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natural (and common) phenomenon causing massive extermination of fish and other marine life; caused by algae Karenis brevis or efflorescence of Pfeisteria piscicida.
[in high concentrations of organism, water turns reddish-brown]
A bloom of plankton, especially dinoflagellates, that causes a usually reddish discoloration of coastal ocean waters. Certain dinoflagellates produce toxins that contaminate shellfish, making them unsafe to eat, and can kill fish.
Under optimal salinity, temperature and nutrient conditions, marine algae, Gonyaulax catanella and G tamarensis proliferate, producing saxitoxin—a potent neuromuscular toxin that blocks voltage-dependent sodium channels in neurons; not all red tides are toxic and some outbreaks of ‘red tide disease’ occur without the red tide; Gymnodinium breve causes red tide off Florida and in the Gulf of Mexico, but evokes milder neurotoxic reactions—e.g., paraesthesias, abnormal temperature sensation, ataxia, nausea, vomiting and diarrhoea. Saxitoxin concentrates in clams and shellfish—but not in lobster or finned fish; birds, mammals, humans feeding on the shellfish rapidly develop neuromuscular blockade with intense centripetal paresthesias, nausea, vomiting, diarrhea, later vertigo, numbness of face and scalp, sensory loss, dysphagia, dysarthria, intention tremor; if severe, intoxication may cause flaccid quadriplegia or respiratory paralysis and death
Infectious disease A popular phrase from the 1950s that died in the 1960s, for the increased prominence of gram-negative—i.e., ‘red’—bacterial infections, attributed to the indiscriminate use of the first antibiotic, penicillin—which is most effective against gram-positive cocci for most infections—resulting in a relative increase in incidence of gram-negative bacterial infections, causing a ‘red’ shift
red tide(red tīd)
A natural phenomenon resulting from higher than normal concentrations of the microscopic algae Gymnodinium breve in seawater. When the causative organism is extremely concentrated, seawater can turn a reddish-brown color.