Rhode Island's Coastal Habitats
Seagrass - Salt
Marsh - Anadromous
History and Impacts | Healthy
vs. Degraded | Eelgrass Restoration |
Case Study | Related Links
|Shallow eelgrass bed
Rhode Island's primary seagrass is eelgrass.
Eelgrass provides many ecologically valuable functions. It produces
organic material that becomes part of the marine food web; helps
cycle nutrients; stabilizes marine sediments; and provides important
Many species of fish and wildlife depend on eelgrass. Eelgrass
beds provide protection for bay
crabs and lobsters.
and other fish lay their eggs on the surface of eelgrass leaves,
and young starfish, snails, mussels, and other creatures attach
themselves to the plant. Waterfowl such as brant
feed on eelgrass. Studies in New England have documented the occurrence
of 40 species of fish and 9 species of invertebrates in eelgrass
As new growth replaces older eelgrass leaves, the dead leaves decay,
becoming a valuable source of organic matter for microorganisms
at the base of the food chain (NOAA Damage Assessment and Restoration
Program, 2001). Eelgrass reduces shoreline erosion caused by storms
and wave energetics thus protecting adjacent coastal properties.
Eelgrass meadows can stabilize sediments and filter nutrients from
the water column. Eelgrass also provides a unique habitat for recreational
SCUBA divers and snorklers to explore (Chesapeake Bay Program, 2000).
History and Impacts
Eelgrass was widespread in Narragansett Bay as late as the 1860s.
Historical accounts record eelgrass beds in the lower Providence
River, at the head of the Bay. During the 1930s wasting disease,
a widespread infection partly attributed to the slime mold Labryinthula zosterae
decimated Atlantic coast eelgrass populations (Short et al. 1987,
1988). Some recovery was documented up until the 1960's. Since 1960,
there has been a 40% decline in Narragansett Bay's eelgrass beds.
Approximately 100 acres of eelgrass remain in Narragansett Bay today
(Save The Bay 2002).
Nine coastal ponds located along Rhode Island's South Shore
are managed by the CRMC through a Special Area Management Plan (SAMP).
The ponds were historically maintained as brackish systems through
natural, seasonal breaches in the barrier beaches, which separate
them from the open ocean. Permanent breachways were constructed
at 5 of the 9 ponds (Point Judith, Ninigret, Winnapaug, Quonochontaug
and Green Hill) during the 1950s and early 1960s. Construction of
the permanent breaches has resulted in significant changes to the
ecology of the ponds. Salinity has increased changing the ponds
from a fresh/seasonally brackish system dominated by widgeon grass
(Ruppia maritima) to a marine system dominated by eelgrass.
Faunal changes have accompanied the changes in the submerged aquatic
vegetation community and salinity regime. Sedimentation has increased
as a result of the permanent breachways. Flood tidal shoals are
expanding within the ponds, encroaching upon eelgrass and shellfish
bed habitat. Attempts to dredge the tidal shoals have only been
partly successful in reducing the rate of encroachment upon the
existing eelgrass beds (USACE-NED 2002).
Seagrass beds are susceptible to an array of human-induced degradations.
Dredge and fill operations associated with navigation channel maintenance
have taken a significant toll. Deterioration of water quality conditions
(increased turbidity, increased nutrient concentrations) associated
with human population density in coastal areas remains a primary
cause of seagrass bed degradation. Increases in surface water nutrient
loads result in phytoplankton blooms and excessive growth of macroalgae,
which shades eelgrass beds, and inhibits plant growth and colonization.
Physical damage to seagrass beds may result from recreational and
commercial propellers in shallow waters. Residential dock structures
often shade eelgrass beds in nearshore areas.
Healthy vs. Degraded Eelgrass Habitats
Eelgrass can form large meadows or small separate beds, which range
in size from many acres to just a yard across. Found in depths up
to 20 feet in some areas, eelgrass growth and survival is dependent
on clear water to provide light for photosynthesis.
Eelgrass beds are susceptible to destruction and degradation by
increased turbidity, increased nutrient loading from urban runoff,
and destruction by boat propellers or invasive predators (Save the
Sound, Inc., 1998). The most significant threats to the remaining
eelgrass beds in Narragansett Bay, and a deterrent to their long-term
recovery, are nutrient pollution from sewage and polluted runoff
from the land. Specific sources of these nutrients are septic systems,
fertilizer runoff from lawns, and wastewater treatment plant discharges.
Declining water quality also increases the opportunity for wasting
disease, which is caused by a marine slime mold that thins eelgrass
beds and makes them more vulnerable to environmental stresses. The
chronic presence of wasting disease has been tied to increases in
water temperature and salinity.
|Healthy Eelgrass Habitat
||Degraded Eelgrass Habitat
- Presence of scallops, blue crabs, fish and other species
that utilize eelgrass for attachment and protection from
- Expanding range of eelgrass
- Potentially able to grow at greater depths
- Propeller scars in eelgrass beds
- Heavy algal coverage of leaf blades
- Evidence of wasting disease
- Loss of historic eelgrass beds
The first attempts to restore eelgrass in Rhode Island were undertaken
in 1996 by the Narragansett Bay Estuary
Program. Since that time, a number of organizations have undertaken
seagrass restoration projects in Rhode Island waters, using
a variety of restoration techniques.
Seagrass restoration is complicated by the fact that seagrass beds
are extremely sensitive to water quality. Most coastal ecologists
agree that declines in water quality have been largely responsible
for the loss of seagrass. Therefore, many areas that once supported
seagrass beds are unsuitable for restoration. Some practitioners
argue that seagrass restoration efforts should focus exclusively
on water quality improvement, in the belief that once the right
conditions are established, seagrass will naturally recolonize.
