Effect of diatom nutrient limitation on copepod development : role of essential lipids

The development of 2 copepod species was studied with nutrient-limited algae as the sole food source. Thalassiosira weissflogii was grown under different levels of nitrogen and phospho- rus limitation. Young copepodite stages of Temora longicornis (Muller) and Pseudocalanus elongatus (Boeck) developed at significantly reduced rates, both when fed with the nitrogen- and the phospho- rus-limited diatom. At high levels of nutrient limitation, the copepods often did not reach maturity. The lipid composition of the diatom was strongly affected by nutrient limitation. Both the proportion and the content of long-chain polyunsaturated fatty acids (PUFAs) were reduced, particularly under phosphorus limitation. The dominant sterol, Δ 5,24(28) C28:2, was reduced by about a factor of 2 both under nitrogen and phosphorus limitation. The results suggest that the different growth rates of the copepods observed can be explained by the different lipid composition of the algae due to nutrient limitation.