Structure, proximate composition, nutrient dynamics and growth characteristics of Penaeus vannamei in indoor biofloc systems with three different salinities and carbon sources

Abstract

In the biofloc systems the continuous application of carbon sources led to the assimilation of nitrogenous nutrients and formation of heterotrophic bacterial biomass. The present experiment was conducted in 0.22m3 capacity tanks in the triplicate to find out the structure, proximate composition, nutrient dynamics and growth characteristics of Penaeus vannamei in indoor biofloc systems with three different salinities (35, 20 and 5ppt) and carbon sources (molasses, sugar and rice flour) with an estimated C:N ratio of 15:1. pre salinity acclimatized P. vannamei , specific pathogen free seeds (0.2±0.04g) were stocked @100 numbers per m3 and fed 4 times a day based on the % of body weight (from 22% to 2.5%) and reared for 10 weeks. The results revealed that the carbon application at different salinities significantly influenced the biofloc structure (Scanning Electron Microscopic images of biofloc 4000x) showed round and rod-shaped structures. Proximate composition: crude protein (p<0.001), ether extract (p<0.001) and crude fibre (p<0.05) showed significant difference between treatments. Similarly, elemental carbon composition (p<0.01), nitrogenous waste assimilation of TAN (p<0.01), nitrite (p<0.05), and nitrate (p<0.05) showed significant differences in the treatments vs. the control group. The variables also influenced the microbiota abundance {the metagenomics analysis of biofloc showed Bray-Curtis overall average dissimilarity index of 81%, and it varied from 49% to 100% between treatments & controls} and growth characteristics {average body weight (p<0.001) and survival rate (p<0.01) between treatments and controls} of P. vannamei indoor biofloc systems. Hence, the application of carbon sources at different salinities influenced the biofloc structure, proximate, elemental carbon composition, biofloc microbiota abundance, enhanced the nitrogenous waste assimilation and growth performance of P. vannamei in indoor biofloc systems.