Coastal wetlands are globally important ecosystems providing valuable ecosystem services, such as carbon (C) sequestration over long timescales, affecting global C cycling and climate modulation. The amount of C 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. This research is critical for effective management of coastal wetlands to maintain their Blue Carbon value under future global change. This is particularly crucial as more countries look to natural climate solutions to offset their greenhouse gas emissions and there are increasing calls for blue carbon to be included in national greenhouse gas inventories.
The primary objective of MarshFlux is to determine the response of biogeochemical reaction rates and greenhouse gas (GHG) fluxes in salt marshes to a variety of environmental factors, which are expected to vary due to future global climate and land-use change. There are three research objectives to achieve this overall aim; 1) to determine the effect, both individually and combined, of changes in nutrient concentrations, salinity and temperature on GHG fluxes in soils from salt marshes along a climatic-gradient, 2) to determine the relative importance and strengths of the various pathways of N2O and CH4 production and consumption in marsh soils, under varying nutrient concentrations, salinity and temperature and 3) to develop indices of the magnitude and direction of GHG fluxes under projected future climate and land-use scenarios to allow more accurate prediction of future GHG emissions from salt marshes. These will be determined by measuring GHG fluxes from the entire marsh system, incorporating soil, water and vegetation, representative of in-situ conditions, under varying environmental stressors (nutrient concentrations, salinity, temperature) and vegetation-types.
