Regional climatic drivers of synchronous zooplankton dynamics in north-temperate lakes

The role that climate plays in determining the temporal dynamics of freshwater zooplankton is poorly understood, despite its potential to synchronize population dynamics on a regional basis. We quantify the spatial synchrony of common zooplankton taxa among lakes in the Dorset, Ontario, area and investigate the climatic mechanisms responsible for these patterns at both annual and seasonal scales. We show that the dynamics of several taxa are characterized by similar patterns of abundance among lakes across the region, suggesting a synchronising effect of climate on zooplankton population abundances. Using multiple regression analyses to compare zooplankton dynamics with climatic and in- lake variables, we find that El Ni (n) over tildeo - Southern Oscillation ( ENSO) events and ice cover variability are among the most important predictors of synchrony at annual and seasonal scales, particularly for Leptodiaptomus and Bosmina. Leptodiaptomus, a dominant herbivore in these lakes, had decreased abundances in years with earlier ice- off dates and shorter periods of ice cover. Secchi depth was also synchronous and appeared to respond to regional meteorological factors ( spring temperature and precipitation, ice duration). A warming climate with the ability to modify ice and ENSO dynamics, as well as temperature and precipitation patterns, may also alter the structure and dynamics of zooplankton communities in north- temperate lakes.