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Abstract:
Phytoplankton and sea ice algae are traditionally considered to be the main primary producers in the Arctic Ocean. In this Perspective, we explore the importance of benthic primary producers (BPPs) encompassing microalgae, macroalgae, and seagrasses, which represent a poorly quantified source of Arctic marine primary production. Despite scarce observations, models predict that BPPs are widespread, colonizing similar to 3 million km(2) of the extensive Arctic coastal and shelf seas. Using a synthesis of published data and a novel model, we estimate that BPPs currently contribute similar to 77 Tg C y(-1) of primary production to the Arctic, equivalent to similar to 20 to 35% of annual phytoplankton production. Macroalgae contribute similar to 43 Tg C y(-1), seagrasses contribute similar to 23 Tg C y(-1), and microalgae-dominated shelf habitats contribute similar to 11 to 16 Tg C y(-1). Since 2003, the Arctic seafloor area exposed to sunlight has increased by similar to 47,000 km(2) y(-1), expanding the realm of BPPs in a warming Arctic. Increased macrophyte abundance and productivity is expected along Arctic coastlines with continued ocean warming and sea ice loss. However, microalgal benthic primary production has increased in only a few shelf regions despite substantial sea ice loss over the past 20 y, as higher solar irradiance in the ice-free ocean is counterbalanced by reduced water transparency. This suggests complex impacts of climate change on Arctic light availability and marine primary production. Despite significant knowledge gaps on Arctic BPPs, their widespread presence and obvious contribution to coastal and shelf ecosystem production call for further investigation and for their inclusion in Arctic ecosystem models and carbon budgets.
