Benthic-pelagic interactions and algal-derived organic matter dynamics along the East Siberian Sea slope revealed by fluorescence and isotope tracers

초록

The Arctic Ocean is undergoing rapid transformation driven by climate change, including declining sea-ice cover and increasing freshwater inputs, with profound consequences for carbon and nutrient cycling. The East Siberian Sea (ESS), one of the largest Arctic shelf systems, plays a central role in linking terrestrial inputs, primary production, and deep-ocean carbon export. In this study, we combined fluorescence spectroscopy with stable isotope and bulk chemical analyses to examine dissolved organic matter (DOM) dynamics along a shelf-slope transect of the ESS. Our results show that slope-associated sedimentary processes exert a strong control on DOM redistribution and transformation. Enhanced algal production across the Russian Arctic increasingly contributes to organic matter transport toward slope regions. Elevated chlorophyll-a concentrations in waters, together with a pronounced enrichment of protein-like fluorescent DOM (C3), point to strong algal inputs to the continental slope. At mid-slope stations (200-900 m), co-enrichment of dissolved and particulate organic carbon with heavier delta 15N signatures suggests intensified microbial remineralization and nitrogen cycling, likely stimulated by sediment resuspension under Atlantic Water influence. These findings highlight the ESS slope as a dynamic benthic-pelagic interface where sedimentary processes reshape DOM composition and act as an important pathway for the supply of bioavailable carbon and nitrogen to the Arctic Ocean interior. Overall, this study highlights the continental slope as an active regulator of Arctic DOM cycling under ongoing Atlantification and sea-ice decline.

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