Karenia brevis (Synonym: Gymnodinium breve oder Ptychodiscus brevis) ist ein einzelliger, ungepanzerter, mariner Dinoflagellat mit einer Größe von 20 bis 40 µm Durchmesser. Der Organismus kommt häufig im Golf von Mexiko vor, wo er vor Florida regelmäßig Planktonblüten verursacht, die so genannten Roten Tiden. K. brevis produziert eine Reihe von Giften, die als Brevetoxine zusammengefasst werden. Diese Gifte können während der Planktonblüten Massensterben bei Fischen, Vögeln und Säugern verursachen. K. brevis ist photosynthetisch, enthält aber kein Peridinin.
K. brevis ist phototaktisch[1] und negativ geotaktisch[2], was bedeutet, dass die Zellen zum Licht hin und gegen die Schwerkraft schwimmen. Dabei können die Zellen eine Geschwindigkeit von 1 m/h erreichen. Die Zellen sind phototroph[3]. In den Küstengewässern südwestlich von Florida kommt es regelmäßig zu Massenansammlungen von K. brevis, wodurch sich das Wasser rötlich verfärbt. Schon die spanischen Seefahrer im 18. Jahrhundert berichteten von solchen roten Tiden in dieser Region.
Um die schädlichen Planktonblüten vorhersagen und eventuell bekämpfen zu können, muss die K. brevis genau beobachtet werden. Traditionelle Nachweismethoden für K. brevis beruhen auf Mikroskopie und Pigmentanalyse, die aber zeitintensiv sind und einen erfahrenen Wissenschaftler benötigen[4]. Darüber hinaus kann die Art in Anreicherungskulturen vermehrt und so nachgewiesen werden, was ebenfalls aufwändig und zeitintensiv ist. Deshalb wurde eine molekulargenetische Nachweismethode auf der Basis der PCR entwickelt[5].
Karenia brevis (Synonym: Gymnodinium breve oder Ptychodiscus brevis) ist ein einzelliger, ungepanzerter, mariner Dinoflagellat mit einer Größe von 20 bis 40 µm Durchmesser. Der Organismus kommt häufig im Golf von Mexiko vor, wo er vor Florida regelmäßig Planktonblüten verursacht, die so genannten Roten Tiden. K. brevis produziert eine Reihe von Giften, die als Brevetoxine zusammengefasst werden. Diese Gifte können während der Planktonblüten Massensterben bei Fischen, Vögeln und Säugern verursachen. K. brevis ist photosynthetisch, enthält aber kein Peridinin.
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.[1] 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.[2]
Each cell has two flagella that allow it to move through the water in a spinning motion. K. brevis is unarmored, and does not contain peridinin. Cells are between 20 and 40 μm in diameter. K. brevis naturally produces a suite of potent neurotoxins collectively called brevetoxins, which cause gastrointestinal and neurological problems in other organisms and are responsible for large die-offs of marine organisms and seabirds.[3]
Karenia brevis was named for Dr. Karen A. Steidinger[4] in 2001, and was previously known as Gymnodinium breve and Ptychodiscus brevis. The classification of K. brevis has changed over time as advances in technology are made.[5] It was first named Gymnodinium brevis in 1948, but was later changed to Gymnodinium breve, which correlates with the guidelines of the International Code of Botanical Nomenclature. In 1979 it was categorized under the genus Ptychodiscus and named Ptychodiscus brevis as new research showed it fit better under this genus because of its morphology, biochemistry, and ultrastructure. Then in 1989, scientists agreed this organism should be referred to as its original name (G. breve). It was then reclassified and transferred to the new genus Karenia, which was established at the University of Copenhagen in 2000.
