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  • Harmful algal bloom

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    A dog swimming through an algal bloom. A harmful algal bloom (HAB) are organisms that can severely lower oxygen levels in natural waters, killing marine life. Some HABs are associated with algae-produced toxins. Blooms can last from a few days to many months. After the bloom dies, the microbes which decompose the dead algae use up even more of the oxygen, which can create fish die-offs. When these zones of depleted oxygen cover a large area for an extended period of time, they are referred to as dead zones, where neither fish nor plants are able to survive. HABs are induced by an overabundance of nutrients in the water. The two most common nutrients are fixed nitrogen (nitrates, ammonia, urea) and phosphate. These nutrients are emitted by agriculture, other industries, excessive fertilizer use in urban/suburban areas and associated urban runoff. Higher water temperature and low circulation are contributing factors. HABs can cause significant harm to animals, the environment and economies. They have been increasing in size and frequency worldwide, a fact that many experts attribute to global climate change. The U.S. National Oceanic and Atmospheric Administration (NOAA) predicts more harmful blooms in the Pacific Ocean.

  • Brevetoxin

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    Brevetoxin (PbTx), 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 shellfish poisoning (NSP). Although brevetoxins are most well-studied in K. brevis, they are also found in other species of Karenia and at least one large fish kill has been traced to brevetoxins in Chattonella. Brevetoxin A Brevetoxin Bchemical structure Brevetoxin A Brevetoxin Bsubtypes Brevetoxin-1 (PbTx-1) R = -CH2C(=CH2)CHO Brevetoxin-7 (PbTx-7) R = -CH2C(=CH2)CH2OH Brevetoxin-10 (PbTx-10) R = -CH2CH(-CH3)CH2OH Brevetoxin-2 (PbTx-2) R = -CH2C(=CH2)CHO Brevetoxin-3 (PbTx-3) R = -CH2C(=CH2)CH2OH Brevetoxin-8 (PbTx-8) R = -CH2COCH2Cl Brevetoxin-9 (PbTx-9) R = -CH2CH(CH3)CH2OHOther Brevetoxins: Brevetoxin-5 (PbTx-5): like PbTx-3, but acetylated hydroxyl group in position 38. Brevetoxin-6 (PbTx-6): like PbTx-2, but double bond 27-28 is epoxidated.Brevetoxin-B was synthesized in 1995 by K. C.

  • Red tide

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    Red tide in a harbor, JapanRed tide is a common name for algae blooms, which are large concentrations of aquatic microorganisms (protozoans or unicellular algae such as dinoflagellates and diatoms). The upwelling of nutrients from the sea floor, often following massive storms, provides for the algae and triggers bloom events. Harmful algal blooms can occur worldwide, and natural cycles can vary regionally. The growth and persistence of an algal bloom depends on wind direction and strength, temperature, nutrients, and salinity. Red tide species can be found in oceans, bays, and estuaries, but they cannot thrive in freshwater environments. Certain species of phytoplankton and dinoflagellates found in red tides contain photosynthetic pigments that vary in color from brown to red. When the algae are present in high concentrations, the water may appear to be discolored or murky. The most conspicuous effects of red tides are the associated wildlife mortalities and harmful human exposure. The production of natural toxins such as brevetoxins and ichthyotoxins are harmful to marine life.

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