- Biotic communities,
- Acid deposition -- Environmental aspects,
- Predatory aquatic animals,
- Predation (Biology)
Invasive species introductions into freshwater ecosystems have had a multitude of effects on aquatic communities. Few studies, however, have directly compared the impact of an invader on communities with contrasting structure. Historically high levels and subsequent reductions of acid deposition have produced landscapes of lakes of varying acidity and zooplankton communitystructure. We conducted a 30-day enclosure experiment in Killarney Provincial Park, Ontario, Canada, to test the effects ofBythotrephes longimanus, an invasive invertebrate predator, on two contrasting zooplankton communities at different stages of recovery from acidification: recovered and acid damaged. Bythotrephes significantly decreased zooplankton biomass and abundance in both communities but had a greater negative effect on the abundance of zooplankton in the recovered community.Bythotrephes reduced species diversity of the recovered zooplankton community but not of the acid-damaged community. Species richness of both community types was unaffected by Bythotrephes predation. The effect of Bythotrephes on small cladocerans, a preferred prey type, differed between the community types and appeared to be related to density-dependent predation byBythotrephes. Both community- and species-level results suggest that recovered and acid-damaged zooplankton assemblages may be negatively affected by an invasion of Bythotrephes but that the specific response is dependent on the original community structure.