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

area were toxic in the MicrotoxTM and cytochrome P450 HRGS 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 (167 and 168) 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, and perhaps,
foremost, were the highly toxic responses in the sea urchin, MicrotoxTM, and cytochrome P450
HRGS tests observed in the strata of inner Elliott Bay and the lower Duwamish River. Toxicity
in these tests generally decreased considerably westward into the outer and deeper regions of the
bay.
Spatial Extent of Toxicity
The spatial extent of toxicity was estimated for each of the four tests performed in central Puget
Sound with the same methods used in the 1997 northern Puget Sound study (Long et al., 1999a),
and reported in Table 9. The critical values used in 1997 were also applied to the 1998 data. The
33 strata were estimated to cover a total of about 732 k m in the central basin and adjoining bays.
In the amphipod survival tests, control-normalized survival was below 80% in only one sample
(station 167 Port Washington Narrows), which represented about 1.0 km, or about 0.1 % of the
total area. In the sea urchin fertilization tests of loo%, 50%, and 25% pore waters, the spatial
extent of toxicity (average fertilization success 4 0% of controls; i.e., highly toxic) was 5.1, 1.5,
and 4.2 km" respectively, or 0.7%, 0.2%, and 0.6% of the total area. Usually, in these tests the
percentages of samples in which toxic responses are observed decrease steadily as the pore
waters are diluted. However, in this case the incidence of toxicity and, therefore, the spatial
extent of toxicity, was higher in tests of 25% pore waters than in the tests of 50% pore waters.
There is no apparent explanation for this discrepancy from past performance.
The spatial extent of toxicity relative to controls in the MicrotoxTM tests was 349 km2,
representing about 48% of the total area. However, there were no samples in which mean
EC50's were less than 0.5 1 mg1L or 0.06 mg/L, the statistically-derived 80% and 90% lower
prediction limits of the existing MicrotoxTM database. In the cytochrome P450 HRGS assays,
samples in which the responses exceeded 1 1.1 pglg and 37.1 pglg (the 80% and 90% upper
prediction limits of the existing database) represented about 237 km%nd 24 km" respectively.
These areas were equivalent to 32% and 3%, respectively, of the total survey area.
Concordance among Toxicity Tests
Non-parametric Spearman-rank correlations were determined for combinations of the four
different toxicity tests to determine the degree to which the results co-varied and, therefore,
showed the same patterns. It is critical with these correlation analyses to identify whether the
coefficients are positive or negative. Amphipod survival, urchin fertilization success and
microbial bioluminescence improve as sediment quality improves. However, cytochrome P450
HRGS responses increase as sediment quality deteriorates. Therefore, in the former three tests,
positive correlation coefficients suggest the tests co-varied with each other. In contrast, co-
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