珠江口外东澳岛海域MG I古菌和藻类的昼夜变化关系的研究

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

摘要:

【目的】海洋古菌MG I (marine group I archaea)是海洋中主要微生物类群，拥有利用氨氮进行氨氧化自养的能力，是海洋环境中氨氧化过程的重要参与者。研究MG I古菌的昼夜变化规律，对揭示海洋中氨氧化过程以及碳氮循环有着重要的意义。【方法】此次研究的样品来自于珠江口东澳岛附近海域，使用无人机采样技术获取了以2 h为间隔的22 h连续时间序列海水样品。本研究重点关注以下科学问题：(1)昼夜尺度下珠江口MG I古菌与藻类的群落和丰度变化特征；(2)昼夜尺度下珠江口MG I古菌受温度和藻类的影响。本研究通过样品DNA，以qPCR、二代基因测序等手段，结合环境参数(温度、盐度、营养盐浓度等)，以探究海水藻类与MG I古菌之间可能存在的关系。【结果】研究发现，MG I古菌丰度为(9.1±3.2)×10⁷ copies/L，藻类的丰度为(3.7±0.7)×10⁸ copies/L。通过古菌的高通量测序发现MG I古菌是该区域最主要的古菌类群(36.2%–50.0%)。在昼夜变化尺度下，MG I古菌与藻类的丰度表现出一定的负相关关系，且环境因子中，温度与MG I古菌之间表现出显著的负相关。【结论】基于前人研究我们提出假说：在昼夜时间尺度下，温度以及藻类可能是影响河口海洋水体环境中MG I古菌变化的重要因素。本研究聚焦MG I古菌的昼夜变化规律，对人类理解海洋尤其是近岸水体中的碳氮循环及对硝化过程认知具有一定的推进作用。

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.