAs that utilize a constant depth.
Consequently, sampling strategies should be adaptive allowing for A horizons with variable
depths.  If constant depths are utilized, our results suggest that samples should be collected to a
depth of approximately 25-30 cm (see Figure 2) as opposed to shallower depths.

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fauna of a mixed coniferous forest and the effects of urea fertilization. Oikos 32:318-327.
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decouple the impact of correlated environmental variables on soil microbial community
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Altesor, A; Pifierio, G;  Lezama, F; et al. (2006) Ecosystem changes associated with grazing in
subhumid South American grasslands. J Veg Sci 17:323-332.
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Borken, W; Kossmann, G; Matzner, E. (2007) Biomass, morphology and nutrient contents of
fine roots in four Norway spruce stands.  Plant Soil 292(l-2):79-93.

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Briones, MJI; Ineson, P; Heinemeyer, A. (2007) Predicting potential impacts of climate change
on the geographical distribution of enchytraeids: a meta-analysis approach. Glob Change Biol
13(ll):2252-2269.

Chalupsky, J. (1986) Czechoslovak enchytraeids (Oligochaeta Enchytraeidae) I. Enchytraeids
from an apple orchard by Bavorov in south Bohemia. Vest cs Spolec zool 50:13-21.

Chiba,  S; Abe, T; Kondoh, M; Shiba, M; Watanabe, H. (1976) Studies on the productivity of soil
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Claus, A; George, E. (2005) Effect of stand age on fine-root biomass and biomass distribution in
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Davis, M; Nordmeyer, A; Henley, D; et al. (2007) Ecosystem carbon accretion 10 years after
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Friedel, JK; Gabel D. (2001) Microbial biomass and microbial C:N ratio in bulk soil and buried
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Giller, KE; Witter, E; McGrath, SP.  (1998) Toxicity of heavy metals to microorganisms and
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Hathaway, JE; Schaalje, GB; Gilbert, RO; et al. (2008) Determining the optimum number of
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Hutha,  V. (1984) Response of Cognettia sphagnetorum (Enchytraeidae) to manipulation of pH
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Kandeler, E; Tscherko, D; Stemmer, M; et al. (2001) Organic matter and soil
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Kutner, MH; Nachtsheim, CJ; Neter, J. (2004) Applied linear regression models.  4th ed.
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Levin, SA. (2005) Self-organization and the emergence of complexity in ecological systems.
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Lundkvist, H. (1982) Population dynamics of Cognettia sphagnetorum (Enchytraeidae) in a
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Lundkvist, H. (1983) Effects of clear-cutting on the enchytraeids in a Scots pine forest soil in
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fcj^lffiYJJ^JL|J^^
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Steinaker, DF; Wilson, SD. (2008) Scale and density dependent relationships among roots,
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Table 1.  Summary of Data Used in Meta-analysis
Reference
Allison et al. (2007)
Altesor et al. (2006)
Borken et al. (2007)
Biological Metric
total PLFA
root biomass
root biomass
Environment Type
grassland
grassland
forest
Na
6
5
24
Briones et al. (2007) (Review Article)
Abrahamsen and Thompson (1979)
Chalupsky (1986)
Chibaetal. (1976)
Hutha(1984)
Kairesalo(1978)
Lundkvist(1982)
Lundkvist(1983)
Makulec (1983)
Nurminen (1967)
Phillipson et al. (1979)
Thambi and Dash (1973)
Yeates (1986)
Claus and George (2005)
Davis et al. (2007)
Davis et al. (2007)
Kemmitt et al. (2008)
Kemmitt et al. (2008)
Steinaker and Wilson (2008)
Steinaker and Wilson (2008)
Steinaker and Wilson (2008)
Steinaker and Wilson (2008)
Steinaker and Wilson (2008)
Steinaker and Wilson (2008)
Tsai et al. (2007)
Zheng et al. (2005)
invertebrate density
invertebrate density
invertebrate density
invertebrate density
invertebrate density
invertebrate density
invertebrate density
invertebrate density
invertebrate density
invertebrate density
invertebrate density
invertebrate density
root biomass
root biomass
root biomass
root biomass
root biomass
invertebrate density
mycelium production
root production
invertebrate density
mycelium production
root production
microbial density
microbial biomass C
forest
forest
forest
forest
forest
forest
forest
forest
forest
forest
grassland
grassland
forest
grassland
forest
grassland
forest
grassland
grassland
grassland
forest
forest
forest
forest
forest
1
1
1
1
1
1
1
1
1
1
1
1
33
5
6
1
6
5
5
5
5
4
5
90
7
aNumber of observations. Each observation represents a discrete depth interval.
                                             12

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Table 2.  Parameter Estimates and 95% Lower and Upper Confidence Intervals" (LCL
         and UCL, Respectively) for the Nonlinear Function (See Equation 1) Fit to
         Standardized Data for Both Forests and Grassland Environment Types
Environment Type
Forest
Grassland
Parameter
A
B
C
A
B
C
95% LCL
0.873
-0.185
-0.527
2.32
-0.295
-1.12
Estimate
1.56
-0.0919
-0.303
4.89
-0.160
-0.641
95% UCL
2.26
0.00127
-0.0783
7.47
-0.024
-0.162
""Confidence intervals for nonlinear functions are only approximate (Kutner et al, 2004).
                                        13

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                        Standard normal scores
      0 -
     10 -

 E  20 -
 o     ^
 Q_
 0)
     30 -
 O) 40 -\
 _c
 "5.
 E
 05
     50 -
     60 -
     70 -
     80 -
     90 -
            -1
-"^^V^ • . :
0 ••••0
A* EH
AC3
T

A OD
^
t o
W T A
A
TT

T
A
• Invertebrate Density
o Microbial Biomass C
T Microbial Density
A Mycelium Production
• Root Biomass
n Root Production
4 Total PLFA
	 Forest: p < 0.0001
- Grassland: p < 0.0001





          Low
Biological Activity
High
Figure 1. Nonlinear (see Equation 1) Relationships Between Standardized (mean = 0;
       SD = 1) Biological Metrics and Their Midpoint Sampling Depths for Forests and
       Grasslands.
                                    14

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                      First derivative of Figure 1
 o>
      0
!10H
.n  20 H
-I—•
Q.
0)  30 -
     40 -
 g- 50 H
 ^5  «n J
 
-------
2. PART 2. AQUATIC BIOTIC ZONE
               16

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                                 2.1. INTRODUCTION

       Benthic organisms alter the fluxes of particulate and dissolved chemical species through
their burrowing, ingestion and excretion, tube-building, and biodeposition activities (Thorns et
al., 1995). Hence, the zone or area of the substrate where these organisms reside is important as
a site of exchange for nutrients and contaminants, especially with overlying waters. The vertical
extent of this zone is often referred to as the depth of bioturbation, or mixed layer. Thorns et al.
(1995) compiled data on the depth of the mixed layer, mainly from radio-isotope tracer studies.
Mixing depths ranged from less than 1  cm (Amazon continental shelf) to greater than 35 cm
(e.g., deep Puget Sound). Based on radio-isotope tracer profiles from a large number of studies,
Boudreau (1994) determined the mean (± SD) mixing depth worldwide to be 9.8  ± 4.5 cm.
Based on tracer profiles, as well as sediment profile imaging literature and surveys, Teal et al.
(2008) estimated the global mean (± SD) mixing depth to be 5.75 ± 5.67 cm. Other studies have
utilized cores to determine the depth distribution of benthic invertebrates from  specific locations
around the world. Ecological risk assessors should consider the depth of this "biotic zone" in the
design and interpretation of sediment sampling programs, as this is where exposure to
contaminants or other stressors will occur.  This zone is also the source of prey for benthic-
feeding fishes (and shore birds in the intertidal) and, potentially, trophic transfer of pollutants.
       Knowledge of the biotic zone is necessary when attempting to delineate the relevant
depth for remediation at sites where an action is needed.  When evaluating remedial alternatives
in cases where contaminant hotspots extend deep within the sediment, it may not be prudent (for
environmental and cost reasons) to consider zones deeper than where the bulk of organisms
reside.  In the case where contaminated sediments are capped with clean substrate, the thickness
of the cap should exceed the depth to which infauna burrow, or the depth of the biotic zone, in
order to avoid infiltration of contaminants through the cap and into the water column. The
present paper explores data from a wide realm of habitat types in an attempt to develop
habitat-specific practical default values for the depth of the biotic zone, where most organism-
substrate interactions occur. We use the 80th percentile of abundance or biomass depth
distributions as a common measure for comparison among  samples. In our judgement, use of the
"80th percentile" strikes a balance by including most of the organisms, but without going to
depths where the biota are very sparse. We acknowledge a degree of subjectivity in choosing
this value, but note that a number of assessment programs (National Oceanographic and
Atmospheric Administration Status and Trends Program; EPA Environmental Monitoring and
Assessment Program) use a 20 percent effects level (i.e. 80% nonaffected) as a threshold of
ecological significance (Long, 2000).
                                           17

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              2.2. BENTHIC ORGANISMS AND THEIR ENVIRONMENT

       For benthic organisms, the nature of their interaction with the sediment is determined by
the manner in which food is obtained (trophic type), where their activities are carried on (life
position) and their mobility (Fisher, 1982).  Feeding types for benthos that are applicable to fresh
water are presented in Fisher (1982; after Walker and Bambach, 1974). Feeding types applicable
to marine waters are presented in Lee and Swartz (1980).  The majority of suspension feeders are
located near the sediment-water interface, while suspension-feeding bivalves with siphon tubes,
and deposit feeders may burrow  deeper. Examples of deep-burrowing species are presented in
Tables.
       Among environmental determinants of the type of organisms, and, hence, benthic
community structure of an area, sediment grain size is very important because it reflects the
hydrodynamic regime and the quantity and quality of organic carbon. High proportions of fines
are representative of deposit!onal environments and provide a greater surface area (compared to
coarse-grained sediments) for sorption of organic carbon and contaminants.
       The microbial degradation of labile organic matter largely determines the redox potential
(Eh) and pH observed at various depths in the sediment and is responsible for a variety of
secondary reactions involving metals (e.g., desorption, release to pore water, formation of sulfide
and associated fixation of trace metals) (Batley et al., 2005). Because the flux of labile organic
matter to the sediment is usually much faster than the diffusive flux of oxygen across the
sediment water interface, it is commonly observed that oxygen concentrations in sediments
become anaerobic close to the sediment-water interface (Batley et al., 2005). The oxic zone may
vary in thickness from a few millimeters in  silty sediments to several cm in coarser riverine and
estuarine sands and is underlain by a suboxic and an anoxic area. This oxygen gradient, along
with other reactions described above, leads to vertical zonation in sediments and pore waters of
pH, Eh and various chemical species, including Pb and Mn, and trace metals (Batley et al.,
2005).
       A number of macroinvertebrates can span both oxic and anoxic layers of sediment.  Some
that ingest particles at depth and egest them upon the sediment surface—the 'head-down'
conveyor-belt species of Rhoads (1974)—are major agents of sediment reworking in many
benthic communities. These species, some  of which are included in Table 3, dominate late
successional stage equilibrium assemblages associated with a deeply oxygenated sediment
surface where the redox zone commonly reaches depths of over 10 cm (Rhoads and Germano,
1986). Tubificid oligochaetes can feed in anoxic sediment layers while waving their tails in the
water column for the purpose of respiration (McCall and Tevesz, 1982). During feeding,
material ingested from several centimeters beneath the sediment surface is deposited at the
                                           18

