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Invasive species change lake
Trade's dark side Hard to control The latest invaders Growing awareness
John Bartlett
Erie Times News
11/16/2002


Roger Kenyon has spent a career studying Lake Erie, and that has meant a career looking at the impacts of species that don't belong in the lake.

"The incursion of alien species over the span of 200 years has changed the lake dramatically, and in recent years even more so," said the Great Lakes fisheries biologist for the Pennsylvania Fish and Boat Commission.

In fact, the so-called invasive species are one of the greatest forces driving changes in the lake's ecosystem.

And from the earliest arrivals on, few of the changes wrought by the invaders have been good.

It is an issue that has received a lot of attention — particularly at the October State of the Lakes Ecosystem Conference in Cleveland, a biennial meeting of the minds among Great Lakes officials, during which a Lake Erie assessment pegged alien species as the lake's worst enemy.

In late 1989, a team led by Cornell University researcher Edward Mills began an exhaustive effort to catalog the invasive species in the Great Lakes and how they got here.

In 1993, Mills and his fellow researchers published their results. They documented 139 non-native species including 59 plants, 25 fishes and 14 mollusks, such as zebra mussels.

The numbers have increased since then.

"I think we are up to around 162 now," Mills said in a telephone interview from the Cornell Biological Field Station in Bridgeport, N.Y.

Some of the alien species were deliberately introduced, such as steelheads, coho salmon and Chinook salmon for sport fishing. Others arrived by working their way through canals, by hitching rides on freighters or from accidental releases from fish farms and aquariums, Kenyon said.

However, Mills' study made clear that efforts to improve commerce and trade on the Great Lakes directly led to the arrival of many of the invasive species.

"There is a direct correlation between the opening of the (St. Lawrence) Seaway and a number of things becoming established in the lakes," Mills said.

Nearly half of all the invasive species in the lakes arrived since the opening of the St. Lawrence Seaway in 1959. Most of those are believed to have hitched rides in the ballast water of ocean-going ships, Mills said.

However, even earlier efforts to improve trade — such as the 1825 opening of the Erie Canal and the Welland Canal in 1829 — provided entry routes for foreign species, he said.

In the 1830s, the sea lamprey entered Lake Ontario, probably through the Erie Canal. In 1921, it reached Lake Erie after changes were made to the Welland Canal, Mills said.

Sea lamprey feed on the body fluids of fish by attaching themselves with a sucking disk and sharp teeth.

The lamprey, native to the Atlantic Ocean, spread throughout the Great Lakes, devastating lake trout populations and hurting many other native species as well.

The impact and vampire-like nature of the sea lamprey grabbed the attention of the public, providing the support for extensive research and control efforts. Several methods were tried to control sea lampreys, including installation of electric barriers on streams where they spawned. However, real control seemed a lost cause until the mid-1950s when researchers discovered TFM (3-trifluoromethyl-4-nitrophenol).

TFM is a chemical that has proved extremely effective at killing sea lamprey larva.

But it has not been cheap. The United States and Canadian governments have spent more than $250 million to control sea lampreys and continue to spend about $15 million a year, said Marc Gaden, a spokesman for the Great Lakes Fisheries Commission.

However, the successful effort to control the sea lamprey is an anomaly, Kenyon said.

"It is the only invasive (species) where there is a proactive control program," he said.

Other invasive fish that spread through the Great Lakes about the same time or shortly after the sea lamprey probably had as much impact on native species and the ecosystem, but in ways that attracted less public attention.

One example is the alewife, which was known in Lake Ontario in the 1870s and discovered in Lake Erie in 1931.

Another is the rainbow smelt, which apparently arrived in Lake Erie in the early 1900s, Kenyon said.

"Smelt took off and exploded in eastern Lake Erie in the 1930s and '40s, and they had a dramatic impact on other species, especially lake herring, white fish and possibly blue pike," Kenyon said. "They are voracious predators and also plankton eaters. They were so abundant they out competed some of the native animals. They may have been the reason along with alewives and heavy fishing the lake trout disappeared."

The original lake trout strain that was native to Lake Erie is believed to have disappeared by the 1940s. By the mid-1950s, Great Lakes' lake trout existed only in a few isolated populations in Lake Superior.

