An algal bloom is a rapid increase or accumulation in the population of algae Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. The US Algal Collection is represented by almost 300,000 accessioned and inventoried herbarium specimens. The largest and most complex marine forms are called in an aquatic system. Algal blooms may occur in freshwater as well as marine environments. Typically, only one or a small number of phytoplankton Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτόν , meaning "plant", and πλαγκτός (planktos), meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye. However, when present in high enough species are involved, and some blooms may be recognized by discoloration of the water resulting from the high density of pigmented cells. Although there is no officially recognized threshold level, algae can be considered to be blooming at concentrations of hundreds to thousands of cells per milliliter, depending on the severity. Algal bloom concentrations may reach millions of cells per milliliter. Algal blooms are often green, but they can also be other colors such as yellow-brown or red, depending on the species of algae.

Bright green blooms are a result of blue-green algae, which are actually bacteria (cyanobacteria Cyanobacteria is a phylum of bacteria that obtain their energy through photosynthesis. The name "cyanobacteria" comes from the color of the bacteria (Greek: κυανός (kyanós) = blue)). Blooms may also consist of macroalgal, not phytoplankton, species. These blooms are recognizable by large blades of algae that may wash up onto the shoreline.

Of particular note are harmful algal blooms (HABs), which are algal bloom events involving toxic or otherwise harmful phytoplankton such as dinoflagellates The dinoflagellates are a large group of flagellate protists. Most are marine plankton, but they are common in fresh water habitats as well. Their populations are distributed depending on temperature, salinity, or depth. About half of all dinoflagellates are photosynthetic, and these make up the largest group of eukaryotic algae aside from the of the genus In biology, a genus is a low-level taxonomic rank (a taxon) used in the classification of living and fossil organisms, which is an example of definition by genus and differentia. The term comes from Latin genus "descent, family, type, gender", cognate with Greek: γένος – genos, "race, stock, kin" Alexandrium and Karenia. Such blooms often take on a red or brown hue and are known colloquially as red tides.

Freshwater algal blooms

Freshwater algal blooms are the result of an excess of nutrients, particularly phosphorus Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus is commonly found in inorganic phosphate rocks. Elemental phosphorus exists in two major forms – white phosphorus and red phosphorus. Although the term "phosphorescence", meaning glow after.^[1] The excess of nutrients may originate from fertilizers that are applied to land for agricultural or recreational purposes, these nutrients can then enter watersheds A drainage basin is an extent or area of land where water from rain and melting snow or ice drains downhill into a body of water, such as a river, lake, reservoir, estuary, wetland, sea or ocean. The drainage basin includes both the streams and rivers that convey the water as well as the land surfaces from which water drains into those channels, through water runoff.^[2] Excess carbon Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. There are three naturally occurring isotopes, with 12C and 13C being stable, while 14C is radioactive, decaying with a half-life of and nitrogen Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere have also been suspected as causes.

When phosphates are introduced into water systems, higher concentrations cause increased growth of algae and plants. Algae tend to grow very quickly under high nutrient availability, but each alga is short-lived, and the result is a high concentration of dead organic matter which starts to decay. The decay process consumes dissolved oxygen in the water, resulting in hypoxic Hypoxia or oxygen depletion is a phenomenon that occurs in aquatic environments as dissolved oxygen becomes reduced in concentration to a point detrimental to aquatic organisms living in the system. Dissolved oxygen is typically expressed as a percentage of the oxygen that would dissolve in the water at the prevailing temperature and salinity ( conditions. Without sufficient dissolved oxygen in the water, animals and plants may die off Dead zones are hypoxic areas in the world's oceans, the observed incidences of which have been increasing since oceanographers began noting them in the 1970s. These occur near inhabited coastlines, where aquatic life is most concentrated. (The vast middle portions of the oceans which naturally have little life are not considered "dead zones& in large numbers.

