Effects of nitrogen stressed algae on different Acartia species

We studied the reproductive response of two copepod species,Acartia tonsa and Acartia clausii, fed algae with differentC:N ratios (4.5 and 9.1 molar ratios respectively) in orderto investigate the influence of nutritional imbalances on calanoidcopepods egg production. Adult females were incubated with thecryptophyte Rhodomonas sp. at saturating concentrations. Thealgae were cultured under nitrogen depleted and sufficient conditions.Ingestion rates of the animals fed with different algae andtheir response in terms of egg production and hatching successof the eggs were quantified. Both species produced more eggwhen fed with nitrogen-limited algae. Ingestion rates and egghatching differed between species, but were not significantlyaffected by the quality of the food. The only difference betweenthe two species in their reaction to food quality was that A.tonsa increased the number of resting eggs, whereas no restingegg production was observed in A. clausii when fed with nitrogenlimited algae. These results support the recent suggestion thata moderately high prey C:N ratio (10–15) supports a higheregg production than a C:N ratio substantially <10.