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

The results in the amphipod tests performed in central and northern Puget Sound differed from
those developed in studies with A. abdita conducted elsewhere in the U.S. The frequency
distributions of the data from both areas are compared to that for data compiled in the
NOAAIEMAP national database (Table 35). Whereas amphipod survival was less than 80% of
controls in 12.4% of samples from studies performed elsewhere, only one of the samples from
central Puget Sound showed survival that low. None of the northern Puget Sound samples
indicated survival of less than 80%. In the national database 47% of samples indicated survival
of 90-99.9%. Similarly, in central Puget Sound 48% of samples had survival within the range of
90-99.9%. In northern Puget Sound, 76% of samples showed comparable survival. In both
Puget Sound areas, the lower "tail" of the distribution (i.e., samples in which survival was very
low) was absent.
With the results of the amphipod tests weighted to the sizes of the sampling strata within which
samples were collected, the spatial scales of toxicity could be estimated. A critical value of
40% of control response was used to estimate the spatial extent of toxicity in this test.
However, because only one of the test samples indicated less than 80% survival relative to
controls, the spatial extent of toxicity was estimated as 0.1% of the central Puget Sound survey
area.
To add perspective to these data, the results from central and northern Puget Sound were
compared to those from other estuaries and marine bays surveyed by NOAA in the U.S. The
methods for collecting and testing the samples for toxicity were comparable to those used in the
Puget Sound surveys (Long et al., 1996). In surveys of 26 U. S. regions, estimates of the spatial
extent of toxicity ranged from 0.0% in many areas to 85% in Newark Bay, NJ (Table 36). The
central and northern Puget Sound areas were among the many regions in which the spatial extent
of toxicity in the amphipod tests was estimated to be 0% to 0.1 %. With the data compiled from
studies conducted through 1997, the samples that were classified as toxic represented about 5.9%
of the combined area surveyed. The data for both regions of Puget Sound fell well below the
national average. These data suggest that acute toxicity as measured in the amphipod survival
tests was neither severe nor widespread in in sediments from the northern and central Puget
Sound study areas.
Sea Urchin Fertilization - Pore Water
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Several features of the sea urchin fertilization test combined to make it a relatively sensitive test
(Long et al., 1996). In these tests, early life stages of the animals were used. Early life stages of
invertebrates often are more sensitive to toxicants than adult forms, mainly because fewer
defense mechanisms are developed in the gametes than in the adults. The test endpoint -
fertilization success - is a sublethal response expected to be more sensitive than an acute
mortality response. The gametes were exposed to the pore waters extracted from the samples;
the phase of the sediments in which toxicants were expected to be highly bioavailable. This test
was adapted from protocols for bioassays originally performed to test wastewater effluents and
has had wide application throughout North America in tests of both effluents and sediment pore
waters. The combined effects of these features was to develop a relatively sensitive test - much
more sensitive than that performed with the amphipods exposed to solid phase sediments.
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