Karenia brevis was first identified in Florida in 1947, but anecdotal reports in the Gulf of Mexico date back to the 1530s.[1][6] Outbreaks of K. brevis have been known to occur since the Spanish explorers of the 15th and 16th centuries, as documented by Spanish explorers like Cabeza de Vaca. These explorers noted large fish kills that resemble the die offs seen in present-day due to K. brevis. C.C. Davis confirmed these die offs were due to K. brevis in 1948.[7]
Karenia brevis has an optimum temperature range of 22–28 °C (72–82 °F),[8] an optimum salinity range of 25-45 Practical Salinity Units (PSU),[9] has adapted to "low-irradiance environments," and can utilize both organic and inorganic nitrogen and phosphorus compounds to survive.[10] In its normal environment, K. brevis will move in the direction of greater light[11] and against the direction of gravity,[12] which will tend to keep the organism at the surface of whatever body of water it is suspended within. The swimming speed of K. brevis is about one metre per hour[13] and the organism can be found throughout the year in the waters of the Gulf of Mexico at concentrations of ≤ 1,000 cell per liter.[2]
Scientists have been unable to determine a definitive geographic range for K. brevis specifically because it is difficult to separate from the ten other species of Karenia, but K. brevis is the most common species occurring in the Gulf of Mexico.[14]
Karenia brevis is the causative agent of red tide, which occurs when the organism multiplies to higher than normal concentrations. During these events the water can take on a reddish or pinkish coloration, giving these explosions in the K. brevis population the name of Florida Red Tide. These algal blooms caused by K. brevis produce brevetoxins, which can result in significant ecological impacts through the death of large numbers of marine animals and birds, to include marine mammals.[15] Large scale fish kills are known to occur due to these Florida Red Tides caused by K. brevis. Fish species through the food chain are impacted, up to and including large predatory species such as sharks, as well as species typical in human consumption.[2]
One researcher has stated that, "There is no single hypothesis that can account for blooms of K. brevis along the west coast of Florida".[10] However, like most algae, their occurrence and survival depends on a variety of factors in their environment including water temperature, salinity, light, and nutrients/compounds present in the water.[10] However it is suspected that abundant use of fertilizers in surrounding coastal areas as well as fertilizer run-off from more distant farms, carried by the rivers, might have an impact on algae growth.
Under favorable conditions, toxin-producing dinoflagellates such as K. brevis flourish and grow to high concentrations, an event termed a "harmful algal bloom" or a "HAB". While there are many different types of these HABs and the effects can vary, K. brevis is the causative agent of Florida Red Tides. Due to the toxin that K. brevis produces, these red tides can be detrimental to marine life and can even affect human populations along coasts where they occur.[16]
In areas where K. brevis is found at normal population levels, the organism is not known to cause harm to human health. It is only at times of unchecked population growth, resulting in harmful algal blooms, when the organism is of concern to human health and activities.[15] The same cannot be said of shellfish harvested and consumed from these algal bloom areas. The brevetoxins released by K. brevis can be found in the flesh of shellfish during Florida Red Tides, potentially causing a condition known as Neurotoxic Shellfish Poisoning (NSP) in humans. Although no recorded human deaths have occurred from NSP, the poisoning does result in nausea, vomiting and a variety of neurological symptoms.[17] Other than NSP, the effects on human health during Florida Red Tide are thought to be limited to respiratory and eye irritation to susceptible persons on the water or close to the shore of areas impacted by the Red Tide, and irritation of skin directly exposed to Florida Red Tide waters. Persons with pre-existing respiratory conditions such as asthma, emphysema or COPD may be more susceptible to harm from the respiratory irritation caused by K. brevis and may be advised to remain away from coastal areas during periods of Florida Red Tide.[15]
The uncontrolled mass explosions of K. brevis populations resulting in Florida Red Tide also has a significant financial impact on the affected coastal areas. The primary source of revenue generation in many of the communities affected by K. brevis red tides is tourism. During periods of red tides this important source of revenue is often lost to the impacted coastal communities of Florida, often on the scale of tens of millions of dollars.[18]
