After exceeding early summer projections on its severity, the harmful algae bloom in Lake Erie has largely disappeared.
According to forecasters with the National Oceanic and Atmospheric Administration (NOAA), this years moderately severe bloom climbed to a 6, on 'severity index' of 10, and it would likely rise to between 4.5 and 2.4, according to NOAA forecaster David Gratz, who predicted in June that it'd range between 2. and 5.
The bloom began to slow down in late July, but it was fast to begin to develop. It reached its peak between late August and early September, before easing off during a string of windy days.
It re-intensified along the Michigan coast in late September and lasted until the end of October longer than in previous years, thanks to persistently hot water temperatures.
At its highest, the bloom covered 530 square miles. Despite its large geographic area, the toxicity levels were lower and scums were less intense than in previous years.
Last years bloom was mild; a 3 on the severity index. Severe years include 2011, when algae reached Cleveland, 2015, when it spread across the lake to Ontario, and 2017, when green scums formed on the Maumee River in Toledo.
The annual severity index is calculated by measuring the amount of bloom biomass using satellite imagery over the peak 30-days of the bloom.
NOAA forecasters believe the larger area this year could be due to heavy rainfall in July, which allowed heavier river discharges to disperse algae-feeding phosphorus and other nutrients further into the lakes shallow western basin.
The annual Lake Erie blooms are caused by microcystis cyanobacteria, (blue-green algae), which may produce toxic substances that can harm coastlines and cause illness to humans and animals.
Bloom size and spread is determined largely by the amount of bioavailable phosphorus entering the lake through the Maumee River and its tributaries in Michigan and Ohio. The rivers nutrient load is largely fed by runoff in the watershed from pelletized fertilizer and liquid manure generated by livestock feeding operations known as CAFOs.
Michigan, Ohio, and Ontario agreed in 2015 to reduce phosphorus entering western Lake Erie by 40 percent by 2025, with 20 percent attainable by 2020 as an interim goal.
Michigan and Ohio have relied more heavily on voluntary programs than mandates to encourage agricultural businesses to reduce nutrient loss from fields and farms than on strict mandated programs.
Environmental groups in the region claim that the approach isn't working.
Global warming is also believed to be reducing the annual blooms by warming lake temperatures and increasing nutrient runoff through intensifying storms, causing the bloom to accelerate.
Related stories:
Mild algae bloom forecast for 2021
NOAA invests $1.7 million in HAB's research.
In 83 years, the 1st plover chick hatch along Ohio cost in 93 years.
In begins. 2020 algae bloom forms in Lake Erie after a 'algae bloom' in lake Ery
Wet spring fuels 2019 algae blooms a blizzard.
What makes lake Erie algae so dangerous?
Lake Erie seiche driven by high winds is a natural phenomenon.
Michigan's governor opposes federal ballast water regulations.
In Lake Erie drinking water, PFAS levels rise.
