Zooplankton life cycles at high latitudes: how is seasonal food availability and predation pressure affecting fat storing strategies?

Animals at high latitudes often face the challenge of a short feeding season. Many marine copepods are adapted to such environments. They produce large fat sacs which serve as energy stores for the winter, and the winter is spent in relatively safe habita ts where activity is reduced and metabolism turned down. However, some copepods seem to be capital breeders in the sense that stored resources are used for the next reproductive event as well. A trade off then arises; survival during the feeding season mu st balance the benefits of reproduction on stored resources. For zooplankton in seasonal environments, we aim at understanding which fat storing strategies are optimal under different predation regimes. A dynamic state variable model will be developed, fi rst for a general scenario. Then it will be parameterised for Calanus finmarchicus and Calanoides acutus, and predictions will be tested against field data on these species. C. finmarchicus inhabits the North Atlantic, C. acutus the Southern Ocean, and th ey are both very abundant species that may structure their pelagic communities.