Sound Facts

Aquatic Invaders of the Sound!

Healthy native ecosystems are constantly changing, but when a non-native species is introduced it can begin to wreak havoc. Non-native species are called “invasive” species when they out-compete native species living in our coastal habitats.

There are many ways aquatic invasive species (plants and animals) can be introduced from other parts of the world into the Sound, including from the ballast water held in the cargo holds of ships, accumulating on ship hulls (known as biofouling), from the packaging material of fish bait, from watercraft and rain gardens, from intentional release fishing bait release, escape from nurseries and water gardens, and intentional release of unwanted aquatic pets. This Sound Fact (published during National Invasive Species Awareness Week) focuses on two plant and one invertebrate species that are now calling the Sound home.

Devil’s Tongue Weed (Grateloupia Turuturu)

Nancy Balcolm/CT Sea Grant

A red alga, or seaweed, this plant was discovered on Long Island Sound in 2004. Since it thrives in warm water, it has the potential to grow in abundance as the Sound’s water temperature increases. Grateloupia attaches to hard surfaces such as rocks and may compete with native red alga for important resources like space, light, and nutrients. One of the algae, Chondrus crispus, or Irish moss, serves as habitat for blue mussels and other invertebrates, as well as algal epiphytes (species that grow on the surface of other plants) that provide food for crustaceans. Want to learn more? CT Sea Grant has a factsheet on Grateloupia on its website. It has the ability to cover 100% of the habitat it invades, and it thrives in disturbed locations, on cobble, and around docks.

Sea Squirt (Didemnum vexillum)

Photo credit: Dr. Stephan Bullard/Sound Update

This soft-bodied marine invertebrate grows on hard surfaces and feeds by filtering particles, such as phytoplankton and bacteria, from the water column. They are called sea squirts because large ones shoot water from their filtering siphons when they are picked up. They grow rapidly, including on docks, pilings, and the hulls of boats, and during outbreaks, they reach incredible densities, as many as hundreds per square foot. Besides compromising human structures sea squirts can out outcompete and suffocate filter-feeding bivalves such as mussels, scallops, and oysters. Want to know more? See the article by Dr. Stephan Bullard in the Summer 2012 issue of Sound Update, a special themed issue on invasive species.

Oyster Thief (Codium Fragile)

Photo credit: Wikipedia

This green seaweed, also known as dead man’s fingers, or green fleece, was first discovered in the US in Long Island waters in the late 1950s. It can be seen year-round on open coasts, estuaries, tide pools, and intertidal and subtidal zones. It attaches to rocks, shells, or other hard substrates, and is often covered with epiphytic species. It is also found in sheltered habitats such as bays and harbors, and can outcompete native seaweed such as kelp and smother mussels and scallops, reduce the biomass of oysters, and lift the shellfish off the seafloor. It is not as abundant in the Sound as it was a decade ago.

What You Can Do

pulling trapa waterchestnut in Portland, CT
CT DEEP staff removes invasive water chestnut (Trapa natans) from an inlet north of Salmon Cove in 2019.  Left unchecked, this area could easily be filled in with Trapa and choke important native underwater vegetation that is critical to spawning and resident fish. Photo credit: Judy Preston

Want to help stop the spread of aquatic invaders? In the summer environmental organizations and agencies may sponsor volunteer invasive species removal events in local rivers and lakes. The Connecticut Department of Energy and Environmental Protection and the New York State Department of Energy and Environmental Protection also have useful information on what you can do on their websites:

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