Yeasts are ubiquitous in their distribution and populations mainly depend on the
type and concentration of organic materials. The distribution of species, as well as
their numbers and metabolic characteristics were found to be governed by existing
environmental conditions. Marine yeasts were first discovered from the Atlantic
Ocean and following this discovery, yeasts were isolated from different sources, viz.
seawater, marine deposits, seaweeds, fish, marine mammals and sea birds. Nearshore
environments are usually inhabited by tens to thousands of cells per litre of
water, whereas low organic surface to deep-sea oceanic regions contain 10 or fewer
cells/litre. Aerobic forms are found more in clean waters and fermentative forms in
polluted waters. Yeasts are more abundant in silty muds than in sandy sediments.
The isolation frequency of yeasts fell as the depth of the sampling site is increased.
Major genera isolated in this study were Candida, Cryptococcus, Debaryomyces and
Rhodotorula. For biomass estimation ergosterol method was used. Classification and
identification of yeasts were performed using different criteria, i.e. morphology, sexual
reproduction and physiological/biochemical characteristics. Fatty acid profiling or
molecular sequencing of the IGS and ITS regions and 28S gene rDNA ensured
accurate identification.