Relationships between primary production and vertical particle export at the Atlantic-Arctic boundary (Fram Strait, HAUSGARTEN)

摘要

The lack of extended dataset has so far prevented an inclusive understanding of the long-term relationships between primary production (PP) and vertical export in the Arctic Ocean. It is urgent to investigate these connections as Arctic ecosystems are on the verge of climate-related shifts, which could be caused by the combined effects of increase in Pacific and Atlantic inflow, climate warming, and sea ice decline. For a period of 6 years we investigated the degree of coupling between PP and export by making use of modelled PP rates and vertical particle fluxes collected with sediment traps moored at ～ 300 m depth in the eastern Fram Strait. Our analyses indicate that total and new simulated PP averaged for different areas centered on the mooring location (5-200 km radius) explain at best 20-44% of the observed biogenic particle fluxes at 300 m, when applying extended time-lagsrn(55-90 days) between PP and vertical fluxes. Based on this phasing, we define a conceptual framework that presents the temporal dimension as a prime determinant of the maximum strength of the PP-export coupling at a given depth. Our results support that planktonic food webs in the Fram Strait process heavily biogenic material in the epi-pelagic zone, but we further suggest that Atlantic-Arctic water interactions induce a particular ecological setting responsible for the extended turn-over. In conclusion, we hypothesize that global warming could promote a transition toward a more retentive ecosystem in the Fram Strait region despite the likely increase of pelagic PP in the Arctic Ocean.