Blooms may be observed in freshwater aquariums A freshwater aquarium is a receptacle that holds one or more freshwater aquatic organisms for decorative, pet-keeping, or research purposes. Modern aquariums are most often made from transparent glass or acrylic glass. Typical inhabitants include fish, plants, amphibians, and invertebrates, such as snails and crustaceans when fish are overfed and excess nutrients are not absorbed by plants. These are not generally harmful for fish, and the situation can be corrected by changing the water in the tank and then reducing the amount of food given.

Water treatment

Algal blooms sometimes occur in drinking water supplies. In such cases, toxins from the bloom can survive standard water purifying treatments. Researchers at Florida International University Florida International University, commonly referred to as FIU, is a public research university located in Miami, Florida, in the United States, with its main campus at University Park. Florida International University is classified as a Research University with high research activity by the Carnegie Foundation, and is a first-tier research in Miami are experimenting with using 640-kilohertz ultrasound Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Although this limit varies from person to person, it is approximately 20 kilohertz in healthy, young adults and thus, 20 kHz serves as a useful lower limit in describing ultrasound. The production of ultrasound is used in many different fields, waves that create micropressure zones as hot as 3,700 °C. This breaks some water molecules into reactive fragments that can kill algae.^[3]

Measurement

Algal blooms are monitored using biomass measurements coupled with the examination of species present. A widely-used measure of algal and cyanobacterial chlorophyll Chlorophyll is a green pigment found in all plants, algae, and cyanobacteria. Its name is derived from the Greek χλωρός (chloros "green") and φύλλον (phyllon "leaf"). Chlorophyll absorbs light most strongly in the blue portion of the electromagnetic spectrum, followed by the red portion. However, it is a poor concentration. Peak values of chlorophyll a for an oligotrophic lake are about 1-10 µg/l, while in a eutrophic lake they can reach 300 µg/l. In cases of hypereutrophy, such as Hartbeespoort Dam in South Africa Coordinates: 29°02′46″S 25°03′47″E / 29.046°S 25.063°E The Republic of South Africa is a country located at the southern tip of Africa, with a 2,798 kilometres coastline on the Atlantic and Indian Oceans. To the north lie Namibia, Botswana and Zimbabwe; to the east are Mozambique and Swaziland; while Lesotho is an independent, maxima of chlorophyll a can be as high as 3,000 µg/l.^{[4] [5]}

Tai Hu Algal Bloom

Lake Tai Lake Tai is a large lake in the Yangtze Delta plain, on the border of the Jiangsu and Zhejiang provinces in the People's Republic of China. The waters of the lake belong to the former in its entirety with part of its southern shore forming the boundary between the two provinces. With an area of 2,250 km² and an average depth of 2 metres, it is in Eastern China has had an algal bloom which has attracted the attention of the ENGO An ENGO is an Environmental Non-governmental organization, such as WWF, Greenpeace, Conservation International or the Environmental Investigation Agency sector. Greenpeace China investigated the algal bloom at Lake Tai and took water samples. Of 25 samples, 20 were too polluted to be used to water plants or in factories.^[6]

Harmful Algal Blooms

A harmful algal bloom (HAB) is an algal bloom that causes negative impacts to other organisms via production of natural toxins, mechanical damage to other organisms, or by other means. HABs are often associated with large-scale marine mortality events and have been associated with various types of shellfish poisonings.^[7]

Background

In the marine environment, single-celled, microscopic, plant-like organisms naturally occur in the well-lit surface layer of any body of water. These organisms, referred to as phytoplankton Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτόν , meaning "plant", and πλαγκτός (planktos), meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye. However, when present in high enough or microalgae, form the base of the food web upon which nearly all other marine organisms depend. Of the 5000+ species of marine phytoplankton that exist worldwide, about 2% are known to be harmful or toxic^[8]. Blooms of harmful algae can have large and varied impacts on marine ecosystems, depending on the species involved, the environment where they are found, and the mechanism by which they exert negative effects. Examples of common harmful effects of HABs include:

1. the production of neurotoxins which cause mass mortalities in fish, seabirds and marine mammals
2. human illness or death via consumption of seafood contaminated by toxic algae^[9]
3. mechanical damage to other organisms, such as disruption of epithelial gill tissues in fish, resulting in asphyxiation
4. oxygen depletion of the water column (hypoxia or anoxia) from cellular respiration and bacterial degradation

Due to their negative economic and health impacts, HABs are often carefully monitored ^[10][11].

