The question of how the presence of cyanobacteria might impact on an irrigation system and what can be done to tackle the problem begins with looking at exactly what cyanobacteria are and how they manifest. The question of exactly what cyanobacteria are is more complex than it might first appear, since there are 2000 species which come in a range of shapes and sizes.
In layman’s terms – and particularly in Florida, as we’ll go on to explain – cyanobacteria are often referred to as blue green algae and they are a natural phenomenon of particular interest to anyone managing, maintaining or installing a large-scale irrigation system. In purely scientific terms, cyanobacteria are a fascinating phenomenon, representing one of the oldest organisms on the planet, with fossil remains having been found which date back 3.5 billion years, and having played a key role in the evolution of life on earth due to the fact that they deliver oxygen into the atmosphere via the process of photosynthesis. For anyone involved in irrigation, however, this is of less importance that the fact that the individual cyanobacteria can form huge blooms, joining and weaving together to form the kind of blue green slime often visible in bodies of freshwater or along the seashore.
Until a recent study by scientists at Loughborough University in the UK, the process by which millions of individual units join together to form sometimes vast blooms capable of choking the life out of water was a mystery, but what wasn’t a mystery was the danger presented by such large blooms, particularly since five types of cyanobacteria have been identified as toxin producers. Among these are hepatoxins, which damage the liver, neurotoxins, which attack the nervous system and dermatoxins which affect the skin.
Cyanobacteria in Florida
According to information published by the Florida Fish and Wildlife Conservation Commission, persistent cyanobacteria blooms have impacted many of the aquatic systems within Florida, including the Harris Chain of Lakes (Apopka, Eustis, Griffin and Harris), the St. Johns, St. Lucie and Caloosahatchee rivers and estuaries and, as our own H2O Zone reported back in July, Lake Okeechobee.
Harmful Algal Blooms (HAB) of this kind, as well as being potentially damaging to any humans who come into contact with them, cause great harm to the natural balance of the bodies of water in question by choking off supplies of oxygen and often prove fatal to animals – such as pets – which come into contact with them. Indeed, a study published by the Center for Disease Control and Prevention and quoted on CBS news found that more than 90% of animals which became ill after coming into contact with a HAB went on to die. While cyanobacteria are present in waters across the face of the planet, they are a problem which seems to be particularly prevalent in the state of Florida
Harmful Blue Green Algal Blooms and Why They Happen
When the open-source research hub Frontiers published a range of studies under the umbrella title of Environmental Threats to the State of Florida—Climate Change and Beyond, they opted for one of the articles – a review of existing literature on the subject – to focus on HABs such as those consisting of large bodies of blue green algae. The article in question stated that cyanobacteria blooms of this kind present a unique risk, impacting on the ‘citizens, stakeholders, visitors, environment and economy’ of the state of Florida.
While blooms of this kind have been recorded for many years, recent events are felt to have triggered a rise in their occurrence and scale. Amongst the causes listed are the growing population of Florida, particularly in coastal areas, and climate change phenomena such as warming water temperature, rising sea levels and increasing hurricane severity. Worryingly, for anyone hoping to guard against the presence of cyanobacteria in their irrigation system, Florida is described as being one of the global epicenters of HABS, many of which involve cyanobacterial species, and can be found in all types of aquatic environment, from freshwater springs and lakes to estuaries and coastal lagoons.
The reasons why algal blooms and cyanobacterial HABs (alongside other types of HAB) are so prevalent in Florida waters are complex and multi-faceted. Some of the triggers are natural, such as the 2,170 kilometer long coastline and the presence of more than 7,800 lakes, as well as a diverse range of climate conditions and the presence of a dry season and a wet season. The concentration of precipitation in the wet season across Florida is thought to lead to greater levels of nutrient rich run-off, as the fertilizers retained by the ground during the dry season are washed into bodies of water such as lakes and rivers.
In addition to the natural primers of algal blooms, other factors such as large scale population growth can also be taken into account. According to figures released in December 2022 by the US Census Bureau Florida is currently the fastest growing state in the US, with a population which grew by 1.9% between 2021 and 2022, to hit 22,244,823. More people means more urban and agricultural development of course, and this, in turn, is likely to have led to increased stormwater, wastewater and agricultural runoff to inland and coastal aquatic systems, as well as a greater overall demand for water.
