Is the algae in my pond dangerous to my dog?

Why some pond algae are dangerous to dogs

Most green growth in a pond is ordinary algae or aquatic plants, which are a nuisance but not poisonous. The concern is cyanobacteria. Several kinds can produce toxins, and the same species can be toxic one week and not the next.

Two groups of toxins come up most often in dog poisonings. Microcystins mainly damage the liver. Anatoxin-a attacks the nervous system and can act very fast. Other cyanotoxins, such as cylindrospermopsin, also occur in fresh water.

Dogs are especially exposed because of how they behave around water. They swim, drink the water, chew on floating mats or dried scum along the shore, and then lick their wet fur. A review of U.S. cases led by CDC scientists counted 231 bloom events and 368 dog poisoning cases between the late 1920s and 2012, and the authors noted that this likely represents only a small fraction of what actually happens.

Can you tell a toxic bloom by looking at it?

No. Color, smell and texture do not tell you whether toxins are present. A bright green, paint-like scum can test clean, and water that looks only slightly cloudy can carry toxin. Toxins can also linger in the water after the visible bloom fades.

That is why the CDC message for pet owners is simple: when in doubt, keep pets out. Treat any of these as a reason to keep your dog away:

• Water that looks like pea soup or spilled paint, or is streaked blue-green, green, brown or red
• Scum, foam or mats floating on the surface or piled up along the shore
• Dried crusts of algae on rocks, docks or the bank
• Dead fish or other dead animals at the water's edge
• Posted advisory signs, or a recent bloom report for that water body

What to do if your dog has been in the water

If your dog swims in or touches water you're unsure about, the CDC advises washing the dog off right away with clean water. The goal is to keep your dog from licking algae or toxin off its coat. Wear gloves if you can, and wash your own hands afterward.

1. Get your dog out of the water and away from the shoreline.
2. Rinse the coat thoroughly with clean water, and keep your dog from licking its fur until it's clean.
3. Watch your dog closely for the next day or so.
4. Call your vet right away if you see any symptom below, and tell them the dog was in water that may have had a bloom.

Do not try to treat a suspected poisoning at home. There is no home remedy for cyanotoxin exposure, and fast professional care is what saves animals. The CDC says plainly that harmful algal blooms can be deadly for animals and that quick supportive care can save their lives.

Symptoms to watch for

According to the CDC, call a veterinarian if your animal shows any of these signs after contact with water:

• Vomiting or diarrhea
• Loss of energy or loss of appetite
• Excessive drooling or foaming at the mouth
• Stumbling or falling
• Tremors, seizures or convulsions
• Any unexplained sickness within a day or so after being in the water

Animals can become seriously ill within hours of exposure, and nerve toxins can act even faster. If you're unsure whether a symptom counts, call anyway. A vet would much rather hear from you early.

How to report a bloom in Florida

Reporting helps state scientists sample blooms and warn others. In Florida, the Department of Environmental Protection takes freshwater algal bloom reports through its toll-free hotline at 855-305-3903 or its online form. Report fish kills to the Florida Fish and Wildlife Conservation Commission at 800-636-0511. If a person has symptoms after exposure, the Florida Department of Health directs people to the Florida Poison Information Center at 1-800-222-1222.

Outside Florida, check your state's environmental or health agency for its reporting line. Many states post bloom advisories online.

Should you test your pond for toxins?

If your dog uses the pond often, testing can tell you what your pond actually produces over a season, which helps you decide when to fence it off or keep the dog leashed. For freshwater ponds we offer a +$89 toxin test (freshwater only: microcystin, anatoxin, cylindrospermopsin) as an add-on to our $179 Pond Health Check. One result is a snapshot. Toxin levels change from week to week, so repeated tests over time tell you far more than a single sample.

Blooms that keep returning usually have a cause, often phosphorus stored in the pond bottom that feeds algae every summer. We look at the water and the sediment over time to find that cause, then guide you through working with the right vendor, and we take no referral fees. If you'd like a first look, you can get a free read of your pond from satellite data (water about 1 acre and up), or talk to a scientist: 573-WATERDX.