Patterns of macrozoobenthic production in the deep Arctic Ocean

With the Arctic Ocean shifting towards a system with a seasonal ice cover solely, Arctic marine ecosystems are facing new challenges. Deep-sea macrobenthic communities are ideal integrators of the upcoming changes as they rely in their nutrition almost entirely on the input from upper layers and hence mirror changes of surface production in their own dynamics. But as benthic studies of the deep Arctic Ocean are scarce we are lacking reliable baseline information on the “pre-change” system state. To overcome this obstacle we combined legacy data from the past 20 years, as well as recent field studies in our approach. We investigated the relationship of standing stock, productivity (P/B) and secondary production (P) of macrobenthos with water depth, geographical latitude and sea ice concentration along a transect from Fram Strait up to the high Arctic basins. Community P/B and P were estimated using the multi-parameter ANN model developed by Brey (2012). Our results confirm the previously described negative relationship of water depth and macrofauna standing stock in the Arctic deep-sea (Bluhm et al. 2011). Furthermore we could show that increasing sea-ice concentration and latitude correlated with decreasing standing stock and P of < 75 mg C m-2 y-1. Stations under influence of the marginal ice zone (MIZ) showed much higher standing stock and P (400-1400 mg C m-2 y-1) - even at depths up to 3700 m. We conclude that particle flux is the key factor structuring benthic communities in the deep Arctic Ocean, explaining both the low values in the ice-covered basins and the high values found along the MIZ. With the ongoing trend of a northward migrating seasonal ice zone carbon fluxes will shift accordingly and Arctic areas that are fueled by high primary production now may experience strong decline in the future. More northern and currently food limited areas on the other hand will probably benefit from the new situation, as deep-sea communities can react very fast on new food input and would so potentially form new hotspots of benthic secondary production.