Dinoflagellates and Red Tides

Dinoflagellates are unicellular, eukaryotic organisms.most of the species are marine.some are found in freshwater.size ranges from 15 to 40microns.A species Noctiluca is larger ,can have size around 2mm.they have two flagella which help them to swim.their chromosomes are in highly condensed form.they have large quantity of DNA.although they are eukaryotes but they don't have histones.many dinoflagellates are photosynthetic.all are not photosynthetic.some dinoflagellates are symbiotic and live in marine invertebrates like sponges,corals,jellyfish etc some live within ciliates,foraminiferans and radiolarians.the non photosynthetic species are heterotrophic.they feed on other planktond or even on each other .noctiluca can even feed on fish eggs.several species of dinoflageyshow bioluminescence. dinoflagellates are second producers after diatoms in aquatic ecosystem. many genera of dinoflagellates cause red tide.these include Gonyaulax, Karenia ,Gymnodinium ,Dinophysis, Noctiluca, Chattonella,Amoebophyra.these contain photosynthetic pigments whose colour varies from brown to red. some red tides are bioluminescent.in addition to dinoflagellates red tides also contain diatoms.some red tides are harmful .some species of dinoflagellates causing red tides produce toxins which cause death of fishes. human can get affected by eating shell fish caught from water having red tide recently. shell fish feeds on dinoflagellates and eating toxic dinoflagellates in large amount during red tide cause accumulation of toxin inshell fish.eating such fish can cause serious health problems to man.

By: Ashwani,Biology Teacher,Phagwara.