Effects of nitrogen stressed algae on different Acartia species

Abstract

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