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sediment-water interface, resulting in the rapid burial of components originally deposited at the
sediment surface as well as the upward transport of subsurface material (including pollutants)
(Krezoski and Robbins, 1985). Many marine bivalves use siphon tubes to inspire overlying
water, while physically residing in deeper anoxic sediment (Batley et al., 2005).
       The benthic community in marine sediments has great taxonomic diversity, including a
number of species that burrow to depths greater than 20 cm (see Table 3; Matisoff, 1995).
Freshwater sediments are inhabited by a variety of macrobenthos, principally arthropods (insects
and amphipods), annelids (oligochaetes and leeches), and mollusks (bivalves and gastropods)
(Fisher, 1982). Along with chironomids, tubificid oligochaete worms are usually the dominant
macrofauna in lake profundal regions (McCall and Tevesz, 1982). Populations of a few score to
a few thousand worms per square meter occur commonly, with higher populations in organically
rich environments (Davis, 1974).


                           2.3.  BENTHIC HABITAT TYPES


       Chapman et al. (2005) summarize environmental characteristics of five types of water
bodies as follows:

   Lacustrine: low-energy environment; generally depositional; groundwater interaction
   decreasing away from shore; organic matter decreasing with distance from shore; often
   fine-grained sediment

   Riverine: low- to high-energy environment; depositional or erosional; potential for
   significant groundwater interaction; significant variability in flow and sediment
   characteristics within and between rivers.

   Estuarine: generally low- or moderate-energy environment; generally depositional; generally
   fine-grained sediment grading to coarse sediment at ocean boundary.

   Estuaries are dynamic, complex, and unique systems that can have  strong physical-chemical
   gradients, particularly of salinity, dissolved oxygen, pH, nutrients, sediment grain size, and
   organic matter content.  Estuarine  systems are divided into a number of categories based on
   salinity (see Boesch, 1977). Estuarine sediments can come from inland and/or the sea,
   depending on the freshwater sediment load and the estuarine circulation patterns.  Due to the
   dynamic nature of sediments in estuaries with strong flows or currents, the stability of
   estuarine benthic environments can vary and should be taken into account in any ecological
   assessment.  Sediment total organic carbon, which typically varies with fine sediment
   particles, provides a good overall index of organic loading  and composition.  It integrates
   carbon enrichment from multiple sources, including land-based inputs, detritus, and algal and
   microbial metabolism.
                                           19

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   Coastal Marine: relatively high-energy environment, decreasing with depth and distance
   from shore; often coarse sediments.

   Offshore Marine: generally low-energy environment; generally depositional; generally fine-
   grained sediment.

   Benthic communities in marine environments are typically below the photosynthetic zone,
   other than along the coastal margins.  Consequently, benthic food chains are typically built
   on organic materials carried into the system; thus, the food chain is primarily allochthonous.
   Materials such as phytoplankton may be filtered from the water, or deposits may provide
   organic material for bacterial growth, which can then be harvested by filtering or grazing
   organisms.

2.3.1. LOTIC VERSUS LENTIC ENVIRONMENTS
       Lotic environments (include rivers and streams) may be either depositional or erosional.
High-gradient  streams and other erosional environments differ significantly from lentic systems
in terms of major physical processes, factors that limit primary production, nutrient dynamics,
types of primary producers, and the relative importance of autochthonous versus allochthonous
energy sources (Chapman et al., 2005). The defining feature of lotic environments is the
unidirectional flow of water, responsible for the downstream transport of biotic and abiotic
materials, including sediments, and the biota (downstream colonization). The potential for
movement of sediments is much greater in lotic than lentic environments.  Due to greater energy
levels and greater potential for sediment transport, grain size is larger, and organic carbon
content is generally lower in lotic erosional environments than in lotic depositional or lentic
environments.  Unlike depositional habitats, fine-grained sediments in erosional environments
are highly mobile.  Materials such as nutrients, sediments, and contaminants are transported
downstream, deposited in slower moving sections of the river, and then resuspended during
periods of high discharge. Because the velocity of water flow decreases downstream, mean
particle size will generally decrease, and amounts of organic carbon increase, from headwater
reaches to downstream reaches (Chapman et al., 2005).

2.3.2. HYPORHEIC ZONE
       The hyporheic zone of rivers and streams is the spatially fluctuating ecotone between the
surface water body and the deep groundwater where exchanges of water, nutrients, and organic
matter occur in response to variations in discharge and bed topography and porosity (Boulton et
al., 1998). The interstitial spaces  among sediment particles in the hyporheic zone are occupied
by a  diverse array of aquatic invertebrates, termed the "hyporheos." The hyporheos includes
many types of crustaceans, segmented worms, flatworms, rotifers, water mites, and juvenile
stages of aquatic insects (Boulton et al., 1998). The organisms inhabiting the hyporheic zone
                                           20

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may be either epigean or hypogean depending upon their affinities for surface or subsurface
habitat, respectively.  Though many insect larvae and epigean crustaceans colonize the
superficial benthos of running waters, epigean species can also penetrate deeper where water
circulates freely through the sediments and much organic matter and oxygen are available (Ward
et al., 1998). The present paper does not cover fauna that live strictly in groundwater zones that
can be located 2-3 km from river channels (noted in Stanford and Ward, 1993).
       The composition of the  hyporheos represents a complex response to interstitial water
velocity,  sediment composition (particularly the amount of fine sediments), sediment pore size,
organic matter content, dissolved oxygen concentration, vertical hydrological exchange, and
other environmental parameters as well as  biological interactions (Boulton, 2007; Dole-Olivier
and Marmonier, 1992; Olsen and Townsend, 2003). The deeper layers of the hyporheic zone can
serve as a refuge from environmental perturbations such as flooding and drought, or from
predation (Griffith and Perry, 1993; Angradi et al., 2001).

                                    2.4. METHODS

       Literature relevant to the biotic zone was obtained by searching on the keyword
combinations (1) "sediment" AND "biotic zone" OR "bioturbation zone," (2) "sediment" AND
"invertebrates" AND "vertical distribution," and (3) "sediment" AND "invertebrates" AND
"vertical  distribution" AND "sediment type."  We searched the literature from 1985 to present
but included a number of key references that were older. Data on organism abundance or
biomass with depth in the sediment were extracted from tables or graphs.  Data from sites that
were acknowledged by the study authors to be impacted by a local pollution source were not
included. The data available consist of 234 datasets, each consisting of one or more  cores from a
particular habitat type (see Table 4) that detail the depth distribution of organisms by abundance
or biomass.  A publication may contain more than one dataset for a habitat type if sets of cores
were taken from different locations (within that habitat type) or at different times.  The data were
summarized by first computing for each dataset an 80th  percentile depth. This was determined as
the midpoint of the stratum containing the  80th percentile of the abundance or biomass
distribution from the  sediment surface to depth.  Where data were presented on a volume instead
of areal basis and the strata were of unequal thickness (e.g., 0-2, 2-5, 5-10 cm), the values were
weighted to account for the fact that thicker strata contain a greater volume of sediment.
       Based on the 80th percentile of depth distributions, we developed practical default values
for the depth of the biotic zone  (i.e., biologically relevant sediment depth) in various habitats for
decisions related to ecological assessment  or remediation. We calculated and graphed the mean
80th percentile depths (for abundance or biomass) for each habitat type; the maximum 80th
                                           21

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percentile depth for each habitat type was also graphed.  Each mean 80th percentile depth was
rounded to the next (deeper) 5-cm boundary (i.e. 5, 10, 15, etc.) to determine the biologically
relevant sampling depth or biotic zone for the respective habitat type. Where the maximum 80th
percentile depth for a habitat type exceeded the mean 80th percentile depth by more than 5 cm,
we added 5 cm to the mean and rounded to the next boundary to arrive at the biotic zone for that
category.
       Habitat types were classified by salinity (within estuarine habitats) and sediment type
within seven broad categories: estuarine intertidal, tidal freshwater, estuarine subtidal, lentic,
lotic, marine coastal, and marine offshore (see Table  4). The lotic category comprised (1) stream
coarse grained/sand, (2) stream coarse grained/sand with fines, and (3) river coarse grained/sand
with fines, where "fines" denote grain sizes <2 mm in substantial quantity (approximately 20%
or more by weight). Sediment types were taken directly from the respective papers or designated
using the classification of Shepard (1954). The "mixed" category refers to muddy sand or sandy
mud, where  mud = silt + clay.

