Nitrogen pollution and recovery from nitrogen pollution in a seagrass-dominated estuary


2014 to 2017


Eutrophication associated with excess nutrient pollution in shallow marine ecosystems is poorly understood relative to deeper systems. This project investigates various feedbacks that may occur during eutrophication that either aggravate or partially mitigate the effects of nutrient pollution in a shallow estuary. A large reduction in nitrogen loading from the watershed allows a unique opportunity to also study the start of ecosystem recovery.


Nutrient--especially nitrogen--pollution is one of the greatest threats to the ecological integrity and functioning of coastal marine ecosystems. In the U.S. two thirds of coastal rivers and bays are moderately or severely degraded from nitrogen pollution. The problem continues to grow in the U.S. and globally, and nitrogen pollution is now considered one of the greatest consequences of human accelerated global change on coastal oceans.
Costanza et al. (1997) estimated that, when not degraded, coastal marine ecosystems are among the most valuable of all systems to society in terms of ecosystem services. Shallow estuaries, including the lagoons prevalent along much of the U.S. Atlantic and Gulf coasts--the focus of this project--are both particularly valuable as habitat and are especially sensitive to the effects of eutrophication on water and habitat quality.
Seagrasses are often dominant features in these shallow estuaries, contributing significantly to primary production and energy flow in the ecosystem, serving as a nutrient filter to help protect adjacent estuarine waters, and providing critical habitat and nursery and spawning grounds to many species of birds, sea turtles, fish and shellfish. Nitrogen pollution can lead to degradation and dieback of seagrass beds.
Globally, 20 percent of seagrass habitat has been lost over the past 20 years, with much of this due to nitrogen pollution (Duarte et al. 2008). The value of ecosystem services provided by seagrass meadows has been estimated at $20,000 ha-1 y-1 (Terrados & Borum, 2004), a value among the highest for any natural or managed ecosystem.


This project draws on and continues studies of West Falmouth Harbor (Cape Cod, Mass.) begun in 2005 with funding from the National Science Foundation, characterizing a variety of biogeochemical and ecological processes and analyzing net flows of nutrients at the whole-ecosystem scale. We will continue to track these over the next three years, as nitrogen loading to the site is expected to greatly decrease. The current study focuses on nitrogen inputs and processes (such as nitrogen fixation), ecosystem productivity and metabolism, water quality parameters, and the distribution and abundance of seagrasses.


This research will further elucidate non-linearities and tipping points in the response of shallow marine ecosystems to nitrogen pollution and will begin to document the time frame and trajectory of recovery from such pollution. Such information is critical to help environmental managers better address the protection and restoration of such ecosystems, and we anticipate that our findings will be of wide interest to both the scientific and environmental communities. The project includes a variety of educational and outreach activities to communicate the findings to researchers, water-quality managers, and the public. Long-term, we expect that our study will lead to more effective protection of shallow marine ecosystems from nutrient pollution.

Submitted by: 

  • Marino, Roxanne M

Researchers involved: 

  • Howarth, Robert W
  • Marino, Roxanne M
  • Hayn, Melanie

Organizations involved: 

  • Marine Biological Lab

International focus: 

  • United States of America

United States focus: 

  • Connecticut
  • Delaware
  • Maine
  • Massachusetts
  • New Hampshire
  • New Jersey
  • New York
  • Rhode Island
  • Virginia

New York State focus: 

  • Delaware
  • Nassau
  • Suffolk