Saltwater incursions into coastal wetlands can increase the release of ammonium into the ocean, complicating coastal management in the face of human development, climate change and rising sea levels.

Marcelo Ardón at East Carolina University in Greenville, North Carolina, and his colleagues analysed the impact of increased saltwater levels on natural and restored wetlands in North Carolina during four droughts from 2007 to 2012. Reduced processing of ammonium by soil microbes and less nitrogen uptake by plants contributed to ammonium runoff, but releases were higher in restored wetlands, probably due to residual nutrients from fertilizer use.

The researchers suggest that the potential for saltwater-induced nitrogen release should be assessed during the development of large coastal wetland-restoration projects.

Glob. Change Biol. http://dx.doi.org/10.1111/gcb.12287 (2013)