       2.5. RESULTS—BENTHIC BIOTIC ZONE: ABUNDANCE AND BIOMASS

       The mean and maximum 80th percentile of benthic abundance depth distributions in
various habitats are shown in Figure 3.  A number of organisms can burrow significantly deeper
than the 80th percentile depth distribution (see Table  3 for examples). Nonetheless, in
performing ecological assessments related to sediment contaminants, it is important to identify
the zone of greatest organism-substrate interaction, i.e., the biotic zone.  We developed practical
default values for the depth of the biotic zone in various habitats based on the 80th percentile of
depth distributions.  First we summarize these distributions.
       In terms of benthic abundance depth distribution, the mean 80th percentile in estuarine
intertidal, tidal freshwater, most estuarine subtidal, and lentic habitats extends to 5-10 cm (see
Figure 3). Exceptions are oligohaline and polyhaline mud, and oligohaline sand, where the mean
80th percentile is less than 5 cm. Overall depth distributions within estuarine habitats tend to be
deepest in mixed substrates and in sand (except oligohaline sand). The maximum 80th
percentiles in estuarine intertidal sand, oligohaline mixed substrates, and polyhaline sand extend
to 15-20 cm. The maximum 80th percentile in lakes  (profundal  mud) extends to 20-25 cm (see
Figure 3).
       In most marine coastal and offshore habitats,  the mean 80th percentile of abundance depth
distributions extends to 5-10 cm. Exceptions are marine coastal sand, and marine offshore
mixed substrates, where the mean 80th percentile is less than 5 cm.  (Note however that only one
data set was available for the latter habitat type.)  Overall depth  distributions in marine coastal
                                           22

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and offshore muds tend to be deeper than in other marine substrates, with the maximum 80th
percentile for marine coastal mud extending to 15-20 cm.
       The mean and maximum 80th percentile of abundance depth distributions in lotic habitats
is deeper than that in the other habitats.  The three lotic habitats covered here are stream coarse
grained/sand, stream coarse grained/sand with fines, and river coarse grained/sand with fines.
The mean 80th percentile for these habitats extends to 25-30, 15-20, and 10-15 cm respectively.
The maximum 80th percentiles extend to 35-40 cm, 30 cm, and 15 cm respectively (see
Figure 3).
       In most habitats where data are available, the 80th percentile of depth distributions based
on biomass exceeds respective distributions based on abundance. Oligohaline mixed substrates
are an exception to this trend (see Figures 3 and 4). The biomass-based depth distribution for
lake profundal muds exceeds that for abundance, but this represents an artifact in that biomass
data were only available for the profundal area of a shallow lake in Japan, where the fauna
(oligochaetes) burrowed deeper than in other localities.
       Based on the 80th percentile of depth distributions, and using the procedure outlined in
the Methods section, we developed practical default values for the depth of the biotic zone in
various habitats. These values, shown in Table 5, may be used for decisions related to ecological
assessment or remediation in aquatic scenarios. The biotic zone, based on benthic abundance, in
most estuarine and tidal freshwater environments is 10 or 15 cm.  Exceptions are oligohaline and
polyhaline mud (5 cm) and oligohaline sand (5 cm). In marine muds (both coastal and offshore),
the biotic zone is 15 cm. In other marine substrates it is  10 cm (marine coastal mixed and marine
offshore sand) or 5 cm (marine coastal sand).  In lentic environments, the biotic zone is 15 cm.
The biotic zone tends to be deeper when biomass is taken into account.  The biotic zone in lotic
systems varies from 15 to 35 cm depending upon water/habitat type.  In areas populated by a
high density of deep dwelling organisms such as those listed in Table 3, the biotic  zone may be
somewhat deeper than our recommended values.

                                   2.6. DISCUSSION

       Organisms in aerobic, sand or mixed (sand and mud) sediments of estuaries tend to
penetrate deeper into the substrate than those in mud habitats (Dauer  et al., 1987; Nilsen et al.,
1982). Deep-dwelling species that exist in mud habitats either have a direct connection to the
surface via a tube or permanent burrow, or are tolerant of high sulfide low oxygen conditions.  In
the present synthesis, in terms of benthic abundance, the practical default values for the biotic
zone in estuarine muds range from 5 cm (oligohaline and polyhaline mud) to 10 cm (mesohaline
mud), whereas in estuarine sands and  estuarine mixed substrates the values range from 5 cm
                                           23

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(oligohaline sand) to 15 cm (polyhaline sand and oligohaline mixed substrate) (see Table 5).  For
most habitat types, the practical default values for the biotic zone are usually deeper when
biomass is taken into account.  For example, in mesohaline mud, the biotic zone in terms of
biomass (25 cm) is relatively deep compared to the biotic zone in terms of abundance (10 cm)
(see Table 5).  This is largely due to the presence of bivalves such as Macoma balthica.
       In our synthesis, the general trend of deeper penetration by the benthos in estuarine sands
or mixed substrates versus mud is not evident in coastal and offshore environments.  In coastal
and offshore environments, factors in addition to sediment type may play an important role in
determining faunal depth distributions. As one proceeds seaward into the marine coastal
environment, the rate of deposition has a controlling effect on the depth distribution  of the
benthos, with depth penetration increasing with reduced deposition (Rhoads et al., 1985).  Areas
of the seafloor where sedimentation rates are « 4 cm y"1  and where the frequency of physical
resuspension or bedload transport is low, display sedimentary fabrics dominated by relatively
large equilibrium species that commonly feed 'head down' at depth within the sediment (Rhoads
etal., 1985).
       With respect to lotic systems, a number of variables are of great importance in
determining the depth of the biotic zone.  These include dissolved oxygen, quantity of fines (less
than 1-2 mm-size grains), and porosity. The lack of pore  space at depth can be a barrier to
penetration of the sediment by benthos Where fines are of sufficient quantity, they can reduce
pore space and lead to clogging of the interstices, or, colmation (Meidl and Schonborn, 2004;
Weigelhofer and Waringer, 2003).  This makes the sediment too dense to provide living space or
to support necessary water exchange between the channel and the hyporheic zone and between
the groundwater and the hyporheic zone (Findlay, 1995).  In the current synthesis, the greater
depth of penetration of benthos in stream coarse grained/sand without fines—versus with
substantial quantities of fines—is probably due in part to greater porosity in the former.  A
similar pattern of greater depth penetration in porous habitats has been noted by McElravy and
Resh (1991) and Maridet et al.  (1992). It is interesting to  note that the more porous coarse
grained/sand without fines category in our synthesis is comprised mainly of higher order reaches
(see Table 4).

                              2.7. RECOMMENDATION

       Ideally, to determine the depth of the biotic zone at a  specific location, it is best to use
data derived from sampling that area. The depth of bioturbation and the degree of contact
between biota  and sediment/pore water is influenced by the life habits of the resident organisms
(e.g., degree of motility, creation of temporary versus permanent burrows, whether tubiculous or
                                           24

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not), and their local environment.  Clarke et al. (2001) noted that in making site-specific
bioturbation depth estimates, it is advisable to obtain the opinions of local experts in benthic
ecology. Where data/expertise are not available, the recommendations in this paper (see Table 5)
can serve as guidelines for determining the depth of the biotic zone.  When considering the biotic
zone depth in the design of a cap for isolating contaminated sediments from the overlying water
column, the thickness of the cap should exceed the depth of the biotic zone by a safety margin
(sensu Brannon et al., 1986).  In areas populated by a  high density of deep-dwelling organisms
such as those in Table 3, the biotic zone may be somewhat deeper than the values shown in
Table 5.


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Table 3. Examples of Deep-Burrowing and/or Feeding Benthos
Faunal Group/Species
Sediment
Depth
(cm)
Reference
Comments"
Annelids (Polychaetes)
Clymenella torquata
Clymenella mucosa
Macroclymene zonalis
(formerly in genus
Clymenella)
Axiothella rubrocincta
Sabaco elongatus (formerly
Asychis elongata)
Maldane sarsi
F 'araonis fulgens
Heteromastus filiformis
Notomastus tennis
Notomastus latericeus
Arenicola marina
Arenicola cristata
Arenicola defodiens
to 30
to 15-20
to 25
to 30
to 50
to 2 1-25
to 20
to 20-35
to 26
to 20
to 20-40
to 30+
to 40-70
Rhoads (1967); Mangum (1964);
Mach et al. (2012); Nilsen et al.
(1982)
Mangum (1964)
Dauer et al. (1987); Moretzsohn
et al. (2015); Mangum (1964)
Kudenov (1978)
Caffrey (1995); Light (1974);
Nichols (1979); Read (2015)
Blanchard and Knowlton (2013);
WoRMS (2015a)
D'Andrea et al. (2004); Gaston
etal. (1992); WoRMS (2015b)
Nilsen et al. (1982); Mines and
Comtois (1985); Frey (1970);
Cadee (1979)
Johnson (1967); Garcia-Garza et
al. (2012)
Swift (1993); Mayhew (2005)
Cadee (1976); Luttikhuizen and
Dekker (2010); Longbottom
(1970); Tyler-Walters (2008)
Lippson and Lippson (2006);
Kaplan (1988)
Cadman (1997); Luttikhuizen
and Dekker (20 10)
Atlantic and Gulf coasts of North America;
introduced to coasts of British Columbia
(Canada), Washington (USA) and United
Kingdom; muddy sand to sand; IT, STa
North Carolina to Florida (USA); Gulf of
Mexico; Caribbean Sea; prefers fine to
medium sands; IT, ST
Maine to Florida, USA; Gulf of Mexico;
medium to fine sand; ST
British Columbia, Canada south to Mexico
and Gulf of California; IT, ST
Maine to Florida, USA; Gulf of Mexico;
Belize; introduced to San Francisco Bay,
California (USA), where can occur in
dense patches; mud and sandy mud; IT, ST
cosmopolitan; IT, ST
widely distributed in N Atlantic; marine,
estuarine; sand; IT, ST
cosmopolitan; marine, estuarine
(polyhaline, mesohaline); mud to muddy
sand; IT, ST
eastern N Pacific from California through
Washington, USA; bays, estuaries; IT,
shallow ST
cosmopolitan; sand or muddy sand; low IT
to deep ST
western N Atlantic (Greenland, Bay of
Fundy to Long Island); eastern N Atlantic;
estuarine, marine; common in fine sand or
muddy sand; predominantly IT
western N Atlantic from Cape Cod to
Florida (USA), Gulf of Mexico, Caribbean
Sea; marine, estuarine (polyhaline,
mesohaline); IT
eastern N Atlantic: British Isles; western
Wadden Sea, North Sea; Skagerrak; high-
energy low IT and ST
                                      46

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Table 3. Examples of Deep-Burrowing and/or Feeding Benthos (continued)
Faunal Group/Species
Abarenicola pacifica
Abarenicola claparedi
vagabunda
Amphitrite ornata
Lanice conchilega (sand
mason)
Thoracophelia mucronata
(formerly in genus
Euzonus)
Bhawania heteroseta
(formerly in genus
Paleanotus)
Cirriformia moorei
Scoletoma zonata
(formerly in genus
Lumbrineris)
Glycera americana
Glycera dibranchiata
Nereis succinea
Alitta virens (formerly in
genus Nereis)
Hediste diversicolor
(formerly in genus Nereis)
Chaetopterus cf.
variopedatus (formerly C.
pergamentaceus)
Spiochaetopterus costarum
oculatus
Sediment
Depth
(cm)
to 20
to 30
to 30
to 20+
to 20
to 20
to 22
to 22
to 40
to 40
to 40
to 40
to 15-20
to 15+
to 15+
Reference
Krager and Woodin (1993);
Rudy and Rudy (1983); Hobson
(1967)
Healy and Wells (1959)
Aller and Yingst (1978);
WoRMS (2015c); Lippsonand
Lippson (2006)
VanHoey et al. (2006); Ager
(2008); de Kluijver et al. (2000a)
Kozloff (1993); Dales (1952)
Dauer et al. (1987); Perkins
(1985)
Ronanetal. (1981) (as C
spirabrancha); Light and Carlton
(2007)
Johnson (1967); Rudy and Rudy
(1983)
Nilsenetal. (1982)
Nilsenetal. (1982)
Nilsenetal. (1982)
Andersen and Kristensen (1991);
Creaseretal. (1983); Glasby
(2015)
Reise (1981); Budd (2008)
Thompson and Schaffner (2000,
2001)
Woodin (1981); Bhaud (1998);
Barnes (1964)
Comments
N Pacific: Alaska to N California (USA);
Japan; muddy sand of coastal bays;
predominantly IT
Eastern N Pacific: Washington (USA);
loose clean sand; low IT
western N Atlantic, including Cobscook
Bay and Gulf of Maine; marine, estuarine
(polyhaline); IT, ST
Arctic to Mediterranean, Persian Gulf;
Pacific; marine, estuarine (polyhaline);
sand or muddy sand; IT,ST
Vancouver Island, BC, Canada to Baja
California (Punta Banda region), Mexico;
sand beaches experiencing fairly heavy
surf; IT
W Atlantic from Virginia, USA to Gulf of
Mexico; sandy estuarine and marine; ST
California, USA; mudflats of estuaries and
bays, often associated with eelgrass beds;
low IT, ST
Alaska to W Mexico; marine, estuarine; IT,
ST
prefers mud mesohaline to polyhaline
wide range of sediments, mesohaline to
polyhaline
wide range of sediments and salinities
western N Atlantic: Gulf of St. Lawrence,
Canada to Virginia, USA; Iceland; eastern
N Atlantic: Norway, North Sea, France,
Ireland; White Sea, Russia; IT, ST
Widespread along eastern N Atlantic
including Baltic Sea, North Sea,
Mediterranean Sea; euryhaline; IT
W Atlantic from NE USA to Florida;
marine, estuarine; IT, ST
W Atlantic from Massachusetts, USA to
Gulf of Mexico; IT, ST
                                           47

