EMPIRE -- Dead birds and fish again are washing up in waves at Sleeping Bear Dunes National Lakeshore.
And park biologist Ken Hyde is concerned that this year's die-off of gulls, loons, ducks and cormorants affects more species, particularly the endangered piping plover.
"One sad thing is we lost four piping plovers," Hyde said. "That is a concern to us because we are trying to increase their populations ... and now we have one more thing that impacts them or can kill them."
Bird and fish deaths became evident by August last year. More than 2,600 fish-eating birds were found dead on Lake Michigan beaches north and south of the Platte River mouth by late 2006.
This year, biologists recorded die-offs by early summer.
The culprit is Type E botulism, a naturally occurring toxin in lake sediments that's apparently entering the food chain through invasive species such as zebra and quagga mussels and round Goby fish.
In turn, birds and larger fish that consume mussels and Gobies are poisoned.
Since mid-June, hundreds of Gobies have washed ashore. More recently, smaller numbers of lake trout, salmon and carp have died and washed up on the beach, Hyde said.
State wildlife experts expressed concern over the sheer number and variety of dead birds.
"I haven't dealt with those kinds of numbers in any die-off," said Tom Cooley, who's tested animals for the Department of Natural Resources since 1977.
Friends of Sleeping Bear Dunes chairman Kerry Kelly said the problem has been discussed at group meetings.
"The loons in particular I think a lot of our members would be concerned about," he said. "A lot of our visitors also enjoy the natural beach setting and being able to walk the beaches, and nobody likes to walk the beach and see dead birds or dead fish."
This year's death toll is impossible to predict, Hyde said.
"We do know from our dive crews that the Goby and quagga mussel populations are really building up along this part of Lake Michigan," he said.
Hyde is using off-shore monitoring devices as well as numerous crayfish, insect and fresh dead bird and fish samples to better understand the toxin's pathway through the ecosystem.
Other agencies also are researching the problem.
Mark Breederland, district educator with the Michigan Sea Grant, said his cohorts in New York and Pennsylvania investigated similar situations in Lakes Erie and Ontario since the late 1990s.
"This is probably going to be a series," he said. "The general trend is for this July-August die-off of species, from what we learned from people in Lake Ontario, but there is also a late October-November die-off."
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