Life under perennial ice-coverage:effects of varying food input on ecology and distributionof smallest benthic organisms in the Arctic Ocean

The present study investigates the influence of ice coverage and various pathways of particulate organic matter on the benthic colonisation of various Arctic deep sea areas. With exception of the Lomonosov Ridge region, central Arctic sediments exhibited generally very low concentrations of plant pigments, emphasising the oligotrophic character of these perennially ice-covered regions, while the Fram Strait was selected as a typical marginal region, where upwelling processes at the ice edge account for highly productive areas. Because of their ecological importance within the deep sea and their well adapted strategies of survival and reproduction, smallest benthic organisms (particularly foraminifera and bacteria) were chosen as model organisms for these investigations. Taking a section from the Fram Strait up to the Alpha Ridge, the results of organism abundance, biomass and activity showed a distinct decline. This decline was strongly coupled with the general availability of deposited phytodetritus. Especially the studies in Fram Strait exhibited the effects of pulsed phytodetritus sedimentation on the smallest benthic biota. In consequence, foraminiferal diversity was noticeably reduced in areas of ice edge blooms, due to a dominance of oligotrophic species. In total the present investigations showed that in ice-covered Arctic regions the processes for primary production, transport pathways and at least the food supply for the benthos are highly heterogeneous. Thus generalizing or regional predictions for the distribution of benthic organisms in the ice-covered Arctic Ocean should be carefully formulated, especially if those assumptions are based on snap-shot investigations with only limited local extent.