Will the declining sea ice extent in the Arctic cause a reversal of net benthic-pelagic exchange directions?

In the Arctic, loss of sea ice due to climate change and the northward shift of the Polar Front are predicted to affect many ecosystem processes such as the ecologically important process of particulate and dissolved matter exchange between the seafloor and the water column. In this study, we show for the first time that a change from an ice-covered, Arctic water-dominated system to an Atlantic -dominated ice-free one is likely to reverse seafloor-water exchange directions. A north – south transect across the Barents Sea was studied over two years with differing sea ice cover conditions, recording biological, biogeochemical, hydrographic, geophysical, and oceanographic data. There was a clear difference between the direction and magnitude of key benthic-pelagic fluxes present at Atlantic-dominated environments, and those in Arctic water – dominated ones. Currently, the southern Barents Sea exhibits a net downward flux of dissolved matter and a net upward flux of particulates, while in the northern region solutes fluctuate upwards and particulates downward, making the North a more depositional region that promotes near-surface primary productivity. Broad scale assessments of net fluxes in rapidly changing ecosystems should be employed to monitor impacts of climate change and anthropogenic activities. • Benthic-pelagic exchange processes are likely to reverse as the Polar Front retreats. • Particulate fluxes are predicted to shift from downward to upward. • Dissolved fluxes are predicted to shift from upward to downward. • Sea ice retreat and bottom trawling are influential drivers of change. • Impacts on benthic biological communities and carbon storage potentials are likely.