PARENT SESSION
Oral Session #79: Conservation Ecology: Biodiversity Case Studies and Models. Presiding: T. Rooney.
Friday, August 10, 2001. 8:00 AM to 12:00 PM. Hall of Ideas J.

How does zooplankton community structure respond to varying rates and magnitudes of environmental change?

Bond, Emily¹, Chase, Jonathan¹, ¹

ABSTRACT- While it is well-known that species composition is affected by a number of environmental stresses, such as nutrient inputs and pH, the relationship between the magnitude of change and the rates at which they occur have received comparably less attention. Nevertheless, there are many reasons to suspect that the rates of environmental change may be as important as the magnitude in causing species compositional turnover. In this study, we manipulated the rates and magnitudes of two environmental stressors, nutrients and pH and observed their consequent effects on zooplankton community composition. Specifically, we hypothesized that: (1) a faster rate of change coupled with low or high magnitude will cause a more dramatic shift in community structure than a slower rate of change at these magnitudes, and (2) species compositional turnover will be less likely to occur in isolated systems rather than those which are receiving more zooplankton through immigration. We found that in general, not only did the magnitude of environmental change influence zooplankton community composition, but the rate of change also influenced the degree of species compositional turnover. Furthermore, when communities were in isolation, compositional turnover was considerably lower than when communities were connected to the regional species pool. These results suggest that projections of the effects of environmental change on communities will require investigators to explore not only the magnitude, but also the rates, at which environments change.

KEY WORDS: species composition, nutrient enrichment, acidification, rate of environmental change