Saltwater Coastal Carbon Flux Synthesis

We collated published and unpublished data from studies that measured net ecosystem exchange as carbon dioxide (CO2) fluxes (and methane, CH4, where available) from wetlands that varied in surface water and porewater salinity concentrations (both manipulative experiments and observations). Studies were selected to minimize the influence of exogenous covariates such as land-use, hydrologic, and water quality changes. We calculated minimum, maximum, and median values from time series of gross ecosystem productivity (GEP), ecosystem respiration (ERCO2, ERCH4), and net ecosystem productivity (NEP). We included data that were measured at daily and monthly scales. Whenever possible, we used measured porewater salinities. If porewater data were not available, we used measured surface water salinities. We calculated the change in salinity as the difference between ambient and elevated concentrations from experimental salinity additions, or as the differences in observed salinities between freshwater and brackish marshes or freshwater and saltwater marshes. We calculated the % difference of change in median values of GEP, ERCO2, ERCH4, and NEP using the following equation: Percent (%) Difference in Median = [(elevated-ambient) / |ambient|] x 100