Shellfish may be next weapon in Sound clean-up

The Fish Site
by The Fish Site
6 August 2007, at 1:00am

US - A federal scientist in Milford wants to add a tool to clean-up efforts in Long Island Sound - shellfish farms.

Shellfish could counteract the effects of excessive nitrogen, such as hypoxia, which creates dead zones, said Gary Wikfors, a fish biologist with the National Oceanic and Atmospheric Administration and a member of the management committee for the Environmental Protection Agency's Long Island Sound Study.

From an economic standpoint, instead of throwing money into sewage treatment plants, the local economy is grown," Wikfors said. "That's a completely alternative approach. I don't see why that can't be an option in Long Island Sound."

Unlike finfish farms, which can pollute water with waste and chemicals used for disease control, bivalves such as mussels and oysters can help clean the water. They are filter feeders that eat by drawing in water and siphoning out nutrients.

The nutrients, including nitrogen, spur algae blooms, a major cause of hypoxia. As they die, the algae use up oxygen in the water that other marine life need to survive.

"They're what's called a keystone species," said Bob Rheault, who owns Moonstone Oysters in Rhode Island and is president of the East Coast Shellfish Growers Association. "They change the environment in a number of different ways, though all are good. When you have a number of oysters, they remove bacteria, viruses, silt and they improve light penetration."

For every hundred or so oysters Rheault harvests from what he called his "tiny farm," he said he removes about 50 grams of nitrogen from Narragansett Bay.

"That might not sound like much, but half a million oysters a year - that's about 40 people pooping in the water," Rheault said.

When shellfish thrived in Chesapeake Bay in Maryland, the water was filtered frequently, said Tim Eichenberg, an attorney with the non-profit organisation Ocean Conservancy. "Now, with all the shellfish populations that are diseased, water is filtered every year or so," Eichenberg said.

Environmental problems can happen with shellfish farms, such as introducing non-native species and spreading viruses through broodstock, but the problems are far fewer than with finfish, Eichenberg said.

Seaweed can also remove nutrients from the water, said Mark Tedesco, who heads the Long Island Sound Study, the federal cleanup effort. His office is trying to expand oyster reefs in the Sound, Tedesco said.

Repopulating shellfish for consumption in the Sound should be left to the state Bureau of Aquaculture, which licenses shellfishermen and monitors water quality, and sewage plant upgrades shouldn't be traded for shellfish farms, Tedesco said.

"We don't believe that oysters and aquaculture would be a replacement for trying to control nutrients, though they would be a valuable complement to it," he said.

Source: The Advocate