Coastal Habitats of Narragansett Bay, Rhode Island
Chart of Narragansett Bay.
Pawtuxet River before restoration. Photo credit: Jim Turek, NOAA FIsheries
Pawtuxet River after restoration, partial dam removal for fish passage. Photo Credit: Jim Turek, NOAA Fisheries
Saltmarsh monitoring in Gooseneck Cove 2010. Photo credit: Save the Bay
By Sue Tuxbury, Greater Atlantic Regional Fisheries Office
Even though the smallest state in the nation, Rhode Island encompasses over 400 miles of coastline, making it appropriately named the Ocean State. More than half of that shoreline rests along Narragansett Bay. It is a true environmental treasure for the state and the region. Covering 147 square miles, Narragansett Bay is an estuary, where fresh water from rivers mixes with salt water from the sea.
This estuary contains diverse and productive habitats including, salt marshes, eelgrass beds, mudflats, and shellfish beds. These habitats serve as nurseries for fish and shellfish species, provide spawning grounds and food sources for marine life, and help buffer coastlines from storm damage and erosion. A number of important river systems flow into Narragansett Bay. They are migratory pathways and spawning grounds for diadromous (fish that spend portions of their lives in both fresh and salt water) species including, alewife, blueback herring, and American shad. The success of commercial and recreational fisheries is contingent on having a healthy supply of fish to catch. To thrive, fish species need places like the Narragansett Bay estuary to feed, spawn and grow.
Threats from human activities
With approximately 1.8 million people inhabiting its watershed, habitats in Narragansett Bay are vulnerable to human activities. Degraded water quality remains a major threat to these coastal habitats, primarily due to excess nutrients from wastewater and stormwater runoff. Too many nutrients in an estuary can cause losses of salt marsh and eelgrass habitat. For instance, nutrients reduce the amount of light available for vegetation growth and reduce oxygen levels needed to sustain healthy fish and shellfish populations.
Dams along the rivers also are a major impediment for productive anadromous fish populations, blocking their ability to migrate upstream to important spawning grounds. Habitat loss through dredging and development projects can also threaten valuable spawning grounds, particularly for winter flounder populations in the bay. Sea level rise, from climate change, is an emerging threat that is already showing impacts to local salt marsh habitats. Scientists from the National Estuarine Research Reserve (www.nbnerr.org) and Save the Bay (www.savebay.org) monitor these habitats and are finding a number of salt marshes in Narragansett Bay that are changing from from lush marsh grass to open water because of rising sea level. Many marshes studied also showed a shift in salt marsh grass species, with high marsh grasses being displaced with less diverse, low marsh grasses, just within the last decade alone, indicating sea level rise is quickly changing the dynamics of these critical habitats. Fewer plant species, may result in less productivity and affect its ability to protect against shoreline erosion.
Over the years, NOAA Fisheries has worked with state agencies, local universities and non-profits to help protect and restore these vital habitats. We provide conservation recommendations on coastal development projects to help minimize threats and protect critical coastal habitats. We also have been involved in number of important dam removal and fishway construction projects to help more migrating fish reach their spawning areas. Our work in Narragansett Bay will continue as the threat of sea level rise grows. Existing marshes will need room to migrate landward, which may require providing sufficient buffers from development surrounding salt marshes and prioritizing restoration efforts to sites that can adapt to sea level rise. Protecting key habitats from rising tides will be an important area of focus for NOAA in the foreseeable future.