Post-bloom feeding of Calanus finmarchicus copepodites: Selection for autotrophic versus heterotrophic prey

Abstract

Feeding and faecal pellet production of late copepodite stages of Calanus finmarchicus were measured in mixtures of cultured autotrophic and heterotrophic food, as well as in a natural post-bloom plankton assemblage, in order to evaluate food selection and its potential effect on sedimentation of organic matter. Calanus finmarchicus consistently selected for diatoms, both in mixtures with the heterotrophic dinoflagellate Oxyrrhis marina, and in natural seston containing dinoflagellates, ciliates and flagellates. Similarly, the filtration, ingestion and faecal pellet production rates were significantly higher feeding on diatoms than when feeding on other food species. Calanus finmarchicus selection appeared relatively inflexible, so that changes in seston composition induced large changes in diet quantity and composition. Our results support the traditional view of C. finmarchicus as a major grazer of diatoms, and suggest potentially high post-bloom faecal pellet production rates.

Keywords:

• Calanus finmarchicus
• diatoms
• faecal pellet production
• heterotrophic food
• post-bloom
• selective feeding

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgments

We wish to thank P. Wassmann for the practical arrangements and S. Jónasdóttir, J. T. Turner and one anonymous reviewer for helpful comments on the previous version of the manuscript. MK was financed by the Academy of Finland and Carlsberg Foundation, and CWR by the Norwegian Research Council through the CABANERA-project (project number: 155936/700). This research was supported by a mobility grant from the Nordic Academy for Advanced Study (NorFA).

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark