Cyanobacteria, Blue Green Algae, Harmful Algal Blooms & Cyanotoxins, All About

Toxic cyanobacteria are ubiquitous in our environment. They are found on earth in the biosphere (areas occupied by living organisms), cryosphere (cold or frost areas), hydrosphere (all waters including lakes, rivers, seas, and airborne clouds), and the lithosphere (the crust and upper mantle of earth).1

Cyanobacteria below to the Bacterial phyla division. Currently there are over 1123 different species, genuses, families, orders, and classes of Cyanobacteria with 60 assigned genera names.
Cyanobacteria over 1100 different species picture 2

As more is learned about cyanobacteria, more toxic blooms and toxic species will be discovered especially in tropical and subtropical areas which are currently under-represented in literature. Mass occurrences of toxic cyanobacteria are not always associated with human activities from pollution or “cultural eutrophication”. Massive blooms of toxic cyanobacteria have been reported in Australian reservoirs with pristine or near-pristine watersheds, and toxic benthic cyanobacteria have killed cattle drinking from oligotrophic, high-alpine waters in Switzerland.3

Cyanobacteria 190 participants from 36 countries picture 25

Cyanobacteria can occur naturally in saltwater and freshwater. Individual organisms can often only be seen under a microscope but some species can join together to form colonies visible to the naked eye. Heavy blooms can overtake water bodies and even choke out portions of streams or rivers.4 Some cyanobacterial blooms can look like foam, scum, or mats on the surface of fresh water lakes and ponds. 5The blooms can be blue, bright green, dark green, olive, brown, red, or purplish and may look like paint floating on the water. Some blooms may not affect the appearance of the water. As algae in a cyanobacterial bloom die, the water may smell bad.6 Blue-green algal toxins can remain toxic in a dry form and lead to significant toxin build up on foliage and the residue can affect livestock.7 Toxin-producing cyanobacteria are an emerging issue for lake managers throughout the world. 8

Cyanobacteria B-N-methylamino-L-alanine BMAA picture
29, 30, 31

Cyanobacterial toxins–Microcystin-LR (2000)10
Health Canada in 2000 approved the following guideline for Cyanobacterial toxins – Microcystin-LR with MAC of 0.0015 mg/L. Toxins are naturally occurring and are released from blooms of blue-green algae. Health basis of MAC: Liver effects (enzyme inhibitor), Other: Classified as possible carcinogen. MAC is protective of total microcystin: avoid algicides like copper sulphate, as they may cause toxin release into water.

World Health Organization (WHO) – Microcystin-LR 11– Has more than 80 microcystins identified to date. Only a few occur frequently and in high concentrations. Microcystin-LR is the most frequent and most toxic of the microcystins identified so far. Microcystins usually occur within cells and substantial amounts are released into the water when the cells rupture (or lysis). WHO has a temporary guideline of 0.001 mg/litre (for total microcystin-LR, free plus cell-bound) value.

Cyanobacteria Canadian Public Health Inspectors state picture 27

watertoday.ca12: Click on the crest of your province to read our report which focuses on drinking water management and on the transparency of public reporting in each of Canada’s 13 provinces and territories. There is a maze of different approaches and public reporting protocols.

Cyanobacteria The WHOs 1 Working Group picture 26

WHO History of guideline development – Cyanobacterial toxins were not evaluated in the 1958, 1963 and 1971 WHO International Standards for Drinking-water or in the first two editions of the Guidelines for Drinking-water Quality, published in 1984 and 1993. In the second edition of the Guidelines, published in 1998, it was concluded there was insufficient data to allow a guideline value to be derived for any cyanobacterial toxins other than microcystin-LR.13

Drinking water contaminated with cyanobacteria can have taste-and-odour problems due to nontoxic compounds, which may prevent ingestion of toxin contaminated water by alerting utilities to a cyanobacteria problem. However, toxic cyanobacteria can also occur without taste or odour problems. Cyanobacteria Health Canada states picture 28 The extent of the threat to humans via drinking water is not completely clear, but a survey done on 45 utility waters (i.e., source waters, treatment and plant intakes, and plant effluents) in the United States and Canada between 1996 and 1998 found 80% of the 677 samples to contain detectable levels of microcystins. About 4% exceeded the WHO`s advisory limit of 1ug L-1 for microcystin LR in drinking water, but only two of the 4% were “finished water” samples, indicating the standard water treatment was relatively effective at removing cyanotoxins. More recently, samples of untreated source water taken from Lake Erie and of finished water in Florida have exceeded the WHO’s advisory limit.14

