Microalgae, a major live feed in aquaculture always coexist with associated bacteria. Hence a better understanding of algal-bacterial interaction is essential for maintaining a stable environment in intensive larval rearing tanks. Therefore, herein we attempted to determine the phylogenetic diversity of culturable bacteria associated with microalgal production system of a marine finfish hatchery with special reference to Chaetoceros gracilis mass culture. The sequencing of 16S rDNA of representative from each phylotypes revealed that the associated microflora belong to the classes Gammaproteo bacteria, Alphaproteo bacteria, and Bacilli. In particular, members of Marinobacter genus showed higher degree of association followed by Leisingera, Alteromonas, Nautella, Halomonas and Ruegeria. The association of bacterial groups belonging to the genera Idiomarina, Albidovulum and Staphylococcus were also detected. The variation of bacterial diversity in microalgal habitat with changes in environmental conditions was also discussed in the present work. In overall, the present study gives a greater insight to the algal microhabitat which would be vital for improving stability, productivity, sustainability and reliability of large scale microalgal cultivation and their feeding to the target aquaculture species.

Algal-bacterial association, live feed, culturable bacteria, aquaculture, molecular phylogeny