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How To Keep Your Dog Safe From Toxic Algae Blooms

We’ve been seeing many posts on social media about dogs being exposed to harmful blue-green algae in lakes and ponds over the last week so I wanted to take a few minutes to write a post to spread awareness. 

Here in Ohio, a warning was just issued by the Weather Channel urging people and pets to stay out of Lake Erie.

Lake Erie experiences harmful blue-green algae blooms every year.

In fact, according to the NOAA, every US coastal and Great Lakes states experience them.

However, they are popping up with increasing frequency due to climate change and increasing nutrient pollution.

Post updated 8/23/19 to include some of the most recent reports of harmful algal blooms. Please keep in mind that it is impossible to keep up with all the latest harmful blooms but we will update as these events are brought to our attention. 

What is blue-green algae?

Algae are natural components of marine and freshwater ecosystems, and form the foundation of most aquatic food chains

Blue-green algae is a bacteria that has qualities similar to algae and other plants. 

These bacteria are cyanobacteria, cyan means “blue-green”, and are commonly found on land and in lakes, rivers, ponds, and in wetlands and marine water.

Blue-green algae or cyanobacteria possess characteristics of algae, they make chlorophyll-a and use sunlight as an energy source for growth, but have bacterial cells rather than algal cells.

They are found in both fresh and salt waters.

Some freshwater cyanobacterial blooms can produce highly potent toxins known as cyanotoxins. These blooms are known as “cyano HABS” or toxic algae outbreaks

What is a blue-green algae bloom?

A combination of warm temperatures, sunlight, and nutrient-rich waters can cause blue-green algae to reproduce rapidly, or “bloom.”

Within a few days a clear lake, pond, or ditch can become cloudy with algae growth.

Blue-green blooms usually float to the surface and can be several inches thick near the shoreline.  

According to the Pet Poison Helpline, not all blue-green algae blooms are toxic BUT it is not possible to determine the presence of toxins without testing.

Thus, all blooms should be considered potentially toxic!

lake in ohio with blue-green algae

Harmful algal blooms are a major environmental problem in all 50 states. 

The most commonly occurring groups of freshwater algae are diatoms, green algae, and blue-green algae, which are more correctly known as cyanobacteria

  • Often looks like green paint floating on the water, but can also look bluish, brownish, or reddish-green.
  • Is made up of extremely small organisms that are hard to pick up or hold.
  • Is most common in the summer and fall but can occur anytime.

What is a toxic bloom?

A toxic algae bloom produces toxins or poisons.

In their toxic form, blue-green algae can cause illness in humans, pets, waterfowl, and other animals that come in contact with the algae. 

Algae are efficient at converting sunlight and nutrients into more algae. When conditions are right, sunny days with lots of phosphorus and nitrogen in the water, algae can multiply very rapidly, causing algae “blooms.” 

Often these blooms have the potential to harm humans or ecosystems in which case they are known as “harmful algal blooms” or HABs.

Different types of HABs may have different impacts; some can block sunlight from underwater habitats and clog fish gills.

When large algal blooms die off, their decomposition can consume much of the oxygen in the water, creating hypoxic “dead zones” where few species can survive. 

In Lake Erie, the primary species of cyanobacteria is Microcystis aeruginosa, which can secrete a toxin called microcystin.

If ingested, this toxin can make humans and animals very sick, or even cause death.

Dangerous levels of microcystin have resulted in several drinking water alerts in the western Lake Erie basin in recent years, including the Toledo outbreak which caused a three-day ban on consumption of municipal water.

In the Gulf of Mexico, especially the west coast of Florida and the Texas coast, the most frequent cause of HABs is Karenia brevis.

The toxin from this HAB is often called “red tide” and becomes airborne when waves break on the beach, which causes severe respiratory irritation.

HABs have different colors and looks. Some colors are green, blue-green, brown, black, white, purple, red and black.

They can look like film, crust or puff balls at the surface.

They also may look like grass clippings or dots in the water. Some HABs look like spilled paint, pea soup, foam, wool, streaks or green cottage cheese curd.

Some HAB’s can not be seen, especially when they are dying off, but the water can still contain toxic algae.

Eventually, the toxins break down in the water and are destroyed naturally.

What Causes HABs To Form?

Some factors that can contribute to HABs include sunlight; low-water or low-flow conditions; calm water; warmer temperatures; and excess nutrients (phosphorus or nitrogen).

The primary sources of nutrient pollution are a runoff of fertilizers, animal manure, sewage treatment plant discharges, stormwater runoff, car, and power plant emissions and failing septic tanks. 

Although all coastal states experience HABs, different organisms live in different places and cause different problems.

Other factors, such as the structure of the coast, runoff, oceanography, and other organisms in the water, can also change the scope and severity of HAB impacts. (NOAA)

How do toxic algae blooms affect dogs?

Ingestion of water that is contaminated with toxic blue-green algae can cause lethargy, vomiting, diarrhea, weakness, pale mucous membranes (the gums on a dog) and death.  (See How To Check Your Dog’s Vitals)

Dogs can ingest the harmful water by drinking it and by licking it off their bodies after swimming. 

Medical attention should be sought immediately if you suspect that your dog has been exposed to a toxic algae bloom because the exposure happens fast. 

How To Test for toxic blue-green algae blooms

I’ve already seen several posts floating around suggesting how a person can easily test for toxic blue-green algal blooms.

They include using a stick and dipping it in the water or scooping water into a jar and letting it sit in your refrigerator overnight to see if the algae floats to the top or sinks.


