Macrobenthic invertebrates and sediments at 1 subtidal and 10 intertidal stations along a transect in Baker Bay of the 1ower Columbia River estuary were sampled monthly from November 1980 to October 1981. Water column temperatures and salinities were also recorded at the subtidal station. The intertidal community consisted primarily of estuarine species, whereas the subtidal community had additional marine species. Marine species declined in abundance after the interstitial salinity minimum (June), indicating the important role of salinity in determining benthic community structure. Filamentous algae, tide pools, and eelgrasses (Zostera spp.) were also important factors determining macrobenthic invertebrate community structure. By altering sediment characteristics, Zostera spp. had a positive effect on deposit feeders and a negative effect on the sand-dwelling amphipod Eohaustorius estuaris.