title: State of knowledge and concerns on cyanobacterial blooms and cyanotoxins.
abstract: Cyanobacteria are ubiquitous microorganisms considered as important contributors to the formation of Earth's atmosphere and nitrogen fixation. However, they are also frequently associated with toxic blooms. Indeed, the wide range of hepatotoxins, neurotoxins and dermatotoxins synthesized by these bacteria is a growing environmental and public health concern. This paper provides a state of the art on the occurrence and management of harmful cyanobacterial blooms in surface and drinking water, including economic impacts and research needs. Cyanobacterial blooms usually occur according to a combination of environmental factors e.g., nutrient concentration, water temperature, light intensity, salinity, water movement, stagnation and residence time, as well as several other variables. These environmental variables, in turn, have promoted the evolution and biosynthesis of strain-specific, gene-controlled metabolites (cyanotoxins) that are often harmful to aquatic and terrestrial life, including humans. Cyanotoxins are primarily produced intracellularly during the exponential growth phase. Release of toxins into water can occur during cell death or senescence but can also be due to evolutionary-derived or environmentally-mediated circumstances such as allelopathy or relatively sudden nutrient limitation. Consequently, when cyanobacterial blooms occur in drinking water resources, treatment has to remove both cyanobacteria (avoiding cell lysis and subsequent toxin release) and aqueous cyanotoxins previously released. Cells are usually removed with limited lysis by physical processes such as clarification or membrane filtration. However, aqueous toxins are usually removed by both physical retention, through adsorption on activated carbon or reverse osmosis, and chemical oxidation, through ozonation or chlorination. While the efficient oxidation of the more common cyanotoxins (microcystin, cylindrospermopsin, anatoxin and saxitoxin) has been extensively reported, the chemical and toxicological characterization of their by-products requires further investigation. In addition, future research should also investigate the removal of poorly considered cyanotoxins (β-methylamino-alanine, lyngbyatoxin or aplysiatoxin) as well as the economic impact of blooms.
authors.affiliation: Department of Chemical and Environmental Engineering, University of Arizona, 1133 James E. Rogers Way, Tucson, AZ 85721, USA. smerel@email.arizona.edu
authors.forename: Sylvain
authors.initials: S
authors.lastname: Merel
authors.forename: David
authors.initials: D
authors.lastname: Walker
authors.forename: Ruth
authors.initials: R
authors.lastname: Chicana
authors.forename: Shane
authors.initials: S
authors.lastname: Snyder
authors.forename: Estelle
authors.initials: E
authors.lastname: Baurès
authors.forename: Olivier
authors.initials: O
authors.lastname: Thomas
mesh_terms: D000470:Alkaloids; D001427:Bacterial Toxins / Q000032:analysis / Q000378:metabolism*; D000458:Cyanobacteria / Q000254:growth & development* / Q000378:metabolism; D000087522:Cyanobacteria Toxins; D060766:Drinking Water / Q000737:chemistry / Q000382:microbiology*; D004784:Environmental Monitoring; D005618:Fresh Water / Q000737:chemistry / Q000382:microbiology*; D052998:Microcystins / Q000032:analysis / Q000378:metabolism; D010456:Peptides, Cyclic / Q000032:analysis / Q000378:metabolism; D014498:Uracil / Q000031:analogs & derivatives / Q000032:analysis / Q000378:metabolism; D014871:Water Microbiology
chemical_list: D000470:Alkaloids; D001427:Bacterial Toxins; D000087522:Cyanobacteria Toxins; D060766:Drinking Water; D052998:Microcystins; D010456:Peptides, Cyclic; C063998:nodularin; C089595:cylindrospermopsin; D014498:Uracil; C078588:microcystin
keywords: Anatoxin; BMAA; Cylindrospermopsin; Drinking water treatment; Microcystin; Saxitoxin