Dataset: Fluxes of carbon dioxide, methane, and nitrous oxide and associated environmental data from estuarine wetlands in the Pacific Northwest, USA

In this dataset we provide fluxes of carbon dioxide, methane, and nitrous oxide as well as associated environmental data for 34 sites from five types of tidal and non-tidal wetlands in five estuaries in the Pacific Northwest. Wetland types included least-disturbed emergent marshes, restored marshes, least-disturbed tidal swamps, and wet and dry non-tidal agricultural areas, most of which were former tidal wetlands. Sampled estuaries were Coos Bay, Columbia River Estuary, Grays Harbor Estuary, Skagit River Estuary, and Padilla Bay. To measure greenhouse gas fluxes, we conducted light and dark flux measurements in six replicate chambers per site about eight times over the course of a year (spring 2021-spring 2022). At the time of flux measurements, we measured soil and air temperature and plant species composition and height inside chambers (to develop a biomass index), and groundwater salinity, pH and water level below the wetland surface in a small groundwater well for each pair of chambers. We measured wetland surface elevation at each flux chamber with RTK-GNSS or by leveling. Additionally, at a single station per site near the chambers, we obtained timeseries of soil temperature, groundwater level, groundwater temperature, and groundwater salinity. The data in this study underlie analyses of methane and nitrous oxide fluxes by Williams et al. (2024) and carbon dioxide fluxes (manuscript in preparation) and can also be used in support of other modeling and blue carbon data applications.