Harmful Algal Blooms | Ohio Sea Grant

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Harmful Algal Blooms

HABs have been a focus of Ohio Sea Grant's work since 1971. Today, Sea Grant's work on reducing and preventing HABs ranges from the local to the international level


After the “do not drink” advisory issued in Toledo, Ohio in August 2014, Ohio Sea Grant compiled a list of frequently asked questions about the event, and about harmful algal blooms in general.

What is a harmful algal bloom? A harmful algal bloom, often called a HAB, is any large increased density of algae that is capable of producing toxins.

When does the majority of phosphorus enter the lake? The largest phosphorus load, about 80-90%, happens during heavy rain storms when fertilizer and other phosphorus sources are quickly washed into rivers and streams that flow into Lake Erie.

What does it do to people? The toxin of greatest concern tends to be microcystin, which causes skin rashes, GI problems and varying degrees of nervous system, liver and kidney damage.

Harmful Algal Blooms

HABs have been a focus of Ohio Sea Grant's work since 1971. Today, Sea Grant's work on reducing and preventing HABs ranges from the local to the international level

During the event, Ohio Sea Grant director Dr. Jeff Reutter and research coordinator Dr. Justin Chaffin were on the phone with the U.S. and Ohio Environmental Protection Agencies (EPA) as well as city officials from Toledo to help inform their management of the issue.

But August 2014 was far from the first time Ohio Sea Grant worked on the front lines to restore the health of Lake Erie. Nutrient loading, algal blooms and the dead zone – an area of low oxygen that develops in the central basin during the summer – have been an important part of Ohio Sea Grant’s work since 1971 when the Center for Lake Erie Area Research (CLEAR) was formed.

Toxic Algae Bloom in Lake Erie

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“Our efforts to bring Lake Erie back from its dead lake image to becoming the walleye capital of the world were a success,” remembers Reutter. “However, once decision makers felt that there was no longer an acute problem, funding and monitoring for further research were diverted to other focus areas.

That change in priorities has come back to haunt Lake Erie again in the past two decades. Steadily increasing concentrations of phosphorus – a vital nutrient for agriculture crops that also fuels harmful algal blooms in the lake – have resulted in an increase in the occurrence and severity of algal blooms. The western basin, which receives runoff from the Maumee River watershed, the largest agricultural watershed feeding into the Great Lakes, is especially affected by phosphorus levels that have returned to what they were during the height of the problem in the 1970s.

While funding from the U.S. EPA for water quality monitoring ended in the mid-80s, students at Stone Lab continued to conduct an informal monitoring effort, and Ohio Sea Grant and Stone Lab began to prepare for the current situation in the mid-90s.

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View live buoy data from the Stone Lab Algal and Water Quality Laboratory

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Much of the phosphorus that causes HABs comes from fertilizer and manure runoff.


Most of Lake Erie's phosphorus load happens during heavy rain storms.


The Maumee River contributes almost half of the total phosphorus load to Lake Erie.


On July 12, 2018, Ohio Sea Grant’s Stone Laboratory hosted an event featuring expert commentary, a discussion of the history of this issue on Lake Erie, and Ohio’s response to the problem.

Visit the event page