Characterization of Bioflocs in a No Water Exchange Super-intensive System for the Production of Food Size Pacific White Shrimp Litopenaeus vannamei

Abstract

Zero exchange super-intensive recirculating aquaculture systems (RAS) represent an environmentally “friendly“ alternative to traditional shrimp culture methods, however the susceptibility to pathogens typically increases as the density of cultured organisms increases. The study describes a greenhouse-enclosed super-intensive RAS, utilizing culture water from a 62-day nursery trial, to grow juvenile (0.99 g) Litopenaeus vannamei, Pacific White Shrimp, to market-size under high stocking density (450/m3). The study evaluated the effects of foam fractionation and settling tank particulate control methods on water quality and microbial particulate related flora in four 40 m3 tanks with two replicates per control method under no water exchange. Microbial communities were distinguished at the gram-stain level using flow cytometric fluorescent activated cell sorter (FACS) methods. Differentiation between all other populations of organisms and particles between 1~20 μm was based upon autofluorescence and forward scatter (a size indicative light parameter) using FACS. Analysis of variance indicated that the microbial communities associated with each particulate control method did not deviate from one another significantly (p>0.05). Gram-positive bacteria were the dominate fraction regardless of particulate control method (p<0.05). Six unique autofluorescence signals were consistently present within each RAS. This study is a first step in using flow cytometry as a tool to document changes in microbial communities in no water exchange super-intensive system for production of marketable shrimp. Shrimp yield and survival was high: 9.34~9.75 kg/m3 and 94.5%~96.9%, respectively. Further, the data suggest that the use of pre-conditioned water may help to prevent ammonia and nitrite overload and decrease pathogenic organism prevalence.