Downeast Dog News

Algae Blooms in Maine

By Judith K. Herman DVM, CVH | Sep 01, 2019

Q. I heard a lot this summer about algae blooms being toxic to dogs. Now that it is September, do I still need to worry about my dog going swimming?

A. There has been a lot of warnings this year about algae blooms. When the weather becomes cooler, the risk of an algae bloom declines. So what is blue-green algae, why do blooms happen, and what makes our dogs sick?

It has been discovered that blue-green algae is really a photosynthetic bacterium called cyanobacteria. This bacteria is part of the natural ecosystem of all lakes. When there is a high nutrient concentration in a lake, especially when the weather is warm, an algae bloom occurs. The blooms have been called blue-green algae blooms because of the color of the water that turns blue-green, green, or brown green.

Cyanobacteria can release toxins called cyanotoxins. These toxins cause liver and nerve damage, gastrointestinal symptoms, and skin irritations. The World Health Organization has concerns for these toxins since 1998. The Environmental Protection Agency developed guidelines for drinking water in 2015 and are developing guidelines for recreation. Maine has been measuring cyanotoxin levels since 2008. Lucky for Mainers the toxin level in our lakes has been low, but the lakes that have annual blooms do produce cyanotoxins.

You can identify an algae bloom by the color of the water that is a pea green, neon green, blue green, or reddish brown. The water is also opaque. You can’t see through the water to the bottom in 6 1/2 feet of water. It can also cause a bad smell, a scum along the shore and foam. It starts with blue green algae on top of the water that moves along to the shore. The water is clear at this time. You cannot drink this water and neither can your dog. The good news is that these blooms can dissipate in a couple of days.

Not all blue green algae blooms are toxic. We really don’t know why, but many factors may play a role in the toxicity of the bloom. One that we do know is the density of the organisms found in the bloom.

The reaction to the toxins is variable and depends on many factors, such as, how sensitive the dog or person is to the toxin, the concentration of the toxin in the water, how much water is swallowed to name a few. Illness to humans have been rarely reported. However, there are many reports of severe illness and death to dogs, other pets, and livestock outside of Maine.

To prevent exposure to your dog, first don’t let him swim in a lake that looks like there is blue green scum on the shore or on the lake. If he does go into the water, bathe him immediately with clean water and soap if possible. Don’t let him drink the water. Watch for signs of illness and take him to your veterinarian immediately.

We are fortunate in Maine to have a low algae bloom problem. That doesn’t mean we don’t have any. Maine DEP has been monitoring and rating our lakes. Here is the website that has the list of Maine lakes and how they rate for algae blooms.


Judith K. Herman DVM, CVH

Animal Wellness Center

Augusta, Maine