Will Lake Erie Succumb to E-Botulism?
We've all seen dead fish and occasional dead birds as we walk along the Lake Erie shore. Sometimes the number of dead fish seems large - the remains of a dozen or so dead carp, for example, scattered across a single beach after a storm. But that's nothing to what wildlife specialists in New York and Pennsylvania have been seeing for the last three years. Helen Domske has been on the front lines. She's a senior wildlife specialist for New York Sea Grant.
Helen Domske: In the New York state waters of Lake Erie, we estimate this past year, well, around 6,000 birds. That's an alarming number. And these are very valuable species of birds. You're looking at loons and mergansers and long-tailed ducks.
Untold numbers of fish have also died. The culprit is a form of botulism scientists say is a normal part of the Great Lakes system. Helen Domske says e-botulism is normally found in the sediments at the bottom of the lake and requires anaerobic - or no-oxygen - conditions to thrive. But for some reason, Domske says the toxin is making its way from sediments into the food chain.
Helen Domske: What we're concerned about is how is it getting from the sediments, where it's not really involved in the food chain, up into fishes that are then eaten by these birds. That's what we're looking at, that's what we're trying to find out.
Along with Domske, wildlife specialists from Pennsylvania and Ohio Sea Grant have been working closely together to keep abreast of the latest developments. So far, the massive bird and fish die-offs have been confined to the Eastern Basin of Lake Erie. No cases have yet been documented in Ohio. But people like Frank Lichtkoppler, the Ohio Sea Grant agent for Lake County, are keeping a close eye on the situation.
Frank Lichtkoppler: I don't see why it won't come this way. The lake is open, you can fish and swim anywhere and so it may be just a matter of time before we see outbreaks of this - or we may not see it.
To understand what's causing the Lake Erie outbreak, scientists are having to untangle a complex web of potential ecosystem interactions. Grace McLaughlin is one of the lead researchers on the issue. She's a wildlife disease specialist with the U.S. Geological Survey's National Wildlife Health Center in Madison, Wisconsin. She believes e-botulism may be entering the food chain through two 1980's invaders from Europe that entered the Great Lakes in the ballast water of ships. The fingernail-sized zebra mussel and its cousin the quagga mussel now coat most hard and soft surfaces on the bottom of Lake Erie.
Grace McLaughlin: One of the hypotheses is that the zebra and quagga mussel beds basically act as incubators for toxin production. As they go about their business of filtering the water, they're putting out a fair amount of fecal material. It starts to decompose, it uses up the oxygen in that area, and the chlostridium botulitum bacteria start to reproduce.
Another recent invader - a fish called the round goby - eats zebra and quagga mussels. They in turn are food for larger fish and birds. The e-botulism toxin can be transferred either in the animals' gut or in some cases, in their flesh. McLaughlin says, while it's rare, type e botulism can cause sickness in humans.
In New York and Pennsylvania, wildlife experts have been gathering up the dead carcasses to incinerate or bury, hoping to keep the toxin from spreading. In Ohio, researchers are wondering why it hasn't spread west. Jeff Ruetter is director of Ohio State University's Stone Lab research facility at Put-in-Bay. Last summer, he testified before a Congressional field hearing about the return of so-called dead zones to Lake Erie. Reutter says along with lowered lake levels and higher water temperatures, the same conditions that created the dead zones may be having an effect on the growth of e-botulism.
Jeff Ruetter: Clearly the dead zone in the Central Basin of Lake Erie is an area of anoxia. We do know that botulism requires anaerobic conditions. Therefore, why are we observing these problems with botulism in area around Erie, PA and east, where they really don't have the severe anaerobic conditions that we have in the Central Basin?
Scientists says it's not yet clear what impact three straight years of botulism kills have had on local species at the eastern end of Lake Erie. Nor do they understand how the outbreak may have affected the waves of migratory birds that pass through the area each spring and fall. Wildlife disease biologist Grace McLaughlin says Lake Erie fisheries don't yet appear to be in trouble. But she says this outbreak of Lake Erie e-botulism should be a wake-up call for Great Lakes policymakers.
Grace McLaughlin: This points up a really huge problem with the introduction of non-native species. We don't know for sure which ones will become invasive. We don't know how they will tip the balance of the system. We don't know and we really can't predict what the ramifications of these introductions will be.
E-botulism is usually quiescent in the cold winter months and only begins to show up in spring and summer. As wildlife officials east of us prepare for another season's onslaught of dead birds and fish, folks here are still watching for signs of e-botulism they hope will never appear. And that's just as well, because scientists say it may take years of research before they understand what's causing the outbreak. In Cleveland, Karen Schaefer, 90.3.