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Table 3. Examples of Deep-Burrowing and/or Feeding Benthos (continued)
Faunal Group/Species
Mesochaetopterus taylori
Marenzelleria neglecta
Marenzelleria viridis
(formerly in genus
Scolecolepides)
Pseudeurythoe ambigua
Sigambra tentaculata
Diopatra cuprea
Onuphis microcephala
Scalibregma inflatum
Sediment
Depth
(cm)
to 30
to 35
to 30
to 40
to 30
to 50-60
to 45
to 30-60
Reference
Sendalletal. (1995)
Zettleretal. ( 1995) (as M
viridis); Sikorski and Bick
(2004); Bastropetal. (1998)
Essink and Kleef (1988);
Sikorski and Bick (2004); Blank
et al. (2008)
Nilsenetal. (1982)
Nilsenetal. (1982)
Mangum et al. (1968)
Frey and Howard (1969)
Ashworth(1901)
Comments
eastern N Pacific from British Columbia,
Canada to Mexico; muddy sand and among
roots of eel grass; IT
Baltic Sea; North Sea (Elbe estuary); Arctic
(Northwest Territories, Canada); western N
Atlantic from Chesapeake Bay to Georgia,
US; predominantly oligohaline to
mesohaline; ST
North Sea; Baltic Sea; western N Atlantic
from Nova Scotia, Canada to Cape
Henlopen, Delaware and Chesapeake Bay,
US; predominantly mesohaline to
polyhaline; IT, ST
wide range of sediments, mesohaline to
polyhaline
muddy sands mesohaline to polyhaline
U.S. Atlantic and Gulf of Mexico coasts;
IT; builds sand and mucous tube
low IT, shallow ST
cosmopolitan; ST
Annelids (Tubificid oligochaetes)
Various
Various
Tubificoides spp.
to 20
to 30
to 25
McCall and Tevesz (1982)
Reinharz and O'Connell (1983)
Mines and Comtois (1985)
mainly freshwater
estuarine
estuarine/marine
Phoronids
Phoronopsis harmeri
Phoronis spp.
to 20
to 20
Johnson (1967)
Nilsenetal. (1982)
mostly intertidal, in tubes
sand polyhaline
Nemertea (ribbon worms)
Cerebratulus lacteus
to 50
Nilsen et al. (1982); Frey (1970)
prefers mud mesohaline to polyhaline; IT,
shallow ST
Bivalves (Unionid, or freshwater mussels)
Elliptic complanata
Unio tumidus
to 20
to 20
Amyot and Downing (1991);
Fisher & Tevesz (1976)
Schwalb and Pusch (2007); Van
Damme (20 11 a)
Eastern North America lotic and lentic
systems; abundant in shallow (< 3 m)
waters; those at depth in sediment are
significantly smaller than those that are
epibenthic
Europe (widely distributed); lowland fresh
waters
                                           48

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Table 3. Examples of Deep-Burrowing and/or Feeding Benthos (continued)
Faunal Group/Species
Unio pictorum
Unio crassus
Anodonta anatina
Sediment
Depth
(cm)
to 20
to 30-35
to 20
Reference
Schwalb and Pusch (2007); Van
Damme (20 lib)
Schwalb and Pusch (2007);
Schultes (2010)
Schwalb and Pusch (2007);
Lopes-Lima (20 14)
Comments
Widely distributed throughout Europe and
Russia; lowland fresh waters
Europe except Iberian Peninsula and British
Isles, to Black Sea region and Iraq; sandy
and stony substrate of lowland clean rivers
and smaller running waters
N Europe and Asia, below 65 degrees, to
Sicily and Turkey; sandy and gravel
substrate of lotic and lentic systems
Bivalves (other)
Macoma balthica
Macoma mitchelli
Macoma nasuta
Solecurtus strigilatus
Tagelus plebeius
Tagelus divisus
Tagelus californianus
Zirfaea pilsbryi
Ensis directus
Ensis ensis
Ensis siliqua
to 30
to 20
to 10-20
to 27
to 40+
to 30
to 50
to 50
to 20
to 54
to 60
Mines and Comtois (1985);
Schaffneretal. (1987)
Reinharz and O'Connell (1983)
Ricketts et al. (1985)
Dworschak (1987a)
Frey (1968); Frey (1970);
Lippson and Lippson (2006)
Frey (1968); Lippson and
Lippson (2006)
Ricketts et al. (1985); Morris et
al. (1980)
Morris etal. (1980)
Nilsen et al. (1982); Gollasch, et
al. (2015)
Keegan and Konnecker (1973)
(as Solen ensis); Von Cosel
(1990); de Kluijver et al. (2000b)
Caspar et al. (1998); de Kluijver
et al. (2000c)
important at mesohaline mud and sandy
mud sites; burrowing depth varies with
shell size
mesohaline, all sediment types
Eastern N Pacific; IT
Adriatic Sea; eastern N Atlantic from
Portugal to Senegal; IT, ST
Massachusetts to S Florida (USA); Gulf of
Mexico; marine, estuarine (polyhaline,
mesohaline); mixed mud-sand; IT, ST
Massachusetts to S Florida (USA); Gulf of
Mexico; Caribbean; marine, estuarine
(polyhaline); prefers sand or muddy sand;
shallow ST
Eastern N Pacific: Humboldt Bay, CA
(USA) to Panama; IT
Alaska to Baja California, Mexico; bays,
estuaries, occasionally open coast; heavy
mud, sticky clay, soft shale; low IT, ST
western N Atlantic: Labrador, Canada to
South Carolina, USA; eastern N Atlantic
(introduced): Spain to Norway, including
UK, and we stern Baltic; marine, estuarine
(polyhaline); prefers fine-medium sand; IT,
ST
eastern N Atlantic: North Sea and British
Isles to Portugal and Mediterranean; sand;
IT, ST
eastern N Atlantic: Norway to the
Mediterranean; sand; IT, ST
                                           49

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Table 3. Examples of Deep-Burrowing and/or Feeding Benthos (continued)
Faunal Group/Species
Solen rostriformis
Solen sicarius
Mya arenaria (soft-shelled
clam)
Lucinoma borealis
Nuttallia nuttallii
Nuttallia obscurata
Saxidomus gigantea (butter
clam)
Tresus nuttallii
Tresus capax
Panopea generosa
(geoduck)
Panopea zelandica
Cyrtopleura costata (angel
wing)
Sediment
Depth
(cm)
to 30
to 30-35
to 30-40
to 20
to 30-40
to 30
to 35
to 100
to 100
to 30-100
to 30-45
to 60+
Reference
Morris et al. ( 1980) (as S.
rosaceus); Light and Carton
(2007)
Morris et al. (1980)
Mines and Comtois (1985);
Zwarts and Wanink (1989);
Kondo (1987)
Dandoetal. (1986)
Morris etal. (1980)
Fofonoffetal. (2003)
Cowles (2005a); Cheney and
Mumford (1986)
Ricketts et al. (1985)
Cowles (2005b)
Willner (2006); Goodwin and
Pease (1989); Gosling (2015)
Ministry for Primary Industries
(2013)
Schaffner etal. (2001);
Gustafson et al. (1991); Lippson
and Lippson (2006)
Comments
eastern N Pacific from Morro Bay,
California (USA) to Mazatlan, Mexico;
protected bays; sandy mud; low IT
eastern N Pacific from Vancouver Island
BC, Canada to Baja California, Mexico;
sheltered bays, especially in beds of
eelgrass; low IT, shallow ST
eastern N Pacific; both sides of Atlantic;
burrowing depth varies with shell size;
marine, estuarine (polyhaline, mesohaline)
soft sediments; IT, ST
NE Atlantic; Mediterranean Sea; low IT,
ST
eastern N Pacific from Bodega Bay Harbor,
California (USA) to Baja California Sur,
Mexico; outer coast and in bays with strong
tidal currents; sand or gravel; low IT
western N Pacific (native): Russia, Japan,
China; eastern N Pacific (introduced): Strait
of Georgia (Canada) to Puget Sound,
Willapa Bay and Coos Bay, Oregon (USA);
prefers estuaries (mesohaline, polyhaline)
but also marine; IT, shallow ST
eastern N Pacific: Aleutian Islands and SE
Bering Sea, Alaska to San Francisco Bay;
prefers sandy or gravelly substrate with
mixed shell; IT, ST
eastern N Pacific; IT
eastern N Pacific from Kodiak Island,
Alaska to central California USA; bays,
occasionally open coast; mud; IT, ST
N Pacific: Alaska to Baja California,
Mexico; Japan; very abundant in Puget
Sound, Washington and British Columbia;
burrowing depth is age-dependent (1-yr to
30 cm depth; 10-yr to 90 cm); sand or sand-
mud substrates; ST, IT
New Zealand: North, South and Stewart
Islands; ST
western Atlantic from Massachusetts, USA
to Brazil; marine, estuarine (polyhaline,
mesohaline); sandy mud; low IT, shallow
ST
                                           50

