Diatom -lipid - copepod nexus under threat by global change

Abstract

The central role of lipids in the ecology of high latitude seas is under threat by global change. This hinges on tight ecological links between diatoms and copepods of the genus Calanus, that produce and accumulate energy rich lipids. Strongly coupled through seasonal water column stability, nutrient supply, spring bloom succession and overwintering life strategies, this nexus is foundational to the highly productive food webs of Arctic/sub-Arctic North Atlantic. We report that the ability of Calanus finmarchicus to accumulate lipids is seriously impaired by changing plankton community and by rising temperatures, being 3 times higher on diatoms than flagellate based diets while suffering around a 60% reduction associated with a 2oC temperature change. This together with higher respiration rates, smaller size at maturity and reduced diatom productivity suggests their ability to overwinter will be compromised, threatening not only their contribution to regional productivity but also in maintaining a significant pool of sequestered carbon via the lipid pump. Similar lipid mediated couplings are prevalent throughout high latitude seas, bringing uncertainty to the ecosystem services they provide.