Abstract

Quantifying variability of lower food web components is important for evaluating the significance of change observed in historical lake-wide studies of Lake Ontario. Water temperature is a major controlling factor of plankton growth rates. Therefore, spatial patterns of temperature should be reflected in patterns of lower food web components. Spatial variability of surface temperature in Lake Ontario over the growth season represent thermal bar structure, stratification, wind-driven upwelling events, and fall overturn. We use MODIS satellite imagery to track the evolution of spatial patterns of temperature and chlorophyll a from April to October, 2003. We then compare these satellite observations to discrete shipboard measurements of lower food web components (nutrients, chl a, zooplankton) collected during lake-wide LOLA sampling in April, August, and September 2003. Primary goals of this analysis are to link physical forcing to nutrient and plankton distributions and to identify regions of differential variability for post hoc stratification of samples. We also compare the spatial variability seen in LOLA stations in 2003 to the spatial variability of previous lake-wide studies in 1990 and 1972 and seasonal variability at station 41 of the Canadian Biomonitoring Program from 1981-1995.