An algal bloom or algae bloom is a rapid increase or accumulation in the population of algae in freshwater or marine water systems. It is often recognized by the discoloration in the water from the algae's pigments. The term algae encompasses many types of aquatic photosynthetic organisms, both macroscopic multicellular organisms like seaweed and microscopic unicellular organisms like cyanobacteria. Algal bloom commonly refers to the rapid growth of microscopic unicellular algae, not macroscopic algae. An example of a macroscopic algal bloom is a kelp forest.
Cyanobacteria, also called Cyanobacteriota or Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name cyanobacteria refers to their color, which similarly forms the basis of cyanobacteria's common name, blue-green algae, although they are not usually scientifically classified as algae. They appear to have originated in a freshwater or terrestrial environment. Sericytochromatia, the proposed name of the paraphyletic and most basal group, is the ancestor of both the non-photosynthetic group Melainabacteria and the photosynthetic cyanobacteria, also called Oxyphotobacteria.
Microcystins—or cyanoginosins—are a class of toxins produced by certain freshwater cyanobacteria, commonly known as blue-green algae. Over 250 different microcystins have been discovered so far, of which microcystin-LR is the most common. Chemically they are cyclic heptapeptides produced through nonribosomal peptide synthases.
Cyanotoxins are toxins produced by cyanobacteria. Cyanobacteria are found almost everywhere, but particularly in lakes and in the ocean where, under high concentration of phosphorus conditions, they reproduce exponentially to form blooms. Blooming cyanobacteria can produce cyanotoxins in such concentrations that they can poison and even kill animals and humans. Cyanotoxins can also accumulate in other animals such as fish and shellfish, and cause poisonings such as shellfish poisoning.
Anabaena circinalis is a species of Gram-negative, photosynthetic cyanobacteria common to freshwater environments throughout the world. Much of the scientific interest in A. circinalis owes to its production of several potentially harmful cyanotoxins, ranging in potency from irritating to lethal. Under favorable conditions for growth, A. circinalis forms large algae-like blooms, potentially harming the flora and fauna of an area.
Anatoxin-a, also known as Very Fast Death Factor (VFDF), is a secondary, bicyclic amine alkaloid and cyanotoxin with acute neurotoxicity. It was first discovered in the early 1960s in Canada, and was isolated in 1972. The toxin is produced by multiple genera of cyanobacteria and has been reported in North America, South America, Central America, Europe, Africa, Asia, and Oceania. Symptoms of anatoxin-a toxicity include loss of coordination, muscular fasciculations, convulsions and death by respiratory paralysis. Its mode of action is through the nicotinic acetylcholine receptor (nAchR) where it mimics the binding of the receptor's natural ligand, acetylcholine. As such, anatoxin-a has been used for medicinal purposes to investigate diseases characterized by low acetylcholine levels. Due to its high toxicity and potential presence in drinking water, anatoxin-a poses a threat to animals, including humans. While methods for detection and water treatment exist, scientists have called for more research to improve reliability and efficacy. Anatoxin-a is not to be confused with guanitoxin, another potent cyanotoxin that has a similar mechanism of action to that of anatoxin-a and is produced by many of the same cyanobacteria genera, but is structurally unrelated.
Cylindrospermopsin is a cyanotoxin produced by a variety of freshwater cyanobacteria. CYN is a polycyclic uracil derivative containing guanidino and sulfate groups. It is also zwitterionic, making it highly water soluble. CYN is toxic to liver and kidney tissue and is thought to inhibit protein synthesis and to covalently modify DNA and/or RNA. It is not known whether cylindrospermopsin is a carcinogen, but it appears to have no tumour initiating activity in mice.
