Program     Biogeochemical processes in land-ocean interfaces, surface estuaries, subterranean estuaries and sediment-water interface       Poster The impact of bioturbating crabs on salt marshes carbon flux. P-C2-05-S Laura Elisabeth Agusto* , The Swire institute of Marine Science, The University of Hong Kong/ School of Biological Sciences, The University of Hong Kong Benoit Thibodeau, The Swire institute of Marine Science, The University of Hong Kong/ Department of Earth Sciences, The University of Hong Kong Jianwu Tang, The Ecosystems Center, Marine Biological Laboratory, The University of Chicago Faming Wang, The Ecosystems Center, Marine Biological Laboratory, The University of Chicago Stefano Cannicci, The Swire institute of Marine Science, The University of Hong Kong/ School of Biological Sciences, The University of Hong Kong Presenter Email: cannicci@hku.hk The effects of bioturbating crabs and related microbial activities within salt marshes, makes it complex to understand the carbon processes and measure the gas fluxes in these coastal ecosystems Gas flux measurements in intertidal salt marshes are generally taken on an undisturbed patch of sediment, void of any animal activity. However, this sampling methodology does not take into account the potential contribution of burrowing crabs, which can reach high densities and proved to be a critical ecosystem component of coastal wetlands. Each burrow is connected to the surface and increases the sediment-air interface, adding another dimension to that hidden world underneath the vegetated areas. An additional and reactive interface area which mediates gas exchange and may complicate measurements. Intertidal marshes store significant amounts of coastal ‘blue carbon’ through carbon sequestration thus playing a crucial role in mitigating global climate change. It is therefore imperative to take crab burrows into account to accurately assess carbon fluxes within wetlands, thus to avoid overlooking the potential flux linked to their faunal component. Here, we present preliminary data collected in a natural salt marsh located at the outlet of the Herring River in Wellfleet, Cape Cod, Massachusetts, US during the summer of 2018. We used an LGR (LGR Corp, CA, USA) ultraportable CO2, CH4 and H2O Analyzer to measure out flux of greenhouse gases from the salt marsh with and without presence of crab burrows. We discuss the importance of crab burrows as an untended factor within carbon stock calculations. We thus propose a new conceptual approach to assess carbon fluxes within intertidal marshes, not overlooking important bioturbators.

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