Clean Water

Toxic Algae



Nearly each year, Lake Erie and many of Ohio’s other waterways, contend with bright green mats of toxic algae. In 2011, Lake Erie experienced one of the worst toxic algae seasons on record, until 2015 when the green slime was so severe it ranked a 10.5 on a 1 – 10 scale. That same year, toxic algae stretched over 650 miles of the Ohio River.

But the landmark event that most people remember is the weekend in early August 2014 when nearly half-a-million Toledo residents were told not to drink their tap water. Toxin concentrations from Lake Erie’s algae made the city’s water too dangerous to use and sent people scrambling to find bottled water, which quickly sold out in the metro-area. Learn more about the Toledo Water Crisis.

The main causes of Lake Erie’s toxic algae are excess chemicals, specifically phosphorus and nitrogen, that feed huge growths of bacteria, called blue-green algae. When the bacteria die and split open, they release toxins that can cause severe abdominal pain, paralysis, or liver and kidney damage sometimes resulting in life threatening conditions.

Toxic algae plagues Ohio’s inland lakes as well, such as Buckeye and Tappan Lakes, but Grand Lake St. Marys is the worst case. Since 2008, the Ohio Environmental Protection Agency has warned people to avoid contact with the water because microcystin levels far exceed what Ohio considers safe for recreation (6 ppb). In 2010 those levels surpassed 1000 pbb. To put that in perspective, the US EPA set a drinking water guideline of 1.6 ppb for adults and 0.3 for children of preschool age or younger.

Undoubtedly toxic algae is an Ohio-wide problem, one fueled by pollution from raw sewage, farm fertilizer and animal manure. Not only do the dangerous toxins threaten people’s drinking water, they also have disastrous impacts on local and regional economies that depend on recreation and tourism. Water and beaches covered in toxic green slime is simply bad for business and Ohio’s reputation.

Algae-causing pollution comes from several sources. But, research demonstrates improper and excessive use of fertilizer and animal manure on cropland is the main source of excess phosphorus feeding Lake Erie’s toxic algae. In fact, one of the lead federal agricultural agencies, the Natural Resource Conservation Service, found that even though 99% cropland acres in the western Lake Erie have at least one conservation practice in place, 42% of these fields still receive more phosphorus than crops actually need, accounting for 78% of total phosphorus loss. See report summary here.


Algae-causing pollution is preventable. Sewage treatment plants, home septic systems and combined sewer overflows are extremely small contributors of phosphorus pollution. Yet they must follow specific state or federal regulations. In fact many must obtain permits that set specific limits on the amount of pollution they can put into local rivers and lakes. Local health departments keep an inventory and maintenance records of all home septic systems.

Unfortunately, very few safeguards are in place to limit pollution from industrial-scale agriculture. In study after study, scientists have shown that reducing the amount of agricultural pollution flowing into Lake Erie will significantly reduce the threat from toxic algae.

It is time for better safeguards and more effective controls to reduce the amount of agricultural pollution allowed to flow into Lake Erie. We need bold action from our state leaders to restore the lake and ensure safe, clean drinking water for our families.

The OEC supports establishing common-sense laws and rules that will effectively curb the algae-causing pollution, while ensuring Ohio’s agricultural sector remains strong. Towards this end, we propose four main policy solutions:

  1. Require Plans that Prevent Pollution – We need farmers and livestock producers to develop and follow individual plans to control pollution. Certainly, no farmer intends to pollute our rivers and lakes, and in fact, many work to curb toxic algae. To ensure these efforts are successful, we need more farmers to be part of the solution by developing and following plans that include specific practices tailored to their farms and operations. This levels the playing field and prevents undermining the good work many farmers are already doing to stop pollution.
  2. Stop Over-Fertilizing Crops – We need reasonable limits on the amount of fertilizer and manure in order to avoid excess applications above what is necessary for optimal crop growth; also called the agronomic rate. Generally crops and soybeans do not require soil phosphorus levels above 40 parts per million to produce good harvests, but oftentimes farmers will apply phosphorus above this level, which increases the risk of pollution. Capping application at the agronomic rate will ensure good crop production while reducing nutrient loss.
  3. Improve Compliance and Enforcement – Laws are only as good as they can be enforced, and are there for those who need them to do the right thing. Ohio needs to strengthen its ability to hold violators accountable and institute a system of verification and compliance that ensures plans and rules are being appropriately followed.
  4. Set Pollution Limits – Ohio needs measurable limits on the amount of phosphorus, nitrogen and soil sediments allowed into our rivers and streams in order to effectively protect our water from toxic algae. We urge Ohio EPA to develop new water quality criteria specific to toxic algae. Development of this statewide criteria would make it possible to establish specific numeric concentrations for total and soluble phosphorus, nitrogen and sediments that applies to specific rivers and streams in the western Lake Erie basin watershed, and other watersheds where toxic algae is a chronic impairment.


  • Annex 4 Objectives and Targets Task Team Final Report. See here.
  • Informing Lake Erie Agriculture Nutrient Management via Scenario Evaluation. See here.