As temperatures continue to rise and days get longer, algal blooms threaten the water quality of reservoirs across Indiana, including Salamonie Lake where algae counts reached more than four times the World Health Organization’s (WHO) action level last year.
WHO uses an action level of more than 100,000 cells per milliliter to warn people when algal blooms pose a “high risk health alert in recreational waters,” according to IDEM’s website.
Algae are photosynthetic bacteria that feed off nutrients in the water and sunlight, and when levels are high enough, the neurotoxins they secrete can cause dogs and humans to get sick if they ingest algae, according to the Indiana Department of Environmental Management (IDEM).
The Indiana State Department of Health cautions swimmers to avoid water that appears scummy or has visible algae growth, which looks like a blue-green mat on the water, because exposure to algae may lead to rashes, skin, eye irritation, nausea, stomach aches and tingling sensation in the fingers and toes.
Algae levels are already ten times higher than last year’s sample during May, reaching 27,000 cells per milliliter on May 21, 2018, according to IDEM reports. Historically as the summer progresses, algae blooms get larger and peak in August, where Salamonie Lake reached 660,000 in 2016.
Algal levels often fluctuate based on the amount of rainfall, temperature and amount of dissolved oxygen in the water, so levels can fall over time, according to the Environmental Protection Agency (EPA).
Longer summer days provide more energy to the bacteria and heat the temperature of the water, which encourages growth. Algae also use excess fertilizer that is washed into the lake from farms and front lawns to grow even more rapidly, and since reservoirs are fed by runoff collected in streams and creeks, reservoirs are susceptible to algal blooms, according to IDEM’s website.
IDEM monitors algae monthly, and alerts the public when levels reach the action level. Salamonie Lake is not currently under any advisories, but residents can check www.in.gov/idem/algae for more information.