What is a harmful algal bloom?

The term “algae” is a bit of a misnomer when used to describe the harmful algal blooms (HAB) that have been occurring at Chippewa Lake and elsewhere. Algae encompasses a variety of organisms native to Ohio’s lakes, ponds, and rivers. Think of organisms as tiny plants but without roots, stems, or leaves. Like house and garden plants, they use light and photosynthesis to convert water and nutrients into the food they need to grow.

Many algae are harmless, but some produce dangerous toxins during times of rapid growth (called “blooms”) or at the end of their life cycles when they decompose. These toxins, also referred to as cyanobacteria, are known to make people, pets, and farm animals sick when they come into contact with the water.

Algal blooms are common occurrences throughout Ohio and around the country. Smaller cyanobacteria blooms have been detected by the park district at Hubbard Valley Park and Lake Medina. 

What is causing the Chippewa Lake algal bloom?

Cyanobacteria blooms occur due to a combination of factors including water temperature, light, and the level of nutrients (particularly phosphorus) present in the lake.

The Chippewa Lake bloom is the result of a microscopic blue-green algae called cyanobacteria, which can produce a harmful toxin called microcystin among others. Although it falls under the broad category of blue-green algae, cyanobacteria is actually bacteria, as its name suggests, and bears little similarity to typical pond algae.

A bloom is a natural phenomenon that often occurs when a water environment is out of balance -- for example, due to an excess of nutrients that promotes rapid growth. The most likely solution to combating algal blooms -- in addition to reducing nutrient levels -- is to introduce other natural processes that will restore balance to the water. Researchers are working on potential ways to accomplish that, but there are no immediate answers.

Where are the nutrients coming from?

A watershed is an area of land where all the water that flows through it drains to a common point. The Chippewa Lake Watershed comprises some 21.9 square miles, or roughly 14,000 acres, that drain into Chippewa Lake, which is approximately 330 acres in size. Major nutrient sources within this watershed include residential lawn fertilizer, agricultural fertilizer, and faulty household septic systems.

What is the park district doing to address the issue?

Over the past several years, the park district has worked to restore native wetlands on park property within the watershed. Natural wetlands act like giant sponges that absorb flood water and nutrients before they reach Chippewa Lake. However, a large portion of the wetlands in the watershed were drained in the 19th century to make the land suitable for farming and residential development.

The park district has conducted regular water tests since a bloom was first reported in 2014, and alerts the public when toxins pose health dangers. The park district is working collaboratively with the Chippewa Lake community to increase public awareness and involvement. In addition, it contracted with Aqua Doc for an in-depth analysis of nutrient levels (click here for the summary) and is partnering with a Cleveland start-up company on new bioreactor technology that may help manage harmful algae.


What do the different warning levels mean?

Per Ohio’s Harmful Algal Bloom Response Strategy for Recreational Waters, a Recreational Public Health Advisory is issued when toxin levels reach six (6) parts per billion. It warns vulnerable persons, as well as pets, to avoid contact with the water.

When toxin levels reach 20 ppb, an Elevated Recreational Public Health Advisory is issued that warns all persons and pets to avoid all contact with the water.

Warnings remain in effect until two consecutive tests taken at least one week apart show levels have dropped below these thresholds. 


How can I find out about current water conditions at Chippewa Lake?

Before heading to the lake, visit www.MedinaCountyParks.com and click on News for the latest information on Chippewa Lake water conditions.

Email parks@medinacountyparks.com if you’d like to receive updates by email. Information is also posted on Twitter and Facebook.

A new color-coded flag system is in place at the lake to alert swimmers and boaters to water conditions. The flags are flown at the public boat ramp on the southwest corner of the lake and are visible from other locations around the lake. Color keys posted at the boat ramp, public beaches, and private boat launch areas explain what each flag means:

Green flag – Lake open

Yellow flag – Boating permitted at idle speed only

Orange flag – Warning: Algal toxins present

Red flag – Danger: Avoid contact with the water


Learn More

U.S. Environmental Protection Agency

Ohio Environmental Protection Agency 

Center for Disease Control