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marine biology

March 29, 2016 | Author: | Posted in ecology, nature

Marine Biology

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Red Tides

The Overview of Red Tide

Red tides are natural and worldwide phenomena , which , in many instances result in discoloration of seawater . The first written record of red tide was in the Bible in 1000 years BC (Exodus 7 : 20 , 21 ) and contained of the occurrence of red-colored river followed by dead fish in Egypt (Hallegraeff , 1993 . Red tide causative organisms may contain red , brown , orange , yellow or green pigments (carotenoids and pigment complexes , and the noticeable sign is generally [banner_entry_middle]

caused by the rapid proliferation and intensive aggregation of microscopic algae (toxic or non-toxic ) to high densities in a particular region

The red tide causative organisms responsible may be dinoflagellates diatoms , chlorophytes , prymnesiophytes , cyanophytes or raphidophytes However , the majority of red tides are initiated by dinoflagellates (yellow-brown color . Therefore , the characteristic reddish brown coloration in the water gives the name of “red tide . Owing to the presence of two powerful flagella (longitudinal and transverse ) for rapid locomotion , dinoflagellates have the ability to select certain depths in the water column (Spector , 1984

In general , red tides can occur in both polluted and unpolluted waters Its occurrences are well documented throughout recorded history and in temperate coastal waters of the northern hemisphere (Kohata et al 1997 . In 1950s , coastal red tides began to attract public attention as a result of their dramatically increase of outbreaks , especially in subtropical regions , including the Indo-Pacific and Asia (Hodgkiss Ho 1997

Hallegraeff (1993 ) noted that the global increase in awareness on harmful algal blooms and red tides can be attributed to four reasons (1 ) increased scientific awareness and survey of harmful or toxin-producing species (2 ) frequently use of coastal waters for commercialized aquaculture (3 ) stimulation of algal blooms by cultural eutrophication and /or unusual climatological conditions which are caused by human activities and (4 ) transport of dinoflagellate resting cysts associated with ballast water or movement of shellfish stocks

On one hand , red tides caused by proliferation and growth of phytoplankton may benefit aquaculture and wild fisheries by providing food to commercially important organisms such as r-feeding bivalve shellfish and larval crustaceans (Jeffrey et al , 1997 . On the other hand , red tides draw significant attention because of their detrimental threats to local mariculture and fishing industries , recreational interests , and human health . Until now , there is no direct means to control or predict the occurrence of red tide

Definition , Seasonality and Range

Harmful algal blooms in the United States are caused by a variety of different single-celled marine algae or phytoplankton , including G breve , Alexandria spp , Aureococcus spp , Pfisteria piscicida , and others (Focal Points 1998 . Major outbreaks have been caused by two species : Ptychodiscus brevis and Gonyaulax monilata (Marine Information Service 1986 . Two species are described as red tide agents for the Texas coast : Alexandrium monilatum and Gymnodinium breve (Villareal 1998 . G . breve is only one of about 60 species of dinotlagellates known to cause red tide , and is only one of about 30 known to be toxic (Sulak 1997… [banner_entry_footer]

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