Botulism Killing Great Lakes Birds

U.S. scientists said botulism spread by zebra mussels is killing thousands of birds along the Great Lakes.

Zebra mussels and round gobies arrived in ship ballast tanks in the 1980s and 1990s. Zebra mussels filter naturally occurring botulism and other toxins from the water. Gobies eat the mussels and birds eat the gobies, the Chicago Tribune said Tuesday.

Studies suggest the new food chain is concentrating botulism and other toxins and passing them up to predators.

Scientists have been studying the problem since 1999, when 311 birds in Lake Erie appeared to have died from Type E botulism. The next year the number increased to 8,000. The toxin spread through Lakes Erie, Ontario and Huron before hitting Lake Michigan in 2006.

The Tribune said researchers estimate 3,500 to 8,500 birds died last year along hundreds of miles of Lake Michigan beach in seven northern Michigan counties.