Many others believe that in areas where water quality is improving,
physical restoration of seagrass through transplantation or seeding
can accelerate the plant's re-establishment. Additionally, seagrass
restoration is threatened by physical damage of restored eelgrass
beds through dredging, aquaculture, and propeller scarring.
In developing eelgrass restoration projects, site selection is
critical. Water clarity, depth, and salinity are among the most
important factors determining where eelgrass can survive, since
the plants need sufficient light in order to photosynthesize. This
is why eelgrass mainly occurs in the well-flushed areas of lower Narragansett
Bay, where the maximum depth at which it grows is generally about
|Eelgrass transplants tied to a mesh frame
Courtesy: Save The Bay
Eelgrass restoration methods to date have focused primarily on
transplantation of either small clusters of plants or denser, sod-like
sections. The transplants may be grown in aquaria or taken from
healthy donor beds. In Narragansett Bay, Save The Bay is restoring
eelgrass using the Transplanting Eelgrass Remotely with Frames (TERF)
method, in which clusters of plants are temporarily tied with degradable
crepe paper to a weighted frame of wire mesh. Once the plants have
become established, the frame is taken off the bottom for re-use
Transplantation has met with some success, but is extremely labor intensive,
as it requires divers to plant the eelgrass by hand. Researchers
at the University of Rhode Island Graduate School of Oceanography
are experimenting with sowing eelgrass seeds mechanically. This
method is being used at McAllister Point, off Newport, in the restoration
of a coastal hazardous waste site, and will also be employed in
south shore coastal ponds as part of the South
Shore Ecosystem Restoration. For more details on seagrass restoration techniques, please refer to the Restoration Methods section of this Web site.
Eelgrass Restoration Case Study: Wickford
|Eelgrass restoration in Wickford Harbor
Courtesy: Save The Bay
To restore eelgrass beds in historic Wickford Harbor, Rhode Island,
a public-private partnership has been developed to improve water
quality and to re-plant eelgrass. The University of Rhode Island
(URI) is using computer modeling and digital mapping to find the
nutrient pollution problems within the harbor's watershed. Save
The Bay and the Town of North Kingstown are working with URI to
develop water quality solutions through better management and treatment
of waste and storm water.
As its water quality improves, Wickford Harbor will become more
hospitable to eelgrass, allowing existing beds to expand. To accelerate
this process, the project is directly restoring eelgrass to the
harbor through transplanting. Save The Bay has developed an innovative
program to involve school children in this effort. Through its "Seagrasses
in Classes" program, Save The Bay teaches the kids about the plant,
and helps them to propagate it in classroom tanks. Volunteer divers
then transplant the new shoots of eelgrass into the harbor bottom
in hopes of establishing a new bed. The project builds on the experience
of earlier transplants by the Narragansett Bay Estuary Program,
the National Marine Fisheries Service, and URI. Save The Bay is
applying the knowledge gained from the Wickford Harbor project to
eelgrass transplants in other areas of Narragansett Bay.
- Rhode Island Web sites
- Coastlines June 1999 - RI
Salt Ponds: Dredging and Restoration
- Coastal Resources Management Council (CRMC) Coastal
Eelgrass Habitats of Rhode Island
- The Cooperative Institute for Coastal and Estuarine Environmental
Technology (CICEET) Project
Spotlight on seed generated seagrass plants
- Save the Bay's Eelgrass: A
Critical Narragansett Bay Habitat
- Rocky Hill School, Grade 7 - Eelgrass
Prodigy Oil Spill Restoration in Narragansett Bay
- Other Eelgrass Web sites
- Battelle Environmental Updates - Enhancing
- Chesapeake Bay Home Page - Chesapeake
- Dr. Frederick T. Short, Research Professor, Jackson Estuarine
- Dr. Short is a leader in seagrass restoration ecology in the
Northeast and faculty member of the University of New Hapshire
- Gulf of Maine (GOM) Times - Eelgrass:
Essential or expendable in the Gulf?
- UNH Global
Seagrass Survey Results
Virginia Institude of Marine Science (VIMS) Seagrass Restoration
Return to Top
Chesapeake Bay Program. 2000. (http://www.chesapeakebay.net/baygras.htm).
NOAA Restoration Center. 2001. NOAA Restoration Center Web site:
Are restored habitats as productive as the previously unperturbed
habitats were? (http://www.nmfs.noaa.gov/habitat/restoration).
Save The Bay. 2002. Restoration projects throughout the Narragansett
Bay watershed. (http://www.savebay.org/bayissues/restoreprojects.htm).
Save The Bay, Inc., People for Narragansett Bay. 2001. Save The
Bay Web site: What is Habitat Restoration? (http://www.savebay.org/).
Save the Sound, Inc. 1998. "The Long Island Sound Conservation
Blueprint: Building the Case for Habitat Restoration In and Around
the Sound." Stamford, CT. Save the Sound, Inc.
Short, F.T., L.K. Muehlstein, and D. Porter. 1987. Eelgrass wasting
disease: Cause and recurrence of a marine epidemic. Biological
Short, F.T., B.W. Ibelings, and C. Den Hartog. 1988. Comparison
of a current eelgrass disease to the wasting disease of the 1930's.
Aquatic Botany 30:295-304.
USACE-NED. 2002. Rhode Island South Shore Habitat Restoration Feasibility
Report and Environmental Assessment (Draft). U.S. Army Corps of
Engineers, New England District.
Return to Top
This site was created through a partnership
Coastal Resources Management Council
Narragansett Bay Estuary Program
Save The Bay®