The spread of Harmful Algae Blooms (HABs) impacting water bodies throughout Central Oregon and surrounding areas creates cause for concern as exposure, ingestion and inhalation can have life threatening affects.
It’s true that many types of algae are safe, so the proper identification of toxic algae can be life saving for humans and pets alike.
Also known as blue-green algae and referred to as HABs or cyanoHABs, cyanobacteria produce dangerous cyanotoxins forming blooms under certain conditions like warm water, nutrient pollution, stagnant water, sunlight, and climate change. While naturally occurring, poisonous algae blooms are increasing in prevalence due to human caused high nutrient levels from agricultural runoff, farm waste leakage, wastewater discharge, septic failures, and even urban and suburban stormwater runoff containing nutrient rich chemicals, as well as the warming of waters around the world resulting, at least in part, from human activities.
According to the National Aeronautics and Space Administration, “It is undeniable that human activities have produced the atmospheric gases that have trapped more of the Sun’s energy in the Earth system. This extra energy has warmed the atmosphere, ocean, and land, and widespread and rapid changes in the atmosphere, ocean, cryosphere, and biosphere have occurred.”
Undeniable scientific evidence exists from experts on the Intergovernmental Panel on Climate Change proving that greenhouse gases, like carbon dioxide, are warming Earth. As waters continue warming and nutrient levels keep rising, protection from cyanobacteria remains emergent.
Particularly vulnerable to this toxic algae are children and pets due to their smaller size and likelihood of swimming in or drinking affected water, with illness ranging from mild to severe, including death.
Effects of cyanotoxins vary by toxin classification and level of exposure. Hepatotoxins can damage the liver, dermotoxins can produce skin reactions and respiratory distress, and neurotoxins can impair neurologic function.
Unfortunately, boiling affected water or using standard home and personal filtration and treatment devices are ineffective at removing cyanotoxins, and eating poisoned fish – even cooked – can cause illness.
For humans, symptoms of ingestion generally appear within 24 hours of exposure, lasting up to 72 hours, and are similar to food poisoning, including headache, nausea and vomiting, diarrhea, cramps, dizziness, numbness, fainting, and fever. Skin and eye irritations can occur when sensitive skin comes into contact with toxic water. If illness arises after exposure to affected, or potentially affected, water, seeking immediate medical care is paramount.
Dogs can become severely ill, or die, within minutes to hours of exposure, from swallowing toxic water, eating floating mats or dried crust along shorelines and rocks, or even from simply licking their fur. Symptoms to look for include vomiting, diarrhea, drooling, trouble breathing, problems walking or standing, convulsions and appetite loss. Immediate veterinary care is crucial if they show any of these signs after exposure to bloom-affected, or suspected, water.
Although toxins can be present even in clear water with no visible signs, this toxic algae often appears in several forms and knowing what to look for – both in the water and nearby warning signage – is imperative to staying safe.
Cyanobacteria blooms manifest as two major types: planktonic (floating in or on top of the water) or benthic (mats attached to the bottom of water bodies). Oregon Health Authority urges that “When recreating, people—especially small children—and pets should avoid areas where the water is foamy, scummy, thick like paint, pea-green or blue-green, or if thick green or brownish-red mats are visible, or bright green clumps are suspended in the water.”
Spring and summer months, when the air warms, sunshine persists and water temperatures rise, are most pervasive for harmful blooms.
In 2018, Oregon Health Authority mandated cyanotoxin monitoring for drinking water throughout the state. Most recreational Oregon water bodies are not routinely monitored for toxic algae blooms, but in some places where HABs have been known to occur, warning signs are posted, including what to look for, symptoms and what to do if a human or pet becomes ill.
CyanoHABs don’t just affect recreational use. They have been reported to affect drinking water in areas where nearby residents rely on lakes and reservoirs, polluting tap water when treatment facilities are outdated or not well maintained, and are commonly known to kill wildlife and plants, ultimately affecting entire ecosystems.
Nontoxic algae blooms are also impacting the environment, causing dead zones where decreased oxygen levels destroy aquatic life.
Natural Resources Defense Council noted the large price of cyanobacteria’s affect in “reducing tourism, recreation, commercial fishing, and property values and increasing water quality monitoring, management, and treatment costs” as upwards of $4 billion annually for the U.S. alone.
When planning a trip to any water body, especially during warmer months, researching current water advisories beforehand is strongly recommended and generally easy to access online.
Central Oregon residents recreating near the McKenzie River, Keizer Slough, Blue River Reservoir, Cougar Reservoir and Blue River can view Eugene Water and Electric Board’s interactive Harmful Algal Bloom Monitoring Map.
Many states with known blue-green algae blooms or affected waters offer current advisories lists and often interactive HABs reports maps. To view current Oregon advisories, HABs interactive map and cyanoHABs photo gallery, or report a HAB or HAB-related illness, visit Oregon Health Authority online, by phone or email.
In situations where the presence of cyanobacteria is unknown, but suspected, Oregon Health Authority warns, “When in doubt, stay out!”
This article appears in Source Weekly June 12, 2025.
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