| Summary: | Benthic macrofauna-habitat relationships were determined estuary-wide in Willapa Bay, WA for four intertidal habitats ((1) eelgrass, Zostera marina, (2) Atlantic cordgrass, Spartina alterniflora, (3) ghost shrimp, Neotrypaea californiensis, (4) mud shrimp, Upogebia pugettensis) in 1996 and seven habitats ((1-4), above, and intertidal (5) oyster, Crassostrea gigas, and (6) mud, and (7) subtidal, undredged) in 1998. Ordination (cluster) analysis and species lists revealed that macrofaunal species composition and abundance was similar in oyster, eelgrass and, to a somewhat lessor extent, mud shrimp habitat, but differed considerably among the other habitats. Macrofaunal density in habitats 1-4 was 2- to 3-fold higher in 1996 than in 1998; however, in relative terms, the differences in macrofaunal community structure among the habitats were remarkably similar in both years. Areal species richness, abundance and total biomass was generally highest in habitats 1, 2 and 5, intermediate in habitats 4 and 6, and lowest in habitats 3 and 7. These results suggest that macrofauna-habitat relationships can be used as relative habitat value indicators in large-scale ecological risk assessments.
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