Seasonal distribution of luminous bacteria in the tropical Vellar estuary

Abstract

Spatiotemporal distribution of luminous microflora in water in relation to environmental parameters was studied at two stations located in the Vellar estuary. Luminous bacteria exhibited a marked seasonal cycle with very low counts during monsoon months followed by an increase in postmonsoon and peak counts during summer. Of all the environmental parameters monitored, salinity appeared to dictate the distribution of luminous procaryotes, as the increase/decrease in the counts corresponded with fluctuation in salinity. Also higher counts of luminous microflora were discernible in the bottom waters than in the surface waters. Species composition of the isolates revealed dominance by Vibrio harveyi, Vibrio fischeri and Photobacterium leiognathi showed a limited distribution, being restricted to one station only, viz the mouth of the estuary.