Cyanobacteria (Blue-Green Algae) FAQ

General Information

  1. What are cyanobacteria (blue-green algae)?
  2. What are cyanobacteria blooms?
  3. What are the concerns associated with cyanobacteria?
  4. When do cyanobacteria blooms occur?
  5. Where do cyanobacteria blooms occur?
  6. Where do the nutrients come from?
  7. How long will a cyanobacteria bloom last?
  8. Why do cyanobacteria blooms occur?
  9. Why do cyanobacteria blooms sometimes appear over night?
  10. Are cyanobacteria blooms predictable?
  11. Can cyanobacteria blooms be controlled?
  12. What can we do about cyanobacteria blooms?
  13. Are cyanobacteria blooms a new problem?
  14. Has there ever been a cyanobacteria bloom in Newfoundland and Labrador?
  15. What is the government of Newfoundland and Labrador doing to monitor cyanobacteria blooms?

1. What are cyanobacteria (blue-green algae)?

Cyanobacteria, commonly called blue-green algae, are plant-like bacteria that most commonly live in fresh and salt water. They are often blue-green in colour but they can also range from olive-green to brown to red. Like algae, they are photosynthetic, capable of converting sunlight and nutrients into the energy required for growth and reproduction. Blue-green algae are usually small and unicellular, but can grow or accumulate in concentrations that are large enough to see.

Anabaena spp, Paddy's Pond
Anabaena spp, Paddy’s Pond

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2. What are cyanobacteria blooms?

When conditions are favorable, cyanobacteria can grow profusely and make pond or lake water look like ‘pea soup’. This condition is called a bloom.

Anabaena spp, Paddy's Pond
Cyanobacteria bloom Paddy’s Pond, 2007

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3. What are the concerns associated with cyanobacteria?

Concerns associated with cyanobacteria include discolored and cloudy water, taste and odor problems, depletion of oxygen and toxin production. Some cyanobacteria species produce toxic compounds inside their cells, called cyanotoxins. Some of these cyanotoxins can affect the liver (hepatotoxins) or the nervous system (neurotoxins); others can irritate the skin (dermatotoxins). Microcystins are the moat common cyanotoxin found in Canada. Toxins are not produced during all blooms and there is no easy way to tell when or if a bloom is producing toxins.

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4. When do cyanobacteria blooms occur?

The main factors which appear to determine the development of cyanobacteria blooms are light, temperature, and nutrient concentrations, particularly nitrogen and phosphorus. Blooms are more likely to develop in warm, shallow, slow-moving water, but they may also be present below the surface in deeper, cooler water.

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5. Where do cyanobacteria blooms occur?

The main factors which appear to determine the development of cyanobacteria blooms are light, temperature, and nutrient concentrations, particularly nitrogen and phosphorus. Blooms are more likely to develop in warm, shallow, slow-moving water, but they may also be present below the surface in deeper, cooler water.

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6. Where do the nutrients come from?

Although blooms are a naturally occurring phenomenon, human activities can provide the physical and chemical conditions cyanobacteria need to thrive. Storm water runoff, industrial effluent, agricultural runoff and effluent from waste management systems including faulty septic systems can lead to the nutrient enrichment of water bodies and promote the occurrence of blooms.

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7. How long will a cyanobacteria bloom last?

Cyanobacteria blooms can persist for several weeks, and can occur more than once per year.

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8. Why do cyanobacteria blooms occur?

Cyanobacteria are well adapted to growth and persistence in nutrient-rich lakes, reservoirs and ponds. They can out-compete other algae for optimal levels of sunlight and nutrients, in part, by regulating their buoyancy in the water. Cyanobacteria cells have the ability to form gas-filled cavities, which enable them to move vertically through the water column to access optimal levels of light and nutrients. They also use their buoyancy to counter the downward drag of wind currents. The cells can become over-buoyant and concentrate near the water’s surface when calm conditions follow windy periods. These surface accumulations intensify if waves carry the cyanobacteria along the shorelines and beaches. The results are cyanobacteria blooms that make the water look like pea soup.

Anabaena spp, Paddy's Pond
Cyanobacteria bloom, Paddy’s Pond

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9. Why do cyanobacteria blooms sometimes appear over night?

Even if you can’t see cyanobacteria floating on the surface of the water in the daytime, that doesn’t mean they aren’t there. Cyanobacteria can be suspended at various depths in the water, and their location depends on a number of factors. The most important of these are light and nutrients (phosphorus and nitrogen). Many species of cyanobacteria have evolved to be able to control their buoyancy as the availability of light and nutrients change with the time of day and local weather conditions. At night, when there is no light, cells are unable to adjust their buoyancy and often float to the surface, forming a surface bloom. Thus, this bloom can literally appear overnight and may linger until wind and waves scatter the cells throughout the water body.

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10. Are cyanobacteria blooms predictable?

The timing, intensity and duration of a cyanobacteria bloom will vary from year to year based on nutrient availability, air and water temperatures, sunlight and wind velocity. Since these factors vary from year to year, blooms cannot be accurately predicted. Blooms may not occur every year in a particular pond or lake, or they may not develop at the same time or with similar intensity each year. The species responsible for each bloom may also differ.

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11. Can cyanobacteria blooms be controlled?

Herbicides and algaecides can be used to kill cyanobacteria in fresh water, but this is not advisable because these treatments may break open cells and release more toxins into the water. These  may also be toxic to other life forms, including fish and the organisms they eat. The use of chemicals in natural lakes and ponds can create more problems than it solves. The mitigation of cyanobacteria blooms is better accomplished through preventive rather than remedial measures. Blooms of cyanobacteria may only form when nutrients are readily available and taking steps to reduce or prevent additional sources of these nutrients from entering the water can reduce their occurrence.

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12. What can we do about cyanobacteria blooms?

A potential long-term solution to problematic cyanobacteria blooms is to reduce the amount of nutrients entering lakes and ponds. The main nutrient sources that can be controlled are sewage effluents, agricultural and lawn care runoff, and industrial effluents.

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13. Are cyanobacteria blooms a new problem?

Research suggests that cyanobacteria have been around for millions of years. Scientists have recorded blooms dating back to the 12th century and they have documented the toxic effects to livestock for more than 100 years. However, it is likely that the frequency and duration of blooms are increasing as a result of increased nutrient concentrations and climate change.

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14. Has there ever been a cyanobacteria bloom in Newfoundland and Labrador?

The first confirmed cyanobacteria bloom in Newfoundland and Labrador occurred in mid-August 2007 and persisted until early October. Documentation of confirmed cyanobacteria blooms can be found in our reports section.

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15. What is the government of Newfoundland and Labrador doing to monitor cyanobacteria blooms?

The provincial Department of Environment and Climate Change monitors cyanobacteria blooms in fresh water bodies that are of concern to the public.

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