High numbers of cyanobacteria can adversely impact a range of drinking water treatment processes such as coagulation and filtration, the main issue for the water supplier is the production by cyanobacteria of algal toxins, or cyanotoxins.15

Cyanobacteria Confirmation of toxins picture 9

The Water Research Australia Limited state the processes to remove dissolved cyanobacteria microcontaminants (toxins, tastes, and odours) from our drinking water treatment plants are influenced by the structure (i.e. size, shape, charge and solubility) of the target compound. If there is the possibility of toxins entering the water treatment plant, water samples should be sent for chemical analysis to identify the toxin most likely to be present. Water suppliers should use their knowledge of past cyanobacteria monitoring to identify the toxins most likely to be present. Some treatment options are effective for some cyanotoxins, but not for others. Applying the wrong treatment process could damage cells and result in the release of cyanotoxins. Scientists say more research is needed to find adequate testing and treatment solutions to ensure our water is potable and safe to drink.16

Cyanobacteria As of 2010 picture 16

Freshwater cyanobacteria toxins can have a broad range of negative impacts on humans, animals, and aquatic ecosystems. Many cyanobacteria can produce neurotoxic (poisonous to nerves or nerve cells), hepatotoxic (toxic to the liver), dermatotoxic (damage to the skin), or other bioactive (effect on living tissue) compounds, and blooms of toxigenic cyanobacteria pose a particular threat if they occur in drinking water sources. 14

Cyanobacteria are a natural component of surface freshwater bodies. Their occurrence may vary radically with seasonal changes from only a few per unit volume in the water column to excessive numbers occurring as “blooms” at the surface of a water body. Their distribution in the water column may vary from surface of the water column, a few metres below the water surface or at the bottom of the water body. 15

Some of the normal or regular growth cells called vegetative cells may rest over winter in a state of senescence in the sediment. For example Microcystis can ‘overwinter’ as vegetative colonies on the lake sediments, where they may survive for several years, apparently without light or oxygen. The new population may then appear in spring from the normal growth of these colonies by cell division. 15

Toxigenic Lyngbya species, adapted to high salinity environments, can form benthic mats that expand over an area equivalent to a football field within an hour, causing ecological damage and endangering human health (Australian Environmental Protection Agency 2003).17

Cyanobacterial blooms can be harmful to the environment, animals, and human health. The bloom decay consumes oxygen, creating hypoxic conditions which result in plant and animal die-off. Under favorable conditions of light and nutrients, some species of cyanobacteria produce toxic secondary metabolites, known as cyanotoxins. Common toxin-producing cyanobacteria are listed in Table 1.
Cyanobacteria Table 1 Cyanotoxins on the Contaminant Candidate List (CCL)

The conditions that cause cyanobacteria to produce cyanotoxins are not well understood. Some species with the ability to produce toxins may not produce it under all conditions. These species are often members of the common bloom-forming genera. Both nontoxic and toxic varieties of most of the common toxin-producing cyanobacteria exist, and it is impossible to tell if a species is toxic or not toxic by looking at it. Also, even when toxinproducing cyanobacteria are present, they may not actually produce toxins. Furthermore, some species of cyanobacteria can produce multiple types and variants of cyanotoxins. Molecular tests are available to determine if the cyanobacteria, Microcystis for example, carry the toxin gene; quantitative cyanotoxin analysis is needed to determine if the cyanobacteria are actually producing the toxin. Water contaminated with cyanobacteria can occur without associated taste and odor problems. 19

In most cases, the cyanobacteria toxins exist intracellularly in the cytoplasm and are retained within the cell. Anatoxin-a and the microcystin variants are found intracellularly approximately 95% of the time during the growth stage of the bloom. For those species, when the cell dies or breaks, the cell membrane ruptures and the toxins are released into the water (extracellular toxins). However, in other species, cylindrospermopsin fo example, a significant amount of the toxin may be naturally released to the water by the live cyanobacterial cell; the reported ratio is about 50% intracellular and 50% extracellular. Extracellular toxins may absorb to clays and organic material in the water column and are generally more difficult to remove than the intracellular toxins. 19

