Effects of Resource Pulses on Nutrient Availability, Ecosystem Productivity, Stability and Food Web Dynamics Following a Stochastic Disturbance

Hypoxia in shallow lakes represents a stochastic disturbance that may elicit a resource pulse through fish decomposition, altering nutrient availability, ecosystem productivity, and food web dynamics. However, the importance of nutrient pulses in productive ecosystems is unknown.  We measured nutrient availability, primary and secondary production, ecosystem stability and energy flow from April through September in complete, partial and non-winterkill lakes following the winter of 2007-2008. Lakes with complete winterkill had an estimated 264 kg/ha of common carp Cyprinus carpio carcass that released an estimated 1,187 g/ha total phosphorus and 6,648 g/ha total Kjeldahl nitrogen whereas lakes with partial kills had an estimated 23 kg/ha of common carp carcass that released an estimated 104 g/ha total phosphorus and 585 g/ha total Kjeldahl nitrogen. Winterkill lakes had higher nutrient concentrations, pH, turbidity, chlorophyll-a, and zooplankton and benthic invertebrate abundances and less periphyton biomass compared to non-winterkill lakes. Additionally, nutrient availability and pelagic productivity were more stable in systems receiving pulses.  Finally, winterkill lake communities relied more on pelagic energy pathways than in non-winterkill lakes. Our results suggest nutrients released during fish decomposition represent an important nutrient pulse in eutrophic lakes, further enriching lake productivity and altering ecosystem structure and function.