Descriptors and correlates of community stability: long-term trends in zooplankton communities of manipulated and unmanipulated lakes

Fiorenza Micheli and the NCEAS Community Dynamics Working Group
National Center for Ecological Analysis and Synthesis
Santa Barbara, California

One major focus of community ecology is to describe and explain temporal variability of species composition within natural communities. More stable communities could be expected to exhibit lower temporal variability in the types and abundances of species present. One effect of anthropogenic disturbance may be to alter the rate of community change through time. Two indices of the rate of community change are shifts in biomass and sequential determinations of similarity between the components of a community over time. We compared long-term trends of biomass change and sequential similarity of zooplankton communities from eight reference lakes with those from ten lakes subjected to various anthropogenic stresses (pH change, invasion of exotic species, nutrient addition, food-web manipulation). Both biomass change and sequential similarity tend to show greater temporal variabilty in stressed than in reference systems. The strongest response emerges when sequential similarity is determined for functional groups rather than for individual species. Regression analyses indicate that variability in biomass change and sequential similarity decrease as species richness increases but are not related to total zooplankton biomass. Indices describing community stability through time proved useful tools for characterizing the response of lake ecosystems to stress.