Aqua-invaders

U of G researcher says another zebra mussel-like disaster is likely

By Steve O'Neill

here's been increased awareness lately about chemical indiscretions in the Great Lakes, but a U of G zoologist says that biological contamination -- which can be just as harmful -- is being largely ignored.

Prof. Paul Hebert, chair of the Department of Zoology, says that lax regulations and bad management techniques are allowing foreign organisms to enter the Great Lakes via the ballast water carried by ships importing goods. The result is an upset in the balance of the lakes' natural ecosystems and serious environmental damage.

"Commercial vessels simply dump their ballast water directly into the lakes, when there should be government regulations that force them to empty it into treatment facilities," says Hebert. "It's an irresponsible movement of goods and it has a serious impact on the natural environment."

He should know. Hebert was the first scientist to identify the presence of zebra mussels in the Great Lakes. They were inadvertently brought in on an ocean-going vessel in 1987 and have since thrived and multiplied. They feed on plankton -- an important part of the food web for native fish -- and cause problems for almost everyone who shares their space: swimmers who step on them, boat owners who have to scrape them off their hulls and municipalities that suffer from clogged water-intake valves. Scientists are still scrambling for ways to control the prolific and resilient creatures.

Zebra mussels may be the most obvious foreign invaders, but Hebert says they're far from the only ones. He suspects, for example, that a foreign pathogen wiped out the blue walleye, once an abundant Great Lakes fish.

"It's comparable to when the first European settlers came to North America," he says. "They brought with them diseases like smallpox, to which the native Indian population lacked immunity, and as a result, a large part of that population was destroyed."

Hebert is trying to provide more information about the incidence of invaders by using genetic methods. He's looking at all sorts of aquatic organisms and trying to identify genetic "markers" that differ between species, to see which are actually native to the lakes. The research has yielded some surprises. One species of Daphnia zooplankton, long thought to be native to the Great Lakes, was identified through genetic markers as a European type that had "immigrated" here.

"The conspicuous invaders like zebra mussels are only the tip of the iceberg," says Hebert. "Using genetic techniques, we can identify the less obvious ones and gain a better understanding of the impact of species' invasions on biodiversity in the Great Lakes."

Hebert's research is sponsored by the Natural Sciences and Engineering Research Council.