Two dogs died after exposure to harmful benthic algae in the Columbia River near Camas, Washington. The incidents have prompted renewed warnings for pet owners across the country, as more evidence emerges of the lethal dangers lurking in increasingly common algal blooms.

According to The Columbian, in the most recent case, the dog’s symptoms began with tremors, drooling, and stumbling, progressing rapidly to death despite emergency veterinary care. The stomach contents tested positive for anatoxin-A, a fast-acting neurotoxin found in blue-green algae.

Toxic algae killed two dogs after a walk near the Columbia River.

What Is Benthic Algae—and Why It’s So Dangerous

Unlike surface algae blooms that float visibly in water, benthic algae grow on riverbeds and lake bottoms. They can detach and rise to the surface, forming gelatinous mats that resemble plant debris. These mats often carry lethal cyanotoxins.

Environmental health specialist Maggie Palomaki explained to The Columbian that Clark County didn’t even begin testing for this specific algae until late 2024. “This is new to all of us,” she said. The algae are often slimy and slippery and may not appear threatening—until it's too late.

Benthic algal mats are hard to spot and extremely dangerous.

Algae Strikes Fast and Leaves Little Time to Respond

Toxic algae exposure is not unique to the Pacific Northwest. A 2-year-old retriever named Cove died in the UK after licking a dead fish contaminated with blue-green algae on the shore of a lake. Cove never entered the water but still collapsed within minutes. His owner, Jan Eggington, said he was already paralyzed by the time she caught up to him, Newsweek reports.

Symptoms like staggering, vomiting, seizures, and respiratory failure can start within 15 minutes of contact, warns the EPA. Unfortunately, there is no antidote.

Dogs can ingest toxins by licking fur or eating shoreline debris.

A Nationwide Threat to Dogs and Wildlife

Across the U.S., blue-green algae have been linked to hundreds of animal deaths. One of the most devastating accounts came from North Carolina, where three dogs—Abby, Izzy, and Harpo—died within hours after playing in a pond.

“What started out as a fun night… ended in the biggest loss of our lives,” their owner, Melissa Martin, described the nightmare to CNN.

Martin and her friend had not noticed any posted warnings, nor had they recognized the danger in the seemingly tranquil water. Within 15 minutes of leaving the pond, Abby began to seize. By midnight, all three dogs had died.

Algae blooms are worsened by warm, slow-moving, nutrient-rich water.

Climate and Human Activity Are Making It Worse

Experts warn the frequency and severity of toxic algal blooms are increasing, exacerbated by warm weather, stagnant water, and nutrient runoff. Nitrogen and phosphorus from fertilizers, sewage, and animal waste feed these blooms. And warmer temperatures speed up their growth.

According to the Washington Post, scientists now consider toxic algae a “major environmental problem” in all 50 states.

Prevention: What Pet Owners Need to Know

Protecting your dog starts with vigilance. Experts warn against letting pets swim or drink from any water that has a film, scum, or unusual color. Be especially cautious during warm months, after rain, or when water is still. The Kennel Club recommends keeping dogs far from not just the water, but also the shoreline, where dried algae or contaminated fish might pose a risk.

If exposure is suspected, rinse pets thoroughly with clean water and contact a veterinarian immediately. Human contact with toxic blooms can also cause illness, the Centers for Disease Control and Prevention reports, so wear gloves and wash thoroughly after handling contaminated pets or water.

Climate change is fueling the rise of harmful algal blooms.

A Call for Action and Awareness

Some survivors have turned their grief into action. After her loss, Melissa Martin launched a campaign to install warning signs and educate pet owners.

“I will not stop until I make positive change,” she told CNN.

In Clark County, officials are now expanding educational outreach, placing warning signs at marinas and boat launches, and tracking incidents through updated maps, The Columbian reports.

Tragic stories like these serve as stark reminders: One moment of contact can become a life-or-death emergency. Staying informed, staying alert, and spreading the word could save another dog’s life.