Documented Cyanobacteria Blooms

Cyanobacteria A cyanobacteria bloom developed in Warragamba Dam picture 18

Warragamba Dam, August 2007 – A cyanobacteria bloom developed in Warragamba Dam in August 2007 and lasted for over three months. The cell count of Microcystis exceeded 100,000 cells/mL in the first week of September 2007, and reached 700,000 cells/mL near the dam wall in October 2007. A cyanobacteria bloom of this proportion has never occurred before near the dam wall. The strength of the bloom started to decline in December 2007. The authority monitored the bloom and the treated water met the Australian Drinking Water Guidelines. More than 120 water samples were tested for toxins, and all but four detected no toxins. On the four occasions where toxins were detected, the toxin levels were well below the guideline values, and immediate re-sampling of the same sites detected no toxins. 18

Toxins that may not be readily detected by traditional methodsTesting of samples found that up to 70 μg L-1 of microcystin could be present in the absence of cells. In the same project, initial studies of water samples used by industry in the Central Queensland region demonstrated the presence of cylindrospermopsin in the absence of species known to produce this toxin. The difficulty in associating specific cell concentrations with toxin concentrations and relative human health risk is evident from the data. A general approximation of 10,000 cells mL-1 of Cylindrospermopsis were present in samples containing 1 μg L-1 of CYN plus deoxy-CYN, this concentration of toxin was also recorded in relation to individual cell counts as low as 835 cells mL-1 or zero. 18

Climate change and drought are expected to have a huge impact and increased risks on Australian water quality with cyanotoxins contaminating drinking water supplies. Risk-based and multi-barrier approaches are required to guarantee organisms and cyanotoxins do not affect water quality. 18

The WHO report most documented cases of human injury through cyanotoxins involved exposure through drinking-water, and they demonstrate that humans have become ill—in some cases seriously—through ingestion or aspiration of toxic cyanobacteria. The low number of reported cases may be due to lack of knowledge about the toxicity of cyanobacteria; neither patients nor doctors associate symptoms with this cause. Symptoms reported include “abdominal pain, nausea, vomiting, diarrhoea, sore throat, dry cough, headache, blistering of the mouth, atypical pneumonia, and elevated liver enzymes in the serum, especially gamma-glutamyl transferase” (Carmichael, 1995, p. 9), as well as hay fever symptoms, dizziness, fatigue, and skin and eye irritations; these symptoms are likely to have diverse causes, with several classes of toxin and genera of cyanobacteria involved. 20


1959: Canada: In spite of a kill of livestock and warnings against recreational use, people still swam in a lake infested with cyanobacteria. Thirteen persons became ill (headaches, nausea, muscular pains, painful diarrhoea). In the excreta of one patient—a medical doctor who had accidentally ingested water—numerous cells of Microcystis spp. and some trichomes of Anabaena circinalis could be identified (Dillenberg & Dehnel, 1960). 21

1989: England: Ten out of 20 soldiers became ill after swimming and canoe training in water with a heavy bloom of Microcystis spp.; two developed severe pneumonia attributed to the inhalation of a Microcystis toxin and needed hospitalization and intensive care (Turner et al., 1990). Swimming skills and the amount of water ingested appear to have been related to the degree of illness. 21

1995: Australia: Epidemiological evidence of adverse health effects after recreational water contact from a prospective study involving 852 participants showed elevated incidence of diarrhoea, vomiting, flu symptoms, skin rashes, mouth ulcers, fevers, and eye or ear irritations within 2–7 days after exposure (Pilotto et al., 1997). Symptoms increased significantly with duration of water contact and density of cyanobacterial cells, but were not related to the content of known cyanotoxins. 21


1931: USA: A massive Microcystis bloom in the Ohio and Potomac rivers caused illness of 5000–8000 people whose drinking-water was taken from these rivers. Drinking-water treatment by precipitation, filtration and chlorination was not sufficient to remove the toxins (Tisdale, 1931). 1968: USA: Numerous cases of gastrointestinal illness after exposure to mass developments of cyanobacteria were compiled by Schwimmer & Schwimmer (1968). 21

1979: Australia: Combating a bloom of Cylindrospermopsis raciborskii in a drinking-water reservoir on Palm Island with copper sulfate led to liberation of toxins from the cells into the water and resulted in serious illness (with hospitalization) of 141 people supplied from this reservoir (Falconer, 1993, 1994). 1981: Australia: In the city of Armidale, liver enzyme activities (a sign of exposure to toxic agents) were found to be elevated in the blood of the population supplied from surface water polluted by Microcystisspp. (Falconer et al., 1983). 21

1985: USA: Carmichael (1994) compiled case studies on nausea, vomiting, diarrhoea, fever and eye, ear and throat infections after exposure to mass developments of cyanobacteria. 21

