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Free-living cyanobacteria are present in the water of rice paddies, and cyanobacteria can be found growing as epiphytes on the surfaces of the green alga, Chara, where they may fix nitrogen. [65] Cyanobacteria such as Anabaena (a symbiont of the aquatic fern Azolla) can provide rice plantations with biofertilizer. [66]
The microcystin-producing Microcystis is a genus of freshwater cyanobacteria and thrives in warm water conditions, especially in stagnant waters. [7] The EPA predicted in 2013 that climate change and changing environmental conditions may lead to harmful algae growth and may negatively impact human health. [ 20 ]
The first published report that blue-green algae or cyanobacteria could have lethal effects appeared in Nature in 1878. George Francis described the algal bloom he observed in the estuary of the Murray River in Australia, as "a thick scum like green oil paint, some two to six inches thick." Wildlife which drank the water died rapidly and ...
Microcystis aeruginosa is a species of freshwater cyanobacteria that can form harmful algal blooms of economic and ecological importance. They are the most common toxic cyanobacterial bloom in eutrophic fresh water. Cyanobacteria produce neurotoxins and peptide hepatotoxins, such as microcystin and cyanopeptolin. [1]
Depending on the organism, its pigments, and the depth in the water column, algal blooms can be green, red, brown, golden, and purple. [2] Bright green blooms in freshwater systems are frequently a result of cyanobacteria (colloquially known as "blue-green algae") such as Microcystis.
Originally, biologists classified cyanobacteria as an algae, and referred to it as "blue-green algae". The more recent view is that cyanobacteria are bacteria, and hence are not even in the same Kingdom as algae. Most authorities exclude all prokaryotes, and hence cyanobacteria from the definition of algae. [87] [88]
Most cyanobacteria produce toxins, of which microcystin is only one group. When a cyanobacterium dies, its cell wall degrades while the toxins are released in the water. Microcystins are extremely stable in water and withstand chemical breakdown such as hydrolysis or oxidation. The half-life of this toxin is 3 weeks at pH 1 and 40 °C.
Anatoxin-a is a neurotoxin produced by multiple genera of freshwater cyanobacteria that are found in water bodies globally. [3] Some freshwater cyanobacteria are known to be salt tolerant and thus it is possible for anatoxin-a to be found in estuarine or other saline environments. [4]