MarshFlux · The effect of future global climate and land-use change on greenhouse gas fluxes and microbial processes in salt marshes

Coastal wetlands are globally important ecosystems providing valuable ecosystem services, such as carbon sequestration over long timescales, affecting global carbon cycling and climate modulation. The amount of carbon sequestered, and therefore the net long-term global cooling potential of coastal marshes, however, is affected by complex biogeochemical reactions in marsh soils, which may produce and/or consume all three of the major greenhouse gases (GHGs) (carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O)). The magnitude and direction of these fluxes, and whether marsh soils act as a source or sink of GHGs, is affected by a variety of environmental factors which are predicted to vary with projected global change. MarshFlux, therefore, aims to address fundamental gaps in understanding of how the global cooling potential of coastal marshes will be affected by responses of biogeochemical reaction rates and GHG fluxes to global change. The effect of multiple drivers of global change on the response of GHG fluxes and key microbial processes for the consumption and production of N2O and CH4, will be investigated using a novel combination of laboratory incubations and mesocosm experiments. Laboratory incubation experiments mimicking modelled global change scenarios will be conducted to constrain the effects of drivers on marsh soil biogeochemical reaction rates and subsequent GHG dynamics, focusing on temperature, nutrient-loading and salinity. The results of these experiments, while critical themselves, will then inform mesocosm experiments to allow for the assessment of the whole ecosystem (soil, water and vegetation) response to global change under current and predicted future conditions. This research is critical for effective management of coastal wetlands to maintain their blue carbon value under future global change.