HABs occur in many regions of the world, and in the United States are recurring phenomena in multiple geographical regions. The Gulf of Maine The Gulf of Maine is a large gulf of the Atlantic Ocean on the northeastern coast of North America frequently experiences blooms of the dinoflagellate The dinoflagellates are a large group of flagellate protists. Most are marine plankton, but they are common in fresh water habitats as well. Their populations are distributed depending on temperature, salinity, or depth. About half of all dinoflagellates are photosynthetic, and these make up the largest group of eukaryotic algae aside from the Alexandrium fundyense, an organism that produces saxitoxin Saxitoxin is a neurotoxin naturally produced by certain species of marine dinoflagellates (Alexandrium sp., Gymnodinium sp., Pyrodinium sp.) and cyanobacteria (Anabaena sp., some Aphanizomenon spp., Cylindrospermopsis sp., Lyngbya sp., Planktothrix sp.). Ingestion of saxitoxin (usually through shellfish contaminated by toxic algal blooms) is, the neurotoxin responsible for paralytic shellfish poisoning Paralytic shellfish poisoning is one of the four recognized syndromes of shellfish poisoning (the others being neurotoxic shellfish poisoning, diarrhetic shellfish poisoning and amnesic shellfish poisoning). All four syndromes share some common features and are primarily associated with bivalve molluscs (such as mussels, clams, oysters and. The well-known "Florida red tide" that occurs in the Gulf of Mexico is a HAB caused by Karenia brevis, another dinoflagellate which produces brevetoxin Brevetoxin , or brevetoxins, are a suite of cyclic polyether compounds produced naturally by a species of dinoflagellate known as Karenia brevis. Brevetoxins are neurotoxins that bind to voltage-gated sodium channels in nerve cells, leading to disruption of normal neurological processes and causing the illness clinically described as neurotoxic, the neurotoxin responsible for neurotoxic shellfish poisoning Neurotoxic Shellfish Poisoning is caused by the consumption of shellfish contaminated by brevetoxins or brevetoxin analogs. California coastal waters also experience seasonal blooms of Pseudo-nitzschia, a diatom Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans (e.g. Meridion), zigzags (e.g. Tabellaria), or stellate colonies (e.g. Asterionella). Diatoms are producers within the food chain. A characteristic known to produce domoic acid, the neurotoxin responsible for amnesic shellfish poisoning. Off the west coast of South Africa Coordinates: 29°02′46″S 25°03′47″E / 29.046°S 25.063°E The Republic of South Africa is a country located at the southern tip of Africa, with a 2,798 kilometres coastline on the Atlantic and Indian Oceans. To the north lie Namibia, Botswana and Zimbabwe; to the east are Mozambique and Swaziland; while Lesotho is an independent, HABs caused by Alexandrium catanella occur every spring. These blooms of organisms cause severe disruptions in fisheries Generally, a fishery is an entity engaged in raising and/or harvesting fish, which is determined by some authority to be a fishery. According to the FAO, a fishery is typically defined in terms of the "people involved, species or type of fish, area of water or seabed, method of fishing, class of boats, purpose of the activities or a of these waters as the toxins in the phytoplankton cause filter-feeding shellfish Shellfish is a culinary and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater environments, some kinds are found only in freshwater. In addition a few species of land crabs are eaten, for in affected waters to become poisonous for human consumption ^[12].

If the HAB event results in a high enough concentration of algae the water may become discoloured or murky, varying in colour from purple to almost pink, normally being red or green. Not all algal blooms are dense enough to cause water discolouration.

