By:
Tom

Source(s):
Maia McGuire MPMcGuire@ifas.ufl.edu, (904) 824-4564
Patrick Baker pbaker@ifas.ufl.edu, (352) 392-9617 ext. 281
Lori Williams lori_williams@ios.doi.gov, (202) 513-7243

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ST. AUGUSTINE, Fla. — Boaters and bathers along northeast Florida beaches this summer may notice a new and unwelcome addition — an invasive mussel that already plagues the state’s Gulf coast where it’s killing native shellfish and covering manmade objects.

The Asian green mussel (Perna viridis) was discovered at St. Augustine in 2002 and now is found from Savannah, Ga., to Mosquito Lagoon near Titusville, said Patrick Baker, a mollusk expert with the University of Florida’s Institute of Food and Agricultural Sciences.

The marine pest, native to tropical parts of the Indian and Pacific Oceans, seems immune to local predators, said Baker, a UF assistant research professor of invertebrate zoology and malacology, the study of mollusks. Baker said some east coast areas could suffer damage on the same scale found in Tampa Bay, where the first — and to date the worst — U.S. infestation was discovered in 1999.

“So far, St. Augustine is the only place on the east coast where the density approaches levels in Tampa Bay,” he said. “Green mussels definitely have the potential to cause problems, but we’re not sure how bad it will get.”

In Tampa Bay, oyster reefs have died after colonies of green mussels sprang up among the oysters and competed for the microscopic floating plants both species eat, Baker said. East coast oyster populations may be vulnerable, and researchers suspect the mussel could interfere with hard shell clam fishing and farming operations.

Green mussels anchor themselves to virtually any hard surface below the waterline, including boat hulls, navigation buoys, dock pilings and seawater intakes for power plant cooling systems, he said. The mussels begin reproducing when two or three months old. When they reach high densities — up to 1,000 adults per square foot in some cases — they may have to be removed from manmade structures, a costly process that can impact consumers.

“They don’t do anything different from barnacles and other fouling organisms native to Florida,” Baker said. “They just do it better and they’re bigger.”

Growing to six inches in length, the mussel has a smooth outer shell with a bright green coating that gradually darkens with age, he said.

Options for controlling the green mussel appear limited, said Maia McGuire, a marine extension agent with Florida Sea Grant, a program of coastal research and education affiliated with UF. No nonnative marine invertebrate has been successfully eradicated in U.S. waters, although mechanical and chemical control is possible in closed systems such as power plants.

Some Florida residents have taken matters into their own hands, removing the mussel from local waters — to eat.

“We don’t recommend this practice,” McGuire cautioned. “Although the green mussel is considered edible in its native range, there’s not much information available yet about the possible risks of eating the ones that grow here. And some areas where the mussels are found are closed to shellfish harvest for health reasons.”

Researchers had hoped north Florida’s winter temperatures would kill expanding populations each year, limiting the mussel’s spread. But McGuire’s observations near St. Augustine in summer 2004 suggest the pest may be a permanent First Coast resident.

“Most of the green mussels I saw were probably less than a year old because they were only an inch long,” McGuire said. “But there were larger ones in the more protected in-shore areas, and those might have made it through the previous winter.”

Experts are uncertain how the mussel arrived at St. Augustine — or any other Florida location — but possible culprits include adult mussels traveling while attached to ship hulls, larvae contained in ship ballast water and larvae floating on ocean currents, she said.

“We want to learn more about their biology and the timing of their reproductive cycle so we’ll have a better idea whether the mussels are reproducing here or if the larvae are arriving from other places,” she said.

Residents are asked to report sightings of green mussel colonies or individual shells at UF’s Green Mussel Homepage, http://greenmussel.ifas.ufl.edu. The Web site, which contains further information and photos, is part of a collaborative effort between UF and other institutions to track the mussel’s spread, McGuire said.

Citizen involvement is crucial in the fight against exotic pests, said Lori Williams, executive director of the U.S. National Invasive Species Council in Washington, D.C.

“Many citizens are very knowledgeable about their own environment,” Williams said. “They know what belongs there and what doesn’t, so they’re often the best resource for early detection.”

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