Benthic Communities and the Invasion of an Exotic Mussel in Mission Bay, San Diego: A Long-Term History

A twenty-year dataset on the subtidal benthic macrofauna within Mis- sion Bay, San Diego, reveals distinct differences in community structure along a back-bay/front-bay gradient. Assemblages in the extreme back bay are character- ized by low diversities and abundances, and are dominated by an exotic mussel, Musculista senhousia. Species richness increases toward the mouth, and because of the very high densities of M. senhousia at a station intermediate in the spatial gradient, total abundance and biomass show sharp peaks in this region. Despite the dramatically increased dominance M. senhousia has achieved in the bay, few negative effects of this invasion on subtidal macrofauna are evident