Ecosystem Targets and Supporting Indicators
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The baseline was changed to 2009 because field verification of the 2012 data could not be done due to Hurricane Sandy.
Eelgrass abundance (as measured by total acreage) has been assessed from 2002 to 2024.
The latest round of eelgrass abundance surveys for eastern Long Island Sound was successfully completed during the summer and fall of 2024. Results of the 2024 eelgrass abundance survey indicate a total of 2,041 acres of eelgrass in eastern Long Island Sound. A change analysis between 2017 and 2024 resulted in 1,057.1 acres of change between the two years, indicating the dynamic nature eelgrass abundance in eastern Long Island Sound over this time span (765.2 acre increase and a 291.9-acre decrease). The result of the change analysis is a net gain of 473.3 acres between the two years. Increases in the eelgrass extent can be attributed to improvements in water and sediment quality. As indicated by Save the Sound’s Unified Waters Study, water quality (e.g., water clarity, macroalgae abundance, etc.) has improved in areas where eelgrass is typically present (Stonington Harbor, Mystic Harbor, Alewife Cove, and Niantic River). On the other hand, eelgrass losses may be due to other water quality factors, such as warmer water temperatures. Some eelgrass meadows are experiencing annual die-offs earlier than usual. In the Niantic River, eelgrass meadows typically experience senescence, or die-off, in early fall after the field surveying occurs. However, in 2024, this die-off occurred in late August and therefore no eelgrass was observed during the field surveys in September. While this annual senescence is normal, losing eelgrass meadows earlier in the season can impact their services, such as, capturing suspended particles in the water column, nutrient recycling, and habitat provisioning for important fish species.
All surveys of eelgrass abundance focus on the Eastern Basin of Long Island Sound (east of the Connecticut River) since eelgrass experts believe that 95% of eelgrass beds occur in this portion of Long Island Sound. While there are some small patches of eelgrass west of the Connecticut River, these beds do not contribute significantly to the total area. However, more reconnaissance of this area will be conducted during the summer of 2025. The target to achieve a total of 3,893 acres by 2035 will be achieved through the successful implementation of additional water quality protections and associated reductions in land- based inputs of nutrients, as well as restoration (replanting) efforts led by academic, government, and nonprofit agencies and partners, primarily in areas west of the Connecticut River. While the Partnership is now meeting the goal to maintain the 2012 baseline of 1,893 acres of eelgrass, there is still work to do to meet the 2,000 additional acres through restoration (3,893 acres total). Check out the map to view the areas where eelgrass is present.
The overall success of eelgrass is dependent on several parameters including water clarity, depth, substrate, temperature, and salinity. Many embayments where eelgrass once thrived, or could have thrived, suffer from changes in water quality and changes to substrate that now does not promote the growth of eelgrass. To restore and enhance eelgrass beds and meet the “Eelgrass Extent” target, practitioners will need to work with partners to improve water quality and substrate issues in embayments.
To date, assessment of eelgrass in Long Island Sound has occurred through aerial surveys every four to five years. Surveys have only focused on the Eastern Basin of Long Island Sound and only a few restoration projects have been successfully completed to date. To increase eelgrass acreage, practitioners will need annual data sets on the status of eelgrass beds (aerial surveys or otherwise), a complete geographic dataset, and a greater number of restoration projects around the Sound.
The Long Island Sound Partnership developed an Eelgrass Management and Restoration Strategy in 2022. The strategy provides guidance for short and long-term actions that should be taken to manage and restore eelgrass meadows in Long Island Sound and act as a resource for other estuaries in the region facing similar issues. Since then, the Partnership has supported projects to better restore and protect our meadows. See them here! Additionally, check out this StoryMap to take a deeper dive into the eelgrass meadows of Long Island Sound.
Aerial surveys for eelgrass are conducted every few years in partnership with the US Fish and Wildlife Service, USGS, and the University of Rhode Island. The Long Island Sound Partnership Habitat Restoration Coordinators track eelgrass restoration projects that are in progress within the watershed by various partners and report the total acres restored annually.
To date, six aerial surveys have been conducted, with the last survey being conducted in 2024. These inventories were started because the Connecticut Department of Energy and Environmental Protection (CT DEEP) was interested in learning the status of eelgrass beds in 2001 and wanted the beds monitored periodically. These surveys are conducted using a combination of aerial photography and field surveys using an underwater video camera. In 2024, aerial photographs were taken June 28th and July 26th and draft orthophotographs were delivered for use during the field surveys in late August.
Eelgrass, Zostera marina, is a rooted, underwater grass that grows along the shallow coastal waters of bays, estuaries, and beaches in the Northern Hemisphere. Eelgrass meadow habitat provides foraging areas for fish and invertebrates, and food for many migratory birds. Healthy eelgrass beds trap sediment and reduce wave energy during storms, improving water quality and protecting coastal areas from erosion.
Eelgrass bed abundance indicates good water quality and good habitat for aquatic life, and acceptable levels of nutrients. Excessive levels of nutrients such as nitrogen and phosphorous from sewage discharge and runoff can stimulate the overgrowth of phytoplankton (algal) blooms that could block the energy from the sunlight that eelgrass needs to grow.
Eelgrass reports:
2024 eelgrass survey2017 eelgrass survey2012 eelgrass survey2009 eelgrass survey
Sara Cernadas-Martin, New York Department of Environmental Conservation sara.cernadas@dec.ny.gov
Harry Yamalis, CT DEEPharry.yamalis@ct.gov
US Fish and Wildlife Service
A diver plants eelgrass in St. Thomas Pt, L.I. Read more about eelgrass on the USDA Plants Database. Photo courtesy of Cornell Cooperative Extension Marine Program.
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