Kim Fundingsland/MDN Blue-green algae can bloom quickly on bodies of water, often releasing microcystins that can be lethal within hours if ingested. Pets and livestock are particularly vulnerable.

BISMARCK – It’s back and it’s dangerous. The North Dakota Department of Health is once again warning about the presence of blue-green algae and accompanying toxins in state waters. There is good reason.

Several livestock are already reported to have died in northwest North Dakota due to drinking water infested with blue-green algae. Elsewhere, State Health has issued exposure advisories at two popular recreational areas – the Stanley Pond in Mountrail County and the Harvey Reservoir in Wells County. It is expected that more bodies of water will be posted with advisory signs in the coming days, especially if hot conditions persist without any rainfall to refresh ponds and lakes where blue-green algae has flourished previously.

Blue-green algae, or cyanobacteria, can release toxic microcystins into the water in large quantities during an algal bloom, and the blooms can occur quickly. Water that is fine for livestock to drink can change to poisonous within hours. Ingesting water with a high microcystin content can be fatal to livestock and pets. People are not immune to the effects of microcystins either.

“Some of these cyanotixins are quick neurotoxins and can kill livestock in a few minutes to a few hours,” said Dr. Michelle Mostrom, North Dakota State University Veterinary Diagnostic Laboratory. “No treatment will be effective after the toxin has been quickly absorbed.”

Four cattle that drank from a pothole on the Lostwood National Wildlife Refuge recently succumbed to toxins produced by a blue-green algae bloom. Not far away, on a different body of water, three more cattle died. Again, blue-green algae is the suspected cause but officials are awaiting laboratory test results for absolute confirmation.

“It is surprising to us. No question about that, especially this early in the year,” said Cory Richardson, Lostwood NWR manager.

The NDDoH and the North Dakota Department of Agriculture have been involved in water sampling at the locations where the dead cattle were located. At Lostwood, the infected wetland has been fenced off so that other cattle cannot access the water. State Health has been active elsewhere as well, posting advisory signs and taking water samples when necessary.

“An advisory is issued to remind people that these blooms are most common in North Dakota in late summer, but it only takes a few hot days to trigger a bloom. Exposure can cause people and animals to become ill,” said Mike Ell, NDDoH.

Ell advises people to be aware of of blue-green algae blooms, noting that discoloration of water and smell are tell-tale signs of the possible existence of microcystins.

“Microcystins are the most prevalent toxin that we find with these blooms,” said Ell.

Not all blue-green algae blooms release nasty microcystins, but State Health urges people to err on the side of caution when it comes to blue-green algae outbreaks. Without a water sample there is no way to be certain if the water is toxic or not. Furthermore, one area of a lake can contain a high amount of toxins and another area of the same lake can be toxin free.

A lack of rainfall that would help refresh bodies of water is cited as one of the reasons for this season’s early outbreaks of blue-green algae. It could make for a very busy year for State Health. Last year they issued advisories for 15 bodies of water, a number that could be surpassed this summer if dry, hot conditions persist and people become increasingly aware of the dangers of microcystins in the water.

“There’s a lag between when we get initial reports and when we post an advisory,” warned Ell. “People need to have an awareness of blue-green blooms.”

Blue-green algae outbreaks can occur in riverine systems as well as in isolated potholes and sloughs. As a precaution in the Minot region, weekly water samples are being taken at both the Des Lacs and Upper Souris National Wildlife Refuges.