An article in the New Hampshire Union Leader last week noted an outbreak of cyanobacteria on some ponds and lakes in New Hampshire. “Amanda McQuaid of the (NH) Algal and Cyanobacterial Bloom Program advises that people be cautious of lake water that has a surface scum with water that changes color or appears to have green streaks or blue-green flecks …(S)he advises pet owners to keep their animals out of the water.”

This is earlier than usual, most likely a result of the unusual June heatwave. The article also stated that regular monitoring and testing is not being done this year, but they will still issue warnings when they are alerted to algae blooms at this website:

I originally wrote about this topic 15 years ago when it came to my attention that toxic algae can be fatal to dogs, other animals and people. Even though most of us have been unaware of this problem, the first instance of cyanobacteria in New Hampshire was as long ago as 1960. Since it can be extremely dangerous, and we have an early start to the bacteria season, this feels like a good time to reprise that column:

An email alert from the “Whole Dog Journal” ( read: “Freshwater ponds, lakes and streams could be deadly to your water dog if they contain toxins borne by blue-green algae (Cyanobacteria).

“If the water where your dog swims looks cloudy, with a green or blue-green cast, you should suspect a dangerous overgrowth of blue-green algae, and prevent your dog from ingesting the water.

“Whole Dog Journal has confirmed a report from a Michigan dog owner whose 9-month-old Border Collie died shortly after swimming in a pond near Fenton, Mo.”

The article went on to say, “The emergency vet told the dog’s owner that he had recently seen other dogs die of blue-green algae toxicity — a condition that can kill pets, livestock and people who drink the contaminated water. ‘Had I ever heard of the danger of blue-green algae, I never would have allowed my dogs to swim in that or any other pond; I would have bought a pool,’ the owner told Whole Dog Journal.

“However, when the man whose dog died this week in Michigan contacted his state’s Department of Natural Resources, looking for more information about the dangerous algae, he says he was told that the toxic blooms rarely occur except in late summer, and not to either panic or panic other people. ‘Had someone else panicked, we wouldn’t be having this conversation right now,’ the grieving owner told the state representative.

“Dog owners should be aware that toxic algae blooms usually occur in late summer or early fall, but can occur at any time. They can occur in marine, estuarine and (especially) fresh water. The latter are of the greatest concern to dog owners, as dogs are commonly taken to ponds, lakes and reservoirs in the summer for recreation, exercise and cooling — and they routinely drink the water. Some of these algae blooms look like foam, scum or mats on the surface of the water. The blooms can be blue, bright green, brown or red (‘red tide’ is perhaps the best-known so-called ‘harmful algal bloom’) — but some blooms may not affect the appearance of the water. The water may or may not smell bad. As a further difficulty to dog owners trying to protect their dogs, not all algal blooms are toxic!”


Gail Fisher, author of “The Thinking Dog” and a dog behavior consultant, runs All Dogs Gym & Inn in Manchester. To suggest a topic for this column, which appears every other Sunday, email gail@alldogsgym. com or write c/o All Dogs Gym, 505 Sheffield Road, Manchester, NH 03103. Past columns are on her website.