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Friday, December 6, 2019
Adrianne Appel* - IPS/IFEJ
MILWAUKEE, Wisconsin, Oct 22 2009 (IPS) - The weather was right for swimming this summer along the shores of Lake Michigan, but on many days, the only living things seen on the beach were gulls, picking away at zebra mussels ensnared in a thick, green slime that covered every rock, pebble and grain of sand for miles.
Scientists so far haven’t found the reason for Cladophora’s overgrowth. The lake is under such profound environmental stress that any of a number of factors, alone or together, could be the cause, they say.
“It’s easy to see what’s happening. It’s difficult to understand why,” J. Val Klump, director of the Great Lakes WATER (Wisconsin Aquatic Technology and Environmental Research) Institute, told IPS.
Top suspects are climate change, which has raised the lake’s temperature and lowered water levels, and the widespread, sinister changes in the lake’s ecosystem wrought by alien zebra and quagga mussels that now cover the lake bottom by the millions.
“These systems are very sensitive to climate change,” Klump said.
“Something has changed,” Paul Horvatin, the federal Environmental Protection Agency’s Great Lakes monitoring director, told IPS while onboard The Guardian research vessel on Lake Michigan.
The Barack Obama administration has pledged to provide five billion dollars over 10 years for the ailing Great Lakes, and part of the first installment of 475 million dollars will be used to research invasives, Horvatin said.
The five Great Lakes extend across 244,000 square kilometres that straddle the U.S. and Canada, just 2,400 kilometres from the polar ice cap. The lakes support shipping to the Atlantic Ocean, and some of the richest commercial fisheries in the world. About 40 million people take their drinking water from the Great Lakes.
At the same time, the lakes are massively polluted with chemicals and heavy metals, particularly the bottom sediment, after hundreds of years of industrialisation. The lakes are closed systems, and they hold onto pollutants. Forty-three Great Lake harbours are considered highly toxic waste sites.
“The good news is we are seeing a decline in PCBs and DDT. The bad news is they haven’t declined enough,” Horvatin said.
Even today, large quantities of sewage flow from urban areas like Milwaukee into Lake Michigan during very heavy rains from overwhelmed storm drains. Thirty percent of Milwaukee storm water pipes test positive for human fecal contamination on a normal day, Klump said.
Incidents of sewage overflow into the lakes are increasing, as climate change brings more days of torrential rains to the Midwest, according to the Nelson Institute at the University of Wisconsin. The Midwest is warming overall, with more extreme hot days in summer, warmer winters with less snow and less ice on the Great Lakes.
According to the Great Lakes WATER Institute, winters in Wisconsin, which borders Lake Michigan, are now four degrees F warmer than before 1980.
As soon as 2030, the amount of spring snow pack would be halved, and Lake Michigan could be devoid of ice for much of the winter, according to models of the National Oceanic and Atmospheric Administration.
Lake Michigan water is already 58 centimetres below normal, near its lowest recorded level, because of evaporation from summer heat, according to the Nelson Institute.
Lake Superior was typically covered 60 percent with ice for most of the winter but today 20 percent is the norm, Klump said.
“The bottom line is by the mid to end of the century, we will be in a different climate zone,” Klump said. The Midwest climate will be like that of the more southern U.S. state of Arkansas, he said.
According to Brian Shuter, a zoologist with the Ontario Ministry of Natural Resources, these changes may cause cold-water fish, like salmon, lake trout and brook trout, to move north, and warm-water fish like carp and catfish to move in.
Today, the native Karner blue butterfly, an endangered species that thrives in the natural habitat of Indiana Dunes National Park, on the southern tip of Lake Michigan, is in trouble, according to the Union of Concerned Scientists. Snow insulates the butterfly’s eggs from the freezing winters but fewer are surviving now because there is less snow.
The temperature, water level and other changes to Lake Michigan have created the perfect habitat for aggressive new species like the hybrid cattail to replace sedge meadows that surround Green Bay, one of the richest commercial fisheries in the world, according to research of the Great Lakes WATER Institute.
The zebra and quagga mussels, originally from Russia and Ukraine, are so plentiful in Lake Michigan, they have drastically altered the lake’s ecosystem during the past 19 years.
The mussels are aggressive filter feeders and during the past five years, their filtering has changed the lake’s trademark murky, plankton-rich water – to clear. Light now penetrates into the lake, where it never has before. Divers love the change and so does Cladophora, whose growth is stimulated by light.
As the mussels filter, they excrete concentrated amounts of phosphorus, which also may be encouraging Cladophora growth. Quagga mussels excrete even more phosphorus as temperatures rise, as has been happening in Lake Michigan, Harvey Bootsma, a scientist at the Great Lakes Water Institute said.
Plankton are a rich food source for many native fish. With large quantities of it being taken up by the mussels, “The fish are getting skinny,” Bootsma told IPS.
Anyone near a Cladophora-clogged beach can tell something isn’t right with Lake Michigan.
“When the stuff decomposes it smells like a pig barn,” Bootsma said.
And that’s not all. The heaps of dead algae on the beach threaten the quality of the water.
Mounds of dead Cladophora wash up on beaches with zebra mussels attached. Gulls and other birds stroll over the algae, eating the mussels and depositing fecal material with high concentrations of toxic e. coli bacteria. The whole mess rots in the sun and stinks, and the bacteria contaminates the water, Bootsma said.
Birds are suffering, too. In 2007, more than 17,000 birds died from botulism, which normally lives harmlessly in small quantities in lake sand but is concentrated by the mussels, Horvatin said.
He and other researchers hope to answers soon.
“We’re trying to look at the whole food chain and how it has changed over time,” he said.
*This story is part of a series of features on sustainable development by IPS and IFEJ – International Federation of Environmental Journalists for Communicators for Sustainable Development (www.complusalliance.org).
This story includes downloadable print-quality images -- Copyright IPS, to be used exclusively with this story.
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