"Red Tides"

"Red tide" is a term often used to describe HABs in marine coastal areas ^[13], as the dinoflagellate species involved in HABs are often red or brown, and tint the sea water to a reddish color. The more correct and preferred term in use is harmful algal bloom, because:

1. these blooms are not associated with tides
2. not all algal blooms cause reddish discoloration of water
3. not all algal blooms are harmful, even those involving red discolouration ^[14]

Causes of HABs

It is unclear what causes HABs; their occurrence in some locations appears to be entirely natural,^[15] while in others they appear to be a result of human activities^[16] Furthermore, there are many different species of algae that can form HABs, each with different environmental requirements for optimal growth. The frequency and severity of HABs in some parts of the world have been linked to increased nutrient loading from human activities. In other areas, HABs are a predictable seasonal occurrence resulting from coastal upwelling, a natural result of the movement of certain ocean currents.^[17] The growth of marine phytoplankton (both non-toxic and toxic) is generally limited by the availability of nitrates and phosphates, which can be abundant in coastal upwelling zones as well as in agricultural run-off. The type of nitrates and phosphates available in the system are also a factor, since phytoplankton can grow at different rates depending on the relative abundance of these substances (e.g. ammonia, urea, nitrate ion). A variety of other nutrient sources can also play an important role in affecting algal bloom formation, including iron, silica or carbon. Coastal water pollution Water pollution is the contamination of water bodies produced by humans and systematic increase in sea water temperature Global warming is the increase in the average temperature of Earth's near-surface air and oceans since the mid-20th century and its projected continuation. According to the 2007 Fourth Assessment Report by the Intergovernmental Panel on Climate Change , global surface temperature increased 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the 20th have also been suggested as possible contributing factors in HABs^{[citation needed]}. Other factors such as iron-rich dust influx from large desert areas such as the Saharan desert are thought to play a role in causing HABs.^[18] Some algal blooms on the Pacific coast have also been linked to natural occurrences of large-scale climatic oscillations such as El Niño El Niño-Southern Oscillation,' often called simply ENSO, is a climate pattern that occurs across the tropical Pacific Ocean on average every five years, but over a period which varies from three to seven years, and is therefore, widely and significantly, known as "quasi-periodic." ENSO is best-known for its association with floods, events. While HABs in the Gulf of Mexico have been occurring since the time of early explorers such as Cabeza de Vaca Álvar Núñez Cabeza de Vaca was a Spanish explorer of the New World, one of four survivors of the Narváez expedition. He is remembered as a proto-anthropologist for his detailed accounts of the many tribes of Native Americans, first published in 1542 as La Relación (The Report), and later known as Naufragios (Shipwrecks),^[19] it is unclear what initiates these blooms and how large a role anthropogenic Anthropogenic effects, processes or materials are those that are derived from human activities, as opposed to those occurring in biophysical environments without human influence and natural factors play in their development. It is also unclear whether the apparent increase in frequency and severity of HABs in various parts of the world is in fact a real increase or is due to increased observation effort and advances in species identification methods.^[20][21]

Notable occurrences

• People may experience respiratory irritation (coughing, sneezing, and tearing) when the phytoplankton Karenia brevis is present along a coast and winds blow its toxic aerosol onshore. Swimming is usually safe, but skin irritation and burning is possible in areas of high concentration.^[22]
• In 1972 a red tide was caused in New England by a toxic dinoflagellate Alexandrium (Gonyaulax) tamarense.^[23]
• In 2005 the Canadian HAB was discovered to have come further south than it has in years prior by a ship called The Oceanus, closing shellfish beds in Maine and Massachusetts and alerting authorities as far south as Montauk Montauk is a census-designated place that roughly corresponds to the hamlet (unincorporated community) with the same name located in the town of East Hampton in Suffolk County, New York on the South Shore of Long Island. As of the United States 2000 Census, the CDP population was 3,851. Montauk is the easternmost census-designated place in New (Long Island Long Island is an island located in southeastern New York, United States, just east of Manhattan. Stretching northeast into the Atlantic Ocean, Long Island contains four counties, two of which are boroughs of New York City, and two of which (Nassau and Suffolk) are mainly suburban or rural. In popular usage, the term "Long Island", NY) to check their beds.^[24] Experts who discovered the reproductive cysts in the seabed warn of a possible spread to Long Island in the future, halting the area's fishing and shellfish industry and threatening the tourist trade, which constitutes a significant portion of the island's economy.

