Response of the rearing water bacterial community to the beneficial microalga Nannochloropsis oculata cocultured with Pacific white shrimp (Litopenaeus vannamei)

As a greenwater technology, coculturing microalgae with shrimp can improve the rearing water microenvironment and optimize aquaculture sustainability. However, little is known about the extent to which rearing water bacterial communities can be regulated by coculturing and how it occurs. Here, using 16S rRNA gene amplicon sequencing, we investigated the assembly of the bacterial community in a shrimp rearing system cocultured with Nannochloropsis oculata . Lower nutrient concentrations were detected in the N. oculata cocultivation system. Furthermore, a significant regulatory effect of N. oculata cocultivation on the bacterial community structure was also observed. Specifically, N. oculata cocultivation enriched the bacteria affiliated with the orders Flavobacteriales, Desulfuromonadales, Rhizobiales and Rhodobacterales but depleted some opportunistic pathogens such as Vibrionales, Sphingobacteriales and Xanthomonadales. Estimation of the β-nearest taxon index (βNIT) indicated that N. oculata cocultivation could drive the bacterial community assembly from stochastic processes to deterministic processes, and these deterministic effects were attributed to the concentrations of orthophosphate and ammonium (explained 24% of community variation) and the microalgae (explained of 12% community variation) through canonical correlation analysis (CCA) and variance partitioning analysis (VPA). Additionally, network analysis revealed that N. oculata cocultivation could also remodel the co-occurrence patterns and niche characteristics in bacterial community. By linking the modules with nutrient factors, two bacteria affiliated with the genus Psychroserpens and the and order Rhizobiales were negatively correlated with nitrate and orthophosphate, thereby identified as functional bacteria that might cooperate with N. oculata to remove nutrients. Our findings about the assembly processes and co-occurrence patterns of rearing water bacterial community will contribute to understanding and developing greenwater technology for improving rearing water quality. • Nannochloropsis oculata cocultivation enhanced nutrient removal and directionally regulate rearing water microbiome. • N. oculata cocultivation enriched beneficial functional bacteria but depleted opportunistic pathogens. • N. oculata cocultivation strengthened the dominance of deterministic process in bacterial community assembly. • Two functional bacteria identified by modular structure might cooperate with N. oculata to remove nutrients.