Calanus finmarchicus abundance, production and population dynamics in the Barents Sea in a future climate

Abstract

Even though change in marine ecosystems due to global warming has been documented in numerous studies, the nature of change for key ecosystem components is often poorly understood. The Barents Sea is an area where strong climate changes are expected to occur, and since the area is also intensively exploited commercially, it is of particular interest to predict how primary and secondary producers which transfer energy to higher trophic levels will be affected. In the present study we have used a model approach where an individual based model that simulate the life history of Calanus finmarchicus is two-way linked to a coupled biogeochemical and ocean circulation model. Using the IPCC 20C3M control run and the A1B emission scenario, a downscaling of the GISS-AOM global climate model has been used to force the ecosystem model for a reference (1981–1999) and a future climate (2046–2064) simulation respectively. The predicted annual primary production under the future climate scenario was on average 106gCm−2y−1 implying a 36% increase from the reference scenario. The strongest increases occurred in the northern and eastern parts of the Barents Sea likely induced by a strong reduction in ice coverage. C. finmarchicus production also increased, but less (23%) and largely in southern and western areas where production was already high under the reference climate scenario. As a consequence, the proportion of the Barents Sea assumed to have C. finmarchicus concentrations high enough to sustain fish larval growth did not increase substantially. The results suggest that C. finmarchicus most likely are unable to take full advantage of the predicted increased Barents Sea primary production in the future, possibly due to too low temperature and a mis-match between the development and spawning of C. finmarchicus and the early primary production peak in Arctic waters. The proportion of C. finmarchicus with local overwintering and reproduction in the Barents Sea versus those advected in from the Norwegian Sea remained unchanged at ∼75%.