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

In this survey of central Puget Sound, 36 of the 100 stations sampled had sediments with
significant toxicity and elevated chemical contamination, while 18 appeared to have benthic
communities that were possibly affected by chemical contaminants in the sediments, including
stations in Sinclair Inlet, Dyes Inlet, Elliott Bay, and the Duwamish River. These stations
typically had moderate to very high total abundance, including high numbers of Aphelochaeta
species N1 and other pollution-tolerant species, moderate to high taxa richness, low evenness,
and low Swartz's Dominance Index values. Often, pollution-sensitive species such as arthropods
and echinoderms were low in abundance or absent from these stations. These 18 stations
represented an area of 8.1 km2, or about 1.1 % of the total survey area. These 18 stations, all
located in urbaldindustrial areas, provide possible "evidence of pollution-induced degradation" as
defined by Chapman, 1996.
In contrast, 25 stations were identified with no indications of significant sediment toxicity or
chemical contamination. All of the benthic indices indicated abundant and diverse populations
of most or all taxonomic groups. These stations, located in Port Townsend, Admiralty Inlet,
Possession Sound, the central basin, Port Madison, Liberty Bay, the Bainbridge Basin, Rich
Passage, Dyes Inlet, and outer Elliott Bay, represented an area of 359.3 km2, equivalent to
approximately 49% of the total survey area, and provide "strong evidence against pollution-
induced degradation" as defined by Chapman, 1996.
The remaining thirty-nine stations, with either significant chemical contamination but no toxicity,
or significant toxicity but no chemical contamination, were located in Port Townsend, Possession
Sound, the central basin, Eagle Harbor, Liberty Bay, the Bainbridge Basin, and Elliott Bay and
the Duwamish River, and represented an area of 272.6 km2, equivalent to about 37% of the total
central Puget Sound study area. Benthic assemblages varied considerably in structure at these
stations, presumably as a result of many factors, including natural environmental variables.
Additional statistical analyses are required to fully describe the multivariate relationships among
the sediment quality triad data, and other variable data collected at all 100 stations.
Comparison of the results of the sediment quality triad analyses for this survey was made with
the 1997 survey of northern Puget Sound (Table 40). In both surveys, the percent of the total
study areas displaying toxicity, chemical contamination and altered benthos was similar (1.3 and
1.1% area, respectively). Of the area surveyed in 1997 (773.9 km2), ten stations representing
10.34 km2 (1.3% of the area) could be considered as having pollution-induced degradation. Nine
of these samples were collected in Everett Harbor and one from Port Gardner. The estimate of
1.3% area was similar to the estimate of 1.1% for the 18 "degraded" stations identified in the
central Puget Sound study area. In addition, 10.6% of the 1997 northern area had both high
chemical contamination and high toxicity, but, was accompanied by high benthic abundance and
diversity. For central Puget Sound, this estimate was similar (12.5%). In contrast, the samples
with no contamination and no toxicity represented 19.6% of the northern area and 49% of the
central area. Conversely, the balance of samples in which results were mixed (i.e., either
chemistry or toxicity was significant, benthos was abundant and diverse) was almost twice as
high in the northern study area (68.5%) than in the central study area (37%).
Because of the natural differences in benthic communities among different estuaries, it is
difficult to compare the communities from Puget Sound with those from other regions in the U.S.
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