Harmful algal blooms (HABs) are overgrowths of algae that negatively impact aquatic ecosystems and shoreline communities.

In freshwater systems like the Huron River, cyanobacteria, also known as blue-green algae, commonly form HABs. These blue-green algae often grow and multiply in nutrient rich, especially phosphorus rich (eutrophic) waters during Michigan’s summer and fall when waters are warm. These blooms block sunlight and remove oxygen from the water as the bloom decays, making it difficult for other aquatic life to survive. Certain cyanobacteria also produce chemicals that are toxic to humans and other animals. These adverse effects impact water recreation, waterfront property values, and local economies. The Huron River Watershed Council has been at the forefront of local and state monitoring and prevention efforts to combat HABs in Southeast Michigan and the Great Lakes Region.

Blue-green (cyanobacterial) blooms often cause the surface of the water to appear blue or green, though other colors are possible, resembling spilled paint or pea soup. The blue-green algae can be well- mixed in the water or form scum at the surface, but the algae do not grow stems or roots which make it difficult to pick up with a stick. While a stick test can help to identify a HAB, the toxicity of the bloom cannot be visually confirmed.

For more examples and guidance on HAB identification consult EGLE’s picture guide, blue-green algae information guide, and video.

Report HABs

Report a suspected HAB to the Michigan Department of Environment, Great Lakes, and Energy (EGLE) via email at [email protected]. Please include:

  1. Photos of the suspected HAB,
  2. name of the waterbody and precise location (pin and share coordinates in Apple Maps or Google Maps),
  3. a brief description of the bloom location in the water (e.g., along the shore or next to the boat dock), and
  4. a description of the algae you suspect is harmful (i.e., color, odor, size)

Email is preferred because scientists can often determine a HAB based on a picture, but HABs can also be reported to EGLE via phone at 1-800-662-9278.

Once you report a HAB, EGLE scientists will try to visually confirm the bloom from the pictures provided. If a HAB is visually confirmed or suspected, EGLE or partner county scientists will visit the location of the HAB to perform a rapid toxin test (results in minutes) and collect additional samples that will be sent to state laboratories to identify and quantify the specific algal species and cyanotoxins present (results in days to weeks). The local and state response will vary depending on the results of these analyses. All confirmed HABs in Michigan will be recorded on the Michigan Harmful Algal Bloom Reports Map and all beach closures are reported on the Michigan BeachGuard System Page.

The name harmful algal bloom (HAB) aptly describes the ability of the algae to affect the health of humans and other animals. Certain blue-green algae can produce toxins, called cyanotoxins, that are poisonous to humans. The most common cyanotoxins produced by HABs include:

  • hepatotoxins(cause liver damage)
  • neurotoxins (alter the nervous system), and
  • dermatoxins (damage the skin and mucous membrane).

Humans can be exposed to these toxins while recreating around contaminated waters through breathing (inhalation), (2) eating/drinking (ingestion), or (3) absorption through the skin. The health risks and symptoms associated with exposure to these toxins will vary based on the type and dose of the toxin, duration and frequency of toxin exposure, and an individual’s risk factors such as preexisting health conditions.

If you suspect you were exposed to cyanotoxins, monitor yourself for signs of illness and seek medical attention for treatment of your symptoms and alert Poison Control at 1-800-222-1222. Inform your healthcare provider and Poison Control that you may have been in contact with a HAB.

Pet and Livestock Health

Other animals, including our pets and livestock, can also be poisoned by these toxins. Dogs have an especially high risk of poisoning. Dogs may be exposed to algal toxins by (1) drinking contaminated water, (2) eating toxic algae or fish from contaminated waters, or (3) by swimming or (4) grooming their fur after swimming in contaminated water. Livestock may also be exposed through similar behaviors. Such algal toxin exposures can cause animals to become ill or even die within hours or days.

If your pets or livestock have spent time in or around contaminated water, wash them off with clean freshwater, provide them with clean freshwater to drink, and seek veterinary care immediately if your pets or livestock show any signs of illness. Alert the Michigan Department of Agriculture and Rural Development (MDARD) via this form or at 1-800-292-3939.


  • Always check for beach closures, follow guidance on posted signs, and know how to identify and report a suspected HAB.
  • The toxicity of a HAB cannot be determined visually. It is difficult to predict when the toxin was released and how long it will remain in the water.

Drinking water safety

In compliance with the Safe Drinking Water Act, the US Environmental Protection Agency (USEPA) has listed cyanobacteria and their toxins on the Contaminant Candidate List (CCL) since 1998. The CCL is a list of known contaminants that may require regulation in the future. While still considered unregulated, the EPA specifically added cyanotoxins to the CCL in 2009 and in 2016, requested public drinking water systems monitor for cyanotoxins.

The Michigan EGLE and DHHS source water protection program aids public water suppliers with cyanotoxin monitoring in surface water supplies. As of 2023, the program monitors cyanotoxins regularly in surface water intakes of willing community water supplier participants. This includes Ann Arbor, the only municipal drinking water supplier that sources from the Huron River. If you are on a public water supply, consult your community’s drinking water report for more detailed information about where your water is sourced from and the water quality.

HABs in Huron River tributaries and other drainages

The Huron River watershed, like much of Michigan, has more than 300 lakes, ponds, and dams that drain into the river. The system’s waterbodies are part of what makes our watershed a beautiful place to live and recreate. These waterbodies, however, can be prone to HABs if not managed appropriately. Excess nutrients, especially phosphorus, inputs, and other stressors have led to occasional or persistent HABs in these waterbodies.

