Habitats

Sea Grass Beds

Sea grass or “submerged aquatic vegetation” (SAV) is one of Narragansett Bay’s most important habitats. This estuarine plant provides protection and forage for fish, shellfish, waterfowl and other fauna. On Narragansett Bay, the major species of concern is eelgrass. Eelgrass is extremely sensitive to increased nutrient loads as well as increased temperatures. Changes in the extent of eelgrass serve as an excellent indicator of habitat quality in the estuary, and can help determine whether eutrophication (over-fertilization of waters by nutrients) is occurring.

The Narragansett Bay Estuary Program, Save The Bay, the Narragansett Bay Research Reserve, and University of Rhode Island have undertaken two studies, one in 1996 and another in 2006, which used aerial surveys and GIS mapping to measure the extent of eelgrass in the Bay. NBEP also developed a long-term assessment of eelgrass in the Bay using historical sources.

The studies show that eelgrass was once widespread throughout Narragansett Bay—during the 1860’s, for example, it was present in the Providence River. Today, it grows only in the lower Bay, from Prudence Island south. Upper-Bay eelgrass beds have been entirely lost over the past 50-100 years. While several factors have been implicated in the loss of eelgrass coast-wide, excess nutrients from wastewater treatment plants and urban runoff are believed to be an important factor.

The 2006 study found 404 acres of eelgrass in Narragansett Bay, an increase compared with the 1996 study. This may represent the beginnings of a reversal in the historic trend, or may simply reflect year-to-year variability. Either way, it appears that eelgrass is no longer declining in Narragansett Bay—good news for fish and wildlife.

Wetlands

Healthy habitats are central to the environmental quality of the Narragansett Bay Region. NBR’s native fish and wildlife depend upon a diversity of natural habitats—fresh and salt water wetlands, undammed rivers, clean lakes and ponds, native forests and grasslands.

Wetlands are another important habitat type in NBR, providing many values beyond fish and wildlife habitat. Freshwater wetlands help maintain groundwater quality and quantity by providing areas where surface and rainwater can recharge aquifers. They serve an important function in protecting developed areas, as riverine wetlands and floodplains store floodwaters after storms. Coastal wetlands such as salt marshes serve as important nursery areas for juvenile fish while helping to protect coastal communities from the impacts of hurricanes and storm surges.

During the 19th and 20th centuries, wetlands were destroyed and altered on a grand scale throughout the Narragansett Bay Region. Wetlands were drained and filled for agriculture, land development and transportation. Many others were flooded, converted to open-water areas by dams—first for mill power, later for drinking-water supply. In Southeastern Massachusetts, natural wetlands were altered to create cranberry bogs. Enactment of state wetlands laws and the federal Clean Water Act in the late 20th century curbed the pace of destruction, but wetlands continue to be lost and damaged throughout NBR.

A new threat to coastal wetlands is global warming. Since the last ice age, coastal wetlands have generally grown in area as mineral and organic sediments accumulated in low-energy areas of the shoreline. As sea level rise accelerates, a concern is that this process of sediment accretion may not keep pace, resulting in loss of coastal wetlands.

There are about 90,000 acres of freshwater wetlands in the Massachusetts portion of NBR. According to an analysis of Massachusetts wetland change data undertaken by NBEP and the R.I. Dept. of Environmental Management, less than one percent of wetlands were lost during the period 1991 – 2001, while certain types of wetlands (primarily wooded swamps) increased in area.

Comparable fresh water wetland change data are not available for In Rhode Island. However, a study by NBEP documented changes to Narragansett Bay’s coastal wetlands over the period 1952-1996. The study found that six percent of the Bay’s vegetated wetlands were lost over this 44 year period.

Return to Invasive Species
Continue to Habitat Restoration