Diurnal variation of marine group I archaea and algae at Dong’ao island

Abstract:

[Objective] MG I (marine group I archaea) are the main microbial group in the ocean, which have the ability to use ammonia nitrogen to carry out ammonia oxidation autotrophic and are one of the main participant ammonia oxidation processes in the marine environment. The study of the diurnal variation of MG I archaea is of great significance for revealing the process of ammonia oxidation and carbon and nitrogen cycling in the ocean. [Methods] Samples for this study were collected from the waters near Dong’ao Island in the Pearl River Estuary, and 22-hour continuous time series of seawater samples were obtained with 2-hour intervals using a drone sampling technology. This study focused on the following scientific issues at the diurnal scale in the Pearl River Estuary: (1) Changes in the community and abundance of MG I archaea and algae. (2) The impacts of light, temperature and algae on the distribution of MG I archaea. DNA extraction, qPCR, second-generation gene sequencing, and other means, combined with environmental parameter tests (temperature, salinity, nutrient concentration, etc.), were used to explore the potential relationship between algae and MG I archaea in seawater. [Results] The abundance of MG I archaea was (9.1±3.2)×10⁷ copies/L and that of algae was (3.7±0.7)×10⁸ copies/L. High throughput sequencing of archaea showed that MG I were the most dominant archaeal group (36.2%–50.0%) in this region. At the diurnal scale, there was a negative correlation between the abundance of MG I archaea and algae. [Conclusion] Based on previous studies, we hypothesize that, temperature and algae might be the important factors that regulate the MG I archaea in estuarine marine water at the diurnal scale. This study highlights the diurnal variation of MG I archaea, which enhances our understanding of the fine-scale nitrification process in the ocean, especially in the nearshore water.