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

data for benzoic acid, 44 samples had at least one chemical concentration greater than a SQS
(25.2% of the area) and 36 samples had at least one concentration greater than a CSL (21% of
the area).
The highest chemical concentrations invariably were observed in samples collected in the
urbanized bays, namely Elliott Bay and Sinclair Inlet. Often, these samples contained
chemicals at concentrations previously observed to be associated with acute toxicity and
other biological effects. Concentrations generally decreased steadily away from these two
bays and were lowest in Admiralty Inlet, Possession Sound, Rich Passage, Bainbridge Basin,
and most of the central basin.
Toxicity tests 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, 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.
Several indices of the relative abundance and diversity of the benthic infauna indicated very
wide ranges in results among sampling stations. Often, the samples collected in portions of
the central basin, Port Townsend Bay, Rich Passage, and outer reaches of Elliott Bay had the
highest abundance and diversity of infauna. Often, annelids dominated the infauna, especially
in samples with unusually high total abundance. Arthropods often were low in abundance in
samples with low overall abundance and diversity. Samples in which the indices of
abundance and diversity were lowest were collected in the lower Duwamish River, inner
Elliott Bay, and Sinclair Inlet.
Statistical analyses of the toxicity data and benthic data revealed few consistent patterns.
Some indices of benthic community diversity and abundance decreased with increasing
toxicity and others increased. Also, the relationships between measures of benthic structure
and chemical concentrations showed mixed results. Total abundance and annelid abundance
often increased significantly in association with increasing chemical concentrations. hi
contrast, indices of evenness, dominance, diversity, and abundance of several of the major
taxonomic groups decreased with increasing concentrations of most individual chemicals and
chemical classes. No single chemical or chemical class was uniquely correlated with the
measures of benthic structure.
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