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

tests; and 3% of the area in the cytochrome P450 HRGS assays. The estimates of the spatial
extent of toxicity measured in three of the four tests in central Puget Sound were considerably
lower than the "national average" estimates compiled from many other surveys previously
conducted by NOAA. Generally, they were comparable to the estimates for northern Puget
Sound. However, in the cytochrome P450 HRGS assays, a relatively high proportion of samples
caused moderate responses. Collectively, these data suggest that central Puget Sound sediments
were not unusually toxic relative to sediments from other areas. The large majority of the area
surveyed was classified as non-toxic in these tests. However, the data from the RGS assays
indicated a slight to moderate response among many samples.
The laboratory tests indicated overlapping, but different patterns in toxicity. Several spatial
patterns identified with results of all the tests were apparent in this survey. First, highly toxic
responses in the sea urchin, Microtox, and P-450 tests were observed in many samples from inner
reaches of Elliott Bay. Toxicity in these tests decreased considerably westward into the outer and
deeper regions of the bay. Second, many of the samples from the Liberty Bay and Bainbridge
basin area were toxic in the Microtox and P-450 assays. The degree of toxicity decreased
steadily southward down the Bainbridge basin to Rich Passage, where the sediments were among
the least toxic. Third, samples from two stations located in a small inlet off Port Washington
Narrows were among the most toxic in two or more tests. Fourth, several samples from stations
scattered within Sinclair Inlet indicated moderately toxic conditions; toxicity diminished steadily
eastward into Rich Passage. Finally, samples from the Admiralty Inlet/Port Townsend area and
much of the central main basin were among the least toxic.
The surficial area in which chemical concentrations exceeded effects-based sediment guidelines
was highly dependent upon the set of critical values that were used. There were 25 samples in
which one or more Effects Range-Median (ERM) values were exceeded. They represented an
area of about 2 1 km, or about 3% of the total survey area. In contrast, there were 94 samples in
which at least one Washington State Sediment Quality Standard (SQS) or Cleanup Screening
Level (CSL) value was exceeded, representing about 99% of the survey area. Without the data
for benzoic acid, only 44 samples had at least one chemical concentration greater than a SQS
(representing 25.2% of the area) and 36 samples had at least one concentration greater than a
CSL (2 1 % of the area).
The highest chemical concentrations invariably were observed in samples collected in the
urbanized bays, namely parts of Elliott Bay and Sinclair Inlet. Often, these samples contained
chemicals at concentrations that equaled or exceeded numerical guidelines or state standards.
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.
Although the study was not intended to determine the causes of toxicity in the tests, a number of
statistical analyses were conducted to estimate which chemicals, if any, may have contributed to
toxicity. As expected, strong statistical associations between measures of toxicity and complex
mixtures of PAHs, pesticides, phenols, other organic compounds, and several trace metals were
observed. However, there was significant variability in some of the apparent correlations,
including samples in which chemical concentrations were elevated and no toxicity was observed.
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