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Table 3. Examples of Deep-Burrowing and/or Feeding Benthos (continued)
Faunal Group/Species
Sediment
Depth
(cm)
Reference
Comments
Insects (Chironomid larvae)
Chironomus plumosus
to 15
McCall and Tevesz (1982)
lakes
Insects (mayfly larvae)
Hexagenia limbata
to 20
Matisoff and Wang (1998)
lakes
Insects (beetle)
Bledius spp
to 40
Wyatt and Foster (1991)
intertidal salt marshes; around lakes/salt
lakes and in river banks
Crustaceans (Thalassinidean shrimp)
Callianassa subterranea
Callianassa tmncata
Callichims major"
Callichims islagrande*
Callichims kraussi*
Callichims laurae
(formerly in genus
Glyptums)
Neocallichims
grandimana" (formerly
Callianassa branneri)
Neocallichims rathbunae*
Neocallichims
jousseaumei*
Trypaea australiensis*
Neotrypaea californiensis*
Neotrypaea gigas*
Sergio guassutinga
(formerly in genus
Neocallichims)
to 86+
to 60-70
to 215
to 50
to 30+
to 150
to 36
to 150
to 90
to 100+
to 75
to 40
to 60
Nickell and Atkinson (1995)
Kristensen and Kostka (2005);
Ziebisetal. (1996)
Griffis and Suchanek (1991);
Heard et al. (2007)
Felder and Griffis (1994)
Griffis and Suchanek (1991)
Whitehead et al. (1988); Griffis
and Suchanek (1991)
Dworschak and Ott (1993)
Griffis and Suchanek (1991);
Abed-Navandi (2000)
Griffis and Suchanek (1991);
Dworschak (2011)
Webb and Eyre (2004)
Hornig et al. (1989); Campos et
al. (2009)
Griffis and Suchanek (1991);
Campos et al. (2009)
Griffis and Suchanek (1991);
Manning and Felder (1995)
North Sea; ST
Mediterranean Sea; sandy sediments; ST
SE USA; Gulf of Mexico; Brazil; open
beaches; primarily IT, but also shallow ST
N Gulf of Mexico; sandy beaches facing
higher salinity (> 15 ppt) embay ments and
the Gulf; IT, shallow ST
S Africa; IT, ST
Red Sea; sand or coral sand, sometimes
with seagrass cover; IT, ST
W Atlantic from Florida, USA to Brazil;
protected back-reef sands; IT, shallow ST
subtropical and tropical western Atlantic;
carbonate sediments; ST, IT
widely distributed in Indo-W Pacific; coral
rubble covered by fine sand; IT, ST
E and SE Australian estuaries; prefers sand
flats; IT, ST
Alaska, USA to W coast Baja California
Sur, Mexico; prefers sand; IT
Vancouver Island, Canada to W coast Baja
California Sur, Mexico; prefers muddy
sand; IT
Brazil; IT
                                           51

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Table 3. Examples of Deep-Burrowing and/or Feeding Benthos (continued)
Faunal Group/Species
Sergio trilobata*
Pestarella tyrrhena*
Pestarella Candida*
Pestarella whitei*
Lepidophthalmus
louisianensis*
Lepidophthalmus sinuensis
Biffarius filholi '
Biffarius arenosus"
Corallianassa longiventris
Corallianassa coutierei"
Nihonotrypaea japonica '
Nihonotrypaea harmandi"
Glypturus acanthochirus
Glypturus armatus
Calocaris macandreae
Neaxius acanthus
Upogebia affmis
Upogebia deltaura
Upogebia pugettensis
Upogebia stellata
Sediment
Depth
(cm)
to 90
to 62
to 65
to 28+
to 250
to 50
to 45
to 58
to 150
to 69
to 65
to 36+
to 160
to 150
to 22
to 50
to 50
to 65
to 90
to 26.5
Reference
Dobbs and Guckert (1988);
Manning and Lemaitre (1993)
Dworschak (1987b, 2004)
Dworschak (2002)
Dworschak (2002)
Griffis and Suchanek (1991);
Felder and Griffis ( 1994)
Felder and Griffis (1994); Nates
& Felder (1999)
Griffis and Suchanek (1991);
Berkenbusch and Rowden (2000)
Bird and Poore ( 1999)
Griffis and Suchanek (1991);
Dworschak et al. (2006)
Kneer et al (2008); Sepahvand et
al. (2013)
Tamaki and Ueno (1998);
Tamakietal. (1999)
Tamaki and Ueno (1998);
Tamakietal. (1999)
Griffis and Suchanek (1991);
Dworschak and Ott (1993)
Griffis and Suchanek (1991)
Nash etal. (1984)
Kneer et al. (2008)
Heard et al. (2007)
Tunberg (1986); Christiansen
(2000)
Griffis and Suchanek (1991);
Campos et al. (2009)
Nickell and Atkinson (1995)
Comments
Gulf coast of Florida, USA; IT, ST
Adriatic Sea; eastern N Atlantic; IT,
shallow subtidal
Adriatic Sea; IT, ST
Adriatic Sea; coarse sand or mud under
stones; IT, shallow ST
N Gulf of Mexico; muddy shorelines of low
salinity (10-15 ppt) estuaries; IT, shallow
ST
estuaries on Caribbean coast of Colombia;
IT, ST
New Zealand; IT and shallow ST
E and SE Australia; sand and mud flats; IT,
ST
W Atlantic from Bermuda to Brazil; back-
reef sediments near seagrass beds; ST
Indo-W Pacific; carbonate sand and coral
rubble; IT, ST
Japan; polyhaline, extensive sandflats of
medium-fine sands; IT
Japan; euhaline, small to medium sandflats
and beaches of medium-fine sands; IT
Florida, Virgin Islands, Belize; bare
sediments of mangrove channels and back-
reef subtidal sediments; IT, ST
S Pacific; Aldabra; Seychelles; sheltered
reef sediments; IT, ST
North Sea; ST
Indo-W Pacific; carbonate sand and coral
rubble with seagrass cover; ST
Massachusetts to S Texas, USA; firm mud
or mud-sand substrates; IT, ST
eastern N Atlantic; North Sea; ST
Alaska to Morro Bay California, USA; IT
North Sea; ST
                                           52

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Table 3. Examples of Deep-Burrowing and/or Feeding Benthos (continued)
Faunal Group/Species
Upogebia pusilla
Upogebia africana
Upogebia tipica
Upogebia macginitieorum
Upogebia major
Jaxea noctwna
Axiopsis serratifrons
Axianassa australis
Sediment
Depth
(cm)
to 80
to 60
to 40
to 60
to 208
to 92
to 100
to 130
Reference
Dworschak (1987b, 2004)
Griffis and Suchanek (1991)
Griffis and Suchanek (1991)
Griffis and Suchanek (1991);
Campos etal., (2009)
Kinoshita (2002)
Nickell and Atkinson (1995);
Pervesler and Dworschak (1985)
Griffis and Suchanek (1991);
Kensley (1980)
Dworschak and Rodrigues
(1997); Felder etal. (2009)
Comments
Mediterranean Sea; eastern N Atlantic; IT,
ST
S Africa; IT, ST
Adriatic Sea; ST
S California, USA to Baja California Sur,
Mexico
Japan; IT
North Sea; Adriatic Sea; ST
Circumtropical; back-reef areas; ST
western Atlantic from Florida USA to
Brazil, including Gulf of Mexico and
Colombia; muddy sand or mud near
mangroves; IT
Crustaceans (snapping shrimp)
Alpheus heterochaelis
Alpheus floridanus (a
species complex)
to 100
to 36
Howard and Frey (1975);
McClure (1995)
Dworschak and Ott (1993);
Soledatde and Almeida (2013)
widespread throughout temperate and
tropical W Atlantic; bays and quiet waters;
IT, shallow ST
W Atlantic: S Florida USA, Bahamas,
Mexico, West Indies, Brazil; IT, ST
Crustaceans (mantis shrimp)
Squilla empusa
Squilla mantis
Lysiosquilla scabricauda
to 15-50
to 31
to 150
Myers (1979); Mead and
Minshall (2012); Lippson and
Lippson (2006)
Atkinson and Froglia (1999);
Ragonese et al. (2012)
Bieler and Mikkelsen (1988);
Foster et al. (2004)
winter burrows up to 410 cm depth;
western N Atlantic from Cape Cod to Gulf
of Mexico; silty substrates; low IT, ST
Mediterranean Sea and eastern Atlantic
from Gulf of Cadiz to Angola; soft
substrates; ST
W Atlantic, from South Carolina USA to S
Brazil, including Gulf of Mexico,
Caribbean, Bahamas, Bermuda; IT, ST
Crustaceans (ghost crabs)
Ocypode quadrata
to 100+
Pombo and Turra (2013); Knott
(2010)
W Atlantic from Rhode Island USA to
Brazil, including Gulf of Mexico and
Caribbean; upper intertidal to fore dunes of
sandy beaches
                                           53

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Table 3. Examples of Deep-Burrowing and/or Feeding Benthos (continued)
Faunal Group/Species
Sediment
Depth
(cm)
Reference
Comments
Crustaceans (fiddler crabs)
Uca pugilator (Atlantic
sand fiddler)
Uca pugnax (Atlantic
marsh fiddler)
Uca minax (red-jointed
fiddler)
to 34
to 15-25
to 30-65
Christy (1982)
Montague (1980); Bergey and
Weis (2008)
Montague (1980); Powers (1977)
Massachusetts to Texas, USA; sandy upper
intertidal and supratidal substrates in tidal
marshes, bays and sounds
Massachusetts to Florida, USA; muddy
intertidal substrates in salt marshes in
sheltered bays and estuaries
Massachusetts to NE Florida, USA; Gulf of
Mexico; freshwater or brackish water tidal
marshes, often supratidal
Crustaceans (other crabs)
Helice tridens
Neohelice granulata
(formerly in genus
Chasmagnathus)
Sesarma reticulatum
(marsh crab)
Eurytium limosum
to 40
to 33
to 30+
to 30
Takeda and Kurihara (1987)
Iribarneetal. (1997)
Koretsky et al. (2002); Abele
(1992)
Koretsky et al. (2002); Felder et
al. (2009)
Japan; salt marsh
SW Atlantic; mud flats and marshes
(deepest burrows in vegetated marshes)
eastern North America and Gulf of Mexico
salt and brackish marshes; IT
W Atlantic from New York, USA to Brazil;
Gulf of Mexico; Caribbean Sea; vegetated
and unvegetated salt marshes; IT
Crustaceans (lobsters)
Nephrops norvegicus
(Norway Lobster)
Homarus americanus
(American lobster)
to 25
to 60-80
Rice and Chapman (1971)
Cooper and Uzmann (1980)

western N Atlantic from Labrador, Canada
to North Carolina, USA; ST
Crustaceans (crayfish)
Cambams diogenes (devil
crawfish)
Procambarus clarkii (red
swamp crayfish)
to 457
to 70
Hobbs and Hart (1959); Hobbs
(1989); Cordeiro et al. (2010)
Oluoch (1990); Hobbs (1989);
FAO (2007)
widespread east of the Rockies and south of
Great Lakes, except peninsular Florida and
the Alleghenies (USA); Ontario, Canada;
ponds and streams in spring season;
burrows in banks of streams
N Mexico to Escambia County Florida, and
north to S Illinois and Ohio; widely
introduced elsewhere; sluggish waters of
lentic and lotic habitats
Crustaceans (amphipods)
Pseudohaustorius
caroliniensis
to 20-30
D ' Andrea etal. (2004)
IT
                                           54