Nodularins are potent toxins produced by the cyanobacterium Nodularia spumigena, among others. This aquatic, photosynthetic cyanobacterium forms visible colonies that present as algal blooms in brackish water bodies throughout the world. The late summer blooms of Nodularia spumigena are among the largest cyanobacterial mass occurrences in the world. Cyanobacteria are composed of many toxic substances, most notably of microcystins and nodularins: the two are not easily differentiated. A significant homology of structure and function exists between the two, and microcystins have been studied in greater detail. Because of this, facts from microcystins are often extended to nodularins.
Bacterioplankton refers to the bacterial component of the plankton that drifts in the water column. The name comes from the Ancient Greek word πλανκτος, meaning "wanderer" or "drifter", and bacterium, a Latin term coined in the 19th century by Christian Gottfried Ehrenberg. They are found in both seawater and freshwater.
Microcystin-LR (MC-LR) is a toxin produced by cyanobacteria. It is the most toxic of the microcystins.
Planktothrix is a diverse genus of filamentous cyanobacteria observed to amass in algal blooms in water ecosystems across the globe. Like all Oscillatoriales, Planktothrix species have no heterocysts and no akinetes. Planktothrix are unique because they have trichomes and contain gas vacuoles unlike typical planktonic organisms. Previously, some species of the taxon were grouped within the genus Oscillatoria, but recent work has defined Planktothrix as its own genus. A tremendous body of work on Planktothrix ecology and physiology has been done by Anthony E. Walsby, and the 55.6 kb microcystin synthetase gene which gives these organisms the ability to synthesize toxins has been sequenced. P. agardhii is an example of a type species of the genus. P. agardhii and P. rubescens are commonly observed in lakes of the Northern Hemisphere where they are known producers of potent hepatotoxins called microcystins.
Cyclamides are a class of oligopeptides produced by cyanobacteria algae strains such as Microcystis aeruginosa. Some of them can be toxic.
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. Microcystis aeruginosa produces numerous congeners of microcystin, with microcystin-LR being the most common. Microcystis blooms have been reported in at least 108 countries, with the production of microcystin noted in at least 79.
Cylindrospermopsis raciborskii is a freshwater cyanobacterium. (name currently accepted taxonomically: Raphidipsis raciborskii)
Cyanopeptolins (CPs) are a class of oligopeptides produced by Microcystis and Planktothrix algae strains, and can be neurotoxic. The production of cyanopeptolins occurs through nonribosomal peptides synthases (NRPS).
Cyanothece is a genus of unicellular, diazotrophic, oxygenic photosynthesizing cyanobacteria.
Gloeotrichia is a large (~2 mm) colonial genus of Cyanobacteria, belonging to the order Nostocales. The name Gloeotrichia is derived from its appearance of filamentous body with mucilage matrix. Found in lakes across the globe, gloeotrichia are notable for the important roles that they play in the nitrogen and phosphorus cycles. Gloeotrichia are also a species of concern for lake managers, as they have been shown to push lakes towards eutrophication and produce deadly toxins.
George S. Bullerjahn is an American microbiologist, a former Distinguished Research Professor at Bowling Green State University in Ohio. He is the founding director of the Great Lakes Center for Fresh Waters and Human Health. His specialty is microbial ecology; his research has focused on the health of the Laurentian Great Lakes, particularly the harmful algal bloom-forming populations in Lake Erie since the early 2000s.
Hans W. Paerl is a Dutch American limnologist and a Kenan Professor of Marine and Environmental Sciences at the University of North Carolina – Chapel Hill (UNC-CH) Institute of Marine Sciences. His research primarily assesses microbially-mediated nutrient cycling, primary production dynamics, and the consequences of human impacts on water quality and sustainability in waters around the world.
Robert Michael Lee McKay is a Canadian microbiologist and presently the executive director and a professor of the Great Lakes Institute for Environmental Research, School of Environment, at the University of Windsor. McKay's research interest center around the physiological ecology of phytoplankton communities in large lakes and oceans. His efforts focus on environmental microbiology including harmful cyanobacterial blooms and blooms of ice-associated algae in the Great Lakes.
