Type of Wetlands Affect How Much Nitrogen is Removed from the Bay’s Tidal Rivers

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Issue: Wetlands are important for removing nitrogen from rivers entering the Chesapeake Bay. More information is needed on how much nitrogen wetlands can remove.

USGS study: Although wetlands can be effective at removing pollutants, little is known about how denitrification changes along riverine wetlands near the head-of-tide, where watersheds first meet the Bay. The USGS measured soil denitrification potential along Chesapeake tidal river sites: landscape gradients from nontidal floodplain, thru tidal freshwater forested wetlands, to salinization impacted ghost forests converting to oligohaline marsh along the Mattaponi and Pamunkey rivers. This is one of the first studies to contrast the ecosystem services of tidal freshwater wetlands with their immediately upriver nontidal systems.

Figure 2

Map of tidal (upper, middle, and lower) and nontidal forested wetland study sites on the Pamunkey and Mattaponi Rivers, their watersheds spanning the Piedmont and Coastal Plain physiographic provinces, and their location in Virginia within the lower Chesapeake Bay watershed, USA


The Upper tidal freshwater forested wetland site along the Pamunkey River, just downstream from the head-of-tide.



Primary Findings:

  • Although the salt-stressed tidal freshwater forests had lower potential for nitrate removal than the continuously freshwater tidal forests, both had much greater rates than the upriver nontidal bottomland hardwood forested floodplain. 
  • Thus, modest sea-level rise should increase Nitrogen removal by upper estuarine wetlands as nontidal wetlands near the head-of-tide convert to tidal wetlands. 
  • The study also found limits on nitrate removal associated with greater riverine nitrate loading from their watersheds.


Read the Article:

Korol, A.R., and G.B. Noe.  2020.  Patterns of denitrification potential in tidal freshwater forested wetlands.  Estuaries & Coasts 43: 329-346. doi.org/10.1007/s12237-019-00663-6.


The article is not open access. Please contact Greg Noe (gnoe@usgs.gov) directly for a copy of the article. 




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