Two harmful algal blooms (HABs) were confirmed this summer in Lenawee County’s lakes. The first bloom was detected at Lake Hudson in Clayton on Aug. 21, while a second bloom was found at Devils Lake in Manitou Beach on Aug. 30. The Michigan Department of Environment, Great Lakes, and Energy (EGLE) confirmed both blooms after investigations and water testing.

Current situation at Lake Hudson and Devils Lake:  Since the confirmation of the HAB at Lake Hudson, staff have made several visits to monitor the situation. Recent observations suggest that the bloom has significantly diminished. 

At Devils Lake, the limited public access — due to most of the shoreline being privately owned — has made monitoring more difficult. However, in the accessible areas, the bloom appears to have dissipated, and there have been no resident reports of algae in the past two weeks. A recent report of potential algae along the northwestern shoreline was investigated, but no bloom was observed. 

Algae types and toxins found: At Lake Hudson, the HAB was caused by microcystis cyanobacteria, which produce microcystin, a potent liver toxin. Initial testing conducted by EGLE on Aug. 21 showed microcystin levels exceeding 10 parts per billion (ppb), which is the maximum the test strips can detect. Further lab testing revealed levels of 87.6 ppb and 81.5 ppb — well above the safety threshold of the microcystin limit of 8 ppb for recreational water activities set by the Environmental Protection Agency. Additional testing found no other toxins such as anatoxin-A, cylindrospermopsin, or nodularin.

At Devils Lake, samples collected on Aug. 30 revealed the presence of planktothrix cyanobacteria, another type of algae known to produce various cyanotoxins. EGLE did not conduct preliminary microcystin testing but sent samples to the state lab for detailed analysis. Test results were pending as of Sept. 16. 

Comparison to previous years: While the presence of HABs in Lenawee County lakes is not unusual, this year marks the first time that Lake Hudson has been tested for toxins. Therefore, there is no historical toxin data for comparison. However, both Lake Hudson and Devils Lake have experienced blooms in recent years, and Lenawee County typically sees one or two HABs every summer. The state of Michigan’s HAB map indicates that this year’s situation is not necessarily worse than in previous years, though awareness has increased.

Understanding HABs and health risks: HABs occur when cyanobacteria, or blue-green algae, grow rapidly in warm, nutrient-rich water, often creating a thick, scummy surface that can be harmful to humans, animals, and the environment. Toxins produced by these blooms can cause a variety of health issues depending on the type of toxin and length of exposure.

Residents and lake visitors should avoid areas where water appears scummy or discolored, resembling spilled paint, pea soup, or floating mats. These visible blooms can contain harmful toxins, and it’s impossible to determine their presence just by looking at the water. EGLE strongly advises people to avoid swimming, wading, or engaging in water activities where the blooms are visible.

Health risks for humans and pets: Direct contact with a HAB can lead to various health problems in humans. Skin exposure to toxic water may cause rashes, hives, or blisters, while inhaling spray from affected waters could trigger asthma-like symptoms, throat irritation, or runny eyes and nose. Swallowing even small amounts of toxin-laden water could result in gastrointestinal issues like vomiting, diarrhea, abdominal pain, and flu-like symptoms. In severe cases, exposure may cause neurotoxic effects, including headaches, dizziness, numbness, and difficulty breathing. Swallowing large amounts could also damage the liver or kidneys.

Pets are particularly vulnerable to the toxins in HABs, as they may drink contaminated water or lick their fur after swimming. Symptoms in animals often appear more quickly than in humans and can include vomiting, diarrhea, staggering, excessive salivation, and in extreme cases, death. If your pet comes into contact with HABs, rinse them thoroughly with clean water and seek veterinary attention immediately if symptoms appear.

Recommendations for safe water use: Residents and visitors are urged to take precautions to avoid exposure to potentially harmful water.

• Avoid swimming, wading, or playing in water that shows signs of algal blooms.
• Refrain from boating or water skiing in areas with blooms, as this can create water spray, which may carry toxins.
• Do not allow pets to drink or swim in water with visible scum or discoloration.
• If fishing in affected water, use caution, as parts of the fish may contain small amounts of toxins.
• After coming into contact with a bloom, shower immediately and wash any affected skin thoroughly.
• Contact a medical provider or veterinarian if you or your pet have ingested or been exposed to contaminated water.

What to do if you spot a bloom:  If you suspect a HAB, report it to EGLE by calling 800-662-9278 or sending an email to [email protected]. EGLE has noted that summer is the peak season for algal blooms, especially during periods of warm temperatures and lots of sunlight. Nutrient runoff from fertilizers and other sources can also contribute to their formation.

For more information about HABs in Michigan and how to protect yourself, visit www.michigan.gov/habs. Stay safe and help keep our waters healthy!