Dec
11
2007

A loon swoon: Deadly bacteria are having a devastating impact

Watch what you eat: Large numbers of loons and other aquatic birds are dying on the eastern Great Lakes as a deadly bacteria is working its way through the lakes' food chains.
Watch what you eat: Large numbers of loons and other aquatic birds are dying on the eastern Great Lakes as a deadly bacteria is working its way through the lakes' food chains.Courtesy U.S. Fish and Wildlife Service
It’s not a good time to be a loon in the Great Lakes region. Record numbers of the dead birds are showing up on a westerly progression along Great Lakes shores. And the story is a classic example of how one little change can have significant impacts through the food chain.

The issue was the cover story of a recent issue of the Star-Tribune. And so far, no signs of the loon deaths are showing up in Minnesota. But what once was a small problem on the eastern rim of the Great Lakes is now showing up in larger numbers and greater territory. This past season, dead loons were found washed up on the western shores of Lake Michigan.

Here’s what’s happening, researchers believe: the loons are getting sick from Type E botulism that is working its way through the Great Lakes food chain. At the bottom of lakes, spores of this type of botulism germinate and develop into bacteria cells. As quagga mussels filter lake water at the lake bottoms, they suck in these bacteria. Fish called round gobies eat the mussels and loons eat the gobies, where the bacteria ultimately do their damage.

It doesn’t take long for the loons – or other aquatic birds like long-tailed ducks, gulls, grebes – to feel the impact. Within hours of consuming the bacteria, they are paralyzed and no longer able to swim, fly or hold their heads up. They ultimately drown.

Wildlife specialists are doing surveys on the impact of the bacteria on aquatic birds. Along one shore of Lake Michigan, twice as many dead loons were found this year compared to last year. Ultimately, however, it will be hard to pin down how many birds are dying each year from this condition. Many Canadian lakes are in remote locations that aren’t regularly visited.

And there are concerns about other links in the food chain. Will fox, coyotes, eagles or other predators of aquatic birds get sick from eating an easy meal of dead, washed up loons?

Part of the problem is that two early links in this chain, the quagga mussels and round gobies, are not native species to the Great Lakes. Invasive species are usually problematic with eco-systems. Also, researchers are trying to pin down if warmer lake temperatures and lower water levels could be having a negative impact in allowing the bacteria to grow better.

But Minnesota and Lake Superior are certainly not out of the woods. There are both quagga mussels and round gobies in the Duluth-Superior area.

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