Cyanobacteria in an Irrigation System is Trouble
All of the above helps to explain why cyanobacteria are more likely to be a problem for irrigation systems across Florida than pretty much anywhere else, but it doesn’t explain why they are a problem which, if apparent, needs to be addressed urgently. After all, although some forms of cyanobacteria are toxic in nature, many aren’t, and the water from an irrigation lake, for example, is only going to be used to irrigate vegetation (although some larger irrigation lakes may also be used for recreational purposes). The risk of cyanobacteria entering an irrigation system isn’t confined to any health risk it may or may not represent, however, although you should always err on the side of caution and assume that cyanobacteria present are of the toxic variety, rather than assuming they are safe - and being proved wrong.
Potential For Widespread Damage
The risk of cyanobacteria being present within an irrigation system is centered more on the damage that a buildup of algae could do to the mechanics of the system itself. Put simply, if left untreated cyanobacteria could build within components such as pipes, sprinkler heads and water pumps to such a degree that the components in question become completely clogged and blocked with algal matter.
From fine filaments blocking inlets and aerators to lines and sprinkler nozzles being clogged by clumps of free-flowing unicellular algae, cyanobacteria are capable of causing immense problems throughout an irrigation system. Not only will the system itself be damaged by blockages, the fact that the water can’t get through a clogged pipe or sprinkler head is also likely to impact on the surfaces which are being irrigated. Tracking down the precise location of a blockage could require shutting the system down entirely and physically unearthing pipes and vulnerable spots such as bends and T-junctions, and the same applies to cleaning sprinkler head or replacing intake filters. Even in the earliest stages the presence of cyanobacteria in an irrigation system could lead to the vegetation itself being damaged, particularly if the toxins within the algae are absorbed into the soil.
Checking for the Presence of Cyanobacteria
The presence of cyanobacteria in an irrigation lake is fairly obvious if a blue green algal bloom forms, but by that stage the cyanobacteria is likely to have made its way into your irrigation system, since the individual bacteria are so small that they can pass through many types of filter. The advice, if you suspect the presence of cyanobacteria, is to have the water from your irrigation lake tasted. The Environmental Protection Agency website lists laboratories around the country which can test a sample of water for the presence of cyanobacteria and, in many cases, whether the cyanobacteria is toxic. Currently, the EPA website lists four laboratories in Florida offering this service and their contact details are below:
GreenWater Laboratories/Cyanolabs
205 Zeagler Drive, Suite 302
Palatka, FL 32177
(386) 328-0882
Everglades Laboratories, Inc.
1602 Clare Avenue
West Palm Beach, FL 33401
(561) 833-4200
Jupiter Environmental Laboratories
150 S. Old Dixie Highway
Jupiter, FL 33458
(561) 575-0030
Toll-free: (888) 287-3218
Department of Environmental Protection Bureau of Labs, Biology Section
(FLDEP Programs, consultation)
2600 Blair Stone Road
Tallahassee, FL 32399
(850) 245-8159
How to Deal With Cyanobacteria
If cyanobacteria are present in the water then your irrigation system components need manual cleaning to remove any build-up of algae. If the infiltration of cyanobacteria has been discovered at the earliest stage then there’s a chance that the buildup of material is not yet sufficient to be visible to the naked eye. In both cases the components – filters, pipes, sprinkler heads etc. – should be cleaned using a solution of hydrogen peroxide, which has an oxidizing effect on the cyanobacteria.
The Algaecide Option
In terms of the larger scale issue of treating the body of an irrigation lake to remove cyanobacteria there are a number of possible options. One of these is the application of an algaecide, a chemical compound designed to kill the cyanobacteria in the water. While this is the approach which was taken by the South Florida Water Management District when dealing with a large and highly toxic algal bloom in Timer Powers Park in Indiantown, it is regarded by many as a controversial choice, since the chemical used to kill the cyanobacteria could also impact negatively on other life within the water, and there is also a suspicion that an algal bloom, having been treated, could very easily return. This is borne out to some degree as according to figures published on the Treasure Coast News website, of the 25 lakes treated with algicides in Florida during August 2023, 92% observed an algal bloom post-treatment - and 32% still had toxicity above the safe limit.
