Salt Marshes Are Disappearing — Mussels Could Help Save Them
Salt marshes provide food and shelter for plants and animals, filter excess nutrients from the water, and prevent coastal erosion. But 50% of salt marshes worldwide have disappeared, so scientists are trying to figure out how best to restore these coastal wetlands and retain these ecological benefits.
One such marsh can be found right in New York, in Jamaica Bay. In a study that appears in Marine Ecology Progress Series, researchers monitored experimental plots in the bay and found that Atlantic ribbed mussels play an important role in reducing nitrogen in salt marshes. That means the mussels could be useful in returning disturbed or vanishing marshes to their previous states.
While plants need nitrogen to grow, too much is a bad thing. In places where nitrogen-rich waste such as fertilizers ends up in the water, excess nitrogen can cause fast-growing “blooms” of algae or other plants that then block light from reaching plants growing underwater. When the blooms die off, they use up lots of oxygen as they decompose.
Microbes in the sediment are responsible for denitrification—a process of chemically reducing the nitrogen that is present so that it can escape into the atmosphere. The researchers found that the mussels produce waste that the microbes need to perform denitrification. So while the mussels themselves don’t remove the nitrogen, they are part of a neat cycle of waste production and consumption that supports the denitrification.
While current restoration efforts have been successful, said Zhu, these projects are slow and could be improved. “Ribbed mussels may be a valuable addition for salt marsh restoration projects in eutrophic, or nutrient-polluted, estuaries since they increase the ecosystem service of nitrogen removal,” she said. The concept could prove useful in cleaning up other waterways like the Hudson River Estuary, which Zhu says is “one of the most nitrogen-loaded estuaries in the world.”