This particular protist is known to be harmful to humans, large fish, and other marine mammals. It has been found that the survival of scleractinian coral is negatively affected by brevetoxin. Scleractinian coral exhibits decreased rates of respiration when there is a high concentration of K. brevis.[3]
Karenia brevis has harmful effects on the Florida manatee, which is already an endangered species. Exposure can be lethal, or can lead to long-term impacts. Through times of more extreme red tide events, more than 10% of manatees don't survive. Back in 2013 during an intense bloom, 300 manatees were lost. Although many manage to survive, they are left with harmful effects, specifically targeting the immune system.[19]
When Karenia brevis is found in high concentrations, it is more likely to be harmful because there is a higher concentration of brevotoxins. These sea cows become affected by these toxins through inhaling them or ingesting the algae.[20] Manatees that have been exposed to the harmful algal bloom have experienced declined lymphocyte proliferation, which is related to adaptive immune function. They have also suffered oxidative stress, leading to tissue damage and inflammation.[19] In addition to that, there is evidence of gastrointestinal and neurological issues.[20]
This is a growing issue for many reasons, including the health of the Florida manatee. The year 2003 saw some intense blooms, contributing to 26% of manatee deaths. In 2018, that number shot up to 35%. The state of Florida has implemented some legislation to help manatees, including the Endangered Species Act and the Marine Mammals Protection Act. Manatees also benefit from the Clean Water Act and the Comprehensive Everglades Restoration Act, which deal with water quality. However, these protections do not help so much with HABs. Manatee mortality is continuing to increase due to these factors.[20]
Traditional methods for the detection of K. brevis are based on microscopy or pigment analysis. These are time-consuming, and typically require a skilled microscopist for identification.[21] Cultivation-based identification is extremely difficult and can take several months.
The traditional methods of detection and monitoring of K. brevis blooms from field measurements is labor-intensive and suffers from practical limitations on achieving real-time detection or monitoring. The "Brevebuster" is a deploy-able instrument that can be deployed on automated underwater vehicles or on stationary platforms that can optically detect the Florida red tides.[6] A molecular, real-time PCR-based approach for sensitive and accurate detection of K. brevis cells in marine environments has therefore been developed.[22] A real-time nucleic acid sequence-based amplification (NASBA) assay has been developed for detection of rbcL mRNA from K. brevis. NASBA is sensitive, rapid and effective, and may be used as an additional or alternative method to detect and quantify K. brevis in the marine environment.[23]
Another technique for the detection of K. brevis is multiwavelength spectroscopy, which uses a model-based examination of UV-vis spectra.[24] Methods of detection using satellite spectroscopy have also been developed.[25][26] Satellite images from Medium Resolution Imaging Spectrometer (MERIS) and Moderate Resolution Imaging Spectroradiometer (MODIS) ocean color sensor, identify K. brevis by making use of its chlorophyll fluorescence and low backscattering characteristics.[27][28][29] In addition to methods of detection of cells of K. brevis, enzyme-linked immunosorbent assay (ELISA) and liquid chromatography mass spectrometry (LCMS) have been developed for detecting brevetoxin in shellfish,[6][30] are more sensitive than the standard mouse bioassay, and as of 2008, were being considered by the Interstate Shellfish Sanitation Conference for regulatory use.
Glibert, P.M.; Burkholder, J.M (22 May 2014). The Complex Relationships Between Increases in Fertilization of the Earth, Coastal Eutrophication and Proliferation of Harmful Algal Blooms. Ecological Studies. Vol. 189. pp. 341–354. doi:10.1007/978-3-540-32210-8_26. ISBN 978-3-540-32209-2.
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Florida manatee 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.
Each cell has two flagella that allow it to move through the water in a spinning motion. K. brevis is unarmored, and does not contain peridinin. Cells are between 20 and 40 μm in diameter. K. brevis naturally produces a suite of potent neurotoxins collectively called brevetoxins, which cause gastrointestinal and neurological problems in other organisms and are responsible for large die-offs of marine organisms and seabirds.
Karenia brevis est une espèce d’algues dinoflagellées de la famille des Brachidiniaceae. Présente surtout dans le Golfe du Mexique, cette espèce est connue pour ses proliférations régulières au large des côtes du Golfe du Mexique (Floride, Texas et Mexique) et pour les toxines qu'elle produit lors de ces efflorescences.
