The Problem with Aquatic Invasive Species in Narragansett Bay

Several new species taking up residency in Narragansett Bay are adversely impacting the neighborhood, and are the focus of much research to protect the local ecology and economy.

Aquatic invasive species (AIS), which are marine plants and animals that are not in their natural environment, have come to Narragansett Bay from as far as Asia and Europe. Most of these species arrive via ballast water from shipping containers, especially as global trade has increased, according to Kevin Cute, Marine Resource Specialist for the Rhode Island Coastal Resources Management Council, who led a Coastweeks event on September 24.

Participants of Coastweeks learn how to identify aquatic invasive species.

Event participants learn how to identify aquatic invasive species.

“When the contents of Tokyo Harbor dump out, most of it dies, but a small percentage lives,” he said explaining that Narragansett Bay is a toxic environment for most non-native species, but that a few manage to survive and thrive.

Some species are introduced as a result of expanding ranges due to changes in water temperature and salinity, or even from university labs, aquaculture sites, and recreational boating. Either way, they’re not something that can be avoided altogether.

“We have no choice but to adapt,” said Cute.

The most problematic of invasive species to Rhode Island include the Asian Shore Crab, the Chinese Mitten Crab, several types of colonial tunicates, and the Oriental Grass Shrimp.

“The problem is that invasive species take over critical habitat for native species,” said he said. “The issue is habitat, and the competition for food and space.”

Orange/Red colonial tunicates engulf mussel

Orange/Red colonial tunicates engulf mussel

Colonial tunicates, or sea squirts, especially, wreak havoc on critical eelgrass and shellfish beds, which provide essential nursery habitat for healthy fisheries. Shellfish are also not only commercially viable but are crucial for maintaining good water quality. Invasive tunicates can grow rapidly to form colonies of hundreds of organisms that spread like mats, engulfing their surroundings. They don’t directly kill eelgrass or shellfish but can block out sunlight and out-compete for vital oxygen and nutrient resources, changing the entire ecosystem.

“[They] are really impacting eelgrass, which is scary,” Cute said, explaining how these species can exacerbate natural environmental stressors on native species and take over.

Some invasive species, he said, are also able to spawn for longer periods of time throughout the year than native species, another added advantage.

"Coral reef of invasives" overtake docks at Point Judith Marina

“Coral reef of invasives” overtake docks at Point Judith Marina

About one to two new species are identified every year, said Cute, who explained the value of the volunteering network in Rhode Island and the floating dock monitoring program for keeping an eye on what new species are doing and what new species are coming in. There are currently five sites being monitored: Save the Bay, Allen Harbor, Point Judith Marina, East Bay Yachting Center, and the Fort Adams Boat Basin.

“These floating docks are excellent proxy habitats and are the foundation of our understanding of invasive species in the Bay,” said Cute explaining that one of the main purposes of the monitoring program is to determine whether these species are spreading in Narragansett Bay. “We need volunteers to find that answer.”

Kevin Cute, Coastal Resources Management Council, shows samples of aquatic invasive species growing along floating docks.

Kevin Cute, Coastal Resources Management Council, shows samples of aquatic invasive species growing along floating docks.

 – Meredith Haas | Rhode Island Sea Grant Research Communications Specialist

For more information on aquatic invasive species and how to participate in the monitoring program, please visit CRMC’s website.