The temporal coherence of zooplankton population abundances in neighboringnorth-temperate lakes

We investigated the temporal coherence (i.e., the correlation or synchrony between time series) of annual abundances among populations of freshwater z ooplankton in eight lakes in Ontario, Canada, from 1980 to 1992. We estimat ed temporal coherence using the intraclass correlation coefficient (r(i)). While values of r(i) were relatively low among comparisons of all eight lak es, they were statistically significant for three of the seven common clado ceran and copepod taxa (Bosmina langirostris, Leptodiaptomus minutus, and M esocyclops edax). These significant: positive correlations imply that a por tion of the interannual variation in abundance was produced by factors oper ating on a scale larger than the individual lake catchments, Because the ei ght-lake analysis might obscure strong, but conflicting, patterns among lak es in the region, we identified homogeneous and temporally coherent subsets of lakes for each species using an exploratory stepwise deletion procedure , The resultant homogeneous subsets exhibited much greater temporal coheren ce, accounting fur 47% (Eubosmina) to 84% (Leptodiaptomus) of the interannu al variation in abundance. Our results suggest that the factors affecting a nnual variation in zooplankton abundance must be sought both within lakes a nd beyond their watersheds.