Better Together: Combining Underwater Eddy Covariance Fluxes with Biodiversity Measures to Explore Benthic C Flows Within a Shallow Coastal Seascape

Shallow seafloor habitats form productive and biodiverse ecosystems of global importance, but we remain widely uninformed about the role of the different habitats in organic C synthesis, remineralization, sequestration and export. We conducted an extensive seasonal field study to investigate rates and pathways of organic C flow within a shallow coastal seascape of the Baltic Sea. Underwater eddy covariance was used to compare productivity (primary production and respiration rates) across six contrasting habitats that included rocky reefs, bare sediments, and macrophyte canopies over a year. Biodiversity sampling was performed in parallel with the eddy fluxes to quantify species’ abundance and biomass. This presentation synthesizes our recent and ongoing efforts to understand how nearshore habitats function as net sources or sinks of organic C, the spatial subsidies they provide through C export, and the role of macrofauna for C turnover. New insights into the temporal variability of eddy fluxes and how these relate to seafloor productivity will also be discussed.