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Great Lakes Article:

Lake Erie's Health Crisis

Buffalo News
07/19/2002

Lake Erie once again is showing signs of an environmental crisis, after nearly two decades of mostly good news about the health of the lake.

Environmentalists say a number of factors are again straining the most vulnerable of the Great Lakes: a fourth straight year of large-scale fish and bird die-offs, a large "dead zone" off the Ohio shoreline and the threat of invasion by another non-native species with a voracious appetite.

"Lake Erie is like the canary in the coal mine," said Margaret Wooster, executive director of Great Lakes United.

"It's the most shallow and the most vulnerable," she said. "It's the one where we're already beginning to see the signs we saw in the 1960s, only now we're looking at a more diverse and complex set of causes."

While pollution was at the root of the lake's woes 40 years ago, lake watchers theorize that the current problems may be the proliferation of invader species like the zebra mussel, quagga mussel and the round goby.

The thinking is that these species are consuming large quantities of the microscopic life forms that constitute the base of energy in the lakes, creating another link in the food chain that is having far-reaching impact.

"It's possible - and this is still a theory - that the exotic species mixture is the real root of the problem," said Bill Culligan, who heads the state Department of Environmental Conservation's Lake Erie Fisheries unit in Dunkirk. "The gobies and the zebra mussels and the things that eat those two things are the ones being affected."

The round goby and the zebra mussel have changed the lake, but lake watchers are bracing for another intruder they fear could be an even larger invader: the Asian carp.

Imported from China in 1973 to improve the water quality in aquaculture operations in Arkansas, the carp managed to escape those confines and multiply rapidly in the surrounding states' rivers and lakes.

They have advanced into the Illinois River as far as Joliet, Ill., only 25 miles from Chicago. If they get that far, they will be at the Great Lakes' door and, as Jerry Rasmussen of the U.S. Fish and Wildlife Service said, "I don't think you want them."

Why?

The larger types of Asian carp, the bighead and the silver, have an appetite that would put Homer Simpson to shame. They can weigh up to 100 pounds and grow to more than four feet long.

"Some say they'll consume up to 40 percent of their body weight in a day," said Rasmussen, who has studied the carp as it has traveled north up the Mississippi River. "Silver carp has been described as not having a stomach: food in and food out, a constantly consuming machine."

Some of the fish grow to 12 pounds in their first year of life, and often become so large that they are no longer a threat to native predators.

 

Asian carp extremely prolific

They are also extremely prolific: A female can carry up to 1 million eggs. The carp quickly supplant native fish. In fact, fishermen have abandoned some of the more fertile commercial fishing zones along the Mississippi because of Asian carp infestation.

"They feed on plankton, so they take the algae that are the basic productivity of the floating population, the things small fish feed on," Rasmussen said. "You can imagine that if you get large (carp) in large schools, they'll tie up a lot of biomass. And right now, that's what we're seeing in our rivers."

Scientists have installed an electrical barrier in the Chicago Sanitary and Ship Canal that they hope will slow the northward movement of the carp. It works by creating impulses that repel the fish.

What would happen if they get in the lakes is anybody's guess, but Rasmussen believes Lake Erie is the most vulnerable.

"It's the shallowest," he said. "It's more (like) the habitat they're familiar with."

Lake researchers already have enough to occupy them, including the reappearance of a large "dead zone" unable to support life in Lake Erie's central basin.

Much of Lake Erie was anoxic, or oxygen-deprived, in the late 1960s, but after millions of dollars was spent on upgraded sewage treatment plants, that condition had been turned around.

Now it appears that an area on the lake between Ohio and Ontario once again contains pockets where oxygen has been stripped from the water. It's enough of a concern to prompt a $2 million research project involving U.S. and Canadian scientists who will take instrumentation out onto the lake throughout the summer.

There are three possible explanations, according to Jan Ciborowski of the University of Windsor, one of the scientists in charge of the program.

One is that warmer water temperatures are reducing the size of the oxygen pool in the middle of the lake.

