Blue-green algae growth, also known as cyanobacteria, can cause a foul odour to the water, a layer of scum on the surface and even pose a health risk. Green algae may colour the water green, look unclear and plants can die. Therefore an algae problem is often unwanted and algae control is desired.
What are algae?
Algae are a diverse group of plant-like organisms that occur in a wide range of environmental habitats. They are photoautotrophic cells that contain chlorophyll, have simple reproductive structures, and their tissue is not differentiated into true roots, stems or leaves. They range from unicellular, or single celled, to fairly complex multicellular organisms. Some algae have such a complex growth that they are mistaken for vascular plants.
The size of average individual microscopic unicellular algal cells is approximately 0.0010 mm in diameter.
Algae are found throughout the world and can cause nuisance problems in water treatment plants, drinking water supplies, ponds, swimming pools and cooling towers. The extermination of algae is a problem, the methods to control algae can be expensive, cumbersome, environmentally unfriendly or all of these.
Algae can be present on vegetation, in the air, in the soil, and in water. Their microscopic spores are continuously introduced into pools and other water reservoirs by wind, dust storms, rain showers, etc. They grow rapidly in stagnant waters when exposed to sunlight and temperatures above 4 degrees Celsius. They can form objectionable slime and/or odours. They can interfere with proper filtration and greatly increase chlorine demand. Phosphates and nitrates in the water encourage their growth.
Types of algae
Algal growth occurs in three basic forms:
Planktonic algae are single-celled, microscopic algae that float freely in the water. When these plants are extremely abundant or “bloom”, they can turn the water green. Less often, algal blooms can turn the water to other colours, including yellow, gray, brown or red.
Filamentous algae are sometimes referred to as “thread algae” or “pond scum”. Filamentous algae occur as fine green threads that form floating mats, which are often moved around the pond by wind. These algae are also commonly found attached to rocks, submerged trees, other aquatic plants and boat docks.
Macrophytic algae resemble true plants in that they appear to have stems and leaves. A commonly-occurring macrophytic algae is called Chara or musk grass (due to its strong musky odour.) Chara feels coarse to the touch, because of lime deposits on its surface, earning it another common name — stonewort.
Overall, algae are of little value to your pond or lake. The filamentous and planktonic forms can reproduce at phenomenal rates, and sudden die-offs can cause oxygen depletion. The necessary oxygen required in fish ponds or lakes can be supplied by other aquatic plant life in the water basin, which will flourish without competition of algae.
Algal problems are usually caused by an overabundance of nutrients (nitrogen and phosphorous) in the pond. From the moment a pond is built, it becomes a settling basin for nutrients washing in from the land that drains into the pond’s watershed.
The older a pond gets, the more nutrients will have accumulated and the more susceptible it is to algal problems. Runoff from fertilized fields, lawns and pastures, feedlots, septic tanks and leach fields accelerate nutrient loading and algal growth in the pond.
Algae growth conditions
Excessive algae growth will starve or suppress other forms of aquatic plant life, and can block sunlight necessary for their proper growth. Taste and odour problems in drinking water and sometimes even fish kills are associated with excessive blooms of planktonic algae.
Filamentous algae and macrophytic algae often form dense growths that make fishing, swimming, and other recreational uses nearly impossible. – im- im- imTotal coverage can restrict sunlight penetration and limit the production of oxygen and food items necessary for fish growth.
When algae abundance interferes with the intended use of the pond, a control method should be considered.
Mats of filamentous algae may be removed with a rake, screen wire, or similar devices. However, this control method is very labour intensive and provides only temporary control. In some instances, the algae may seem to grow as fast as they are pulled out.
Before using chemicals, you should consider potential contamination of domestic water supplies and the waiting periods for watering livestock, eating fish, swimming and irrigation.
A “biological control” is when one form of life is used to control another or the balance of life is manipulated in such a way to adversely affect an undesirable pest. It is wise to be very cautious when deciding on the use of a biological control. It can backfire when the introduced species becomes more of a problem than the original pest.
Barley Straw has been tested in England by the Centre for Aquatic Plant Management for the control of planktonic and filamentous algae. This testing has been going on over the last 15 years. Barley Straw and other straws have been used sporadically in the United States, with very mixed results, and will not totally eliminate the problem.