Please do not put yourself or your dog in harm’s way by trying to test it yourself.

If you have a pond that you’re concerned about you can purchase a pond water test kit. (Amazon affiliate link)

It won’t test for cyanobacteria but most kits will test Nitrite levels and phosphate content.

Laboratory testing is the only way to test for cyanobacteria.

How Can you and your dog Avoid exposure to toxic blue-green algae blooms?

First, if you wouldn’t swim in the water, don’t let your dog swim in the water. 

If the water doesn’t look right or smell’s funky, avoid it!

Check for signs posted in the area before you enter a lake or pond. If the body of water is being monitored and has tested for blue-green algae there will be signs posted to avoid the water. 

Stay away from ponds or rivers that less frequented and stay away from ponds and rivers on private property. These bodies of water may not be tested and will very rarely have signs posted. 

Stay up to date with your local news and weather stations.

Do not feed raw fish to a dog that was caught during a harmful algal bloom. 

Do not let your dog eat algae off the beach.

Check your state’s beach advisories. Ohio has an active list of water quality and beach advisories

Currently, there are 23 advisories for beaches along the shore and inland. The advisories consist of bacteria contamination alerts, recreational public health advisories, and elevated recreational public health advisory. 

You can also check the Environmental Working Group which released a map that tracks all toxic algae outbreaks reported in the U.S. from 2010 until the present.

They even have an interactive map that monitors for microcystins in public lakes for years 2007, 2012 and 2018 but keep in mind that this is only for lakes and bodies of water that have been reported.

Just because an area is not marked on the map doesn’t mean that it’s free from toxic algae blooms.

The NOAA has a HAB Bulletin that predicts the likelihood of respiratory irritation to people in the area in the coming days.

HAB Bulletins are posted twice a week during the bloom season.

Once again, keep in mind that only reported and/or tested bodies of water are listed on these maps. If the lake or pond doesn’t look right or if you suspect any algae, at this point it would be wise to avoid the area until blooms are no longer a threat.

Blue-green algae blooms can occur anytime during the summer, though they are normally associated with warm weather and low rainfall.

Unfortunately, dogs being exposed to and dying from toxic algae blooms is not new but with the recent reports of multiple dogs dying, the dog-loving community is nervous and rightfully so.

While harmful algal blooms may not be new to some areas like the Great Lakes, they are spreading and dog owners should stay up to date by visiting their state’s board of health department or visiting the EPA’s State HABs Resource page.

There’s an app for that! EPA’s Cyanobacteria Assessment Network mobile application (CyAN app) is an easy-to-use and customizable app that provides access to algal bloom satellite data for over 2,000 of the largest lakes and reservoirs across the United States.

EPA scientists developed the CyAN app to help local and state water quality managers make faster and better-informed management decisions related to cyanobacterial blooms.

Be safe out there friends!

It’s impossible to list all of the harmful blooms happening across the country but we’ll update as needed for what is brought to our attention. 

8/23/19 Columbia Road Beach in Bay Village, Ohio has been closed until further notice due to a toxic algal bloom. (Huntington Beach remains open as of now) Blooms are moving all around and the Lake Erie HAB has a forecasted position of the bloom for August 25th.

8/22/19 Westminster, Colorado is warning people about potentially dangerous algae at Faversham Lake. Toxic blooms have also been reported at Horseshoe Pond, Sloan’s Lake, Wonderland Lake, Thunderbird Lake and Windsor Lake Reservoir earlier in the month.

8/22/19 Shelby Farms Park in Tennesse, where 2 dogs passed away after playing in the Outback Dog Park, have closed all lakes in The Outback while they await test results.

8/22/19 In Richmond, Virginia the Virginia Department of Health is urging the public to avoid portions of Lake Anna Due to the presence of a HAB. The impacted areas include the Upper and Middle Pamunkey Branches as well as the Upper North Anna Branch.

8/22/19 Spanaway Lake in Spanaway, Washington issues an advisory, “Toxic algae advisory at Spanaway Lake. Areas of the lake with algae are unsafe for people and pets. Please visit the Tacoma-Pierce County Health Department website for more information about algae conditions.”

8/21/19 Carver Lake in Woodbury, Minnesota is advising lake users to avoid contact with the lake until further notice due to the suspected presence of blue-green algae.

New Jersey has an ongoing list from the beginning of July of lake-specific HAB information. There’s too many to list here so check it out here

We went fishing at Spencer Lake in Ohio last week. The side of the lake that we were not fishing on, a small inlet, had an algal bloom. I don’t know if it was toxic or not but there was a report of a chemical spill into the lake back in July. There were NO signs posted and the main body of the lake did not show any signs of a bloom. 


How To Keep Your Dog Safe From Toxic Algae Bloomins In ponds, rivers, and lakes



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Monday 26th of August 2019

Shelby Farms park is in Tennessee, not North Carolina.


Monday 26th of August 2019

Thank you. I've updated with the correct information

Rebecca G Bell

Wednesday 14th of August 2019

I found your site because my 6.5 mo old Labrador ate rocks unbeknownst to me until he vomited them up yesterday morning. I am monitoring him like a hawk now because of your heartbreaking article about your sweet Leroy. I am so grateful for this article too as I live around quite a few lakes and have been planning on taking both my boys for a swim soon. Thank you so much.

Tails Around the Ranch

Monday 12th of August 2019

Whoa...had no idea about the seriousness of this condition. Thanks for sharing this info. Maybe I should be grateful for living I live in a high mountain desert. Stay safe!

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