Understanding the Toxic Blue-Green Algae

By Kayla Moxley, Girls Who Hike Los Angeles Ambassador

It all started out as a fun, adventurous road trip up to the Pacific Northwest. Two humans and their dogs living out of a car for over a week driving over 3,500 miles to see four states and as many trails as we could hike along the way. Somewhere in Oregon, we were driving down Highway 58 through the Willamette National Forest when we spotted a stunning green lake. My boyfriend asked me to pull over so we can let the dogs out to stretch their legs and of course, for the picture opportunity. I pulled over to a small parking lot that was clearly for the trailhead nearby, but we found a smaller trail that went down to the lake. We both took our dogs down to this lake which clearly was below its normal levels as we walked on a grassy bank. I walked my dog, Tucker down to the water, in awe of the beautiful green color of the water. The trees above were green and yellow and it looked like a view off of a postcard.

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I let Tucker put his paws on the water and drink some fresh natural water. I contemplated letting him off leash to get some play time in, but I knew I wanted to hit the road again soon so I left his leash on. After Tucker slurped up some water, I placed my hand in the water and to my surprise, it was decently warm. I looked over and saw a child fully in the water playing with a floating log. After spending some time wading in the water and getting our pictures, my boyfriend and I decided we needed to get back on the road to make our next destination on time. We put the dogs in the car and I ran over to the other side of the parking lot to read quickly about the nearby trails. We saw the signs and admired the amount of trails that one trailhead had to offer and right next to it I saw a sign that read “CAUTION: Toxic Algae May Be Present. Lake may be unsafe for people and pets”.

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My heart immediately sank. We immediately got into the car and admitantly drove with the end goal of getting out of the forest so I can rush my dog to a vet. When we got a spot of service, my boyfriend looked up the symptoms and prognosis of dogs who drank water with this algae. Eventually he had to stop reading it to me because there was not one story of a dog surviving drinking water contaminated with this algae. While we had service, I called animal poison control and asked what I should be looking for and how long before symptoms will appear. The poison control representative assured me that since an hour has passed since Tucker drank the water and he was not showing any symptoms, he is likely in the clear as most symptoms show within the first hour and hit the digestive system first. It was reassuring to hear, but the paranoid part of me still wanted to get out of the forest to get to a nearby vet. We were two hours away from civilization and I drove as fast as I could in snow and rain while worried sick that my dog was going to pass away in the backseat before I could get him help. As soon as I drove us out of the forest, I pulled over and offered food to Tucker, which he gobbled down normally. Since he showed no symptoms and it had been nearly three hours since he drank the water, I made the decision to keep driving to our destination and that he did not drink any contaminated water. 
Since I have never heard of a toxic algae that could be lethal, I decided to dig deeper and did a ton of research on it because I would’ve drank the water myself if I were backpacking.

So what is this toxic algae? Blue-green algae, also known as cyanobacteria, is a bacteria that produces toxins called microcystins, which has the ability to cause some serious damage to the liver, as well as anatoxins, which is a neurotoxin. Cyanobacteria is what we know as “pond scum” and is often blue-green in color but can also be blue, “pea green”, red-ish purple, or brown. Blue-green algae can produce quickly under the right environmental conditions and they gather and float to the surface creating an algae bloom where it forms scum layers. Cyanobacteria thrives most in warmer conditions, typically late May-October, when water levels are low, and when water is stagnant. An increase in agricultural runoff provides more nutrients for the bacteria to feed on and grow into larger blooms. Toxicity to humans are likely not to be lethal, but can cause serious health reactions through ingesting contaminated fish, dermal (skin) contact, inhaling aerosolized contaminated water, or consummation through drinking contaminated water. Symptoms of contact with blue-green algae that produce microcystins include skin rash, vomiting, diarrhea, cramps, dizziness, black-tarry stool, lethargy, weakness, and liver damage. Symptoms of blue-green algae that produce anatoxins include tremors, difficulty breathing, inability to walk, muscle rigidity, convulsions, and respiratory paralysis.

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Rivers and lakes across the country have seen an increase of blue-green algae blooms that are putrid smelling and looks like thick pea soup. Cyanobacteria occur naturally in lakes with low concentration that are not harmful, but when levels of key nutrients like phosphorus increase and combined with hot temperatures and stagnant water, the toxicity increases. Pets and children are particularly susceptible as both typically ingest more water while swimming while dogs will lick their fur clean. Symptoms can be seen typically within 15 minutes to an hour of exposure of cyanobacteria. There is no known way of identifying if an algae bloom is benign or toxic without a laboratory analysis. As hikers, we have to use our better judgement. Boiling and chemically treating the water may kill the algae, but once the cyanobacteria cells rupture, the toxins are released and are still viable and can become more potent rather than having the cells rupture and toxins released in the gastrointestinal system. It is safest to study recent blooms recorded on http://www.mywaterquality.ca.gov/habs/ and if you come across a body of water that appears green with thick paint-like scum layer, it is best to take heed and avoid swimming or consuming the water for both humans and pets. Even though it can cause illnesses in humans, it is extremely life threatening for pets and prognosis is poor when pets are exposed. It is so important for hikers, backpackers and adventurers to carry their own drinkable water for themselves and for their pets. If you have had physical contact with potentially contaminated water (such as swimming), immediately rinse off with fresh water. Report any pungent smells or taste in your drinking water to a local water utility and adhere to signs posted around a body of water that toxic algae may be present. Resources for potential contamination and exposure are ASPCA Animal Poison Control Center (888) 426-4435 and American Association of Poison Control Center (800) 222-1222.


Kayla is the ambassador for our Los Angeles, California chapter. You can join her local meetups and discussions through the Los Angeles chapter by clicking here.