Another is that algae that normally produce oxygen are, for some reason, unable to do so now.

A third explanation is that decaying fecal matter, animals and algae are draining oxygen from the water.

"Each of these is a possible explanation, and the reason we're looking together is to see which of these hypotheses is supported by the data," Ciborowski said."

Signs of a disrupted ecosystem became apparent on the lake in 1999, when scientists dissecting dead wildlife found along the lake shores discovered the animals were killed by type E botulism. Last found in some of the other Great Lakes in the 1960s, it had never been found before in Lake Erie.

The number of dead birds and fish mushroomed in 2000. Early in the summer, it was a large die-off of mud puppies, an aquatic salamander, on the Canadian shore, but as the year went on, larger creatures began floating up on the shoreline between Buffalo and Erie, Pa.

Culligan said it's safe to say that "tens of thousands" of fish, mostly sheepshead, rock bass and smallmouth bass, have been killed in each of the last two summers.

 

Bird deaths from botulism

According to estimates based on samples of sections of the shoreline, the state believes around 6,000 water birds died along New York's Lake Erie shore in 2000. There were another 2,600 estimated deaths last year, almost half of which were common loons, but DEC senior wildlife pathologist Dr. Ward Stone thinks that estimate is low.

Some of the fish deaths can be attributed to natural causes or natural conditions, like thermal shock, which occurs when temperatures change too quickly for the fish to adjust. But Stone said many died from botulism.

This year, there has been another large mud puppy die-off, this time on the New York shore, as well as a large number of dead ring-billed gulls.

"A few days ago, there were at least 2,000 (gulls) dead," said Stone, noting that this year's bird die-off has come earlier than the previous two years. "They got the Type E botulism somewhere."

 

Botulism may be due to invaders

Botulism has not been identified yet this summer in fish, but Stone believes testing on fish brought in late last week will confirm its presence.

Stone believes the appearance of botulism is related to the invaders, the round goby and the quagga and zebra mussels.

The mussels filter microscopic food call phytoplankton from the water. That makes the water clearer, allowing sunlight to promote algae growth at deeper than usual levels. The algae eventually dies and combines with decomposing mussel waste to provide a fertile breeding ground for the bacterium that leads to botulism.

The mussels, which absorb the bacterium, are eaten by gobies and other fish, which then are weakened by the disease. The debilitated fish attract larger predatory fish, mud puppies and diving fish-eating birds like loons who, in turn, become sick.

"What I think is that the botulism started out in fish or mud puppies, and now it is going through by birds eating fly larvae" coming out of the decomposing fish and birds along the shoreline, Stone said.

Scientists admit they're still trying to prove some of their theories on how invasive species are changing the lake ecology. Lake advocates like Gordon Fraser, director of the Great Lakes Center at Buffalo State, say additional research is essential.

"We don't have a lot of hard data," he said. "And we're not getting a lot of support to go out and get it."

 

Lake has dead zone

By John Bartlett
07/19/2002
Go Erie.com


Two research vessels, one Canadian and one American, crisscrossed Lake Erie's central basin Friday looking for a "dead zone," an area of water deprived of oxygen.

The work is taking place with urgency, and with concern for how an oxygen-poor lake would affect marine life and the communities that rely on the lake's water quality.

Lake Erie's central basin is showing signs of excessive oxygen depletion, a problem officials believed they had solved decades ago with the cleanup of the lake and tough new pollution standards in the 1970s.

Fish and other aquatic creatures need oxygen. When too little oxygen is in the water, fish and other aquatic species cannot survive, and a "dead zone" forms.

Most species are OK until the dissolved oxygen levels fall below 6 parts per million, or ppm. Below that, they are stressed, much as a person would be breathing at a high altitude. At below 4 ppm, most aquatic species will be literally choking for air.

