We monitored the response of microbial, phytoplankton, and zooplankton communities in addition to oxygen concentrations. Carbaryl concentrations peaked shortly after Sevin application and degraded quickly and treatment differences were undetectable after 30 days. Zooplankton richness, diversity, abundance, and oxygen concentrations all decreased in pulsed treatments, while phytoplankton and microbial abundance increased. Zooplankton composition in the high pesticide treatment consisted primarily of rotifers as compared to dominance by copepods in the other three treatments. While many of the community and ecosystem properties showed signs of recovery within 40 days after the pulsed pesticide disturbance, important and significant differences remained in the microbial, phytoplankton and zooplankton communities after the pesticide degraded.