When the blue-green algae does bloom it is very likely that someone, somewhere, is going to suffer in some way as a result of this seasonal phenomenon that has been going on for literally millions of years. Whether it is an individual, one of their pets or livestock owned by them, some animal is likely to become ill from drinking water from a source in which a toxic member of the blue-green algae family grows. Not all blue-green algae are toxic but about 200 known species are, so taking a risk by drinking water from a source where the bloom is present is not worth chancing. Toxic blue-green algae are commonly known as cyanobacteria and there are a host of subsets that can produce illness if ingested. Most often the symptoms observed are the result of either nervous system or the liver involvement.
Experts tell us that blue-green algae existed on Earth long before man took his tentative first step on this planet. During the course of its long history it has had the opportunity to modify its growth patterns to meet the ever-changing climatic and other conditions it has encountered. It has survived where other forms of plant life have failed, continuing to cause varying levels of misery wherever it is found. Not all cyanobacteria are harmful, though. Many serve useful roles fertilizing soils, capturing nutrients and releasing oxygen into bodies of water. If the conditions are optimal for the growth of cyanobacteria then the growth of the plants can be impressive, forming colonies that can be quite sizable. The possible effects of these plants run the full range of possibilities from harmless to extremely toxic. The latter group have been given a number of names: blue-green algal toxins, cyanobacterial toxins or cyanotoxins. If water containing toxic cyanobacterial cells is swallowed by an individual or animal it is possible that death may follow within a remarkably short period of time. Even touching or inhaling the fumes of such material may result in illness of a less serious nature.
Domestic livestock and wildlife may, due to a variety of circumstances, have as their source of water a contaminated pond or lake which may cause poisoning. A case occurred in California where a group of sea otters died as the result of eating clams, mussels and oysters which contained large quantities of the toxin. The source of the toxins proved to be a freshwater pond about a mile from the bay where the otters fed. The tributaries of the pond carried the toxins to the bay, which in turn was consumed by the shellfish. The report did not suggest any ill effects to the shellfish.
Some climatic changes have occurred over the past several years resulting in earlier springs and later falls. This change has enabled the cyanobacteria to expand their growing season, resulting in more luxuriant growth over a longer period of time, thus increasing the time frame during which animals might ingest them.
Another factor which has had a major impact in creating a favorable environment for these organisms to grow and flourish is the amount of nutrients made available to them by the run off of fertilizers from agricultural land bordering bodies of water and the streams and rivers feeding them. Agricultural lands as well as recreational areas such as golf courses and homeowners striving to have the greenest lawns in their neighborhood also provide a source of these materials. The contribution of each household may be small, but when all of them in a given watershed are added together the tonnage of unneeded and unwanted nutrients can be considerable.
The agricultural community is coming to the realization that for many years the applications of some components of commercial fertilizers, especially phosphorus, have far exceeded the quantities necessary for good crop growth. This element added to a stagnant or slow draining pond is certain to ensure to an excellent growth of cyanobacteria. Not only are commercial fertilizers often misused, but manure applications are too often mismanaged, especially where the lay of cropland slopes naturally to bodies of water.
An article a recent issue of Yankee Magazine discussed Luke Persons, a resident of the Lake Champlain region of Vermont. He has come up with a material that he believes is the answer to the blue-green algae problem. It should be noted that much of the region involved is an intense dairy area. Abutting Franklin County, part of the Lake Champlain watershed is home to about 36,000 cows, each of which is capable of producing well over 100 pounds of manure daily. A quick calculation would reveal that this amounts to over 4 million pounds of phosphorus-rich material produced each day. A percentage of this finds its way into the lake every day.
Persons’s research has led him to a product called biochar, which has been used since pre-Columbian times. In South America, it has been used for many years in agricultural areas, where its ability to trap nutrients (including phosphorus) is well documented. Persons improvised a way to produce biochar, leading him to construct a furnace-like unit that heated wood chips to very high temperatures (800-1200 degrees F) in the absence of oxygen, with the result being a very porous, high carbon product that has the ability to trap large quantities of water and nutrients such as phosphorus. Persons’s idea is to place the material in areas of high run off to trap the phosphorus before it enters the lake.
There is no specific treatment available at this time for those unfortunate animals who have had the experience of ingesting cyanotoxin. Symptomatic treatment includes rest, quiet, and staying out of direct sunlight. In some cases activated charcoal has been used to reduce some of the predictable effects of blue-green algae intake. If there is any upside to an episode like this it is the fact that the toxins have a sharp dose response curve which makes the chances for a full recovery good for those animals who do not succumb in a short time.
Control measures are available but the best approach is to completely avoid access to effected ponds and lakes. There are a few materials that can be added to infested bodies of water, the most reliable being copper sulfate, added at the rate of 1.4 – 2.8 pounds per acre foot of water. The best thing to do is to avoid animal contact with infested areas.
Measures that need to be taken to better control the problem posed by cyanotoxins are conservation of water and more controlled applications of fertilizers. The widespread use of cover crops is to be encouraged. Preexisting wetlands need to be restored and native plants encouraged to grow around ponds and lakes.
At this time there is no mandatory requirement for reporting toxic blooms although many states do have a reporting system in place. The Centers for Disease Control (CDC) has developed a program which has been designated the One Health Harmful Algal Bloom System. It is part of its National Outbreak Reporting System which is unique in that it allows states to report animal cases in addition to human illnesses. Present plans call for a summary of the data collected over a five year period to be published to give all interested parties a clearer picture of the extent of the blue-green algae problem.