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Marine Microbiology

The study of microorganisms living in the sea is known as marine microbiology. Nearly three fourths of the earth's surface is covered by the sea .The sea therefore is the largest natural environment inhabited by the microorganisms. The marine environment, as does land, contains bacteria, Protozoa, algae, yeasts and moulds, as well as viruses forms organisms that live in the sea.

Microorganisms which are found in the surface layers of the sea and other aquatic environment are collectively known as plankton. Plankton may be further sub divided into phytoplank­ton (photosynthetic microorganisms, algae) and zooplankton (Protozoa, and other microscopic animals). The former are more important plankton organisms, as they arc the primary producers of organic matter.

The concentration of dissolved salts (salinity) averages about 35 gin/kg or 3.5% by weight. Out of this 75% is NaCl. Marine microorganisms, there­fore; may be divided into two general types: (I) those indigenous to the sea and not growing on media without sea water or high salt concentra­tion and (2) transient organisms whose natural habitat is terrestrial and which are able to grow in media without sea water, but can tolerate high salt concentration.

There is also another group of microorganisms in the sea, in the depths of the sea microorganisms live at tremendous hydrostatic pressures, upto 1000 atmospheres. These organisms when brought to the surface require not only sea water but high pressure in order to grow. Such pressures are toxic to organisms normally living at one atmosphere at the surface.