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

many trace metals either analyzed with partial or total digestions. Similarly, fertilization success
was strongly correlated with the concentrations of PCBs in both central and northern Puget
Sound. However, urchin fertilization was highly correlated with the concentrations of both high
and low molecular weight PAHs in central Puget Sound, but not in northern Puget Sound.
Because the solvent extracts would not be expected to elute trace metals, MicrotoxTM and RGS
results were expected to show strong associations with concentrations of PAHs and other organic
compounds. The data indicated that microbial bioluminescence decreased with increasing
concentrations of most individual PAHs and most PCB congeners in the northern samples, but
not in the central samples. MicrotoxTM results were correlated with benzoic acid in both areas. In
both survey areas, RGS enzyme induction increased with increases in the concentrations of most
of the organic compounds, notably including all of the individual PAHs, all classes of PAHs, and
many of the PCBs, some pesticides, and dibenzofuran.
There were a few similarities between the two study areas in the relationships between benthic
indices and chemical concentrations, but there were more differences. For example, the data
indicated highly significant correlations between the guideline-normalized concentrations of
trace metals and taxa richness in both areas. Also, Swartz's Dominance Index was highly
correlated with trace metals and mean ERM quotients for 25 substances in both surveys.
However, total abundance was correlated with PAHs in central Sound, but not in northern Sound
sediments. The very high correlations observed between mollusc abundance and many chemical
classes in northern Sound were not apparent in central Sound. In contrast, annelid abundance
was correlated with many chemical classes in central Sound, but not in northern Sound.
There were almost no similarities between the two studies in the correlations between benthic
indices and toxicity results. The highly significant correlation between echinoderm abundance
and urchin fertilization in northern Puget Sound was not observed in central Sound. The
significant correlation between cytochrome P450 HRGS induction and Pielou's Evenness Index
was positive in northern sediments and negative in central sediments. Annelid abundance
increased significantly with increasing cytochrome P450 HRGS induction and decreasing urchin
fertilization in central Sound, but not in northern Sound samples.
Although the chemicals for which analyses were performed may have caused or contributed to
the measures of toxicity and/or benthic alterations, other substances for which no analyses were
conducted also may have contributed. Definitive determinations of the actual causes of toxicity
in each test would require further experimentation. Similarly, the inconsistent relationships
between measures of toxicity and indices of benthic structure suggest that the ecological
relevance of the toxicity tests differed between the two regions of Puget Sound.
Benthic Community Structure, the "Triad" Synthesis, and
the Weight-of-Evidence Approach
The abundance, diversity, and species composition of marine infaunal communities vary
considerably from place to place and over both short and long time scales as a result of many
natural and anthropogenic factors (Reish, 1955; Nichols, 1970; McCauley et al., 1976; Pearson
and Rosenberg, 1978; Dauer et al., 1979; James and Gibson, 1979; Bellan-Santini, 1980; Dauer
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