TOLEDO, Ohio — Lake Erie is sick. A thick and growing coat of toxic algae appears each summer, so vast that in 2011 it covered a sixth of its waters, contributing to an expanding dead zone on its bottom, reducing fish populations, fouling beaches and crippling the tourism industry.
Spring rains reliably predict how serious the summer algae bloom will be: The more frequent and heavy the downpours, the worse the outbreak.
This year the National Weather Service says there is a higher probability than elsewhere of above-normal spring rains along the lake’s west end, where the algae first appear.
It is perhaps the greatest peril the lake has faced since the 1960s, when relentless and unregulated dumping of sewage and industrial pollutants spawned similar algae blooms and earned it the nickname “North America’s Dead Sea.” Erie recovered, thanks to a multibillion-dollar cleanup by the U.S. and Canada. But although the sewage and pollutants are vastly reduced, the blooms have returned, bigger than ever.
Once, fisheries and sports anglers pulled 5 million walleye from the rejuvenated lake every year. Today the catch is roughly one-fifth that, the Environmental Protection Agency says. Commercial fisheries’ smelt catch is three-fifths of past levels. The number of charter fishing companies has dropped 40 percent.
The algae are fed by phosphorus, the same chemical that U.S. and Canadian authorities spent billions to reduce — for good, they thought — in the 1970s and ’80s. The phosphorus level plunged by two-thirds, and the algae subsided. But in the mid-1990s, it began creeping back.
This time, new farming techniques, climate change and even a change in Lake Erie’s ecosystem make phosphorus pollution more intractable.
The spring of 2011 was the wettest spring on record. That summer’s algae bloom, mostly poisonous blue-green algae called Microcystis, sprawled nearly 120 miles, from Toledo to past Cleveland. It produced lake-water concentrations of microcystin, a liver toxin, that were 1,200 times World Health Organization limits, tainting the drinking water for 2.8 million consumers.
Dead algae sink to the lake bed, where bacteria that decompose the algae consume most of the oxygen. A dead zone now covers a large portion of the lake bottom in bad years.
Last spring, the rains arrived amid a record drought, and the algae retreated to waters near Toledo. But no one hopes for a drought. To cut phosphorus levels this time, scientists say, the habits — and the expensive equipment — of 70,000 farmers near the Erie shore must change because most of the phosphorus that feeds algae these days comes from farmland.
