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.
The dinoflagellates are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered protists. Dinoflagellates are mostly marine plankton, but they also are common in freshwater habitats. Their populations vary with sea surface temperature, salinity, and depth. Many dinoflagellates are photosynthetic, but a large fraction of these are in fact mixotrophic, combining photosynthesis with ingestion of prey.
Paralytic shellfish poisoning (PSP) is one of the four recognized syndromes of shellfish poisoning, which share some common features and are primarily associated with bivalve mollusks. These shellfish are filter feeders and accumulate neurotoxins, chiefly saxitoxin, produced by microscopic algae, such as dinoflagellates, diatoms, and cyanobacteria. Dinoflagellates of the genus Alexandrium are the most numerous and widespread saxitoxin producers and are responsible for PSP blooms in subarctic, temperate, and tropical locations. The majority of toxic blooms have been caused by the morphospecies Alexandrium catenella, Alexandrium tamarense, Gonyaulax catenella and Alexandrium fundyense, which together comprise the A. tamarense species complex. In Asia, PSP is mostly associated with the occurrence of the species Pyrodinium bahamense.
Karenia brevis is a microscopic, single-celled, photosynthetic organism in the genus Karenia. It is a marine dinoflagellate commonly found in the waters of the Gulf of Mexico. It is the organism responsible for the "Florida red tides" that affect the Gulf coasts of Florida and Texas in the U.S., and nearby coasts of Mexico. K. brevis has been known to travel great lengths around the Florida peninsula and as far north as the Carolinas.
Heterosigma akashiwo is a species of microscopic algae of the class Raphidophyceae. It is a swimming marine alga that episodically forms toxic surface aggregations known as harmful algal bloom. The species name akashiwo is from the Japanese for "red tide".
The genus Ceratium is restricted to a small number of freshwater dinoflagellate species. Previously the genus contained also a large number of marine dinoflagellate species. However, these marine species have now been assigned to a new genus called Tripos. Ceratium dinoflagellates are characterized by their armored plates, two flagella, and horns. They are found worldwide and are of concern due to their blooms.
Alexandrium fundyense is a species of dinoflagellates. It produces toxins that induce paralytic shellfish poisoning (PSP), and is a common cause of red tide. A. fundyense regularly forms massive blooms along the northeastern coasts of the United States and Canada, resulting in enormous economic losses and public health concerns.
A harmful algal bloom (HAB), or excessive algae growth, is an algal bloom that causes negative impacts to other organisms by production of natural algae-produced toxins, mechanical damage to other organisms, or by other means. HABs are sometimes defined as only those algal blooms that produce toxins, and sometimes as any algal bloom that can result in severely lower oxygen levels in natural waters, killing organisms in marine or fresh waters. Blooms can last from a few days to many months. After the bloom dies, the microbes that decompose the dead algae use up more of the oxygen, generating a "dead zone" which can cause fish die-offs. When these zones cover a large area for an extended period of time, neither fish nor plants are able to survive. Harmful algal blooms in marine environments are often called "red tides".
Karenia is a genus that consists of unicellular, photosynthetic, planktonic organisms found in marine environments. The genus currently consists of 12 described species. They are best known for their dense toxic algal blooms and red tides that cause considerable ecological and economical damage; some Karenia species cause severe animal mortality. One species, Karenia brevis, is known to cause respiratory distress and neurotoxic shellfish poisoning (NSP) in humans.
Dinophysis is a genus of dinoflagellates common in tropical, temperate, coastal and oceanic waters. It was first described in 1839 by Christian Gottfried Ehrenberg.
Alexandrium is a genus of dinoflagellates. It contains some of the dinoflagellate species most harmful to humans, because it produces toxic harmful algal blooms (HAB) that cause paralytic shellfish poisoning (PSP) in humans. There are about 30 species of Alexandrium that form a clade, defined primarily on morphological characters in their thecal plates.
Pyrodinium is a genus of dinoflagellates. It was first discovered in 1906 in the waters around New Providence Island in the Bahamas. Pyrodinium is a monospecific species with two varieties, Pyrodinium bahamense var. compressum and Pyrodinium bahamanse var. bahamense. Pyrodinium is well known for producing Paralytic Shellfish Toxins (PSTs), e.g. saxitoxin, and the bioluminescence that lights up the bioluminescent bays in the Bahamas, Jamaica and Puerto Rico.
