With rising temperatures and record heat waves across the planet, we are seeing an increase of blue-green Algae blooms in bodies of water. Sometimes, these blooms are toxic and can be harmful, and even deadly to dogs.

Harmful blue-green algae blooms are just one of the many potential dangers to look out for when it comes to recreating with dogs.

Knowing that blue-green algae blooms exist and understanding how to avoid them are key to keeping your dog safe when you are planning a trip near water.

What are Blue-green Algae Blooms?

Blue-green algae is not actually algae. It’s a bacteria that has similar qualities to other aquatic plants and algae. The bacteria are called cyanobacteria–”cyan” meaning blue-green.

They are thought to be the oldest known fossils at 3.5 billion years old and are one of the largest and most important groups of bacteria on the planet.

Some cyanobacteria species cause toxins. 

The algae blooms are most commonly found in non-flowing freshwater sources, usually along the shores of lakes, ponds, and rivers during hot months with little rainfall. They can also form in backyard pools and ponds if not cleaned regularly, as well as in estuaries and marine waters. 

When a bloom occurs, the often electric green blooms float to the surface of the water, causing a scene that looks like a paint spill. 

However, not all blooms are large or even noticeable. Some blooms are blue, brown, or reddish-green.

Most bodies of water are not tested for cyanobacteria, so there is no way to know without testing. 

Some state health departments will issue a warning for certain bodies of water in more populated areas, but the rule of thumb is that if it looks like there was a paint spill or the water looks like pea soup, stay out.

What Causes Blue-green Algae Blooms?

Harmful algal blooms are most common during the summer or early fall, when the combination of hot temperatures, nutrient-rich water, and lots of sunshine create the perfect scenario for rapid reproduction, or blooms. 

Blue-green algae prefer water temperatures higher than 75°, which is why they are often found near shorelines in places where the water does not generally reach that temperature, like in the Pacific Northwest.

Other factors that can lead to toxic algae blooms include pH changes in the water, nutrient loading, trace metals, and change in water flow.

The blooms can happen quickly, much like the plants in your garden. Ever noticed how small they seem one day, and then after several days of hot weather and sun, they’ve exploded? Blue-green algae behaves the same way.

There is evidence that certain human activities are leading to an increase in the incidence of harmful algae blooms worldwide. These activities may include:

• Discharges from wastewater treatment plants
• Concentrated feeding operations (factory farming)
• Runoff from storms, agricultural fields, and roadways

What is a Toxic Algae Bloom?

Not all blue-green algae produces the cyanobacteria.  When toxic, the blue-green algae can cause illness in humans and animals, including death in pets and livestock that ingest the water.

The majority of blue-green algae blooms are not toxic, but it is impossible to identify blue-green algae blooms by sight alone. In order to confirm a toxic algae bloom, the water needs to be tested.

The Minnesota Pollution Control Agency listed a couple ways you can test the algae for free at home or directly at the source. No test for blue-green algae is definitive, but can give you an idea of what you’re looking at in the water.

Will Blue-Green Algae Hurt My Dog?

Toxicity presents differently in humans than it does dogs and other animals, mainly because people are not generally drinking water or ingesting much while swimming or recreating. 

Dogs can become exposed to cyanobacteria through:

• Ingestion
• Direct contact with the skin
• Inhalation from breathing in contaminated water

When dogs swim or play, they ingest a lot of water, which is a problem when it comes to cyanobacteria. They can also consume the bacteria by licking it off their fur or paws once they exit the water.

Signs of toxic bloom poisoning in humans includes:

• Skin rashes on humans after swimming
• Vomiting
• Diarrhea
• Sore throat
• Cough
• Headache
• Eye irritation

Because dogs are more likely to ingest a higher concentration of harmful bacteria, the effects are much worse, and can often result in death. Animals can experience symptoms within 15-20 minutes after ingestion.

Symptoms of Blue-green Algae Toxicity in Dogs

In addition to diarrhea and vomiting, cyanobacteria can cause nerve and liver poisoning in dogs, which is what leads to fatalities.

Neurotoxin (Nerve) Poisoning symptoms include:

• Weakness
• Inability to walk or stand
• Difficulty breathing
• Seizures
• Death

Hepatotoxin (Liver) symptoms include vomiting and diarrhea and can present within hours or days after exposure.

If you notice any of these symptoms in your dog, contact your veterinarian immediately. When caught early enough, your vet may be able to flush out the toxins before damage sets in.

Rinse your dog off with fresh water immediately after exiting the water if you suspect they have swum in an harmful algae bloom.

Tips for Avoiding Blue-Green Algae Poisoning in your Dog

Again, you cannot tell if the blue-green algae bloom is toxic just by appearance. It has to be tested to confirm toxicity. 

Check before Heading out

Local governments will often test popular bodies of water and put up signs, update websites, and send out notifications on social media and news outlets. Follow your regional government health authorities and news sources for up-to-date information. 

Lesser used bodies of water, however may not be tested. 

If you notice what looks like an algae bloom, you can take a photo, note the location, and send it to your regional government to request a test. They won’t always test, but it’s good for them to know what’s out there.

When in doubt, stay out

If the water looks suspicious, don’t let your dog near it. It’s just not worth the risk. 

Control Your Dog around Water

If you have a dog like Sitka who will just beeline for any body of water in sight, keep them on a leash or in heel around bodies of water. 

If your dog does not have a solid recall, then you should keep them on leash if you know you will be retreating around water.

Blue-green algae blooms can definitely be a bummer if your dog likes to swim, or if you enjoy paddle boarding together, so it’s good to have a second recreation option if you are planning a water adventure. 

Last time I was turned away from a lake, my friend and I discovered a beautiful waterfall nearby and the dogs happily frolicked in the river. You never know what you might discover when Plan A doesn’t work out!