Benthic Macroinvertebrate communities of Southwestern Lake Ontario Following Invasion of Dreissens

Abstract

Changes in benthic macroinvertebrate communities inhabiting natural cobble and artificial reef substrates in southwestern Lake Ontario were quantified before and after the invasion of dreissenid mussels in the late 1980s. Dreissenids comprised 79% and 93% of the cobble and reef communities in 1991-1992 (post-invasion) and replaced the amphipod, Gammarus fasciatus, which was the most abundant species at both habitats in 1983 (pre-invasion). Total abundance of non-Dreissena species was significantly greater in 1991-1992 than in 1983. Comparisons of macroinvertebrate community similarity in 1983 and 1991-1992 indicated that previously established taxa did not change substantially between sampling periods, but their proportions in the community did. Although many factors may have contributed to the changes we observed, our results support theories that Dreissena is facilitating energy transfer to the benthos by pseudofecal/ fecal deposition and that mussel colonies are providing additional habitat for other invertebrate taxa.