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Table 3. Examples of Deep-Burrowing and/or Feeding Benthos (continued)
Faunal Group/Species
Sediment
Depth
(cm)
Reference
Comments
Echinoderms (Holothurians or sea cucumbers)
Pseudocucumis mixta
Holothuria arenicola
Molpadia oolitica
Molpadia intermedia
to 15-25
to 15-20
to 20
to 35
Konnecker and Keegan (1973)
Mosher(1980)
Rhoads and Young (1971);
Pawsonetal. (2010)
Lambert (1997)
W coast Ireland
circumtropical
western N Atlantic from Massachusetts to
Florida (USA); Gulf of Mexico; mud; ST
eastern N Pacific from Kodiak Island,
Alaska to Gulf of Panama; mud; ST
Echinoderms (heart urchins)
Echinocardium cor 'datum
to 15-20
Rees and Dare (1993); Kroh
(2015)
cosmopolitan; typically sand or muddy
sand; mainly ST
Cnidarians (anthozoans)
Ceriantheopsis americanus
Pachycerianthus
fimbriatus
to 60+
to 100
Nilsen et al. (1982); Frey (1970)
Light and Carlton (2007);
Cowles (2010)
IT, shallow ST
S Alaska to Baja California, Mexico;
predominantly in very soft mud; ST, rarely
IT
Sipunculids (peanut worms)
Golfmgia elongata
Golfmgia vulgaris
Sipunculus nudus (a
species complex)
to 40
to 30-50
to 15-35
Keegan (1974); Cutler (1994); de
Kluijver et al. (2000d)
Swift (1993); de Kluijver et al.
(2000e)
Volkel and Grieshaber (1992);
Kawauchi and Giribet (2014); de
Kluijver et al. (2000f)
widespread: western and eastern N
Atlantic, including Mediterranean; Pacific
(East and South China Seas); muddy sand
or gravel; low IT, ST
widespread but patchy distribution: N
Atlantic from Greenland and northern
Norway to W Africa and eastern
Mediterranean; Indo-West Pacific region;
Antarctic; muddy sand or gravel; low IT to
several hundred meters
cosmopolitan; low IT, ST
Echiuran worms
Maxmuelleria lankesteri
Urechis caupo (fat
innkeeper worm)
Echiums echiums
to 80
to 36+
to 50
Hughes etal. (1996)
Julian et al. (2001); Arp et al.
(1992)
Anker et al. (2005); Pilger and
Murina (2015); Ricketts et al.
(1985)
widespread around British and Irish coasts,
most commonly in fine muds
California, USA; mudflats; IT, ST
widely distributed in the arctic, both in
northern part of N. Atlantic and in N.
Pacific, as far south as 45° N Latitude; IT,
ST
                                           55

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Table 3.  Examples of Deep-Burrowing and/or Feeding Benthos (continued)
Faunal Group/Species
Sediment
Depth
(cm)
Reference
Comments
Enteropneusts (acorn worms)
Balanoglossus gigas
Balanoglossus aurantiaca
(= B. aurantiacus)
Balanoglossus clavigerus
Balanoglossus
australiensis
Saccoglossus kowalevskii
Saccoglossus horsti
Saccoglossus ruber
(synonymised with S.
cambrensis)
to 30
to 60
to 60
to 20-25
to 25-40
to 10-20
to 5-25
Bjornberg (1959); van der Land
(2015)
Duncan (1987); Frey 1970);
Konikoffetal. (2015)
Bromley (1996)
Morton (1950); Konikoff and van
der Land (20 15)
Carey and Farrington (1989);
Smith etal. (2003)
Burden- Jones (1951)
Knight-Jones (1953); Burdon-
Jones and Patil ( 1960)
W Atlantic from Georgia, USA to SE
Brazil, Gulf of Mexico; Greater Antilles; IT
W North Atlantic; IT, shallow ST
Mediterranean Sea; British Isles; IT
Gulf of Carpentaria; New Zealand; New
South Wales, Australia; Solomon Sea,
Great Barrier Reef; fine sand; IT, ST
Georgia to Maine, USA; IT, shallow ST
The Solent, UK; IT
Welsh coast; W coast Ireland; IT
alntertidal and subtidal represented by IT and ST, respectively.




'formerly in genus Callianasssa
                                              56

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Table 4. Data Sources and Information (Realms/Ecoregions after Spalding et al., 2007 [marine] and Abell et al., 2008
        [freshwater]) used to Determine 80th Percentile of Benthic Abundance (see Figure 3) and Benthic Biomass (see
        Figure 4) Depth Distributions. Abundance and biomass data denoted by A and B, respectively. N = number of datasets.
        (The total number of cores comprising datasets from each habitat type/reference pair is noted in parentheses.)
Habitat Type
Reference
TV
(Total
Cores)
Location
Sampler; Sample Area
and Depth; Sieve Size
Realm/
Ecoregion(s)
Estuarine Intertidal
Intertidal Mixed
Intertidal Sand
Intertidal Poikilohaline
Mixed
Intertidal Poikilohaline
Sand
Mermillod-Blondin et al.
(2003) (A)
Johnson (1967) (A)
Rodil et al. (2008) (A)
D'Andreaetal. (2004) (A)
Mucha et al. (2004) (A)
Mucha et al. (2004) (A)
1(3)
4(32)
18(54)
4(12)
1(3)
4(12)
St. Lawrence Estuary, Canada
White Gulch and Lawsons Flat,
Tomales Bay, California, USA
Sheltered beach on inner part of Ria
of Arousa on NW coast of Iberian
Peninsula, Spain
Debidue Flat, South Carolina, USA
Douro Estuary, Portugal
Douro Estuary, Portugal
Cylindrical tube; 78.5
cm2 by 20 cm; 0.5 mm
Brass coring tube; 25
cm2 by 25 cm; core
dissected
Metal core; 188.7 cm2
by 25 cm; 1 mm
Core; 38. 5 cm2 by 30
cm; 0.5 mm
Core sampler; 35 cm2
by 15 cm; 0.5 mm
Core sampler; 35 cm2
by 15 cm; 0.5 mm
Temperate N. Atlantic/Gulf of
St. Lawrence-Eastern Scotian
Shelf
Temperate N. Pacific/
Northern California
Temperate N. Atlantic/
South European Atlantic Shelf
Temperate N. Atlantic/
Carolinean
Temperate N. Atlantic/
South European Atlantic Shelf
Temperate N. Atlantic/
South European Atlantic Shelf
Tidal Freshwater
Tidal Freshwater Mixed
Daueretal. (1987) (A,B)
Schaffner et al. (1987) (A,B)
1(3)
3(3)
Lower Chesapeake Bay tributaries
(James, York and Rappahanock
rivers), USA
James River Estuary (Chesapeake
Bay Tributary), USA
Box corer; 184 cm2 by
25 cm; 0.5 mm
Spade box corer; 600
cm2 by 50 cm; 0.5 mm
Temperate N. Atlantic/
Virginian
Temperate N. Atlantic/
Virginian

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       Table 4.   Data Sources and Information (Realms/Ecoregions after Spalding et al., 2007 [marine] and Abell et al., 2008
               [freshwater]) used to Determine 80th Percentile of Benthic Abundance (see Figure 3) and Benthic Biomass (see
               Figure 4) Depth Distributions (continued).
Habitat Type
Reference
TV
(Total
Cores)
Location
Sampler; Sample Area and Depth;
Sieve Size
Realm/
Ecoregion(s)
Estuarine Subtidal
Oligohaline
Mixed
Oligohaline Mud
Oligohaline Sand
Mesohaline
Mixed
Mesohaline Mud
Schaffner et al.
(1987) (A,B)
Reinharz and
O'Connell (1983)
(A3)
Schaffner et al.
(1987) (A3)
Reinharz and
O'Connell (1983)
(A3)
Reinharz and
O'Connell (1983)
(A3)
Schaffner et al.
(1987) (A3)
Reinharz and
O'Connell (1983)
(A3)
Daueretal. (1987)
(A3)
Hines and Comtois
(1985) (A3)
2(2)
2(4)
1(1)
1(3)
2(3)
2(2)
2(8)
2(6)
1(10)
James River Estuary (Chesapeake Bay
Tributary), USA
Upper Chesapeake Bay
James River Estuary (Chesapeake Bay
Tributary), USA
Upper Chesapeake Bay
Upper Chesapeake Bay
James River Estuary (Chesapeake Bay
Tributary), USA
Central Chesapeake Bay
Lower Chesapeake Bay tributaries
(James, York and Rappahanock
rivers), USA
Mouth of Rhode River, Chesapeake
Bay, USA
Spade box corer; 600 cm2 by 50 cm;
0.5 mm
Spade box corer; 630 cm2 by up to 60
cm; 0.5 mm
Spade box corer; 600 cm2 by 50 cm;
0.5 mm
Spade box corer; 630 cm2 by up to 60
cm; 0.5 mm
Spade box corer; 630 cm2 by up to 60
cm; 0.5 mm
Spade box corer; 600 cm2 by 50 cm;
0.5 mm
Spade box corer; 630 cm2 by up to 60
cm; 0.5 mm
Box corer; 184 cm2 by 25 cm; 0.5 mm
Scuba-collected cores; 80 cm2 by 35
cm within 900 m2 area; 0.5 mm
Temperate N.
Atlantic/Virginian
Temperate N.
Atlantic/Virginian
Temperate N.
Atlantic/Virginian
Temperate N.
Atlantic/Virginian
Temperate N.
Atlantic/Virginian
Temperate N.
Atlantic/Virginian
Temperate N.
Atlantic/Virginian
Temperate N.
Atlantic/Virginian
Temperate N.
Atlantic/Virginian

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Table 4.   Data Sources and Information (Realms/Ecoregions after Spalding et al., 2007 [marine] and Abell et al., 2008
         [freshwater]) used to Determine 80th Percentile of Benthic Abundance (see Figure 3) and Benthic Biomass (see
         Figure 4) Depth Distributions (continued).
Habitat Type

