In Great Lakes, 'the sky really IS falling'

How should we react to news that the world’s fourth largest lake is rapidly dying before our eyes and that practically nothing is being done to stop it?

Horror and outrage seem appropriate. However, the lead researcher tracking this particular slow-motion death says the response he’s gotten is more of a shrug because “people are getting tired of hearing that the sky is falling.”

The lake in question is Lake Michigan, the second-largest (by volume) of the US-Canadian Great Lakes. (It’s actually the second-largest lake in the world, after the Caspian Sea, if you consider that it and Lake Huron are physically a single body of water.) It also appears to be in its biological death throes, just 12 short years after scientists first discovered the presence of a unique large-scale “river of phytoplankton” that forms the foundation of the lake’s food chain.

In 1998, W. Charles Kerfoot, a biologist at Michigan Technological University, and his research team used NASA’s then-new, satellite-based Sea-viewing Wide Field-of-view Sensor (SeaWiFS) to identify the circular “river” flowing counter-clockwise in the southern end of Lake Michigan. They determined that the roughly doughnut-shaped current of phytoplankton was created when large winter storms kicked up nutrient-rich sediment carried into the lake from the region’s cities and farms. As that sediment floated through the water column along a large circular path, it created a “Thanksgiving feast” for the lake’s phytoplankton, algae and other microscopic plants.

“We saw that with each storm, you get a ring, and it can persist for weeks or even months,” Kerfoot said. “We were floating in the clouds, saying, ‘Hey, we discovered a new phenomenon.’ ”

During the region’s cold winters, that seasonal phenomenon of circulating phytoplankton apparently was enough to feed the lake’s tiny zooplankton, which in turn provided a food source to small fish, which then fed the lake’s larger fish. Ultimately, that doughnut of tiny marine plants has likely been one of the reasons Lake Michigan has long been such a fisherman’s paradise.

However, almost as soon as Kerfoot and his team discovered it, that phytoplankton river has begun to shrivel. The apparent reason? An invasive species from Europe known as the quagga mussel. Now found in all the Great Lakes after arriving in untreated ballast water dumped there by ocean-going ships, the quagga are hungry mollusks who love phytoplankton … and are apparently devouring the marine plant life faster than it can reproduce — up to seven times faster in some parts of the lake.

In fact, between 2001 and 2008, graduate student Foad Yousef has calculated, chlorophyll — a measure reflecting phytoplankton abundance — has declined by a full 75 per cent.

But the voracious quagga are doing more than depriving other creatures up the food chain of their meals. The waste they excrete at the lake’s bottom can stimulate growth of Cladaphora algae. When those algae die and decompose, life-critical oxygen gets sucked out of the water.

“When things go anaerobic, that kills off everything, including the quaggas, and creates conditions for botulism,” Kerfoot said. “We’ve had massive kills of fish-eating birds — loons, mergansers. Isn’t that bizarre? Who would have predicted that?”

A few more years of such conditions, and Lake Michigan’s storied catches of alewives, chubs, Atlantic salmon, muskies, smelt, walleyes, perch and more could soon be history.

“A high percent of the fish biomass could be lost in the next couple years,” Kerfoot said. “We have a system that’s crashing.”

He added that the message he’s heard from the National Oceanic and Atmospheric Administration, which is in charge of protecting the Great Lakes from invasive species, is anything but encouraging.

“I asked why they weren’t swimming in money to do something about this,” he said. “They say people are getting tired of hearing that the sky is falling. Now, when the sky really is falling, they aren’t paying attention.”

In fact, Kerfoot believes, the impact of the tiny quagga — which is no larger than a fat Lima bean — could soon render moot the more headline-grabbing concerns about the invasive zebra mussel and Asian carp.

“By the time the carp get here, there won’t be anything left for them to eat,” Kerfoot predicts.