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Visualizing Methane-Cycling Microbial Dynamics in Coastal Wetlands
Published on: January 31, 2025
Drought-induced saltwater incursion leads to increased wetland nitrogen export
Marcelo Ardón1, Jennifer L Morse, Benjamin P Colman
1Department of Biology and North Carolina Center for Biodiversity, East Carolina University, Greenville, NC, 27858, USA.
Global Change Biology
|June 11, 2013
Summary
Saltwater intrusion into coastal wetlands, driven by sea-level rise, disrupts nitrogen cycling. This process can release significant amounts of ammonium (NH4+) into coastal waters, impacting ecosystem health.
Area of Science:
- Environmental Science
- Ecology
- Biogeochemistry
Background:
- Coastal wetlands are crucial for processing nitrogen (N), mitigating excess nutrient inputs to marine environments.
- Wetland loss and saltwater intrusion threaten the nitrogen retention capacity of these vital ecosystems.
- The effects of salinization on nitrogen cycling in freshwater coastal wetlands are not fully understood.
Purpose of the Study:
- To investigate the impact of saltwater intrusion on nitrogen (N) export and transformation in coastal freshwater wetlands.
- To quantify the potential release of reactive nitrogen from coastal wetlands under future sea-level rise scenarios.
Main Methods:
- Field observations of nitrogen export from a restored wetland in North Carolina.
- Laboratory experiments using intact soil columns to assess salinization effects on nitrogen dynamics.
- Estimation of nitrogen release based on predicted wetland inundation.
Main Results:
- Annual saltwater incursions doubled ammonium (NH4+) export from a restored wetland.
- Salinization increased soil solution ammonium (NH4+) concentrations in mature wetlands.
- Cation exchange between salt and sediment ammonium (NH4+) largely explained the observed nitrogen release.
Conclusions:
- Saltwater incursion significantly alters nitrogen cycling in coastal freshwater wetlands, promoting inorganic nitrogen export.
- Projected sea-level rise and associated saltwater intrusion could lead to substantial nitrogen loading into coastal waters.
- These findings highlight a potential global threat to coastal ecosystems from salinization-induced nitrogen release.
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