MEPS 264:73-82 (2003)  -  doi:10.3354/meps264073

ABSTRACT: The mortality rate of female calanoid copepods Temora longicornis and Pseudocalanus elongatus was measured in relation to the concentration of different algae as a food source. Female copepods were fed either good-quality food (Rhodomonas sp.) or nutritionally poor food (Dunaliella sp., Amphidinium sp., Chrysochromulina polylepis and Synechococcus sp.) in high (>300 µgC l^-1) or low (<100 µgC l^-1) concentrations and survival was monitored. Both copepod species had low mortality rates (≤5% d^-1) when fed with a high concentration of Rhodomonas sp. or Dunaliella sp., somewhat higher rates with the same species at a low concentration (4 to 12% d^-1), and highest rates with all the other algae (12 to 18% d^-1), irrespective of the concentration. Hence, some poor-quality algae can supply part or all of the energy required for survival. Diet-specific differences were more pronounced at high than at low food concentrations, suggesting that at low concentrations, qualitative differences of the algal food source decrease. The clearest copepod-specific difference was observed in survival without food: probably due to internal energy reserves, P. elongatus survived in filtered water nearly twice as long as T. longicornis. We suggest that, in low food environments, food quantity and species-specific ability to resist starvation might be as important as food quality in determining the success of copepod populations.

KEY WORDS: Copepod · Survival · Food quality · Temora longicornis · Pseudocalanus elongatus · Mortality · Food quantity