WetCAT and climate resilience of wetlands for water quality
Using the online mapping tool to investigate how sea level rise could change the way wetlands improve water quality
About WetCAT
A Virginia freshwater wetland with native Lizard's Tail (Saururus cernuus). Preferring streambanks and freshwater or slightly brackish wetlands, Lizard's Tail is one of the many wetland plant species that filter out pollutants in wetlands. Photo: CCRM
Wetlands improve water quality in the Chesapeake Bay
Wetlands are valuable parts of our landscape, and provide many ecosystem services including reducing erosion of shorelines and riverbanks, recharging groundwater supplies, providing habitat, mitigating flooding, and improving water quality, to name a few.
Poor water quality can cause harmful algae blooms and oxygen dead zones that are hazardous to human health, kill fish, and impact sea grass beds which are home to many important Bay creatures including blue crab. Well-functioning wetlands improve water quality across the Chesapeake Bay by absorbing excessive nutrients from septic systems, lawns, and agricultural fields, and filter out excessive sediments.
Figure 1 from Mitchell et al (2020) depicts current salinity ranges of the Chesapeake Bay. Higher salinity ranges are projected to migrate upriver with sea level rise, and tidal fresh and brackish marshes (in the tidal fresh and oligohaline regions) are likely to be vulnerable transitioning to saltmarsh.
How will sea level rise affect water quality services provided by freshwater and brackish wetlands?
Sea level rise is projected to bring higher salinity waters flowing further into the Chesapeake Bay, resulting in the transition of vulnerable freshwater and brackish wetlands into saltwater marshes. Marshes that are most vulnerable to this change are located in lower salinity areas that are adjacent to higher salinity ranges, typically located in the middle to upper reaches of tributary rivers. This has important implications for water quality services provided by wetlands.
Research has shown that freshwater and brackish wetlands can be more effective at absorbing nutrients and removing excess sediment from waters than saltwater marshes. Thus, it is important for managers to be aware of where these changes may affect water quality services of wetlands.
(For links to more references, see the Summary section.)
Using WetCAT to identify where water quality services may be impacted by sea level rise
Finding wetlands that are providing effective water quality services that may be vulnerable to sea level rise
Using geoprocessing tools to find wetlands vulnerable to sea level rise
Summary
Water quality improvement is a key ecosystem service that wetlands provide for the Chesapeake Bay. As stressors including stress from increasing salinity resulting from sea level rise increase on wetlands, water quality services are likely to be affected. WetCAT can be used to identify those individual wetlands and upland locations where these impacts may be felt.
Go to the WetCAT tool
To learn more:
Additional reading on wetlands, nutrients, and sea level rise:
Mitchell, M., Herman, J. & Hershner, C. (2020) Evolution of Tidal Marsh Distribution under Accelerating Sea Level Rise. Wetlands 40, 1789–1800 . https://doi.org/10.1007/s13157-020-01387-1
Loomis, M. J., & Craft, C. B. (2010). Carbon sequestration and nutrient (nitrogen, phosphorus) accumulation in river‐dominated tidal marshes, Georgia, USA. Soil Science Society of America Journal, 74(3), 1028–1036. https://doi.org/10.2136/sssaj2009.0171
Sundareshwar, P. V., & Morris, J. T. (1999). Phosphorus sorption characteristics of intertidal marsh sediments along an estuarine salinity gradient. Limnology and Oceanography, 44(7), 1693–1701. https://doi.org/10.4319/lo.1999.44.7.1693
