Hundreds of common loons, ducks, grebes and gulls are dead and others are at risk following the return of Type E botulism this fall.
The state Department of Environmental Conservation said it has found 200 to 300 loons washed up on shorelines in Jefferson and Oswego counties, the largest such outbreak for the Lake Ontario region since 2006.
DEC said bird carcasses did not wash ashore until late October, with most surfacing in the last two weeks. In past years, mortality events have not occurred much later than the third week of November, which DEC said led it to believe there may not be many more deaths, although carcasses may continue to wash ashore.
According to a DEC news release, Type E botulism is caused by a bacterial toxin produced by clostridium botulinum, a widespread bacterium in the sediments of the Great Lakes. Certain environmental conditions cause this strain of clostridium to produce a toxin that can spread through the food web of the lakes.
First documented in water birds from Lake Michigan in the 1960s, Type E botulism was recorded irregularly for three decades in the lower Great Lakes.
The department attributed the problem to a pair of invasive species, round gobies and quagga mussels. It said the botulinum toxin, generated in the vicinity of mussel beds, possibly in rotting mats of algae, is picked up by the filter-feeding mussels that become food of the goby, which is sensitive to the toxin. Intoxicated gobies in turn become easy prey for diving water birds, such as loons, grebes and some duck species. The remains of gobies are the most common component in the stomach contents found in botulism-killed diving birds. Since the emergence of this new disease system, thousands of birds have perished annually.
D. Lee Willbanks, executive director of Save the River, an environmental advocacy group based in Clayton, said the deaths indicated overall water-quality problems in the lake.
Were seeing a disturbed system that goes through cycles, he said. This equilibrium is worse than others.
Mr. Willbanks said the best thing that could be done to help fight the problem was to reduce the amount of unprocessed nutrients that enter the water, limiting the areas where the toxin can develop.
The department said in its news release that the public is encouraged to report dead birds to its regional offices. Carcasses contain small amounts of toxin and pose some threat to animals that feed on them. DEC has removed carcasses from portions of state-owned shoreline.
Shoreline residents are encouraged to bury carcasses if feasible.
To report dead birds found in Jefferson County, call the DEC at 785-2263. To report birds found in Oswego or Cayuga counties, call the DEC at 607-753-3095, ext. 247.