Basic Information on Cyanobacteria
Cyanobacteria (blue-green algae) blooms have been occurring throughout the world for thousands of years. Cyanobacteria produce a number of nuisance compounds, including those that are toxic or cause severe taste-and-odor problems in drinking water supplies. Cyanobacterial toxins can make drinking water and recreational use of water unsafe. Animals die yearly as a result of cyanotoxins, and though human death is not common, many people experience symptoms indicative of cyanotoxin exposure. Very little is known about the long-term side affects of ingestion of cyanotoxins, so alhtough there is a guideline set by WHO for safe concentrations, minimal concentrations could cause an effect over time.
- Nutrient Availability: Nutrients are a limiting factor for cyanobacteria populations. As long as the correct nutrients are in excess, they can grow until some other factor, often light or temperature, becomes limiting.
- Competition: Ability to adapt to the environment is a big factors determining whether a bloom will form. Many blue-greens are less edible, have gas vacuoles that help them float, can sequester nutrients at the sediment water interface, or can fix dissobled nitrogen, any of which can give them a competitive advantage over other algae and lead to bloom formation.
- Light Intensity: Since cyanobacteria are phytoplankton, light is important and different species thrive under different light intensities. If light is not extinguished by particles or color in the water, a bloom is more likely. Many blue-greens thrive under low light, and so may be favored unless light is nearly absent (such as in some high particulate reservoir systems).
- Mixing: Mixing allows nutrients to be more evenly distributed and affects other aspects of water quality that in turn affect algal abundance and composition. Mixing can also move algae to depths with less light, limiting growth and survival. In general, blue-greens do better wtih less mixing (Cylindrospermopsis is one taxon that seems to do well in mixed systems, though).
- Temperature: Surface water temperatures consistently above 28 degrees Celsius (82 degrees Fahrenheit) encourage blue-green blooms, although blooms may still occur in late fall (October, November) in the Northern U.S.
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Toxicity: Not all blue-greens are toxic, so while risk may be higher during a bloom, high biomass does not necessarily result in toxicity. Also, although many toxin producing algae produce taste and odor compounds, the presence or absence of geosmin or MIB is not a predictor of the presence of toxins.
Cyanotoxins and Taste/Odor Compounds
Major Classes of Toxins
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Hepatotoxins
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Neurotoxins
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Dermatotoxins-Lyngbyatoxin
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BMAA - beta-n-methylamino-L-alanine
Australian Research Network for Algal Toxins
Major Taste and Odor Compounds
Common Cyanotoxins: Lethal Dose based on weight for 50% of the population. Figure contributed by Jennifer Graham, USGS, based on data from Chorus and Bartram, 1999.
Major Taxa
Although there are about 50 toxigenic algal taxa, most fall into one of a handful of genera.
| Microcystis | Anabaena | Aphanizomenon | Cylindrospermopsis | Oscillatoria (Planktothrix) |
|---|---|---|---|---|
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Toxin and Taste-and-Odor Producing Cyanobacteria (list is not exhaustive)
[LYN, lyngbyatoxin-a; APL, aplysiatoxins; LPS, lipopolysaccharides; CYL, cylindrospermopsins; MC, microcystins; NOD, nodularins; ANA, anatoxins; BMAA, β-N-methylamino-L-alanine; NEO, neosaxitoxins; SAX, saxitoxins; GEOS, geosmin; MIB, 2-methylisoborneol]
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Dermatoxins |
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Hepatotoxins |
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Neurotoxins |
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Tastes and Odors |
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LYN |
APL |
LPS |
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CYL |
MC |
NOD |
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ANA |
BMAA |
NEO |
SAX |
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GEOS |
MIB |
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Cyanobacterial Genera |
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Colonial/Filamentous |
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Anabaena |
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X |
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X |
X |
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X |
X |
X |
X |
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X |
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Anabaenopsis |
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X |
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X |
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Aphanizomenon |
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X |
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X |
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X |
X |
X |
X |
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X |
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Aphanocapsa |
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X |
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X |
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Cylindrospermopsis |
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X |
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X |
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X |
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X |
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Fischerella |
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X |
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X |
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X |
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| Gloeotrichia | X |
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Haplosiphon |
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X |
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X |
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Hyella |
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X |
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X |
X |
Lyngbya (Plectonema) |
X |
X |
X |
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X |
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X |
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X |
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X |
X |
Microcystis |
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X |
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X |
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X |
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Nodularia |
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X |
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X |
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X |
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Nostoc |
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X |
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X |
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X |
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X |
X |
Oscillatoria (Planktothrix) |
X |
X |
X |
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X |
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X |
X |
|
X |
|
X |
X |
Phormidium |
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X |
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X |
X |
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X |
X |
Pseudanabaena |
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X |
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X |
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X |
Raphidiopsis |
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X |
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X |
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X |
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Schizothrix |
X |
X |
X |
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Umezakia |
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X |
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X |
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Unicellular |
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Synechococcus |
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X |
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X |
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X |
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X |
X |
Synechocystis |
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X |
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X |
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X |
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Table courtesy of Jennifer Graham, USGS
Concentration Limits for recreational & drinking waters
World Health Organization
Nebraska Department of Environmental Quality
California Division of Drinking Water and Environmental Management
Oregon DHS Environmental Toxicology Program
Iowa DNR/DPH Beach monitoring - State Park Algae Results
Florida DEH Aquatic Toxins Program
Health Canada
Blue-Green Algae (Cyanobacteria) and their Toxins
Other non-bluegreen freshwater toxic algae
Prymnesium parvum. A toxic Haptophyte
Pyrmnesium is primarily an issue for fisheries. It acts on exposed cells such as gill tissue and has not been linked directly with human or mammalian illness or death.
Reports, Publications, and other links
U.S. EPA
NOAA
USGS
World Health Organization
WHO Report: Toxic cyanobacteria in water: A guide to their public health consequences, monitoring and management
Links to Various Other Toxic Algal Sites
