Team Explores the Recovery, Resilience of a Stressed Salt Marsh

Day in and day out for 13 years, scientists slowly dripped fertilizers into a pristine section of salt marsh north of Boston. They were simulating, in a controlled experiment, the pollution that marshes in densely populated areas receive from sewage, lawn fertilizer, and other human sources.

By the time they stopped dripping the nutrients -- nitrogen and phosphorus -- in 2016, they had observed changes in the marsh's plant and animal community and even in its physical structure.

The creek banks had begun to crack and slump down, indicating that the over the long term, nutrient pollution could be a factor in converting “a vegetated marsh into a mudflat, which is a much less productive ecosystem,” said MBL Fellow Linda Deegan, lead investigator of the project at the Plum Island Ecosystems Long-Term Ecological Research Site (PIE-LTER).

Losses of healthy salt marsh have accelerated in recent decades, with some losses caused by sea-level rise and development. “Salt marshes are a critical interface between the land and sea,” Deegan said. “They provide habitat for fish, birds, and shellfish; protect coastal cities from storms; and take nutrients out of water coming from upland areas, which protects coastal bays from pollution.”

Now, the team wants to know, “Will this marsh be able to recover?” Buoyed by a new, three-year grant from the National Science Foundation, they are watching how the marsh is responding now that the nutrient addition has stopped.