Deviations from synchrony: spatio-temporal variability of zooplankton community dynamics in a large lake

Horizontal patterns of plankton communities in lakes are assumed to be transitory resulting from instantaneous weather conditions and water currents. High dispersal is suggested to constrain local optimization of communities and to result in strong synchrony of temporal dynamics at different sites. However, spatio-temporal dynamics of plankton are rarely analysed in lakes mainly due to the sampling effort involved. Here, we present a long-term (14 years) data set of zooplankton abundance sampled fortnightly at five stations simultaneously in a large lake. This unique data set allows us to distinguish instantaneous from persistent horizontal pattern. As expected, population dynamics were highly synchronized among stations, whereas synchrony declined with distance between sites. Synchronization varied strongly among taxa but also between sites. Despite the observed synchrony, coherency distinct spatial variations were found in community structure, abundance, life history traits (clutch size) and life cycle strategies (diapause). Spatial differences varied among taxa, sites and season and could be large with spatial differences in mean abundances of the same taxon of two orders of magnitude. Spatial patterns persisted throughout the whole study period and cannot be fully explained by passive transport due to wind-induced water currents. Hence, local optimization of communities is indeed possible in lakes. We relate our findings to metacommunity theory since the observed patterns suggest a community structured by species sorting.