In 2022 eight HABs were confirmed and in 2023 five were confirmed in waterbodies draining into the Huron River, including Lake Sherwood, Whitmore Lake, and Little Portage Lake (see below for other confirmed sites).

The number of HAB occurrences in the watershed is rather small compared to the number of lakes, ponds, and impoundments. This may be due to a lack of reporting, however. HAB reports and occurrences in the state are on the rise though.

Before visiting or recreating in or around a waterbody in Michigan, check for beach closures or the Michigan’s HAB tracker to see if a HAB was recently spotted or confirmed at that location.

HABs in the Main Stem of the Huron River

In addition to the many lakes that drain into the Huron River, the main stem of the river also experiences HABs behind dams (impoundments) or in other slow-moving areas. There are 19 dams located on the main stem between Big Lake and the river mouth at Lake Erie Metropark and Pointe Mouillee. Historically, Ford and Belleville Lakes, which are technically impoundments behind the Ford Lake and French Landing dams, have had persistent HABs beginning in the 1970s. In response to these HABs and the need for developing a state phosphorus total maximum daily load (TMDL) for these lakes, HRWC created a monitoring program to track nutrient inputs into Ford and Belleville lakes.

The findings from HRWC’s monitoring program helped shape the TMDL for Ford and Belleville lakes and both the Manufactured Fertilizer Ordinance and Michigan Phosphorus Fertilizer Act that banned residential application of phosphorus fertilizers in Ann Arbor and later statewide. These regulations, broad public education, and numerous reduction projects have led to a decrease in the amount of phosphorus entering Ford and Belleville lakes. While this has reduced the frequency and intensity of HABs in these lakes over the years, HABs still occur and were present in 2022 and 2023.

Huron River Connection to Lake Erie HABs

The Huron River is a tributary to Lake Erie. The Western Lake Erie Basin (WLEB), where the Huron River drains, has been plagued by toxic cyanobacterial blooms every summer and fall since the 1970s. The 2014 bloom even poisoned the Toledo, Ohio drinking water for days during the infamous Toledo water crisis. This bloom persists today and is routinely monitored by the University of Michigan in partnership with state and federal agencies. Each year the National Centers for Coastal Ocean Science provides a bloom forecast based on phosphorus discharges into the lake from WLEB tributaries, mainly the Maumee River. Thus, efforts to track and reduce nutrient pollution, especially phosphorus, in the Huron River is vital not only to the health of the Huron River ecosystem and communities, but also the health of Lake Erie and our neighbors residing around the lake.

Monitoring and preventing HABs is more important now than ever, as experts agree that the impacts from HABs have increased over the past several decades and will continue to worsen due to climate change and other drivers such as excess nutrient supplies. HRWC is dedicated to restoring and protecting the Huron River watershed from HABs and other threats with data-driven approaches to address the root causes.

HRWC Nutrient and HAB Monitoring Programs

1. Chemistry and Flow Monitoring program: HRWC’s volunteer Chemistry and Flow Monitoring Program, originally formed to track phosphorus inputs to Ford and Belleville Lakes, has expanded to monitor phosphorus and other contaminant sources in Livingston, Washtenaw, and Wayne counties. Data is publicly available on our Chemistry Dashboard and Washtenaw and Wayne County Results pages.
2. Lake Erie Volunteer Science Network (LEVSN): In 2020, HRWC became a local hub for a network that includes 16 organizations monitoring water quality in 3 states around Lake Erie. This network helps to amplify our monitoring data through collaboration and the contextualization of the data to the Lake Erie watershed. More information is available in our blog post and the 2022 LEBAF Field Season Report.
3. MI Corps Cooperative Lakes Monitoring Program: HRWC is part of the Michigan Clean Water Corps (MI Corps) leadership team that supports the Mi Corps’ volunteer lake monitoring program. The program provides training, supplies, and laboratory support for community members interested in tracking the health of their lake.

HRWC HAB Prevention and Restoration Efforts

1. Policy: HRWC has played a key role in advancing legislation to reduce nutrient pollution and HABs (e.g., Michigan Phosphorus Fertilizer Act). HRWC continues to advocate for local, state, and federal regulations that promote clean waters and combat climate change.
2. TMDL Implementation Plans: HRWC develops and updates implementation plans to reduce nutrient pollution and meet total maximum daily load (TMDL) regulations. This includes plans for Ford and Belleville lakes, Brighton lake, and Strawberry lake to address phosphorus pollution.
3. Watershed Management Plans: HRWC creates plans to guide restoration and protection efforts throughout the watershed and works with our partners to implement these efforts. These plans quantify current nutrient loading and identify best management practices to reduce nutrient loading into the watershed.
4. Green Stormwater Infrastructure and Land Protection: HRWC and our partners implement and promote green stormwater infrastructure, shoreline and wetland restoration, and land protection projects to reduce nutrient runoff, fight against climate change, and prevent HABs.


Volunteer: Consider volunteering with HRWC’s or MiCorp’s water monitoring programs.
Adopt: Reduce nutrient pollution and contamination by adopting a storm drain or installing a rain garden.
Protect: Protect waterways from nutrient pollution while also fighting against climate change by upgrading your residential landscaping, shoreline buffers, or farming practices, or through conserving natural lands within the watershed.
Support: Reach out to your local, state, and federal representatives in support of legislation aimed at combating pollution and climate change.