Effects of food and temperature on the lipid accumulation strategy of arctic copepods: experimental approach

Crucial organisms in Arctic food webs are large lipid rich copepods. Their size and high energy content makes them directly sought after food source by pelagic fish, birds, and whales. Lipid accumulation by copepods is a life history trait that allows them to leave the surface for deep waters to overwinter during periods of low food availability, where they can stay torpid and avoid predators at low metabolic cost. This period can last up to 9 months. An important question is, if and how increasing temperatures and freshening in the Arctic will affect phytoplankton community, and then the copepod lipid accumulation rate and type. The lipid type accumulated, wax esters, is crucial for this life history trait, and is composed of fatty acid types linked to the phytoplankton food source and can therefore be directly affected by such changes. We investigated the effect of food type, temperature and salinity on the lipid accumulation and wax ester structure of the copepod Calanus finmarchicus in experimental settings. There was a clear difference in both amount and type accumulated, with diatoms giving the best accumulation rate.