See also

• Algae fuel Algae fuel, also called algal fuel, algaeoleum or third-generation biofuel, is a biofuel which is derived from algae. During photosynthesis, algae and other photosynthetic organisms capture carbon dioxide and sunlight and convert it into oxygen and biomass. Up to 99% of the carbon dioxide in solution can be converted, which was shown by Weissman
• Amnesic shellfish poisoning
• Brevetoxin Brevetoxin , or brevetoxins, are a suite of cyclic polyether compounds produced naturally by a species of dinoflagellate known as Karenia brevis. Brevetoxins are neurotoxins that bind to voltage-gated sodium channels in nerve cells, leading to disruption of normal neurological processes and causing the illness clinically described as neurotoxic
• Ciguatera Ciguatera is a foodborne illness caused by eating certain reef fishes whose flesh is contaminated with toxins originally produced by dinoflagellates such as Gambierdiscus toxicus which lives in tropical and subtropical waters. These dinoflagellates adhere to coral, algae and seaweed, where they are eaten by herbivorous fish who in turn are eaten
• Cyanotoxin A cyanotoxin is a toxin produced by certain cyanobacteria . When produced during algal blooms ("red tide"), cyanotoxins 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
• Dead zone (ecology) Dead zones are hypoxic areas in the world's oceans, the observed incidences of which have been increasing since oceanographers began noting them in the 1970s. These occur near inhabited coastlines, where aquatic life is most concentrated. (The vast middle portions of the oceans which naturally have little life are not considered "dead zones&
• Dinoflagellate The dinoflagellates are a large group of flagellate protists. Most are marine plankton, but they are common in fresh water habitats as well. Their populations are distributed depending on temperature, salinity, or depth. About half of all dinoflagellates are photosynthetic, and these make up the largest group of eukaryotic algae aside from the
• Domoic acid
• Emiliania huxleyi Emiliania huxleyi, often abbreviated to simply "EHUX", is a species of coccolithophore with a global distribution from the tropics to subarctic waters. It is studied for the extensive blooms it forms in nutrient depleted waters after the reformation of the summer thermocline. Like other coccolithophores, E. huxleyi is a single-celled
• Eutrophication Eutrophication is an increase in the concentration of nutrient content to an extent that increases the primary productivity of the waterbody. In other terms, it is the "bloom" or great increase of phytoplankton in a water body. Negative environmental effects include particularly anoxia, or loss of oxygen in the water with severe
• Paralytic shellfish poisoning Paralytic shellfish poisoning is one of the four recognized syndromes of shellfish poisoning (the others being neurotoxic shellfish poisoning, diarrhetic shellfish poisoning and amnesic shellfish poisoning). All four syndromes share some common features and are primarily associated with bivalve molluscs (such as mussels, clams, oysters and
• Pfiesteria Pfiesteria is a genus of heterotrophic dinoflagellates that has been associated with harmful algal blooms and fish kills. Pfiesteria complex organisms were claimed to be responsible for large fish kills in the 1980s and 1990s on the coast of North Carolina and in tributaries of the Chesapeake Bay. In reaction to the toxic outbreaks, six states
• Phytoplankton Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτόν , meaning "plant", and πλαγκτός (planktos), meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye. However, when present in high enough
• Neurotoxic shellfish poisoning Neurotoxic Shellfish Poisoning is caused by the consumption of shellfish contaminated by brevetoxins or brevetoxin analogs
• Raphidophyte
• Saxitoxin
• Spring bloom

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