Expert warns of toxic algae in water

One of the most dangerous developments in livestock and fishing ponds during the peak of summer is the appearance of blue-green algae blooms, said Scott Jones, small impoundment extension specialist

One of the most dangerous developments in livestock and fishing ponds during the peak of summer is the appearance of blue-green algae blooms, said Scott Jones, small impoundment extension specialist for the University of Arkansas at Pine Bluff. When seeking relief from the summer heat in ponds and lakes, individuals should be careful not to expose themselves or their pets to these potentially harmful algae blooms.

Jones said cyanobacteria (or blue-green algae) are photosynthetic bacteria that can out compete beneficial green algae and dominate the algal community of a pond during the hottest parts of the year.

"Not all blue-green algae species are toxic," he said. "However, of the few thousand species of blue-green algae, several are capable of producing neuro- or hepatotoxins that can cause sickness to mortality in animals hours to days after ingestion. Fish are also vulnerable to these toxins, and significant mortalities can occur during excessive blue-green algae blooms."

When blue-green algae scums appear on the surface of a pond, they often resemble spilled paint in hues of bright to deep green, bright blue, brown, red and grey.

Jones said there are two do-it-yourself methods individuals can use to test water for blue-green algae.

"Fill half of a pint or quart-sized clear jar with the affected water and leave it in the refrigerator overnight," he said. "If by morning the green material in the water has settled to the bottom, non-toxic green algae are likely the dominant variety. However, if the green in the water is congregated near the water's surface, potentially dangerous blue-green algae are likely present."

Another test can be performed if surface mats are present in the affected water. Dip a long, sturdy stick into the mat and slowly pull it back out. If the stick returns with stringy filaments hanging off, the mat is probably harmless filamentous algae or pondweed. But if the stick appears to have been dipped in green paint, the mat likely consists of potentially dangerous blue-green algae.

Potentially toxic blue-green algae species are not always producing toxin, Jones said. The only way to confirm the presence of toxin is through laboratory testing. The Arkansas Water Resources Center Water Quality Lab, which can be reached at (479) 502-9843, and several private labs can identify algae and test for the presence of algal toxins. For a list of additional labs, contact the Arkansas Department of Environmental Quality at (501) 682-0744. The analysis can take several days, so avoid exposure and keep animals from the affected water until results are returned.

"Signs of acute blue-green algae poisoning in livestock include weakness, lethargy, staggering, difficulty breathing, convulsions, bloody diarrhea, pale-colored mucous membranes and death in severe cases," Jones said. "Survivors of acute exposure, and likely those exposed to chronic lower concentrations of cyanotoxins, can experience weight loss and photosensitivity (sunburns to exposed skin)."

Human external exposure to cyanotoxin can result in skin, eye, nose, mouth and throat irritation. Ingestion can cause headache, lethargy, abdominal pain, vomiting and diarrhea. High levels of cyanotoxin consumption can even cause death.

HOW TO CONTROL BLUE-GREEN ALGAE

Jones said blue-green algae blooms can be treated with copper sulfate or sodium carbonate peroxyhydrate. Animals should be excluded from the pond for at least one week after herbicide treatment because toxin concentration will likely temporarily increase as the blue-green algae is dying from the herbicide.

For long-term control, a nutrient binder is recommended to strip phosphorous from the water to slow the return of the bloom. Apply either aluminum sulfate or a commercially available flocculant (such as Phoslock or Phosclear) about one week after herbicide application. It may take a few cycles of this herbicide/flocculant treatment during the year to slowly bring nutrients and algae blooms back under control.

"Aquatic dye, particularly those containing Acid Yellow 23 and that are EPA-registered, can help somewhat with suppressing algae blooms," he said. "There are no practical biological controls. The best solution is prevention by minimizing nutrient input from fertilizer runoff, poultry litter, livestock loafing/wading in the pond and over-feeding fish."

Old, excessively shallow livestock ponds (with an average depth of less than 3 feet) may be better off with a full pond renovation, which entails draining and excavating accumulated sediment, restoring shoreline slopes and deepening the pond back to at least an average depth of 4 feet with a max depth up to 10 to 12 feet. If renovation is deemed the best solution, individuals should strongly consider installing external watering systems and fencing off the pond from animal contact.

For more information on blue-green algae or pond maintenance, contact Jones at [email protected] or (870) 575-8185.

Will Hehemann is an Extension Specialist -- Communications with the University of Arkansas at Pine Bluff School of Agriculture, Fisheries and Human Sciences.

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Expert warns of toxic algae in water