DECODing arctic sympagic-pelagic-benthic coupling: essentiAl for undeRstanding CO2 sequesTration and Food web dynamICs – DECOD-ARCTIC

Due to the cold and extreme environmental conditions prevailing in the Arctic Ocean (AO), its primary production mainly relies on algae associated with sea ice (sympagic algae) and those that develop in open waters (pelagic algae). These microalgae play an essential role in sustaining the food web, which is crucial for Inuit communities, while also contributing to carbon sequestration through their significant input to the vertical fluxes of organic matter (OM) from the surface to the sediments, in a process known as sympagic-pelagic-benthic (SPB) coupling. However, although the AO is warming nearly four times faster than the rest of the globe, it is currently impossible to accurately predict the future of its SPB coupling.
Indeed, the mechanisms governing the export and degradation of OM, particularly sympagic OM, remain poorly understood. The DECOD-ARCTIC project aims to characterize the processes that modulate the contribution of sympagic algae to SPB coupling. To achieve this, three main tasks have been defined: (1) analyzing the degradation processes of sympagic algae in sea ice, (2) tracking the export pathways of algae and their impact on sedimentation, and (3) understanding the fate of this OM in sediments, whether it contributes to CO2 sequestration or supports benthic food webs.
The methodology relies on an innovative multiproxy approach based on lipid biomarkers, combined with in vitro experiments and in situ sampling on the CCGS Amundsen icebreaker and at the Qikiqtarjuaq research station (Nunavut, Canada). The DECOD-ARCTIC results will fill key gaps in our understanding of SPB coupling and offer essential insights into the future evolution of Arctic ecosystems, crucial for Inuit communities whose livelihoods depend on marine resources.