Lipid production in natural phytoplankton communities in a small freshwater Baltic lake, Lake Schöhsee, Germany

1. Seasonal patterns in lipid production and the photosynthetic parameters describing lipid production in Lake Schöhsee (a small freshwater, mono‐dimictic and moderately eutrophic North German Baltic lake) were determined. 2. The mean lipid fraction of C fixation (LIP‐FCF) was 13.2% (range 7.6–21%), measured bimonthly from January to December 1995. Periods of high nutrient concentration, low temperatures and particular species of algae (diatoms and/or cryptophytes), were associated with the highest LIP‐FCF values. 3. None of the static indicators of nutrient status [dissolved nitrate, soluble reactive silica (SRS); C/N or N/P] are apparently related to the allocation of carbon to lipid in Lake Schöhsee. 4. The light saturation parameters ( I k : I k ‐LIP) indicated that carbon fixation into lipid was saturated at much lower light than that of total carbon fixation. This suggested that carbon fixation into lipid was more light efficient than total carbon fixation. 5. The relative allocation of carbohydrate and protein was related to daylength and temperature, respectively.