1988: Brazil: Following the flooding of the Itaparica Dam in Bahia State, some 2000 cases of gastroenteritis were reported over a 42-day period, of which 88 resulted in death. Investigation of potential causes of this epidemic eliminated pathogens and identified a very high population of toxic cyanobacteria in the drinking-water supply in the affected areas (Teixera et al., 1993). 21

1993: China: The incidence of liver cancer was related to water sources and was significantly higher for populations using cyanobacteria-infested surface waters than for those drinking groundwater (Yu, 1995). 1994: Sweden: Illegal use of untreated river water in a sugar factory led to an accidental crossconnection with the drinking-water supply for an uncertain number of hours. The river water was densely populated by Planktothrix agardhii and samples taken a few days before and a few days after the incident showed these cyanobacteria to contain microcystins. In total, 121 of 304 inhabitants of the village (as well as some dogs and cats) became ill with vomiting, diarrhoea, muscular cramps and nausea (Anadotter et al., 2001). 21

Cyanobacteria On July 19 2014 Toledo State of Emergency picture 22

2014: USA: Water crisis grips more than 500,000 Toledo area residents scrambling for bottled water and a state of emergency declared when a toxin produced by harmful blue-green algae known as microcystis was drawn from 39 metro Toledo sites. Toledo draws its water from the Great Lakes. The water plant is Lake Erie’s largest and most sophisticated consisting of an eight-phase treatment process including: 22

  • Permanganate applied to the water-intake crib 3 miles north of the shoreline,
  • The water then travels six to 12 hours which helps reduce contaminants,
  • Powdered activated carbon for taste and odor,
  • Alum to bind particles together and make them easier to remove,
  • Lime to reduce hardness,
  • Soda ash to neutralize excess alum,
  • Polyphosphate for stability,
  • Chlorine for disinfection, and
  • Fluoride to combat tooth decay.



1975: USA: Endotoxic shock of 23 dialysis patients in Washington, DC, was attributed to a cyanobacterial bloom in a drinking-water reservoir (Hindman et al., 1975). 21

1996: Brazil: In total, 131 dialysis patients were exposed to microcystins from the water used for dialysis; 56 died. At least 44 of these victims showed the typical symptoms associated with microcystin, now referred to as “Caruaru Syndrome”, and liver microcystin content corresponded to that of laboratory animals having received a lethal dose of microcystin (Jochimsen et al., 1998). 21


Vegetables exposed to water contaminated with cyanotoxins increases the risk of food contamination. An individual weighing 60 Kg consumes 40g of lettuce (approximately four leaves) exposed to Microcystin (MC) concentrations of 0.62-12.5 lg, they could ingest 0.33-7.11 lg of MC per meal and exceed the tolerable daily intake recommended by the WHO (Chorus and Bartram 1999). Even low concentrations of MCs in irrigation water can put humans at risk. 23

Test results showed significant embryo and larval toxicity to Microcystis aeruginosa and compensatory growth after pre-exposure from a cyanobacterial extract containing microcystins. 24

Sharks are known to bioaccumulate toxins that may pose health risks to consumers of shark products. The feeding habits of sharks are varied, including fish, mammals, crustaceans and plankton. The cyanobacterial neurotoxin β-N-methylamino-l-alanine (BMAA) has been detected in species of free-living marine cyanobacteria and may bioaccumulate in the marine food web from lower trophic levels (teleosts and crustaceans) to marine apex predators. The researchers sampled fin clips from seven different species of sharks in South Florida to survey the occurrence of BMAA. BMAA was detected in the fins of all species examined with concentrations ranging from 144 to 1836 ng/mg wet weight. Since BMAA has been linked to neurodegenerative diseases (including Alzheimer’s and Lou Gehrig’s), these results may have important relevance to human health. We suggest that consumption of shark fins may increase the risk for human exposure to the cyanobacterial neurotoxin BMAA. 33

Humans can be exposed to cyanotoxins, especially Microcystins (MCs), through aquatic animals, edible plants, and dietary supplements. Food is an exposure route which MCs can enter the human body. The precise doses of these toxins still need to be solved in order to prevent possible health risks. National and international legislation is needed to preserve aquatic environments and human human health. 32

Health Canada Recalls

Cyanobacteria Health Canada Spirulina picture 28

Click here for Health Canada Recalls – Search for “Spirulina”, “Blue-Green Algae”, “Algae”, and “Paralytic Shellfish Toxin”. These search terms may not be inclusive so use caution.

