Testing Biomass-Size Spectrum Theory with Whole-Lake Experiments

Aquatic freshwater ecosystems are changing at a dramatic pace, as a result of a range of anthropogenic stressors including species invasions, climate change and eutrophication. However, it is not always immediately clear how these community-level changes resulting from disturbance impact rates of energy transfer or overall ecosystem productivity. Whole aquatic ecosystems at the Experimental Lakes Area have undergone dramatic community-level change in response to acidification, eutrophication and biomanipulation, both during manipulation and recovery. Data from many of these manipulations lend themselves to analysis of normalized biomass size spectra (NBSS) to better understand how community changes have affected energetic transfer efficiency in ecosystems. Preliminary NBSS analyses focused on phytoplankton and zooplankton indicated a significant resilience in the fitted slopes around the expected slope of -1, but that residual variance around the slopes tended to increase during manipulations. Here, we amend these analyses by including fish size spectra to help improve NBSS assessments, and provide a more complete analysis of how community changes in response to experimental disturbance affect NBSS fits and parameter estimates, and in turn how that informs our interpretation of the effects on energy transfer rates in these systems.