Bacterial Flora of Water and Rotifers in Outdoor Mass Culture Tanks Fed with Different Microalagal Diets

Abstract

Investigations were carried out on the bacterial flora of water and the quality of rotifers in outdoor mass culture tanks. Brachionus plicatilis and B. rotundiformis were cultured in 10 numbers of 1 tonne tanks and the physico-chemical parameters and microbial loads of water, and total bacterial and Vibrio loads of microalgae and rotifers, during the period 2014-15, were studied. The study revealed a significant variation of the ammonia levels and total bacterial loads with different diets (P < 0.05). A positive correlation was observed between the total bacterial loads of algal concentrations and loads of rotifers, but no correlation was observed between Vibrio loads of water and rotifers. The prevalence of Vibrio loads of rotifers was low in tanks fed with Nannochloropsis oculata and maximum Vibrio loads were recorded in Chaetoceros calcitrans fed rotifers. The Vibrio loads significantly varied with days of culture and also with the algal diets. A positive correlation was observed between the total Vibrio loads of water and rotifers.