The Ohio River, transformed by mining and industrial waste and sewage overflows into the nation’s most polluted major waterway, has a new and unexpected tormentor this fall: carpets of poisonous algae.
Pads of toxic blue-green algae have speckled nearly two-thirds of the 981-mile river in the last five weeks, experts say, in an outbreak that has curbed boating, put water utilities on alert and driven the river’s few hardy swimmers back to shore.
The only other recorded toxic algae bloom, in 2008, covered perhaps 40 miles of the river. In contrast, the latest bloom stretches 636 miles from Wheeling, W.Va., to Cannelton, Ind., and traces of algae have appeared as far west as Illinois.
The poisonous alga, called microcystis, increasingly plagues polluted waters across the country. The Ohio River blooms arrived as another persistent algae outbreak, in western Lake Erie, grew in recent weeks to near-record proportions.