Toxic Algae Season Is Approaching—Know the Signs, Avoid the Risks
As summer heat settles across Idaho, its rivers, lakes, and reservoirs become magnets for outdoor recreation. From boating and swimming to fishing, picnicking, or casually strolling along the shore, Idaho's waterways offer countless ways to beat the heat. With more than 2,000 lakes and 93,000 miles of rivers and streams, Idahoans are never far from a place to cool off and connect with nature.
Unfortunately, these water bodies are not always safe for recreation due to recurring outbreaks of toxic algae. These impacts are felt across the state, with 43 health advisories issued on Idaho’s lakes and reservoirs in the last three years, from Priest Lake in the panhandle all the way to Henrys Lake in eastern Idaho.
In 2022, a horse died after drinking contaminated water. Sadly, each year toxic algae is the presumed cause of death for family pets, cattle, and wildlife. Decaying blooms can cut off the oxygen in water and suffocate fish and other aquatic life. No doubt, these are tragic outcomes—made even more tragic because these deaths are preventable.
What is toxic algae?
Blue-green algae or cyanobacteria naturally occur at background levels in many freshwater ecosystems. But when conditions are right (or wrong…), populations of toxic algae have the potential to explode, producing potentially fatal cyanotoxins that can cause severe illness or death from direct contact, ingestion, and even exposure to wind-borne spray. These outbreaks are also referred to as HABs—harmful algal blooms.
Symptoms can include abdominal pain, vomiting, blistering around the mouth, fever, headache, diarrhea, cough, hives, rashes, and respiratory paralysis, and even lead to death. Dogs, cattle, and other livestock can be especially susceptible to toxic algae.
How do these outbreaks occur?
Outbreaks generally occur when there is a combination of high water temperatures and excessive phosphorus and nitrogen, which feed these bacteria. In many cases, it can be difficult to control water temperature, but there are steps that can be taken to reduce the nitrogen and phosphorus pollution that contribute to these outbreaks.
The primary sources of this pollution are wastewater systems and treatment plants, runoff from over-fertilized crops and lawns that drain to surface or groundwater, beef and dairy feedlots, fish farms, and other industrial discharges. Disturbed soils from construction sites can also contribute to this pollution.
Health Districts and other partners rely upon citizen reports to monitor potential outbreaks. Currently, the Idaho Department of Health and Welfare is responsible for issuing health advisories when IDEQ’s water sampling indicates a toxic algae outbreak. Stay tuned for more content from ICL on how to identify and report toxic algae outbreaks as well as how to advocate for more effective and proactive toxic algae prevention and monitoring.
