Traverse City, Mich. — It was the largest algae bloom in Lake Erie’s recorded history – a scummy, toxic blob that oozed across nearly one-fifth of the lake’s surface in the summer and fall of 2011. It sucked oxygen from the water, clogged boat motors, and washed ashore in rotting masses that turned beach-goers’ stomachs.
It also was likely an omen of things to come, experts said in a study released earlier this year. The warming climate and modern farming practices are creating ideal conditions for gigantic algae formations on Lake Erie, which could be potentially disastrous to the surrounding area’s multi-billion-dollar tourist economy. The shallowest and southernmost of the Great Lakes, Erie contains just 2 percent of their combined waters but about half their fish.
According to the report, which was compiled by more than two-dozen scientists, the 2011 runaway bloom was fueled by phosphorus-laden fertilizers that were swept from corn and soybean fields during heavy rainstorms. Weak currents and calm winds prevented churning and flushing that could have short-circuited its rampant growth.
The combination of natural and manmade circumstances “is unfortunately consistent with ongoing trends, which means that more huge algal blooms can be expected in the future unless a scientifically guided management plan is implemented for the region,” said the report’s lead author, Anna Michalak, of the Carnegie Institution for Science.
The United States and Canada limited the use of phosphate laundry detergents and cracked down on Great Lakes pollution from industry and municipal sewage systems four decades ago. Those policies led to a drastic algae drop-off in Lake Erie, which had been declared all but dead. But algae began creeping back in the mid-1990s, and the blooms have gotten progressively bigger.
They consist largely of blue-green strains that are poisonous and cause skin irritation. Measurements in 2011 found that concentrations of a liver toxin they produce were hundreds of times higher than levels approved by the World Health Organization for drinking and recreational waters.
The building blocks of algae blooms, particularly phosphorus, are well known. The newly released paper was compiled by experts from a range of disciplines to determine why the 2011 bloom got so huge and whether it's a harbinger of things to come. At its peak, that bloom covered 1,930 square miles, making it more than twice as big as the freshwater sea’s second-biggest bloom on record, which happened three years earlier.
Published in the online version of Proceedings of the National Academy of Sciences, the report said soil management practices in the region’s corn and soybean fields are partly to blame.
One such practice is no-till farming, in which seeds are planted in small holes and the ground is not plowed. While it helps the environment by preventing erosion, no-till farming keeps fertilizer in the upper soil.