Sediment Quality in Puget Sound Year 2 - Center for Coastal ...

Isomers of DDT and most PCB congeners are not known to induce the cytochrome P450 HRGS
enzyme response, therefore, it is likely that these compounds co-varied with the PAHs and other
organic substances that more likely induced the response.
Summary
The toxicity bioassays performed for urchin fertilization, microbial bioluminescence, and
cytochrome P450 HRGS enzyme induction indicated correspondence with complex mixtures of
potentially toxic chemicals in the sediments. Often, the results of the urchin and cytochrome
P450 HRGS tests showed the strongest correlations with chemical concentrations. As expected,
given the nature of the tests, results of the cytochrome P450 HRGS assay were highly correlated
with concentrations of high molecular weight PAHs and other organic compounds known to
induce this enzymatic response. In some cases, samples that were highly toxic in the urchin or
cytochrome P450 HRGS tests had chemical concentrations that exceeded numerical, effects-
based, sediment quality guidelines or the state criteria, further suggesting that these chemicals
could have caused or contributed to the observed biological response. However, there was
significant variability in some of the apparent correlations, including samples in which chemical
concentrations were elevated and no toxicity was observed. Therefore, it is most likely that the
chemical mixtures causing toxicity differed among the different toxicity tests and among the
regions of the survey area. These chemical mixtures may have included substances not targeted
in the chemical analyses.
Benthic Community Analyses
Community Composition and Benthic Indices
A total of 700 benthic infauna taxa were identified in the 100 samples collected in central Puget
Sound (Appendix E). Of the 700 taxa identified, 5 17 (74%) were identified to the species level.
Among the 5 17 species identified, 243 (47%) were polychaete species, 147 (28%) were
arthropods, 78 (1 5%) were molluscs, and 49 (10%) were miscellaneous taxa (i.e., Cnidaria,
Platyl~elminthes, Nemertina, Sipuncula, Phoronidae, Enteropneusta, and Ascidiacea) and
echinoderms. Several of the species encountered in this survey may be new to science.
As described in the Methods section, five benthic infaunal indices were calculated to aid in the
examination of the community structure at each station. These indices included total abundance,
major taxa abundance (calculated for Annelida, Arthropods, Mollusca, Echinoderinata, and
miscellaneous taxa), taxa richness, Pielou's evenness (J'), and Swartz's Dominance Index (SDI),
and were calculated based on the abundance data collected for the 700 taxa found (Tables 22 and
23). Total abundance is displayed in both tables to facilitate comparisons among indices. All
data were based on analysis of a single sample collected at each station.
Total Abundance
Total abundance (number of individuals per 0.1 m2) of benthic invertebrates at each station
(Tables 22 and 23) ranged from 3,764 organisms at station 203 (Duwamish) to 110 organisms at
station 1 18 (Possession Sound). In approximately half (1 5 of 32) of the strata, total abundance
was relatively consistent among the samples collected within each stratum. However, among
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