Narragansett Bay

Category: Marine and Oceanic Biomes.

Geographic Location: North America.

Summary: A good stewardship plan is in place to help Rhode Island’s premiere ecological jewel recover from its rough industrial history.

Narragansett Bay, situated on the eastern side of Rhode Island, comprises about 15 percent of the state’s total land mass. Ninety-five percent of the bay’s surface area is in Rhode Island, with the remainder in southeastern Massachusetts; about 60 percent of the bay’s watershed is in Massachusetts, as well. At the head of Narragansett Bay lies the city of Providence. This area of Narragansett Bay, called the Providence River, derives its major freshwater from four rivers: Blackstone, Moshassuck, Woonasquatucket, and Pawtuxet. The bay then widens into a more typical estuary that traverses suburbs and rural areas, and past Patience, Prudence, Conanicut, and Aquidneck Islands.

The mouth of Narragansett Bay opens into Rhode Island Sound, where the North Atlantic Ocean brushes up against Block Island, the state’s largest offshore island. The bay has numerous smaller side embayments, the largest of which is Mount Hope Bay to the east; it receives fresh water from the Taunton River. Narragansett Bay’s watershed areas have a legacy that combines indigenous, colonial, nautical, and industrial heritage manifest in its villages, ponds, beaches, forests, and rivers.

Narragansett Bay is a classic temperate drowned-river-valley estuary, formed from the action of glacial scouring and interglacial sea-level rise. It has two passages split by the islands in its center. The average depth is 26 feet (8 meters), and the bay deepens to more than 180 feet (55 meters) at its mouth. The average salinity is about 30 parts per thousand; it is saltier at the mouth and fresher at the head of the bay, where 90 percent of the freshwater flows in. The Providence River is highly stratified with a discernible freshwater layer above more saline waters, whereas the lower portion of the bay is well mixed by tidal and wind-induced circulation.

These coastal habitats have been identified in and around the bay: beaches, brackish marshes, common reed stands, sand dunes, eelgrass beds, oyster reefs, rocky shores, subtidal sand and mud sediments, salt marshes, shrub wetlands, streambeds, and tidal flats.

Biodiversity

Because of the rich assembly of habitats, many important fauna have been observed throughout the bay. The base of the food web is phytoplankton, the tiny free-floating plants that are the principal primary producers consumed by fish, crustaceans, and shellfish. These tiny plants use the sunlight, carbon dioxide, and dissolved nutrients to bloom in the late winter and early spring, mainly as diatoms. As the season progresses, other phytoplankton bloom, and tiny zooplankton and other animals—such as jellylike animals (comb jelly), clams (filter feeders), and small fish—actively consume them.

Numerous species of aquatic invertebrates—such as the hard-shell clam, bay scallop, horseshoe crab, and American lobster—inhabit the bay. Larger, more conspicuous animals, such as the northern diamondback terrapin and the harbor seal, dwell in the near-shore environment. Myriad benthic and pelagic fin fish—including black sea bass, bluefish, and winter flounder, as well as the American eel—are common throughout the bay. Shorebirds such as the American oystercatcher, black-crowned night-heron, common tern, double-crested cormorant, glossy ibis, great blue heron, herring gull, least tern, piping plover, and little blue heron thrive in and around this biome.

Human Activity

Narragansett Bay played a large role in the industrial development of the United States. It is often considered the birthplace of the American Industrial Revolution. The calm and sheltered waters of the bay provided easy transport of both raw materials and products of the industrial period, including textiles and jewelry. Due to these activities, the shoreline of the northern portion of Narragansett Bay has been significantly altered from its natural state.

Nowadays, the industrial sector is almost nonexistent, as economic changes have transformed commerce into the service and tourist industries of today. The population of the watershed increased markedly during the 20th century, reaching nearly 1.8 million. The bay now is the centerpiece of Rhode Island’s tourist activity, with nearly 8 million people visiting for bathing, boating, fishing, and other recreational activities each year.

Threats and Conservation

The historical legacy of the region has left its mark on the environmental makeup of the bay, evidenced by sediments that were contaminated by both heavy metals and toxic organics. Since the exodus of the old industrial activities and effective regulation under the Clean Water Act, cleaner sediments have been deposited on top of contaminated layers. Over recent decades, bacterial and nutrient pollution, along with climate-related changes, have overtaken toxics as the main environmental concerns for the estuary.

Major planned and current upgrades to wastewater and storm water infrastructure are expected to improve the quality of the Bay. In 1987, Narragansett Bay was designated an “estuary of national significance,” which marked it, along with 27 other estuaries, for special consideration, protection, and restoration under the U.S. Environmental Protection Agency’s National Estuary Program (NEP). Each NEP site has developed a Comprehensive Conservation and Management Plan (CCMP) spelling out goals for the estuary and the steps needed to achieve them.

The goals of the CCMP for Narragansett Bay reflect the priorities that were current when the plan was written in 1992. Today, the state of Rhode Island, federal partners, and regional stakeholders are updating the management objectives through a visioning process that will articulate current priorities in light of what has been learned and achieved over the past 20 years.

The future ecological health of Narragansett Bay is not clear. The fisheries of the bay have changed over the years, with early data indicating an abundance of alewife, shad, and smelt. Recent data show declines in flounder species, scup, and menhaden; losses of soft-shell clams, scallops, and oysters also are apparent. By contrast, late-20th-century increases in hard-shell clams and lobster had been documented. These species, however, have shown more recent declines that seem due to increased fishing pressure, as well as to environmental changes such as water-temperature increases.

Narragansett Bay and its watershed have benefited from the cultural shift toward environmental stewardship that began in the 1970s. There have been clear success stories, including reduced toxic inputs resulting in lower sediment contamination, reduced shellfish harvesting, and beach-closing restrictions from better stormwater management. Today, however, the combination of larger-scale issues such as climate change, suburbanization, and competition for scarce resources pose a risk to continued improvements. Nevertheless, there is a strong environmental commitment by the citizens of southern New England, which, coupled with a concentration of educational and research institutions in the Narragansett Bay watershed, makes for a strong possibility of improvement in ecological and human well-being in the years to come.

Bibliography

Benoit, Jonathan. "Contextualizing Thermal Effluent Impacts in Narragansett Bay Using Landsat-Derived Surface Temperature." Frontiers in Marine Science, 7 Sept. 2021, doi.org/10.3389/fmars.2021.705204. Accessed 1 Sept. 2022.

Burroughs, R. H. and V. Lee. “Narragansett Bay Pollution Control: An Evaluation of Program Outcome.” Coastal Management 16 (1988).

Desbonnet, A. and B. A. Costa-Pierce, eds. Science for Ecosystem-Based Management: Narragansett Bay in the 21st Century. New York: Springer, 2008.

Desbonnet, A. and V. Lee. Historical Trends: Water Quality and Fisheries: Narragansett Bay. Narragansett, RI: University of Rhode Island Coastal Resources Center, 1991.

Ionescu, Andrei. "Narragansett Bay Needs a New Approach for Restoration." Earth.com, 17 Nov. 2021, www.earth.com/news/narragansett-bay-needs-a-new-approach-for-restoration/. Accessed 1 Sept. 2022.

Narragansett Bay Estuary Program (NBEP). NBEP Website. http://www.nbep.org.