Carbon Fixation Into Lipid in Small Freshwater Lakes

Algal lipid is a critical food resource for zooplankton, a solvent for lipophilic contaminants, and a useful indicator of phytoplankton nutrient status in culture. Seasonal patterns in lipid production and the photosynthetic parameters describing lipid production were determined for three mesotrophic to oligotrophic, headwater lakes. The mean lipid fraction of C fixation (LFCF) was 15.8% (range 8.5-22.5%) measured bimonthly from 2 May to 21 October 1988. Periods of highest nutrient stress were associated with the lowest LFCF, contradicting findings from algal culture experiments and suggesting that nutrient deficiency does not govern lipid synthesis in natural aquatic ecosystems. LFCF was related instead to temperature and daylength, suggesting that it is related to changes in the physical environment.