Narragansett Bay: Always Changing, but Not Too Clean

by Mike Jarbeau, Baykeeper

The question of whether Narragansett Bay has become too clean to sustain a healthy fishery was the main topic of the annual Ronald C. Baird Sea Grant Symposium, held at the University of Rhode Island’s Bay Campus in December. While there was certainly no consensus among the communities present in the room, one theme was clear: the Bay has been changing since humans first settled in New England, and changes continue to occur today. But what are those changes? And is there a “Goldilocks” level of nitrogen or other nutrients to which the Bay should be managed?

In the science and research communities, Narragansett Bay is often touted as the most studied estuary in the world. State and federal agencies work closely with local colleges and universities to gather and interpret data in all reaches of the Bay. The University of Rhode Island’s Fish Trawl Survey, for example, began in 1959 and is one of the longest continuous records of marine species abundance in existence. And anyone who spends time on the water is also familiar with the many buoys, probes and gauges dotting the Bay that collect information to help us understand its complex dynamics. 

The Narragansett Bay Estuary Program’s recent State of Narragansett Bay and Its Watershed report does a great job summarizing what we know about the Bay, illustrating changing conditions and highlighting areas that need more investigation. 

Save The Bay staffers Joan Abrams and Topher
Hamblett pull up mats of Cladophora macroalgae
littering Little Narragansett Bay.

One major success has been a reduction of nutrients—nitrogen and phosphorus—entering the Bay from many sources, but particularly from the process of treating human wastewater. Just as nutrients in fertilizer cause our grass to grow, excessive amounts of nutrients in our water stimulate algae growth. Too much algae starves the water of oxygen as it dies and decomposes, harming marine life that needs that oxygen to survive. The good news is that the amount of nutrients going into the Bay has gone down by almost 60 percent over the last 15 years. But this success has led to questions about whether these nutrient reductions are negatively affecting fisheries by starving the Bay of its productivity. 

We must not be confused by the discussions. No, Narragansett Bay has not become some sort of dead zone incapable of supporting marine life. Yes, the Bay of several decades ago was different. And yes, we hear stories of the glory days gone by and the difficulty of making a living on inshore fisheries today. But we must take into account that many factors have caused the types and numbers of fish and shellfish in our waters to change. We can’t ignore decades of closed beaches and stories of ear infections or other health issues still felt by people who spend time in the water. And we must remember the extensive shellfish closures that are just now beginning to be lifted in parts of the Upper Bay, opening up new opportunities for fishermen. 

Reports from the 1800s tell us that Narragansett Bay was teeming with fish and natural resources readily available for harvest. Researchers point to many reasons why fisheries in the Bay have changed since then. But changed by what? 

Habitat quality is a critical component of a healthy ecosystem, and our Bay habitats have changed significantly over the past century. A Bay high in nutrients is not natural or conducive to the growth of critical habitats that support an abundant fishery. Much of the nuisance seaweed that washes up on our beaches in the summer is a result of excess nutrients. Eelgrass beds that were once plentiful all over the Bay floor, supporting a robust oyster population and providing habitat for fish and other shellfish, are scarce now, killed off by pollution, disease, and scallop trawls, despite significant efforts by Save The Bay and others to restore native beds.

A timeline and description of changes in the
Narragansett Bay fish community as water temperature have risen.

Water temperature also influences the types and abundance of fish in Narragansett Bay and surrounding waters. The water in Narragansett Bay has risen almost four degrees Fahrenheit since 1960. This temperature change is believed to have had a large effect on the types of fish that live in the Bay. In the 1960s, colder water temperatures supported a high abundance of bottom fish such as winter flounder. But in the next few decades, populations of these bottom fish declined as temperatures rose and allowed lobster and crab populations to grow. Finally, scientists say, in the last several decades, warmer-water species, such as black sea bass and scup, typically found in Mid-Atlantic waters (see illustration) have become more common.

The fact is: spawning conditions, habitat availability, pollution, and fishing pressure are among the many factors at play when we consider the current health and productivity of the Bay. As noted in the State of Narragansett Bay and Its Watershed report, more study is needed to fully understand the complexities of our marine ecosystem. We have many questions about how evolving Bay conditions affect the health and productivity of the microscopic phytoplankton that forms the basis of the entire marine food chain. More study is also needed to characterize the Bay’s response to improving conditions and how weather and water flow patterns influence offshore nutrient inputs, among many other topics. 

While we may not be able to pinpoint a “Goldilocks” scenario where conditions in the Bay are “just right” for every interest, there is no question that recent efforts are moving us closer to a Narragansett Bay that is fully fishable, swimmable and accessible. The Bay has been changing for centuries, requiring us to adapt to evolving conditions and new opportunities, just as we have always done. We should all be proud of the fact that beach closures are down, shellfish beds are reopening, and our investments in a cleaner Bay are paying off.

Algae blooms, caused by excessive nutrients in the water, can be seen along
the shores at Sabin Point.