Abundance, contribution, and possible driver of ammonia-oxidizing archaea (AOA) in various types of aquatic ecosystems

Abstract

In some habitats, ammonia oxidation highly depends on the activity of ammonia-oxidizing archaea (AOA), which are therefore important for studying biogeochemical nitrogen cycling. However, the behavior and distribution of AOA in aquatic ecosystems are not well characterized, especially on a global scale. We sampled 66 sites across all five continents to analyze the global abundance of AOA. Ammonium oxidation rates were measured using the dicyandiamide (DCD) and octyne inhibition method to separately evaluate the contributions of AOA to ammonium oxidation. High-throughput pyrosequencing and phylogenetic analysis were applied to study AOA community compositions, combined with DNA-stable isotope probing (DNA-SIP). The archaeal amoA gene was widespread and abundant across all aquatic ecosystem types. The average abundance was 3.59 × 108 copies g−1, with the highest values in lake samples and the lowest in river samples. The AOA abundance was influenced by pH. Archaeal ammonia oxidation rates were 0.81 ± 0.45 mg (NO3−-N) kg−1 day−1, corresponding to 63.75% of the total ammonia oxidation rate. Pyrosequencing analysis showed that the AOA community was dominated by the Group I.1b lineage (65.8%). Candidatus Nitrosocosmicus franklandus showed the highest positive correlation with archaeal ammonium oxidation rates and had the highest carbon use efficiency. Abundance, activity, and community composition of AOA were highly heterogeneous. pH negatively impacted the abundance of the archaeal amoA functional gene. AOA were the main ammonia oxidators in aquatic ecosystems. Ca. N. franklandus was found to dominate archaeal ammonium oxidation.