Environmental Geochemistry- Wetland Resilience

Science Center Objects

Tidal wetlands are key ecosystems because they are unique ecological systems that provide essential habitat for fish, shellfish, birds and other fauna and flora, many of which have great economic importance.  At the same time, tidal wetlands provide critical services to society by serving as a physical barrier between our cities, roads and homes and the rising sea. If healthy and properly managed, those barriers have an increased potential to respond to sea-level rise through ongoing elevation gain and landward migration, maintaining important services to society into the future.

Tidal wetlands are geological structures that are built and sustained, or degraded and lost, primarily due to ongoing productivity and preservation of below ground plant material, and the biogeochemical processes that lead to preservation or degradation of soil organic matter. Over a period of years to millennia, root material and sediment are transformed into peat or mineral soil. Their future persistence relies on critical processes that drive vertical growth and landward migration, such as plant photosynthesis and growth, plant trapping of sediment suspended in tidal water, growth of plant roots, and preservation and retention of soil organic matter and mineral sediment. 

Research in the Environmental Geochemistry group strives to understand current and future persistence of marshes through studies that measure, model, and map the biogeochemical, geological, and hydrological factors that affect these ecosystems. These include distributions and vitality of plant communities across gradients of environmental conditions, including hydrology and hydrodynamics, salinity, long-term weather, latitude, and sea-level rise.

Tidal wetlands are undergoing rapid change on a national and global scale, in response to a host of environmental changes and challenges. Where observations have been made, past elevation reconstructions over the past several millennia suggest that tidal wetlands have generally maintained a nearly constant position with tidal frames, while transgressing in response to ~1mm/year of sea level rise and eroding on their seaward edges. In the 20th century, and particularly in the 21st century, the global rate of sea-level rise has increased several-fold, while local rates in some areas are now greater than 5 mm/year. The enhanced rate of sea-level rise is an unprecedented challenge for tidal wetlands, and their continued persistence will be determined by their capacity to gain elevation through storage of organic and inorganic soil components, while migrating landward. One important consequence of the marsh elevation recovery has been the coincident intensification of carbon storage, largely driven by an expanding accommodation space favorable for organic matter preservation, made possible by sea-level rise. Therefore, coastal wetlands provide a negative feedback on climate, through enhanced carbon storage that is stimulated by the climate warming that drives accelerating sea-level rise.

 

marsh platform is completely submerged during a spring tide

High tides are one challenge of working in tidal wetlands! Here the marsh platform is completely submerged during a spring tide. The boardwalk, which scientists use to access the site, is also under water during this extreme high tide, while the solar panels powering some instruments remain dry. Sensors are deployed in the tidal creek to measure the water chemistry and flow as water enters and exits the marsh. Here we are measuring the export of carbon and nutrients from the marsh to the estuary.