Ammonia-oxidizing bacterial and archaeal communities in tropical bioaugmented zero water exchange shrimp production systems

Abstract

Ammonia oxidation is an important process in the removal of ammonia generated from feed and metabolic wastes in aquaculture systems. Considering the biogeochemical importance of ammonia oxidation in bioaugmented zero water exchange aquaculture systems, the diversity and abundance of bacterial and archaeal ammonia-oxidizing communities were analyzed in three selected ponds at different time intervals during the culture period, to unravel the key environmental factors influencing their distribution in the system. The diversity and abundance of ammonia-oxidizing bacteria (AOB) and archaea (AOA) in three tropical bioaugmented zero water exchange (ZWE) shrimp culture systems were analyzed using ammonia monooxygenase A (amoA) gene from the sediment metagenome during different phases of culture. The environmental factors associated with the variability in bacterial and archaeal amoA gene abundance and diversity were elucidated using RDA and Pearson correlation analysis. Ammonia-oxidizing archaea (AOA), Nitrosopumilus sp., Nitrosospharea sp., and ammonia-oxidizing bacteria (AOB), Nitrosomonas sp., were the dominant ammonia-oxidizing communities in the ZWE ponds studied. AOA shared 41 OTUs, and the maximum distribution was influenced by dissolved oxygen in the system, whereas AOB shared 4 OTUs. The copy numbers amoA gene determined using qPCR showed that the AOA amoA gene was 10- to 100-fold abundant than AOB amoA gene. Gene abundance of AOA was positively related to total organic carbon (TOC) and salinity of sediments, and the temperature had a negative impact on bacterial amoA gene abundance. The dissolved oxygen and TOC had a negative and redox potential a positive impact on the diversity of AOA, whereas pH had a negative impact on the diversity of AOB. The ammonia-oxidizing archaeal communities dominated the bioaugmented zero water exchange aquaculture systems compared to bacteria based on the abundance and diversity analysis using amoA gene sequence-based OTU analysis and gene copy numbers. Dissolved oxygen, total organic carbon, and Eh of the sediments contributed to the distribution and abundance of AOA group in the ZWE ponds. This study points to the importance of environmental management in these culture systems for maintaining ammonia-oxidizing populations for optimal ammonia removal. The relative contribution of the archaea and bacteria to ammonia oxidation in these systems is to be further resolved along with that of anammox and comammox bacteria, which would help to develop appropriate biostimulation or bioaugmentation strategies for the management of these sustainable aquaculture production systems.