Eelgrass Abundance

Eelgrass Abundance
2002 1598.5
2006 1904.7
2009* 1980.0

What is Eelgrass?

Eelgrass, Zostera marina, is a rooted underwater grass that grows along the coast. Eelgrass meadow habitat provides food and nesting grounds for fish, and food for many migratory birds. Today eelgrass is only found in the eastern Sound, but it was once common throughout. Eelgrass was nearly wiped out, first by a fungal disease in the 1930s, and more recently by poor water quality attributed to the effects of nitrogen pollution from sewage discharges and stormwater runoff.

What does this indicate?

Eelgrass beds 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 can stimulate the overgrowth of phytoplankton (algal) blooms that could block the energy from the sunlight that eelgrass needs to grow.


A total of 172 eelgrass beds accounting for 1,980 acres were inventoried in 2009. Most (63%) of the sites with eelgrass were estimated to have medium stem density. They accounted for nearly 1,209 acres. High density beds totaled 615 acres based on an inventory of 36 such beds. Only 157 acres of low density beds were inventoried. Seven sub-basins had over 100 acres of eelgrass beds. Quiambog Cove had the most acreage with 407 acres. Two areas had over 300 acres of eelgrass: Fishers Island (346) and Little Narragansett Bay (343), while Niantic Bay had about 212 acres. The remaining sub-basins with more than 100 acres of beds were Mystic Harbor (162), Goshen Cove (124), and Rocky Neck State Park (103).

Data Notes

  • The US Fish and Wildlife Service’s National Wetlands Inventory Program (NWI) has conducted eelgrass inventories for the eastern end of Long Island Sound since 2002. To date, three surveys have been conducted: one in 2002, another in 2006, and the most recent in 2009. These inventories were started because the State of Connecticut’s Office of Long Island Sound Programs was interested in learning the status of eelgrass beds in 2001 and wanted the beds monitored periodically. Eelgrass beds are vital habitats for marine and estuarine biota.
    (US Fish and Wildlife Service 2009 Eelgrass Survey).

*Two large beds totaling 122.1 acres on the south side of Fishers Island could be seen on the 2009 imagery from the survey while they were not visible on 2006 imagery due to environmental conditions. Field inspections in 2006 had located robust beds in this area and recorded their occurrence as points since the beds could not be accurately delineated on the imagery. Consequently, the 2009 Eelgrass Survey does not treat this acreage as a gain because the Fishers Island beds were noted in 2006, but  their boundaries could not be established.

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