Canada Blue-green advisories – 2015 34
Not all provinces publish online lists of blue-green advisories; the list below is of the advisories that were published. Québec, British-Columbia, Saskatchewan, Nova Scotia, PEI, and Yukon, the Northwest Territories and Nunavut do not maintain an online list of blue-reen outbreaks in lakes/rivers in their provinces.


1. Planet Earth: Cosmology, Geology, and the Evolution of Life and Environment by Cesare Emiliani, Cambridge University Press, 1992
2. Komárek J. & Hauer T. (2013): – On-line database of cyanobacterial genera. – Word-wide electronic publication, Univ. of South Bohemia & Inst. of Botany AS CR
3. World Health Organization (WHO) – Toxic Cyanobacteria in Water: A guide to their public health consequences, monitoring and management, 1999
4. Agriculture and Agri-Food Canada – Algae, Cyanobacteria and Water Quality, 2002
5. Centers for Disease Control and Prevention – Harmful Algal Blooms (HABs), Page last updated July 24 2012
6. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Environmental Health, Division of Environmental Hazards & Health Effects – Facts About Cyanobacteria & Cyanobacterial Harmful Algal Blooms
7. The Alabama Cooperative Extension System (ACES) – Drinking Water / Human Health Domestic Animal Supply Systems
8. North American Lake Management Society – Position Statement 8 – Toxic Cyanobacteria Blooms
9. Health Canada – Guidelines for Canadian Recreational Water Quality, Date modified 22-Aug-2012
10. Health Canada – Table 2. Chemical and Physical Parameters, Last modified 26-Nov-2014
11. World Health Organization – 12. CHEMICAL FACT SHEETS, Last modified 2003
12. Water Today – A Guide to Canada’s Drinking Water, Part 1, Last modified 12-Aug-2012
13. World Health Organization (WHO) – Guidelines for Drinking Water Quality, Last modified 2003
14. Council on Environmental Quality, Office of Science and Technology Policy, Executive Office of the President – Scientific Assessment of Freshwater Harmful Algal Blooms, 2008
15. Global Water Research Coalition – International Guidance Manual for the Management of Toxic Cyanobacteria, 2009
16. Water Quality Research Australia – Management Strategies for Cyanobacteria (Blue-Green Algae) and their Toxins – a Guuide for Water Utilities, 2010
17. Australian Environmental Protection Agency 2003
18. Cyanobacterial Bloom Management, Current and Future Options – Abstracts from the meeting held 12 & 13 August, 2009, Parramatta, NSW
19. United States Environmental Protection Agency – Cyanobacteria and Cyanotoxins: Information for Drinking Water Systems, July 2012
20. World Health Organization – Guidelines for safe recreational water environments – Volume 1: Coastal and fresh waters, 2003
21. World Health Organization – Guidelines for safe recreational water environments – Volume 1: Coastal and fresh waters, 2003, Chapter 8, Algae and cyanobacteria in fresh water
22. The Blade – Water crisis grips hundreds of thousands in Toledo area, state of emergency declared – 3-Aug-2014
23. Phycological Society of America – BIOACCUMULATION OF MICROCYSTINS IN LETTUCE1, 2012
24. International Journal of Molecular Sciences – Compensatory Growth Induced in Zebrafish Larvae after Pre-Exposure to a Microcystis aeruginosa Natural Bloom Extract Containing Microcystins, 2009
25. Federal Environmental Agency (Umweltbundesamt) – Current approaches to cyanotoxin risk assessment, risk management and regulations in different countries, June, 2005
26. WHO – Toxic Cyanobacteria in Water: A guide to their public health consequences, monitoring and management, 1999
27. Sudbury & District Health Unit – Blue green algae confirmed in Sudbury’s Long Lake, Oct/2014
28. Health Canada – Environmental and Workplace Health – Blue-Green Algae (Cyanobacteria) and their Toxins, 30-Jan-2013
29. PLOS – Diatoms: A Novel Source for the Neurotoxin BMAA in Aquatic Environments, 2-Jan-2014
30. Acta Neurologica Scandinavica – Cyanobacterial neurotoxin BMAA in ALS and Alzheimer’s disease, 26-Feb-2009
31. PNAS – Transfer of a cyanobacterial neurotoxin within a temperate aquatic ecosystem suggests pathways for human exposure, 8-Apr-2010
32. Human Exposure to Cyanotoxins and Their Effects on Health, Feb/2013
33. Cyanobacterial Neurotoxin β-N-Methylamino-l-alanine (BMAA) in Shark Fins, 21-Feb-2012
34. Canada: Blue-green advisories – 2015


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