Summer blooms of algae in Lake Erie are nothing new. But the most severe algae outbreak in the past decade is now under way, according to the National Oceanic and Atmospheric Administration.
The bloom has been advancing eastward from the lake shoreline near Toledo, Ohio, since July. NOAA experts have predicted that algae levels will approach a level of 9.5 on the agency’s 10-point scale for both extent and duration.
A severe algae bloom in 2014, driven by climate-change-induced weather changes and fertilizer runoff, led to dangerous levels of the neurotoxin microcystin in Lake Erie. When winds kept the algae pinned to the southwestern shore near Toledo’s water intakes, the toxin poisoned the water supply for nearly half a million people in that city.
Federal and state scientists track the annual advance of the green glop on Lake Erie in part because some algae produce toxins that can harm people and animals. The blooms also block sunlight and use up oxygen in the water, choking off fish and other aquatic life.
The causes of severe algae blooms on Lake Erie are largely human-driven: weather patterns influenced by climate change, and fertilizer runoff from industrial-scale farming.
June rainfall totals in much of the Lake Erie region were much higher than historic averages. Cleveland recorded 8.52 inches of rain in June, according to the National Weather Service, compared with its typical average of 3.83 inches. Toledo saw 7.22 inches of rainfall during the same period, compared with an historic average of 3.57 inches.
The National Climate Assessment released in 2014 forecast that heavy rainfall events will occur four times more frequently within the next 85 years unless greenhouse gas emissions are reduced significantly.
Storm water runoff from these high spring rains carried heavy loads of nitrogen and phosphorous fertilizer from croplands and livestock lots into rivers and streams that flow into Lake Erie, creating a huge oversupply of nutrients for algae in the lake.
Scientists and farmers have long known about the nutrient runoff problem in the watershed surrounding the western end of Lake Erie. The latest federal farm bill has allotted $17.5 million to help farmers in Ohio, Michigan, and Indiana curb the escape of excess nitrogen and phosphorous from their land, The Toledo Blade reported in June.
Techniques include “more cover crops, controlled drainage structures, precision nutrient application, buffers, and windbreaks, all strategies that aim to keep more nutrients on the land and out of Lake Erie tributaries,” a federal scientist told the paper.
This year’s massive mat of green goop on Lake Erie is so far more a slimy nuisance than a threat to the public water supply, but scientists are watching it closely for signs of high microcystin.