The shallow bays, estuaries and lagoons of Southern New England and New York have historically been ideal environments for eelgrass (Zostera marina), a type of seagrass. Coastal waters were once fringed with eelgrass beds, lush with swaying leaves that sheltered important fishery species—including flounder, bay scallop and hard clam.
But in 1931, disaster struck. A parasitic slime fungus known as wasting disease destroyed up to 90 percent of meadows on both coasts of the North Atlantic Ocean. Eelgrass eventually rebounded in most locations, supporting vibrant fisheries such as New York’s world-famous Peconic Bay scallop fishery. In fact, eelgrass was so thick in some areas that in the mid-1970s local governments were exploring ways to eliminate it from places where it was impeding navigation.
Where Have the Prairies of the Sea Gone?
Today, Southern New England and New York have lost over 65 percent of their eelgrass meadows. Losing eelgrass can have a detrimental effect on the entire ecosystem and the people who rely upon healthy bays for food, livelihood and recreation. According to a 2006 report, species that rely on seagrass produced over $1.9 billion dollars in sales, $41 million in employment impacts and $1 billion dollars of earned income nationwide .
But declining eelgrass meadows are not always linked to an easily identifiable cause, making recovery difficult and raising questions about the conditions eelgrass needs to thrive. In addition, regional efforts to restore eelgrass through planting seeds or transplanting shoots are expensive and have shown limited success.
Research for Recovery
Scientists from The Nature Conservancy and partner institutions are now asking questions for which the answers are needed to help revive this critical ecosystem that sustains numerous species and supports our way of life, and to make restoration efforts everywhere a smarter investment.
The Nature Conservancy, together with U.S. Representatives Tim Bishop (D-NY) and Rosa DeLauro (D-CT), sponsored research, funded by the National Oceanic and Atmospheric Administration, that centered on laboratory analysis of plants from 10 locations—from Cape Cod to Long Island.
The first phase of the research was led by world-renowned seagrass expert Fred Short, a research professor in the University of New Hampshire’s Department of Natural Resources, and focused on several key questions:
- Is genetic diversity limited among surviving eelgrass populations, creating a genetic bottleneck that limits growth and recovery?
- What are the effects of multiple sources of stress on eelgrass?
- What are the best conditions for eelgrass growth?
- Why do some restoration efforts take where others don’t? And is it possible to replicate that success?
What We’ve Learned
The results of this study highlight the need to reduce nitrogen pollution and protect the resilient seagrass populations throughout the region. Specific findings include:
- Eelgrass in the region is surprisingly diverse. Of 709 plants tested, 688 had unique genetic material, indicating that a genetic bottleneck is not limiting eelgrass growth.
- Nitrogen in our coastal waters and warming ocean temperatures are the biggest threats to eelgrass. Nitrogen comes from sewage treatment plant wastewater discharges, septic systems, polluted groundwater and runoff from storm water containing fertilizers and pet waste. Atmospheric nitrogen from burning fossil fuels is another significant source of nutrient pollution.
- The best conditions for eelgrass growth include full sunlight; low organic soil matter; and normal, seasonal, ambient temperatures.
- Some eelgrass populations are more resilient to multiple sources of stress than others. In particular, plants from Great South Bay in New York, Narragansett Bay in Rhode Island and Great Bay in New Hampshire are better adapted to survive under increased nitrogen and ocean temperature conditions.
- Restoration efforts could be significantly improved by focusing on the use of grasses as donors from resilient areas that are tolerant to the conditions in restoration locations.
We now have the research and understanding to address the threats to eelgrass habitat in the region. In the next phase of this initiative, The Nature Conservancy will apply these results to develop a protection and restoration strategy that offers a larger-scale and longer-term approach than has ever been undertaken.
This strategic “road map” will help protect remaining eelgrass meadows and other estuarine habitats from further declines and ensure long lasting restoration success—both critical components of protecting hard shell clams, scallops and other fisheries that are meaningful for our culture and economic future.
To maintain and restore eelgrass, The Nature Conservancy recommends:
- Aggressively reducing and managing all sources of nitrogen (atmospheric, surface and groundwater) entering our coastal waters.
- Protecting remaining eelgrass from further declines, recognizing that once a meadow is lost, the possibility of fully restoring it is very low.
- Protecting eelgrass populations with unique genetic characteristics and sites that can tolerate poorer growing conditions.
- Using seed or shoots for restoration that are taken from areas tolerant to the conditions where the restoration is occurring, while ensuring that source populations are not depleted.