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

Stratum 6, in Puget Sound's central basin (Figure 39), included stations 121-123, with levels of
4-methylphenol exceeding both state criteria at stations 122 and 123, and significant reduction in
amphipod survival at station 123. Comparison of infaunal assemblages between stations
indicated similarities in species composition at stations 122 and 123, collected from 200-220 m
depth. Sediments from both of these deep stations were composed of 86% fines. Assemblages
from these two stations shared 6 of 10 dominant species and had relatively similar infaunal
indices. The infaunal indices generated for station 12 1, located in 10 m of water, with sediments
composed of 5% fines, differed from the other two stations. Station 121 had a higher total
abundance of 1272 (verses 240 and 3 14 for stations 122 and 123, respectively), higher abundance
of arthropods (677) and molluscs (475) (verses 53/92 and 1271147 for stations 122 and 123,
respectively), and no dominant species shared with stations 122 and 123 in this stratum. There
was no clear association between triad parameters at station 123, rather, it appeared that the
infaunal assemblage at this station was structured by depth and grain size.
Four samples were collected in stratum 8, near West Point (Figure 39), in depths ranging from
168m to 239m. Sediment from these stations ranged from a mixed grain-size composition (42%
and 72% silt-clay - stations 129 and 128, respectively) to silt-clay (85% and 90% silt-clay -
stations 1 13 and 127, respectively). Infaunal composition was more similar between stations
127-129 than in station 113, which had the lowest total, annelid, arthropod, and mollusc
abundance. Station 113 did have levels of 4-methylpl~enol exceeding both state criteria, and
displayed significant cytoclu-ome P450 HRGS toxicity response.
The three stations (1 36- 13 8) collected from 2 13-250m in Puget Sound's central basin (stratum
1 1) (Figure 40) were homogeneous in sediment composition (8 1-94% fines), toxicity (all
displayed significant cytochrome P450 HRGS toxicity response), chemistry (no chemical
concentrations in the sediments exceeded state or national guidelines), and infaunal indices,
displaying moderate total abundance and taxa richness values and sharing 6 out of 10 dominant
species. There was no clear association among triad parameters at these stations.
The final three stations (139, 140, and 141) collected from Puget Sound's central basin (stratum
12) (Figure 40) were quite dissimilar from one another, being collected at differing depths
(235m, 190m, and 97m, respectively) and possessing differing grain sizes (54%, 98%, and 12%
fines, respectively). Station 139 and 140 displayed significant cytochrome P450 HRGS toxicity
response and shared 7 of their 10 dominant species, although infaunal indices between the two
stations differed. Station 140 also displayed chemical contamination (4-methylphenol
concentration measured above both state and national guidelines). Station 141, located the
farthest south of the three stations, displayed very different infaunal indices and species
composition, and had no significant toxicity results or elevated chemical concentrations. No
clear relationships could be seen among the three triad parameters at station 140.
As with the more northern stations in this study area, examination of the benthic infaunal
community structure in sediments collected from Puget Sound's central basin stations revealed
no clear patterns related to chemistry or toxicity data. Instead, similarities of infaunal indices and
species composition among stations appeared to be correlated with similarity in station depth,
grain size, and distance between stations.
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