The Ultrasound Option
An alternative to tackling cyanobacteria and the presence of algal blooms with potentially harmful chemicals is to use ultrasound devices. Ultrasound waves have been promoted as a possible solution to the problem of algal blooms for some years now, with much of the material relating to their effective ness being produced and disseminated by manufacturers or retailers of the devices and therefore not necessarily completely objective in terms of their appraisal of effectiveness.
The open-source research portal MDPI, however, has published a research paper entitled ‘Improved Cyanobacteria Removal from Harmful Algae Blooms by Two-Cycle, Low-Frequency, Low-Density, and Short-Duration Ultrasonic Radiation’. This study, carried out using a prototype of an ultrasound device, found that the right frequency of sound applied for relatively short periods at a time was effective in reducing 86.7% of the algae present. A similar study, carried out in real-time conditions at a water treatment plant and using a commercially available ultrasound product, found that, at best, the device was able to remove 80-90% of certain types of algae.
Prevention Rather Than Cure
Given the difficult nature of removing cyanobacteria once they are present within an irrigation lake it’s hard to avoid the conclusion that prevention is better than cure. This was certainly the approach intended by the Blue-Green Algae Task Force created and created and appointed by Gov. Ron DeSantis in 2019, which, in a ‘consensus document’ published in October of that year, stated that:
‘Increased delivery of nutrients to Florida’s water bodies is widely recognized as the primary driver of algal proliferation and subsequent degradation of aquatic ecosystems. Major sources of nutrients include, but are not limited to, agricultural operations, wastewater treatment plants, onsite sewage disposal systems and urban storm water runoff. Legacy nutrients, i.e. nitrogen and phosphorus sequestered in soils, groundwater and sediments, contribute also to excessive nutrient loading of surface waters throughout the state.’
Monitoring Nutrient Levels
Admittedly, an evaluation of progress made by the task force in 2023, carried out by a number of bodies including Florida Spring Council, Save the Manatee, Waterkeepers Florida and Friends of the Everglades, was fairly scathing about the progress made thus far, but the principle of prevention over remediation is one which anyone in charge of an irrigation system can apply to their own irrigation lake. It really comes down to having the water in the lake checked on a regular basis to ensure nutrient levels are healthy, and in particular that the levels of phosphorous and nitrogen are not too high. If they are too high then the introduction of products such as Alum and Phoslock could be used to rebalance things, but solutions of this kind should only be utilized by experts with a strong working knowledge of lake water health and the art of rebalancing nutrient levels. Aeration can have a similar impact by circulating more oxygen through the water, either through the operation of a submerged pump or, in shallower lakes, the introduction of a floating fountain. If the nutrient levels in an irrigation lake are where they should be then the trick is to introduce measures to prevent things becoming unbalanced.
Controlling the Surrounding Environment
There are some very commonsense and simple ways you can control the surrounding environment of an irrigation lake. Control the health in the neighborhood of a lake and you stand a good chance of reducing the potential for cyanobacteria to proliferate.
Check whether the soil in the flower beds needs to be fertilized at all, by monitoring the nutrient levels. If you feel fertilizer is needed then a firm understanding of the existing nutrient levels will ensure that you are not applying too much (incidentally saving money on fertilizer purchasing). Try to use a fertilizer which is phosphorous free and make sure that you never fertilize to the very edge of the irrigation lake shoreline. Run-off into your irrigation lake following periods of heavy rain can play a key role in encouraging cyanobacteria to thrive, washing not only substances such as weedkillers and fertilizers into the water but also the likes of grass clippings, leaves and animal waste. The impact of many of these can be minimized with a strict policy of garden maintenance and the removal of any waste products off-site, but the creation of buffer zones around the shore of the lake can also stop run-off reaching your irrigation water. Dense turf planted some 3-6 feet from the edge of the water can help to absorb any nutrients before they reach the lake, as well as protecting the shore from natural erosion. Native grasses and flowers can be planted along such a buffer zone to improve and enhance the environment as a whole, as well as attracting wildlife such as native birds.
