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

samples within several strata there were differences in total abundance up to an order of
magnitude of ten. These strata included South Admiralty Inlet (stratum 4), Central Basin
(stratum 6), Sinclair Inlet (stratum 19), Elliott Bay (strata 24, 25, 28, and 29), and the Duwamish
(stratum 32). In most of these cases, high numbers of a single polychaete species (Aphelochaeta
species N 1) accounted for the inflated abundance in one of the samples within the stratum.
Major Taxa Abundance
Total abundance and percent total abundance of five major taxonomic groups (Annelida,
Arthropoda, Echinodermata, Molluscs, and miscellaneous taxa) are shown in Table 22. Results
also are compared among stations in stacked histograms (Appendix F).
The total abundance of annelids ranged from 2,970 animals (station 203, Duwamish) to 30
animals (station 123, Central Basin). Annelid abundance calculated as the percentage of total
abundance ranged from 94% (station 1 15, Shoreline Elliot Bay) to 6% (station 177, Shoreline
Elliot Bay). hi 36% of the 100 stations sampled, fifty percent or more of the total benthic
infaunal animals were annelids. In 67% of the samples, one-third or more of the animals in the
benthic communities were annelids.
Total abundance of arthropods ranged from 1,349 animals (station 1 12, South Admiralty Inlet) to
3 (station 160, Sinclair Inlet). Percent total abundance of arthropods ranged from 58% in South
Admiralty Inlet (station 1 12) to 1% in Elliott Bay (station 11 5), the Duwamish (station 205), and
East Harbor Island (station 202). Arthropods made up 50% or more of the total benthic infaunal
assemblage in only 5% of the 100 stations sampled (stations 134 and 12 1, Central Basin; 17 1,
Dyes Inlet; 190, Mid Elliott Bay; and 1 12, South Admiralty Inlet), and 33% of the total
abundance in only 20% of the samples.
Total abundance of molluscs ranged from 822 animals at station 177 (Shoreline Elliott Bay) to 4
at station 142 (Liberty Bay). Percent total abundance of molluscs ranged from 75% (station 155,
Rich Passage) to 1% at station 142 (Liberty Bay). Molluscs were numerically dominant (i.e.,
made up 50% or more of the total assemblage) in 13% of the samples, including those from
stations in Port Townsend (1 lo), Port Orchard (157), west of Bainbridge Island (149, 152),
Shoreline (1 77) and Mid Elliott Bay (1 86- 188, 193- 194, 196), and Rich Passage (1 54- 155).
Thirty-eight percent of the samples had a 33% or greater portion of their infaunal assemblage
composed of molluscs.
Total abundance of echinoderms ranged from 42 1 at station 108 (South Port Townsend) to 0 at
20 stations, sampled primarily in the central basin (strata 6, 8, and 11) and Elliott Bay (strata 23,
25, and 28-32). These stations also represented the highest and lowest percent total echinoderm
abundance, ranging from 60% (South Port Townsend, station 108) to 0% at the suite of 20
stations in the central basin and Elliott Bay. There were no echinoderms in 20% of the samples,
and five or fewer individuals in 60% of the samples. Echinoderms made up greater than 50% of
the total benthic infaunal assemblage in only 2 of the 100 stations sampled, stations 146
(Keyport) and 108 (South Port Townsend), and 33% of the total abundance in only 5 of the
stations (stations 146, 108, and stations 148, 150, and 15 1 (northwest of Bainbridge Island).
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