"A lake trout might prefer it above 6 (ppm) or close to 10 (ppm), which is about as saturated as you can get," said Roger Kenyon, a Lake Erie fisheries biologist with the Pennsylvania Fish and Boat Commission. "A carp may not be affected until it falls to 2 (ppm). Much below 2, it's fairly toxic for everything."

By the end of August, oxygen levels fell below 2 parts per million throughout the central basin, creating what biologists are calling a massive dead zone.

"Last year was one of the most rapid and largest oxygen depletions we've seen since 1983," said David Rockwell a senior scientist with the federal Environmental Protection Agency's Great Lakes National Program office.

It does not bode well for the lake, nor for the communities and people who are so heavily dependent on its water quality, said Gerald Matisoff, a Case Western Reserve University professor who is co-coordinating the current U.S.-Canadian research effort.

Every summer, oxygen levels decline in the central basin when the water in the Great Lakes separates into two layers in which the warmer, top layer traps the colder waters beneath it. The top layer mixes with oxygen from the air, while the bottom layer is cut off from the air supply. Whatever oxygen the bottom layer has when the separation occurs is all that is available until the end of the season and the annual remixing of the waters.

Lake Erie's western basin is shallow enough for the winds to stir the entire water column, providing the opportunity to dissolve oxygen throughout its depths. The eastern basin is so deep, its volume alone largely ensures an adequate oxygen supply.

The central basin, however, falls somewhere in the middle and the annual oxygen loss can become severe if something goes wrong, Kenyon said.

Apparently, something has gone wrong, but what it could be remains a puzzle.

In the dark days of Lake Erie's past, the problem played out fairly directly.

Phosphorus and other nutrients were dumped into the lake from sewage plants and other sources. The nutrients fertilized algae, which led to massive algae blooms, which eventually would die and decay. As the algae decayed, it used up the oxygen in the lake, creating anoxic, or oxygen-poor, conditions.

The cycle nearly overwhelmed Lake Erie by the end of the 1960s, leading to its portrayal as a dead lake.

U.S. and Canadian communities and governments spent billions of dollars on new and updated sewage systems, and the use of phosphorous in detergents and other products was reduced.

Lake Erie quickly rebounded in one of the great environmental success stories of all time.

What particularly puzzles scientists now is that the conditions in the central basin do not seem to correspond with large algae blooms.

"Based on studies in the '60s and '70s, we cut the amount of phosphorous we put in the lake to 11,000 tons a year. It had been running as much as 25,000 tons a year before," Case Western Reserve's Matisoff said. "We met that goal in about a decade and saw steadily improving water quality, and now we see the problems we had in the '70s and earlier. We don't understand that."

Looking back, researchers now realize the seasonal oxygen declines in the central basin started to become a problem in 1995. The realization that anything unusual was going on came as Great Lakes researchers compared notes at a conference in 1999, said Jan Ciborowski, Matisoff's Canadian co-coordinator.

"The change was almost imperceptible at first in 1995 through 1999, then it became quite rapid in the last couple of years," he said.

Several theories have been suggested for the increased levels of phosphorus and the ensuing oxygen-deprived conditions.

Basically the theories fall into three general categories — climate change, unaccounted for sources of phosphorous and the effects of zebra mussels and their cousins, the quagga mussels.

Matisoff said the invasive mussels are highest on his suspect list, and the focus of most of the current research.

"The idea is the lake functioned one way before the zebra mussel, and that the zebra mussel has changed how it functions," Matisoff said.

Zebra mussels have created clearer lake waters, allowing sunlight to penetrate deeper, which possibly has led to algae growths at deeper levels where there is less oxygen and where the impact of decay, pulling oxygen from the water, would be greater.

Mussel feces contains phosphorous, and the sheer volume of mussels and their waste might be what is throwing things out of balance.

"What we are seeing could be the result of a whole bunch of factors happening at once," Ciborowski said. "We don't know, and that's scary. We spent a huge amount of resources to correct the problems we had in the past. We developed a model that seemed to be working nicely until now. Are we deluding ourselves that we can manage the lake?"

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