Mesohaline Sand
Polyhaline Mixed
Polyhaline Mud
Polyhaline Sand
Reference
Schaffner et al.
(1987) (A,B)
Reinharz and
O'Connell (1983)
(A3)
Hines and Comtois
(1985) (A3)
Reinharz and
O'Connell (1983)
(A3)
Daueretal. (1987)
(A3)
Nilsenetal. (1982)a
(A)
Daueretal. (1987)
(A3)
Nilsenetal. (1982)b
(A)
Nilsenetal. (1982)a
(A)
TV
(Total
Cores)
3(3)
2(20)
1(10)
1(2)
2(5)
6(6)
1(2)
3(3)
6(6)
Location
James River Estuary (Chesapeake Bay
Tributary), USA
Central Chesapeake Bay
Mouth of Rhode River, Chesapeake
Bay, USA
Central Chesapeake Bay
Lower Chesapeake Bay tributaries and
mainstem, USA
Lower Chesapeake Bay, USA
Lower Chesapeake Bay Mainstem,
USA
Lower Chesapeake Bay, USA
Lower Chesapeake Bay, USA
Sampler; Sample Area and Depth;
Sieve Size
Spade box corer; 600 cm2 by 50 cm;
0.5 mm
Spade box corer; 630 cm2 by up to 60
cm; 0.5 mm
Scuba-collected cores: 80 cm2 by 35
cm within 900 m2 area; 0.5 mm
Spade box corer; 630 cm2 by up to 60
cm; 0.5 mm
Box corer; 184 cm2 by 25 cm; 0.5 mm
Spade box corer; 620 cm2 by up to 50
cm; 0.5 mm
Box corer; 184 cm2 by 25 cm; 0.5 mm
Spade box corer; 620 cm2 by up to 50
cm; 0.5 mm
Spade box corer; 620 cm2 by up to 50
cm; 0.5 mm
Realm/
Ecoregion(s)
Temperate N.
Atlantic/Virginian
Temperate N.
Atlantic/Virginian
Temperate N.
Atlantic/Virginian
Temperate N.
Atlantic/Virginian
Temperate N.
Atlantic/Virginian
Temperate N.
Atlantic/Virginian
Temperate N.
Atlantic/Virginian
Temperate N.
Atlantic/Virginian
Temperate N.
Atlantic/Virginian
Lentic
Lake Profundal
Mud
Fukuhara et al.
(1987) (A3)
4(8)
Profundal region of shallow lake
(Suwa), Central Japan; tubificid
oligochaetes (Limnodrilus)
Lenz grab; 225 cm2 by 33 cm; 0.2 mm
Palearctic/Biwa Koc

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       Table 4.   Data Sources and Information (Realms/Ecoregions after Spalding et al., 2007 [marine] and Abell et al., 2008
               [freshwater]) used to Determine 80th Percentile of Benthic Abundance (see Figure 3) and Benthic Biomass (see
               Figure 4) Depth Distributions (continued).
Habitat Type

Reference
Newrkia and
Wij egoonawardana
(1987) (A)
Cole (1953) (A)
Milbrmk (1973) (A)
Boyer and Whitlatch
(1989) (A)
Sarkka and
Paasivirta (1972)
(A)
TV
(Total
Cores)
2(14)
2(90)
4(15)
1(16)
1(35)
Location
prealpine lake (Mondsee), Upper
Austria; oligochaetes
Douglas Lake, Michigan, USA;
tubificid oligochaetes (Limnodrilus)
Lake Malaren and Lake Erken,
Sweden; tubificid oligochaetes
Caribou Island Basin of Lake
Superior; oligochaetes
Lake Paijanne, Finland; tubificid and
lumbriculid oligochaetes
Sampler; Sample Area and Depth;
Sieve Size
Modified Kajak corer; 19.6 cm2 by 20
cm; 0.2 mm
Small vertical core sampler; 3.8 cm2
by 24 cm; 0.18 mm (upper 10 cm) -
0.2 1mm (below 10cm)
Microstratification sampler; 167 cm2
by up to 19 cm; 0.3 mm
Modified 225 cm2 Eckman box corer;
subcores 13.7 cm2 by up to 16 cm; 0.3
mm
Lenz sampler; 260 cm2 by 30 cm; 0.8
mm
Realm/
Ecoregion(s)
Palearctic/Upper Danube
Nearctic/
Laurentian Great Lakes
Palearctic/N. Baltic
Drainages
Nearctic/
Laurentian Great Lakes
Palearctic/N. Baltic
Drainages
Lotic
Stream Coarse
Grained/Sand
James et al. (2008)
(A)
Omesova and
Helesic (2007) (A)
Olsen and
Townsend (2005)
(A)
Olsen etal. (2001)
(A)
6(24)
1(10)
1(14)
3(18)
Three small streams, southern North
Island, New Zealand
Loucka Paver, 4th-order stream, Czech
Republic
Kye Burn, 4th-order stream, South
Island, New Zealand
Kye Burn, South Island, New Zealand
Hyporheic colonization chambers;
78.5 cm2 by 40 cm; 0.5 mm
Liquid nitrogen freeze cores; 19.6 cm2
by 20 cm; 0.1 mm
Liquid nitrogen freeze cores; 9.6 cm2
by 50 cm; 0.25 mm
Liquid nitrogen freeze cores; 9.6 cm2
by 50 cm; 0.25 mm
Australasia/New Zealand
Palearctic/Upper Danube
Australasia/New Zealand
Australasia/New Zealand
o\
o

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Table 4.   Data Sources and Information (Realms/Ecoregions after Spalding et al., 2007 [marine] and Abell et al., 2008
         [freshwater]) used to Determine 80th Percentile of Benthic Abundance (see Figure 3) and Benthic Biomass (see
         Figure 4) Depth Distributions (continued).
Habitat Type

Stream Coarse
Grained/Sand
with Fines
Reference
Maridet et al. (1992)
(A)
Angradietal. (2001)
(A)
Angradietal. (2001)
(A)
Strommer and
Smock (1989) (A)
Winkelmann et al.
(2003) (A)
Adkins and
Winterbourn(1999)
(A)
Meidl and
Schonborn (2004)
(A)
TV
(Total
Cores)
3(4)
3(90)
1(30)
1(415)
2(12)
2(40)
4(20)
Location
Loire River (S^-order reach), Galaure
(3rd-order reach) and Drac (alpine
torrential stream, 3rd-order reach),
France
2nd, 3rd and 4th-order reaches of Elklick
Run at Fernow Experimental Forest,
West Virginia, USA
lst-order reach of Elklick Run at
Fernow Experimental Forest, West
Virginia, USA
lst-order stream in Blackwater River
watershed, Virginia, USA
Two small 2nd-order mountain
streams, Gauernitzbach and
Tannichtgrundbach, that drain into the
River Elbe, Germany
Two upland streams, Middle Bush and
Grasmere, South Island, New Zealand
Schwarza Brook, low mountain stream
in Thuringian Slate Mountains,
Germany
Sampler; Sample Area and Depth;
Sieve Size
Liquid nitrogen freeze cores with in
situ electro-positioning; 19.6 cm2 by
60 cm; macroinvertebrates separated
by elutriation
Multilevel colonization samplers; 95
cm2 by 30 cm; 0.25 mm
Multilevel colonization samplers; 95
cm2 by 30 cm; 0.25 mm
Cores frozen on dry ice; 18.1 cm2 by
up to 40 cm; 0.053 mm
Liquid nitrogen freeze cores; 19.6 cm2
by 30 cm; macroinvertebrates
separated by hand-picking and
elutriation
Dry ice freeze cores; 9.6 cm2 by 30
cm; 0.12 mm
Liquid nitrogen freeze cores with in
situ electro-positioning; 19.6 cm2 by
60 cm; macroinvertebrates separated
by sorting
Realm/
Ecoregion(s)
Palearctic/Central and
Western Europe
Nearctic/Teays-Old Ohio
Nearctic/Teays-Old Ohio
Nearctic/
Appalachian Piedmont
Palearctic/
Central and Western Europe
Australasia/New Zealand
Palearctic/
Central and Western Europe

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       Table 4.   Data Sources and Information (Realms/Ecoregions after Spalding et al., 2007 [marine] and Abell et al., 2008
               [freshwater]) used to Determine 80th Percentile of Benthic Abundance (see Figure 3) and Benthic Biomass (see
               Figure 4) Depth Distributions (continued).
Habitat Type

Reference
Varricchione et al.
(2005) (A)
McElravy and Resh
(1991) (A)
Maridetetal. (1996)
(A)
Weigelhofer and
Waringer (2003) (A)
Marchant (1988) (A)
Poole and Stewart
(1976) (A)
Marchant (1995) (A)
TV
(Total
Cores)
4(54)
5(40)
3(35)
2(66)
1(17)
5(10)
6(30)
Location
Glaciated stream sites (Montana; 2
data sets), and unglaciated stream sites
(Idaho; 2 data sets), USA
2nd-order reach of Big Canyon Creek,
northern California Coast Range, USA
Three streams (Vianon, Ozange,
Triouzoune) in French granitic Massif
Central mountains, France
3rd-order reach of the Weidlingbach, a
tributary of the Danube, northwest of
Vienna, Austria
Thomson River, 10 km downstream of
Thomson Dam, Victoria, Australia
Brazos River, Texas, USA
Acheron River, Victoria, Australia
Sampler; Sample Area and Depth;
Sieve Size
Liquid nitrogen freeze cores with in-
situ electro-positioning; 19.6 cm2 by
50 cm; 0.063 mm
Substrate colonization samplers; 44.2
cm2 by 35 cm; 0.063 mm
Liquid nitrogen freeze cores with in
situ electro-positioning; 19.6 cm2 by
60 cm; 0.5 mm
Liquid nitrogen freeze cores with in
situ electro-positioning; 19.6 cm2 by
60 cm; 0.1 mm
Dry ice freeze cores; 9.6 cm2 by 30
cm; 0.15 mm
Vertical stratification colonization
sampler; 201. 1 cm2 by 40 cm; 0.5 mm
Dry ice freeze cores; 9.6 cm2 by 30
cm; invertebrates separated by
floatation
Realm/
Ecoregion(s)
Glaciated: Nearctic/
Columbia Glaciated; Upper
Missouri
Unglaciated: Nearctic/
Columbia Unglaciated;
Upper Snake; Bonneville
Nearctic/Sacramento-San
Joaquin
Palearctic/Cantabric Coast-
Languedoc
Palearctic/Upper Danube
Australasia/Bass Strait
Drainages
Nearctic/East Texas Gulf
Australasia/
Murray-Darling
Marine Coastal
Marine Coastal
Mixed
Dauweetal. (1998)
(A3)
Rhoadsetal. (1985)
(A3)
2(7)
l(?)d
Frisian Front and German Bight,
North Sea
East China Sea off Changjiang
Cylindrical Reineck type box corer;
754.8 cm2 by up to 50 cm; 0.5 mm
0.25 m2 spade box corer; 181.5 cm2 by
up to 43 cm; 0.5 mm
Temperate N. Atlantic/
North Sea
Temperate N. Pacific/
East China Sea
to

