Temporal dynamics of aquatic microbiota and their correlation with environmental factors during larviculture of the shrimp Litopenaeus vannamei

Abstract

In-depth knowledge of aquatic microbiota succession and their correlation with water variables during shrimp larviculture plays a pivotal role in larval health. In this study, rearing water from 12 Litopenaeus vannamei hatchery ponds, named CX1-CX12, was surveyed to characterize the microbiota, environmental factors and presumptive vibrio count (PVC) across the following larval stages: nauplii 5 (N5), zoea 1–3 (Z1, Z2, Z3), mysis 1–3 (M1, M2, M3), and postlarvae 2 (PL2). The results showed that PVC increased, in a range of 7.1 × 102–2.3 × 104 cfu ml−1, in healthy ponds, which correlated positively with total ammonia nitrogen (TAN), dissolved inorganic phosphorus (DIP), dissolved organic carbon (DOC) and temperature, and negatively with dissolved oxygen (DO) (P < .05). There was a sudden rise in PVC to 8.9 × 104 cfu ml−1 in pond CX6 at M1, with a mass larval mortality at M2, which led to only 10% survival for CX6 compared to 70–80% in healthy ponds at PL2 stage. A detrended correspondence analysis revealed that the microbiota was stage-specific from stages N5 to M1, and from M1 onwards, the bacterial communities at various stages converged but were increasingly heterogeneous among parallel ponds. For healthy ponds, the bacterial alpha diversity declined from N5 to Z3, and then rose until PL2. The water variables including TAN, pH, temperature, DO, and DIP had the great influences on variation of the microbiota, followed by salinity and DOC (P < .001). Relative to the healthy ponds, the microbiota structure of pond CX6 deviated from Z3 onwards. A co-occurrence network analysis further confirmed the simple and dispersive interactions of bacterial taxa and water variables in pond CX6. Therefore, the microbiota of rearing water was highly dynamic with low diversity during Z3 to M2, which may result in disease and larval mortality if the dysbacteriosis is coupled with an abrupt change of specific populations. Thus, great attention should not only be focused on opportunistic pathogens and water quality, but also on succession and deviation of the entire microbial community during shrimp larviculture to prevent the outbreak of disease.