There has been a 30-year effort to restore lake trout, but with only limited success.

Researchers are now beginning to understand one of the long-term impacts of the introduction of alewives and smelt, Kenyon said.

The two species are rich in thiamanese, an enzyme that destroys thiamin (vitamin B-1). Thiamin is necessary for the development of lake trout embryos. Researchers increasingly believe lake trout that feed on the alewives and smelt, which are now a primary forage fish, take in excessive amounts of thiamanese, which hinders their reproductive ability, Kenyon said.

The heavy dose of thiamanese from alewives and smelt may also be affecting many other species.

Such unusual and long-term affects from introduced species are the great unknowns, Kenyon said.

Take zebra mussels for instance.

If any invasive species has surpassed the sea lamprey in the amount of media attention and public interest, it is the zebra mussel.

In reality, the term zebra mussel generally refers to two species — the zebra mussel and its cousin, the quagga mussel.

To the casual observer, the two mussels are nearly indistinguishable. Zebra mussels prefer shallow waters, while the quagga thrives in deeper water, said Eric Obert, an environmental specialist for the Pennsylvania Sea Grant.

The first discovery of the zebra mussel came in June 1988 in Lake St. Clair, the connecting channel between Lake Huron and Lake Erie.

Arriving in the ballast water of an ocean-going ship, it quickly spread throughout the Great Lakes and beyond.

In 1991, the quagga was identified as a separate species in Lake Ontario and it too rapidly spread throughout the lakes.

The zebra and quagga mussels' impacts were sudden and highly noticeable. For one thing, they attached themselves to everything, costing municipalities, ports and lake businesses an estimated $30 million, according to a federal Environmental Protection Agency report.

Zebra mussels have also displaced native mussels in most areas, leaving the future of the natives in question.

But the real impact has to do with the changes they created in the lake, Obert said.

"In my opinion, zebra mussels overall by far most affected the ecosystems because of their filtering ability," Obert said.

Not only do they take in the plankton — microscopic plants and animals — that would otherwise be available to other species for food, but they filter so effectively that they clear the water allowing for greater light penetration. More light at greater depths leads to changes in plant communities, increased weed beds and algae blooms, Obert said.

Researchers are now wondering whether there are some totally unexpected impacts of the zebra and quagga mussels.

There is growing suspicion that the two mussels — coupled with the round goby, another recent invader — play a significant role in the outbreaks of avian botulism along the Lake Erie shoreline over the past four years, Obert said.

More ominously, a dead zone — an area depleted of oxygen where most fish and other aquatic species cannot survive — has begun to develop each summer in Lake Erie.

Such dead zones were thought to be a thing of the past, corrected by the massive effort to clean up the lake in the 1970s and 1980s and tough new pollution controls.

Puzzled scientists now have a working hypothesis and it points to the quagga mussel.

The quagga expels the phosphorous contained in its food. The phosphorous enhances the growth of algae, which takes up the oxygen in the water. In addition, the organic matter in the mussels' feces decomposes on the lake bottom, consuming more oxygen. Eventually, there is not sufficient oxygen left to support fish or other aquatic creatures.

Other species that could have equal or greater impacts are knocking on the door, including Asian carp, which are just a few miles from entering Lake Michigan through the Chicago Sanitary Canal. An electric barrier has been installed to keep them out and another is planned.

After many years, the issue of invasive species has surfaced and it is becoming a national priority.

The International Joint Commission pushed the issue in its 2002 11th Biennial Report on the Great Lakes issued in September.

Also in September, U.S. Rep. Phil English of Erie joined with other lawmakers to introduce the National Aquatic Invasive Species Act of 2002 that closes some loopholes on ballast water transfers and takes other steps to control the spread of invasive species.

On Wednesday, attorney generals from four Great Lakes states went to federal court in San Francisco asking that the federal government be required to take tougher steps to protect the lakes from invasive species.

Friday, the International Association of Great Lakes Researchers issued a report calling invasive species one of the greatest risks to the health and productivity of the Great Lakes. It called for a commitment of an additional $30 million annually in federal funding to combat invasive species.

"We don't have control and we will never have control over everything" Kenyon said. "But there is more we could do."
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