Seasonal trends in zooplankton lipid concentration and class in freshwater lakes

The lipid concentration of the zooplankton population from three small lakes in Central Ontario and Lake Ontario, measured biweekly from May to October, ranged from 7 to 24% of dry weight. The seasonal mean of zooplankton lipid concentration for each lake was between 9 and 16% of dry weight, and non-polar lipids were always <50% of total lipid, except for a brief period in Lake Ontario. In the smaller lakes, zooplankton biomass (r2 = 0.37, P = 0.001), but not zooplankton lipid concentration, was related to edible (<60 nm) phytoplankton biomass and total phytoplankton biomass. Zooplankton lipid was neither related to primary production nor lipid production; however, the seasonal mean of lipid concentration was related to the seasonal mean of chlorophyll a-specific primary production (assimilation number) (r2 = 0.96, P = 0.020) and lipid assimilation number (r2: = 0.94, P = 0.033). The lipid concentration of the zooplankton community and the non-polar fraction of that lipid were somewhat lower than expected from the literature on individual species of zooplankton.