DOES CONSIDERATION OF THE WIND FIELD IMPROVE PREDICTIONS OF ZOOPLANKTON ABUNDANCE IN HARP LAKE, ONTARIO?

The predictability of zooplankton abundance under wind-driven currents has rarely been explored and further study can help improve the understanding of zooplankton communities in aquatic ecosystems. In this study, we sought relationships between the wind field and fortnightly abundances of 8 zooplankton species at a mid-lake station in Harp Lake, Ontario from 1980 to 2004. Over the study period, average wind speed has declined by 25%, while direction has shifted 21 degrees towards the north. Multiple linear regressions were generated to predict seasonal and interannual changes in daily zooplankton abundance combining year, Julian day, chemistry and, finally, wind speed and direction. The wind field was successfully loaded into these models for 6 of the 8 species, although improvements in predictive power were modest. We suspect that the decrease in wind speed has contributed to a change in zooplankton heterogeneity in the lake, and thus a change in bias of lake-wide abundance estimates derived from a single station. Zooplankton are patchily distributed, but most long-term monitoring programs sample only at one station. Our work suggests that we may well be able to correct for any bias emanating from a changing wind field and improve the predictability of abundance.