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Table 4.   Data Sources and Information (Realms/Ecoregions after Spalding et al., 2007 [marine] and Abell et al., 2008
         [freshwater]) used to Determine 80th Percentile of Benthic Abundance (see Figure 3) and Benthic Biomass (see
         Figure 4) Depth Distributions (continued).
Habitat Type
Marine Coastal
Mud
Marine Coastal
Sand
Reference
Simonini et al.
(2004) (A,B)
Hayashi (1988)
(A3)
Moodley et al.
(1998) (A3)
Moodley et al.
(2000) (A3)
Rhoadsetal. (1985)
(A3)
Dauweetal. (1998)
(A3)
Spies and Davis
(1979) (A)
Oliver etal. (1980)
(A)
Oliver etal. (1980)
(B)
TV
(Total
Cores)
2(48)
1(5)
6(12)
2(4)
2(?)d
1(3)
1(5)
1(10)
1(4)
Location
Off of Po and Adige-Brenta river
deltas, North Adriatic Sea
Sado Strait, Sea of Japan
Adriatic Sea, northern basin
Adriatic Sea, northern and middle
basins
East China Sea off Changjiang
Broad Fourteens, North Sea
Santa Barbara Channel, California,
USA
Monterey Bay, California, USA
Monterey Bay, California, USA
Sampler; Sample Area and Depth;
Sieve Size
Box corer; 200 cm2 by 20 cm; 0.5 mm
0. 1 m2 box corer; 225 cm2 by 25 cm (2
or 3 per box core); 0.5 mm
Large box corer; 283.5 cm2 by 20 cm
perspex cores (2 per box core); 0.5
mm
Large box corer; 283.5 cm2 by 20 cm
perspex cores (2 per box core); 0.5
mm
0.25 m2 spade box corer; 181.5 cm2 by
up to 43 cm; 0.5 mm
Cylindrical Reineck type box corer;
754.8 cm2 by up to 50 cm; 0.5 mm
Tin core samplers; 73.9 cm2 by up to
35 cm; 0.5 mm
Diver-operated corer; 180 cm2 by up
to 60 cm; 0.5 mm
Hydraulic suction dredge; 0.25 m2
cylinder; 1.0 mm mesh bags
Realm/
Ecoregion(s)
Temperate N. Atlantic/
Adriatic Sea
Temperate N. Pacific/
Sea of Japan
Temperate N. Atlantic/
Adriatic Sea
Temperate N. Atlantic/
Adriatic Sea
Temperate N. Pacific/
East China Sea
Temperate N. Atlantic/
North Sea
Temperate N. Pacific/
S. California Bight
Temperate N. Pacific/
N. California
Temperate N. Pacific/
N. California
Marine Offshore
Marine Offshore
Mixed
Marine Offshore
Mud
Rhoadsetal. (1985)
(A3)
Stall etal. (1996)
(A3)
l(?)d
1(3)
East China Sea off Changjiang
Palos Verdes Shelf, California, USA
0.25 m2 spade box corer; 181.5 cm2 by
up to 43 cm; 0.5 mm
Gray-O'Hara box corer; 500 cm2 by
up to 50 cm; 1.0 mm
Temperate N. Pacific/
East China Sea
Temperate N. Pacific/
S. California Bight

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Table 4.   Data Sources and Information (Realms/Ecoregions after Spalding et al., 2007 [marine] and Abell et al., 2008
          [freshwater]) used to Determine 80th Percentile of Benthic Abundance (see Figure 3) and Benthic Biomass (see
          Figure 4) Depth Distributions (continued).
Habitat Type

Marine Offshore
Sand
Reference
Dauweetal. (1998)
(A3)
Rhoadsetal. (1985)
(A3)
Hayashi (1988)
(A3)
Moodley et al.
(2000) (A3)
Josefson(1981)(A)
Simonini et al.
(2004) (A3)
Oliver etal. (1980)
(A)
Oliver etal. (1980)
(B)
TV
(Total
Cores)
1(2)
l(?)d
2(10)
1(2)
2(30)
1(24)
2(14)
1(4)
Location
Skagerrak, North Sea
East China Sea off Changjiang
Sado Strait, Sea of Japan
Adriatic Sea, northern and middle
basins
Skagerrak, North Sea
North Adriatic Sea, offshore
Monterey Bay, California, USA
Monterey Bay, California, USA
Sampler; Sample Area and Depth;
Sieve Size
Cylindrical Reineck type box corer;
754.8 cm2 by up to 50 cm; 0.5 mm
0.25 m2 spade box corer; 181.5 cm2 by
up to 43 cm; 0.5 mm
0. 1 m2 box corer; 225 cm2 by 25 cm (2
or 3 per box core); 0.5 mm
Large box corer; 283.5 cm2 by 20 cm
perspex cores (2 per box core); 0.5
mm
0. 1 m2 box corer; 500 cm2 by 28 cm (1
per box core); 1.0 mm
Box corer; 200 cm2 by 20 cm; 0.5 mm
Diver-operated corer; 180 cm2 by up
to 60 cm; 0.5 mm
Hydraulic suction dredge; 0.25 m2
cylinder; 1.0 mm mesh bags
Realm/
Ecoregion(s)
Temperate N. Atlantic/
North Sea
Temperate N. Pacific/
East China Sea
Temperate N. Pacific/Sea of
Japan
Temperate N.
Atlantic/ Adriatic Sea
Temperate N. Atlantic/
North Sea
Temperate N. Atlantic/
Adriatic Sea
Temperate N. Pacific/
N. California
Temperate N. Pacific/
N. California
includes data sets from meso-polyhaline (2) and poly-euhaline (2) transition zones.
Includes two data sets from meso-polyhaline transition zone.
The ecoregion Biwa Ko is described as one consisting of large lakes habitat.  Lake Suwa, the location for our data, is a small lake near Lake Biwa Ko.
dNumber of subcores representing a box core is not specified.

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Table 5. Biologically Relevant Sediment Depths—Biotic Zones—for Decisions Related
         to Ecological Assessment or Remediation. The biotic zone noted in column 2 is
         based on benthic abundance. The biotic zone shown in column 3 is based on
         benthic biomass (where information was available). Note that the biotic zone tends
         to be deeper when biomass is taken into account.
Habitat Type
Biotic Zone (cm)
Biotic zone (cm)
(Considering Biomass)
Estuarine Intertidal
Estuarine Intertidal Sand
Estuarine Intertidal (Other Substrates)
Estuarine Intertidal Poikilohaline
15
*
10



Tidal Freshwater
Tidal Freshwater Mixed Substrate
10
15
Estuarine Subtidal
Oligohaline Sand
Mesohaline Sand
Polyhaline Sand
Oligohaline Mud
Mesohaline Mud
Polyhaline Mud
Oligohaline Mixed Substrate
Mesohaline Mixed Substrate
Polyhaline Mixed Substrate
5
10
15
5
10
5
15
10
10
10
20

5
25
*
15
30
15
Lentic
Lake Profundal Muda
15
20
Lotic
Stream Coarse Grained/Sand
Stream Coarse Grained/Sand with Finesb
River Coarse Grained/Sand with Finesb
35
25
15



Marine Coastal
Sand
Mud
Mixed Substrate
Marine Offshore
Sand
Mud
Mixed Substrate
5
15
10

10
15
*
20
15
15

20
20
*
'Biotic zone not estimated because based on only one data set.
aBiotic zones for this category are based on oligochaetes.
bFines denote grain sizes <2 mm in substantial quantity (approximately 20% or more by weight).
                                            65

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                        80th Percentile of Benthic Depth Distribution - Abundance
Figure 3. Mean 80th Percentile of Benthic Abundance Depth Distribution (+ Maximum 80th Percentile) in Various Habitats.
        Number of data sets in parentheses (the number of cores comprising data sets from each habitat type is noted in Table 4).
        Also see Table 4 for data locations.

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                     80th Percentile of Benthic Depth Distribution - Biomass
           .^
      -5
     -10
     -15
     .20    Tidal
         Fresh\\ ater
  Q -25
     -35


     -40
                                    f  f  -f  4
Estuarine Subtidal
                                  /       *   s   ;
                                 •^        ^   ^  ^


                                      if?   *f?   *f?
                                                         Lentic
                                                                   Marine Coastal
                                                                                               //
                                                                                     Marine Offshore
Figure 4. Mean 80th Percentile of Benthic Biomass Depth Distribution (+ Maximum 80th Percentile) in Various Habitats.
        Number of data sets in parentheses (the number of cores comprising data sets from each habitat type is noted in Table 4).
        Also see Table 4 for data locations.

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                                       APPENDIX
    ECOLOGICAL RISK ASSESSMENT SUPPORT CENTER REQUEST FORM
ERASC Request No. 0015
Requestor: Marc Greenberg, Environmental Response Team
Problem Statement: What is a scientifically defensible definition for the depth of the biotic zone
in soils and sediments?
Background: We are frequently faced with the challenge of defining the "biotic zone" in soils and
sediments during the design and interpretation of soil and sediment sampling programs. This may
pose challenges later when we evaluate sediment concentrations (e.g., depth-integrated, mass per
unit area, surface-weighting, etc.), calculate or model current and future risks to ecological
receptors and humans, and attempt to delineate the relevant depth for remediation at sites where an
action is needed. This can have large implications on the cost, protectiveness, and effectiveness of
a selected remedy (e.g., capping, dredging, monitored natural recovery, excavation, etc.). Other
terms used to describe the biotic zone include "ecologically-relevant zone," "biologically-active
zone" and "bioturbation zone."
Expected Outcome: The ERASC should develop a document that will provide a defensible
approximation or a range of reasonable approximations for what the depth of the biotic zone is
within certain environments.  For example, there are those who assume that 4 cm is adequate to
define the biotic zone for sediment benthos. Others would argue that 0-2 cm, 10 cm (6 in.) or even
as far as 12 in. are reasonable. We need some clarity.
Additional Comments: For sediments, this question should be answered with a primary focus on
benthic macroinvertebrates (e.g., bugs and bivalves) and their distribution among various sediment
microhabitats.  The reason for focusing on benthic macroinvertebrates is because they are
measurement endpoints that provide decision-oriented data. The document should provide general
explanations of the biotic zone in various aquatic habitats (e.g., stream, river, lake, coastal,
estuarine environments) where a remediation may occur.  For soils, the focus should be on both
invertebrates and vertebrate receptors.
                                            68

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