Using zooplankton biomass size spectra to assess ecological change in a well-studied freshwater lake ecosystem: Oneida Lake, New York

We explored the sensitivity of three descriptors of zooplankton size spectra (slope, periodic, and Pareto II models) to environmental changes in Oneida Lake, New York, and then used documented environmental changes to model the responses of zooplankton biomass using a general linear model. Using multiple regressions, we identified significant ecological events in Oneida Lake that could affect zooplankton biomass before actual model testing and assessed the three size spectrum models based on their sensitivity to these known variables. The intercept of the slope (linear regression) model was responsive to changes, but the slope was not. The periodic (quadratic) model showed no sensitivity in detecting ecological change. The Pareto II model (probability distribution function) demonstrated the most sensitivity to all ecological variables but was complex to model and there was no direct relationship between its parameters and biological events. The general linear model regression approach proved relatively sensitive to environmental change and had the added benefit of providing a graphical means of biologically assessing differences between years. In general, zooplankton biomass size spectra were responsive to changes in conditions in the Oneida Lake environment, and we believe that size-based approaches have potential as a biotic index in freshwater lake ecosystems.