Hazardous algae blooms create potential challenges for livestock producersWritten by Natasha Wheeler
Blue-green algae is a problem worldwide and can occur almost anywhere with fresh, open water and the right combination of nutrients and sunlight.
“It’s a really challenging problem because, as human beings multiply, we are obliged to provide food,” noted Deon van der Merwe, toxicology section head and associate professor at Kansas State University.
“Arguably, the largest source of nutrients that eventually make their way into lakes and cause the trigger of blooms is nutrients from crop production,” he continued.
Blooms of algae
Algal blooms are composed of normal organisms that are part of the natural ecology of lakes and other water bodies.
“In many ecosystems, those organisms – called cyanobacteria – are very important primary producers. They produce the initial food for other organisms to build on, and we eventually have fish,” he explained. “The whole production of the animal ecosystem is dependent on these organisms being there.”
Cyanobacteria become a problem if conditions promote an overgrowth of the algae. Too many nutrients, coupled with intense sunlight, may lead to hazardous blooms.
“Conditions in the summer, for example with a heat wave and many cloudless, hot days, tend to promote the growth of the organisms,” he says.
One of the reasons algae blooms have become more common, according to van der Merwe, is that the landscape is changing. Many years ago, there were fewer open bodies of water.
“We create small water bodies, such as ponds for livestock and lakes for recreation and water management. This creates opportunities for the organisms to cause a problem when the conditions are right,” he comments.
Often, when there is an economic impact, it is not directly related to livestock or human poisoning. Costs are more commonly incurred when risk mitigation efforts are implemented to prevent poisoning events.
“When we have risky conditions, and we have to take action, we have to close lakes, farmers have to provide alternative water sources for livestock, etc. It really is a wide economic footprint if we think about conditions that lead to risk,” he noted.
There are various species of cyanobacteria that cause alga blooms and a variety of risks associated with them. One of the most common types of toxins created by cyanobacteria is called microcystin.
When van der Merwe first began looking into alga blooms, there was a particularly severe case of mycrocystin in a pond that dogs had access to.
“When the dogs visited the lake and ingested the material, they would typically die within a couple of days of ingestion from a very serious, rapidly developing disease due to liver failure,” he explained.
At first, the toxin causes a rapid inflammatory response, but if it is ingested, it will cause vomiting and diarrhea, leading to liver failure and death if the dose is high enough.
“Liver toxins are very important, but probably the second most important toxins, looking at the impact and number of cases we see, are some of the neurotoxic substances that are produced by cyanobacteria,” continued van der Merwe.
Anatoxin-a and anitoxin-as are two common neurotoxins that can be produced in algal blooms.
“These are quite similar in effect, but they are different toxins,” he explained. “They affect the muscular-skeletal system, and the control of the muscle becomes abnormal.”
Initially, muscle spasms or convulsions will be observed, and if the condition persists, paralysis or death can follow.
“It acts very fast. Anatoxin-a’s original name was ‘Very Fast Death Factor’ because when they injected mice with an extract of this algal scum, the mice would die very fast. Later on, when they described the structure and figured out more exactly what it was, they called it anatoxin-a,” he commented.
Toxins from algal blooms can affect any number of species, from livestock and pets to people, wildlife and even fish.
“If fish are swimming in a lake where there are high concentrations of the toxins and they are not able to avoid those high concentrations, fish might actually die,” noted van der Merwe.
The main factor impacting how different species are affected by the toxins is generally related to their exposure or how much of the toxin they ingest.
If a case of hazardous algal bloom occurs in a body of water, the first sign is typically a change in water color. In many cases, the change will be toward green, but it can be brownish or reddish, as well.
“It’s variable. Just a change in color is a danger sign,” stated van der Merwe.
Another sign is a collection of scum or an accumulation of blue, green, brown or red material along the downwind edges of a pond.
“It can be that the algal bloom will form a scum that floats on the surface, which is quite common but not always the case. Because they float to the surface, if there is a breeze that blows across the pond, they tend to blow along the water surface,” he remarked.
If a hazardous bloom is suspected, van der Merwe recommended preventing access to the water.
“What we can do about the problem depends on the type of pond and the circumstances,” he added.
In some cases, chemicals can be used to break up the algae, although they may only be effective for killing the current cyanobacteria. If conditions in the water remain the same, a new bloom can form.
“Things like copper can effectively kill the organisms. If we have a serious bloom, that is an option if the conditions are right,” he suggested.
Preventing light from reaching the water is also a recommended remedy. Adding trees for shade or adding specific products to the water that shade penetrable light are also potential solutions.
“If we have a lot of water plants in and around the water, they compete for nutrients with the cyanobacteria, so that can reduce the incidence as well. There are a lot of different things that can be used to prevent the problem from reoccurring,” said van der Merwe.