Evaluation of the Physiological Bacterial Groups in a Tropical Biosecured, Zero-Exchange System Growing Whiteleg Shrimp, Litopenaeus vannamei.

To elucidate the individual and multiple roles of physiological bacterial groups involved in biogeochemical cycles of carbon,
nitrogen, phosphorus and sulfur, the changes in the abundance of aerobic bacteria (heterotrophs, methane oxidizers, ammonia
oxidizers, sulfur oxidizers, phosphate solubilizers, phosphate accumulators) and anaerobic bacteria (total anaerobes, nitrate
reducers, denitrifiers and sulfate reducers) were investigated in a biosecured, zero-exchange system stocked with whiteleg
shrimp, Litopenaeus vannamei for one production cycle. Key water quality parameters during the 96-day production cycle fell
within the normal range for L. vannamei culture. Results of Spearman’s correlation matrix revealed that different sets of variables
correlated at varying levels of significance of the interrelationships between bacterial abundances and water quality parameters.
The three nitrogenous species (ammonia, nitrite and nitrate) strongly influenced the physiological bacterial groups’ abundance.
The strong relationship of bacterial groups with phytoplankton biomass and abundance clearly showed the trophic interconnections
in nutrient exchange/recycling. Canonical correspondence analysis performed to assess the total variation revealed that the
three dissolved nitrogen species followed by salinity, temperature, phytoplankton biomass and pH collectively accounted for as
much as 82% of the total variation. In conclusion, the results of the study revealed that the major drivers that interweaved
biogeochemical cycles are the three dissolved nitrogen species, which microbially mediated various aerobic-anaerobic
assimilation/dissimilation processes in the pond ecosystem. Considering the pond microbial ecology becoming an important
management tool where applied research could improve the economic and environmental sustainability of the aquaculture
industry, the findings of the present study are practically relevant.