Environmental Engineering Reference
In-Depth Information
isms collected from test sites are often compared with
the responses of organisms collected from reference
sites. Reynoldson
et al.
(1995, 1997) and MacDonald
& Ingersoll (2000) describe procedures for assessing
BICS (Fig. 7.5). Similarly, procedures for evaluating
fi sh health data are shown in Fig. 7.6.
Although the BICS assessment should provide
useful information for evaluating the status of benthic
invertebrate communities, all of these potential appli-
cations of BICS assessments are limited by uncertain-
ties in the relation between exposure to COPCs and
effects on the benthic community. This uncertainty
arises because the sampling methods used in BICS
evaluations only rarely provide matching data on
whole-sediment and/or pore-water chemistry. In
addition, variability in BICS metrics among selected
reference sites (i.e., owing to factors other than
sediment contamination) makes it diffi cult to dis-
criminate COPC-related effects on the benthic com-
munity. As a result, BICS data are often of limited
value for evaluating the effects of contaminated
sediments in freshwater, estuarine, and marine
ecosystems.
appropriate supporting data, the factors that are
contributing to any adverse effects that are observed
(USEPA 1992a,b, 1994).
The IJC (1988) suggested that benthic community
surveys should be the fi rst assessment tool used to
evaluate areas of the Great Lakes with suspected
sediment contaminant problems. If no effects are
demonstrated in an initial survey, IJC (1988) recom-
mended no further assessment. However, the absence
of benthic organisms in sediment does not necessar-
ily indicate that contaminated sediment caused the
observed response. Benthic invertebrate distributions
may exhibit high spatial or temporal variability.
Furthermore, short-term exposure to chemical (for
example ammonia, dissolved oxygen) or physical
(for example temperature, abrasion) factors can
infl uence benthic invertebrate distribution and abun-
dance, even in the absence of measurable levels of
COPCs in sediment. Most importantly, evaluations
of BICS only infrequently have suffi cient statistical
power to detect effects associated with exposure to
contaminated sediments (i.e., owing to high variabil-
ity in the selected metrics). Therefore, information
on BICS alone is not always indicative of ambient
sediment quality conditions and is certainly not diag-
nostic of sediment contamination or sediment toxic-
ity (USEPA 1992a,b, 1994).
One objective of a BICS assessment is to determine
whether sediment-associated COPCs may be contrib-
uting to a change in the distribution of benthic
organisms in the fi eld. These assessments can be used
to measure interactive toxic effects of complex chem-
ical mixtures in sediment. Furthermore, knowledge
of specifi c pathways of interactions among sediments
and test organisms is not necessary for assessments
of the benthic community. Assessments of the benthic
invertebrate community can be used to:
•
determine the relation between toxic effects and
bioavailability;
•
investigate interactions among chemicals;
•
compare the sensitivities of different organisms;
•
determine spatial and temporal distribution of
contamination;
•
rank areas for clean up; and
•
evaluate the effectiveness of remediation or man-
agement practices.
The results of benthic community assessments can
also be used to assess the bioavailability of COPCs
in fi eld-collected sediments. The responses of organ-
7.3.4 Selection of metrics for whole-
sediment bioaccumulation assessment
Contaminated sediments represent important sources
of the substances that accumulate in aquatic food
webs (Ingersoll
et al
. 1997). Because these contami-
nants can adversely affect aquatic-dependent wildlife
species and/or human health, tissue chemistry repre-
sents an important indicator in sediment quality
assessments (USEPA 2000a; ASTM 2008b). In
general, the concentrations of bioaccumulative
COPCs in the tissues of sediment-dwelling organisms
represent the primary metrics for tissue chemistry. As
wildlife species typically consume the entire prey
organism, whole-body COPC levels are the most
relevant for assessing risks to aquatic-dependent
wildlife. In contrast, the levels of COPCs in edible
tissue represent the most important metrics for
human health assessments. Assessments that are
directed at evaluating COPC residues in the tissues
of benthic macroinvertebrates should focus on the
bioaccumulative COPCs that are known or sus-
pected to occur in sediments at the site under inves-
tigation. Typically, the COPCs that are considered
