Deep-sea benthic communities and oxygen fluxes in the Arctic Fram Strait controlled by sea-ice cover and water depth

Abstract

Arctic Ocean surface sea-ice conditions are linked with the deep sea benthic oxygen fluxes via a cascade of dependencies across ecosystem components like primary production, food supply, the activity of the benthic community, and their functions. Additionally, each of the ecosystem components is influenced by abiotic factors like light availability, temperature, water depth or grain size structure. In this study, we investigated the coupling between surface sea-ice 5 conditions and deep-sea benthic remineralization processes through a cascade of dependencies in the Fram Strait. We measured sea-ice concentrations, nutrient profiles, different sediment compounds, benthic community parameters, and oxygen fluxes at 12 stations in the HAUSGARTEN area of the Fram Strait in water depth between 275-2500 m. Our investigations reveal that the Fram Strait is bisected in a permanently and highly sea-ice covered area and a seasonally and low sea-ice covered area, which both are long-lasting and stable. Within the Fram Strait ecosystem, sea-ice concentration 10 and water depth are two independent abiotic factors, controlling the deep-sea benthos. Sea-ice concentration correlates well with the available food, water depth with the oxygen flux, and both abiotic factors correlate with the macrofauna biomass.However, in water depths >1500 m the influence of the surface sea-ice cover fades out and water depth effect becomes more dominant. Remineralisation across the Fram Strait is ~ 1 mmol C m -²d -1 . Owing to the contrasting primary production pattern, our data indicate that the portion of newly produced carbon that is remineralised by the benthos is ~2.6 % in the 15 seasonally low sea-ice covered Fram Strait but can be >15 % in the permanently high sea-ice covered Fram Strait.Furthermore, by comparing a permanently sea-ice covered area with a seasonally sea-ice covered area, we discuss a potential scenario for the deep-sea benthic ecosystem in the future Arctic Ocean, in which an increased surface primary production can lead to increasing benthic remineralisation in water depths <1500 m. 20Biogeosciences Discuss., https://doi

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