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  2.  The organisms inhabiting the pelagic zone are grouped into two broad categories-plankton & nekton.  The word plankton was first of coined by Henson ,which means that which drifts.  Plankton further divided into phytoplankton & zooplankton.  Most phytoplankton are too small to be individually seen with the unaided eye.  When they present in high enough numbers ,they may appear as green discoloration of the water due to the presence of chlorophyll within their cells. INTRODUCTION
  3.   Phytoplankton include wide variety of photosynthetic organism like 1) Diatoms 2) Dinoflagellates 3) Cryptomonads 4) Green algae 5) Blue green algae  Out of these diatoms & dinoflagellates are predominate. TYPES OF PHYTOPLANKTON
  4.   The diatoms are enclosed within a box made up of two parts or valves fitting one over another.  The box is made up of silicon dioxide & is ornamented with species specific designs pits & perforations.  They are dominant in temperate & colder regions.  They may occur singly or may occur in chains. DIATOMS
  6.   The second major group of phytoplankton is recognizable by possesssing two flagella.  They use flagella to move themselves through the water.  They lack the external skeleton of silicon but are often armored with plates of the carbohydrates cellulose.  They are solitary , single small organisms. DINOFLAGELLATES
  7.   The microscopic phytoplankton float on or near the surface of water.  As they are autotrophic components of the plankton community they are responsible for much of the oxygen present in earth’s atmosphere.  The population of phytoplankton in any aquatic system is biological wealth of water for fishes & constitutes a vital link in the food chain.  Phtyoplankton have definite role in proper growth & maintenance of a water body. ECOLOGICAL BALANCE
  8.   Phytoplankton is a key food item in both Aquaculture & mariculture .And it is utilized as food for animals being farmed.  In mariculture , the phytoplankton is naturally occuring & is introduced into enclosures with the normal circulation of sea water.  In aquaculture, phytoplankton must be obtained & introduced directly.  Phytoplankton is also used to feed many varieties of aquacultured molluscs, including pearl oysters. BENEFITS
  9.   As the marine phytoplankton have declined substantially in the world’s oceans over the past century.  Phytoplankton in surface waters have decreased by about 40% since 1950 alone, at a rate of 1% per year due to ocean warming.  Due to emission of carbon dioxide from humans it causes increases in disturbances in marine food web & due to this there is a percentage decline in the fish species which feed on phytoplankton HUMAN IMPACTS
  10.   As marine phytoplankton is declining substantially in the world’s ocean.  There must be decrease in not only in air borne fraction of pollutions but also in other type of pollutions from humans.  Due to this there will be a enrichment in marine ecology. CONCLUSION
  11.   Buschbaum, Ralph and Milne, Lorus J. 1960. The Lower Animals, Doubleday and Co. New York.  Silverberg, Robert. 1972. The World Beneath the Ocean Wave. Weybright and Talley, New York. REFERENCES