Jin Jian, Liu Xiujie, Zhao Wenbin, Sun Hao, Tan Siyin, Zhang Xiao-Hua, Zhang Yunhui
Frontiers Science Center for Deep Ocean Multispheres and Earth System, College of Marine Life Sciences, Ocean University of China, Qingdao, China.
Key Laboratory of Evolution and Marine Biodiversity (Ministry of Education), Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, China.
Front Microbiol. 2024 May 27;15:1377001. doi: 10.3389/fmicb.2024.1377001. eCollection 2024.
The Pollution Nagasaki (PN) section of the East China Sea (ECS) is a typical area for studying the complex hydrographic dynamics between Changjiang River discharge and Kuroshio, displaying intense variations of environmental gradients from nearshore to offshore. However, the temporal and spatial changes of microbial communities along the PN section have long been overlooked. In this study, we performed a comprehensive investigation into the abundance, diversity and ecology of free-living (FL) and particle-associated (PA) microbial communities in seawater samples along the PN section during both summer and winter. Distinct hydrological conditions and resulting environmental gradients were observed between summer and winter, with clear features of intrusive Kuroshio subsurface water in summer and strong vertical mixing of seawater in winter. Bacterial abundance along the PN section was higher in summer (1.11 × 10 copies·L - 7.37 × 10 copies·L) than in winter (1.83 × 10 copies·L - 1.34 × 10 copies·L). Microbial diversity, as indicated by α-diversity indices, remained at relatively stable levels in summer, while a clear decreasing trend was observed in winter along the PN section. Additionally, the winter communities exhibited a more evident spatial shift along the PN section compared to the summer communities. 16S rRNA gene amplicon sequencing showed that microbial community composition varied considerably between different seasons (summer and winter) and lifestyles (FL and PA), with a notable dominance of species. in winter. Regarding the assembly of microbial communities, the stochastic process represented by dispersal limitation was the dominant process in summer, while the deterministic homogeneous selection was the most important process in winter. Correspondingly, distinct topological properties of the microbial co-occurrence networks were shown between different seasons and along the PN section. These results enhance our understanding of how hydrological conditions influence dynamic changes of microbial communities along the PN section, providing new insights for the microbial community assembly and interactions in such a complex environment.
东海长崎污染区（PN）是研究长江径流与黑潮之间复杂水文动力的典型区域，呈现出从近岸到近海强烈的环境梯度变化。然而，长期以来，PN断面微生物群落的时空变化一直被忽视。在本研究中，我们对夏季和冬季PN断面海水样品中自由生活（FL）和颗粒附着（PA）微生物群落的丰度、多样性和生态进行了全面调查。夏季和冬季观测到不同的水文条件及由此产生的环境梯度，夏季有明显的黑潮次表层水入侵特征，冬季海水垂直混合强烈。PN断面夏季细菌丰度（1.11×10⁷拷贝·L⁻¹ - 7.37×10⁷拷贝·L⁻¹）高于冬季（1.83×10⁶拷贝·L⁻¹ - 1.34×10⁷拷贝·L⁻¹）。α多样性指数表明，夏季微生物多样性保持在相对稳定水平，而冬季PN断面则呈现明显下降趋势。此外，与夏季群落相比，冬季群落沿PN断面的空间变化更为明显。16S rRNA基因扩增子测序表明，微生物群落组成在不同季节（夏季和冬季）和生活方式（FL和PA）之间存在显著差异，冬季某物种占主导地位。关于微生物群落的组装，夏季以扩散限制为代表的随机过程是主导过程，而冬季确定性均匀选择是最重要的过程。相应地，不同季节及沿PN断面微生物共现网络呈现出不同的拓扑特性。这些结果加深了我们对水文条件如何影响PN断面微生物群落动态变化的理解，为如此复杂环境中微生物群落的组装和相互作用提供了新的见解。