Karenia brevis est un organisme unicellulaire photosynthétique dont le diamètre varie entre 20 et 40 µm, pour une épaisseur de 10-15 µm, de forme plus ou moins carrée[3]. Contrairement à d'autres espèces de dinoflagellés, il ne possède pas de thèque ni de péridinine[3]. Deux flagelles sont insérés sur la cellule, lui permettant de nager activement[3]. Karenia brevis peut se multiplier de manière asexuée ou se reproduire de manière sexuée. Dans le premier cas, il y a division binaire de la cellule. La reproduction sexuée s'effectue grâce à la production de gamètes mâle et femelle de même taille (isogamie). L'intervalle de températures optimales pour sa croissance est 22-28 °C, et elle est adaptée à des intensités lumineuses faibles[4]. Ce dinoflagellé peut utiliser des composés azotés organiques et inorganiques comme source d'azote[4].
L'espèce se retrouve essentiellement dans le Golfe du Mexique[1],[2]. Elle est également présente dans le nord et nord-est de l'Atlantique, en mer Méditerranée et mer Noire, au Japon, en Australie, en Nouvelle-Zélande et en Chine[1].
Karenia brevis a un comportement phototactique positif et chimiotactique positif. L'espèce prolifère régulièrement le long des côtes du Golfe du Mexique, particulièrement sur le plateau continental de Floride occidentale où ces évènements sont fort étudiés[5],[6]. Une combinaison de plusieurs facteurs expliquant l'initiation, la maintenance et la fin des efflorescences ont été décrits, incluant des aspects hydrodynamiques (accumulation des cellules par les vents, courants marins et phénomènes d'upwelling et downwelling)[5],[7], l'influence des nutriments[5] et les capacités de migration verticale dans la colonne d'eau et de phototaxie[5]. Lorsque les conditions sont favorables, des proliférations spectaculaires sont initiées, pouvant dépasser 1000 km² et persister plusieurs mois[4],[5].
Les cellules produisent des brévétoxines, famille de toxines affectant les humains, oiseaux marins, poissons et mammifères marins[8] en influençant les flux de sodium dans les cellules[9]. Les toxines sont directement libérées dans l'eau, ou atteignent les côtes sous forme d'aérosols[10]. Les humains sont également affectés par la consommation de mollusques contaminés[10].
Karenia brevis est une espèce d’algues dinoflagellées de la famille des Brachidiniaceae. Présente surtout dans le Golfe du Mexique, cette espèce est connue pour ses proliférations régulières au large des côtes du Golfe du Mexique (Floride, Texas et Mexique) et pour les toxines qu'elle produit lors de ces efflorescences.
Gymnodinium breve Davis 1948
Ptychodiscus brevis (Davis 1948) Steidinger
カレニア・ブレビス（Karenia brevis）は海洋性の渦鞭毛藻の一種である。神経毒であるブレベトキシンを産生する有毒渦鞭毛藻である。
カレニア・ブレビスは単細胞の植物プランクトンである。細胞の形状は 18-40 x 15-70 µm と扁平で、2本の鞭毛により水中を回転しながら遊泳する。細胞内には 10-20 個の葉緑体を持っており、光合成を行う独立栄養生物である。この葉緑体は板状で黄褐色（クロロフィル a/c 型）をしており、ハプト藻の3次共生に由来する。
世界各地の沿岸域に分布し、特にメキシコ湾やフロリダ近海に普通である。日本近海では東京湾以西で確認されている。近年は九州の養殖場近海でも発生が見られる。カレニア・ブレビスは大発生して赤潮を形成する場合があり、毒素の産生等により海洋生物や海鳥の大規模斃死を引き起こす。
この項目は、原生生物に関連した書きかけの項目です。この項目を加筆・訂正などしてくださる協力者を求めています（ポータル 生き物と自然／プロジェクト 生物）。 
