Lake diseases linked to invasive species
Written by Syracuse Post-Standard   
Sunday, 05 November 2006 12:23

Paralyzed water birds drown and float dead to shore. Virus-infected fish bleed out of their eyes. Invasive mussels and fish interact to spread toxic bacteria. It's not a worst case-scenario. It's what's happening now on Lake Ontario, and scientists say invasive species and diseases are to blame.

In recent weeks, a toxic form of botulism has killed more than 500 common loons on the lake. A virus that causes uncontrolled bleeding has infected thousands of fish, killing hundreds and prompting federal officials to ban the transport of more than three dozen species.

"It's a horrible feeling, walking around the beach and seeing a bunch of corpses," said Jack Manno, executive director of the Great Lakes Research Consortium at the State University College of Environmental Science and Forestry. "People who have a sense that something is wrong are right."

Botulism spores have long been found in the sediment lining the bottom of Lake Ontario, but until quagga mussels arrived in the early 1990s, no toxic outbreaks bloomed, according to Helen Domske, a Buffalo-based senior extension specialist for New York SeaGrant. Many scientists believe the outbreaks began when quagga mussels started interacting with another invasive species: round gobies.

"You can have quagga mussels, but until you have round gobies, it's no problem," Domske said. "It's the two working together that causes these outbreaks."

Quagga musselssuck oxygen from Lake Ontario, creating a perfect breeding ground for toxic botulism, Manno said. While feeding, the mussels absorb botulism spores and concentrate them in their systems. Round gobies feed on the mussels, then pass the toxin on to the loons, gulls and mergansers that eat them.

The disease that is killing fish, viral hemorrhagic septicemia, also has no roots in Lake Ontario.

"We think VHS is an exotic, a recent introduction to the Great Lakes," said Gerry Barnhart, director of fish, wildlife and marine resources for the state Department of Environmental Conservation. "The virus was likely transported in ballast water in vessels coming from the Atlantic, through the St. Lawrence Seaway into the Great Lakes."

The recent diseaseoutbreaks have the potential to affect almost every aspect of the lake, including baitfish sales, sport and recreational fishing, tourism and property values.

he U.S. Department of Agriculture recently banned the interstate transport of 37 species of live fish to try to curb the spread of VHS. The state Department of Environmental Conservation this week is discussing enacting similar rules, Barnhart said.

"It's an economic problem," said Manno, of the Great Lakes Research Consortium. "Much of the commercial fisheries on the Great Lakes are baitfish."

Anglers, boaters and tourists in 2003 spent $600 million in the regions bordering the Great Lakes and Finger Lakes, according to a 2004 SeaGrant study, the most recent available.

"All the communitiesalong the lake and at the tributaries rely very heavily on summer tourism for their economic development, whether it's boating, fishing or sailing," said Christine Gray, director of the Oswego County Department of Promotion and Tourism. "When there's a lot of reporting about issues on the lake, it has an impact on whether people will come here. They often won't."

Said Manno: "Who wants to go to the lake and see a bunch of dead birds?"

Barnhart said VHS could crush sport and recreational fishing if species such as smallmouth bass and walleye, both popular local game fish infected by the disease, start dying off in large numbers.

It's too early to tell if that will happen. Since VHS appeared only a few months ago in Lake Ontario, biologists are holding out hope that the fish may build a resistance to the disease.

But with no cures in sight, scientists expect problems to get worse before they get better - if they ever do. Biologists at the DEC agree that outbreaks of botulism, viral hemorrhagic septicemia and other diseases likely will become yearly events on Lake Ontario, as they have on other Great Lakes.

"Even if it ends during this migration period, we could see it again next year," DEC spokeswoman Maureen Wren said.

Like many invasive species, neither quagga mussels nor round gobies have natural predators in Lake Ontario. Scientists' only hope is to stop the spread of invasive species before they begin to choke and sicken inland water bodies, too.

That, however, takes funding, legislation and international cooperation, the experts said.

"We're really at the turning point," Manno said. "We're either going to do it now or we're going to regret it later."
 
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