Alexandrium catenella is a species of dinoflagellates. It is among the group of Alexandrium species that produce toxins that cause paralytic shellfish poisoning, and is a cause of red tide. ‘’Alexandrium catenella’’ is observed in cold, coastal waters, generally at temperate latitudes. These organisms have been found in the west coast of North America, Japan, Australia, and parts of South Africa.
Polykrikos kofoidii is a species of phagotrophic marine pseudocolonial dinoflagellates that can capture and engulf other protist prey, including the toxic dinoflagellate, Alexandrium tamarense. P. kofoidii is of scientific interest due to its status as a predator of other dinoflagellates, a behavior that is significant in the control of algal blooms. It has a complex life cycle of both vegetative (asexual) and sexual reproduction complicated by its pseudocolonial structure.
Cochlodinium polykrikoides is a species of red tide producing marine dinoflagellates known for causing fish kills around the world, and well known for fish kills in marine waters of Southeast Asia. C. polykrikoides has a wide geographic range, including North America, Central America, Western India, Southwestern Europe and Eastern Asia. Single cells of this species are ovoidal in shape, 30-50μm in length and 25-30μm in width.
Dinophysis acuminata is a marine plankton species of dinoflagellates that is found in coastal waters of the north Atlantic and Pacific oceans. The genus Dinophysis includes both phototrophic and heterotrophic species. D. acuminata is one of several phototrophic species of Dinophysis classed as toxic, as they produce okadaic acid which can cause diarrhetic shellfish poisoning (DSP). Okadiac acid is taken up by shellfish and has been found in the soft tissue of mussels and the liver of flounder species. When contaminated animals are consumed, they cause severe diarrhoea. D. acuminata blooms are constant threat to and indication of diarrhoeatic shellfish poisoning outbreaks.
Dinoflagellates are eukaryotic plankton, existing in marine and freshwater environments. Previously, dinoflagellates had been grouped into two categories, phagotrophs and phototrophs. Mixotrophs, however include a combination of phagotrophy and phototrophy. Mixotrophic dinoflagellates are a sub-type of planktonic dinoflagellates and are part of the phylum Dinoflagellata. They are flagellated eukaryotes that combine photoautotrophy when light is available, and heterotrophy via phagocytosis. Dinoflagellates are one of the most diverse and numerous species of phytoplankton, second to diatoms.
Polykrikos is one of the genera of family Polykrikaceae that includes athecate pseudocolony-forming dinoflagellates. Polykrikos are characterized by a sophisticated ballistic apparatus, named the nematocyst-taeniocyst complex, which allows species to prey on a variety of organisms. Polykrikos have been found to regulate algal blooms as they feed on toxic dinoflagellates. However, there is also some data available on Polykrikos being toxic to fish.
Ceratocorys is a genus of photosynthetic free-living marine dinoflagellates first described in 1883 by Friedrich Stein. Currently consisting of 12 species, this genus is typically found at the water surface in tropical and subtropical ocean regions, and has both low nutrient requirements and salinity sensitivity. All species in the genus have a theca; 29 membrane-bound armored plates with anywhere from 2 to 6 spines protruding from the cell. They reproduce through binary fission at temperatures above 20 °C during asexual reproduction and whether or not they have sexual reproduction is not known. Due to its bioluminescent capabilities, the type species of this genus, Ceratocorys horrida, has many practical applications. Its bioluminescent response to water flow means it can act as a model organism for understanding planktonic reaction to water movement. It is also sensitive to environmental molecules; by measuring the bioluminescent response it can be used in rapid toxicity tests to detect the levels of different contaminants in water systems. Its presence is also an indicator of different oceanic phenomena like upwellings or tropical waters.
Coolia is a marine dinoflagellate genus in the family Ostreopsidaceae. It was first described by Meunier in 1919. There are currently seven identified species distributed globally in tropical and temperate coastal waters. Coolia is a benthic or epiphytic type dinoflagellate: it can be found adhered to sediment or other organisms but it is not limited to these substrates. It can also be found in a freely motile form in the water column. The life cycle of Coolia involves an asexual stage where the cell divides by binary fission and a sexual stage where cysts are produced. Some of the species, for example, Coolia tropicalis and Coolia malayensis, produce toxins that can potentially cause shellfish poisoning in humans.
