Blue-green algae—scientifically known as cyanobacteria—are a group of microscopic, photosynthetic bacteria found in diverse environments, particularly freshwater, but also in marine and terrestrial habitats. Despite the name "blue-green algae," they are not true algae but belong to the bacterial domain. Their common name arises from their color, which is produced by the pigments chlorophyll a (green) and phycocyanin (blue pigment).[1][2][3][4][5]
Key Characteristics
- Classification: Prokaryotic bacteria, not algae. They lack a nucleus and membrane-bound organelles, but possess internal photosynthetic membranes.[2][4][5]
- Photosynthesis: Cyanobacteria perform oxygenic photosynthesis, producing oxygen as a byproduct. They played a major role in the original oxygenation of Earth’s atmosphere more than 2 billion years ago.[4][2]
- Pigments: Contain chlorophyll a, various carotenoids (yellow/orange), the blue pigment phycocyanin, and sometimes the red pigment phycoerythrin, giving rise to various colors.[5][2][4]
- Morphology: Appear as unicellular, colonial, or filamentous forms. Some filaments develop specialized cells for nitrogen fixation (heterocysts) or spore-like survival forms (akinetes).[2][4]
- Nitrogen Fixation: Many cyanobacteria can fix atmospheric nitrogen, making them ecologically important in nutrient-poor environments.[4]
Ecological and Health Impacts
- Blooms: Under warm, nutrient-rich conditions (notably excess phosphorus and nitrogen), cyanobacteria can proliferate rapidly, forming dense "blooms" on water bodies. These blooms often appear as green, blue-green, or even reddish scums or mats on the surface.[3][6]
- Toxins: Some cyanobacterial species produce potent toxins (cyanotoxins) that can harm humans, pets, livestock, and wildlife. Toxins may affect the liver, nervous system, or skin, with exposure resulting from drinking, swimming in, or inhaling aerosolized water during blooms.[6][3]
Importance
- Evolution: Cyanobacteria are among the oldest organisms on Earth and are considered essential to the evolution of early life, as their oxygen production enabled the rise of aerobic (oxygen-breathing) organisms.[2]
- Modern Uses: Certain cyanobacteria, such as Spirulina, are cultivated for food and nutritional supplements.
Four views illustrating the morphology and structure of Nostoc pruniforme cyanobacteria colonies.
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- https://dem.ri.gov/environmental-protection-bureau/water-resources/research-monitoring/cyanobacteria-blue-green-algae
- https://en.wikipedia.org/wiki/Cyanobacteria
- https://www2.gov.bc.ca/gov/content/environment/air-land-water/water/water-quality/algae-watch/what-are-algae/cyanobacteria
- https://www.britannica.com/science/blue-green-algae
- https://science.cen.ulaval.ca/warwickvincent/PDFfiles/228.pdf
- https://pmc.ncbi.nlm.nih.gov/articles/PMC9025173/
- https://doh.wa.gov/community-and-environment/contaminants/blue-green-algae/faqs
- https://ucmp.berkeley.edu/bacteria/cyanointro.html
- http://www.ontario.ca/page/blue-green-algae
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