Ma Yuan, Chen Zhijie, Gao Dezhuang, Wang Ruiyu, Zhang Junyi, Deng Jie
Shanghai Key Lab for Urban Ecological Processes and Eco-Restorations, School of Ecological and Environmental Sciences, East China Normal University, Shanghai, China.
School of Environment and Ecology, Jiangnan University, Jiangsu, China.
Environ Res. 2025 Mar 1;268:120754. doi: 10.1016/j.envres.2025.120754. Epub 2025 Jan 2.
Eutrophication caused by human activities has severely impacted freshwater ecosystems, leading to harmful cyanobacterial blooms that threaten water quality and ecosystem stability. During blooms, denitrification is a key process for nitrogen removal, which can occur both in the sediment and in the waterbody mediated by cyanobacterial aggregate (CA)-associated microorganisms. In this study, the structure, dynamics and assembly mechanisms of CA-associated nirK-, nirS-, and nosZ-encoding denitrifying communities were investigated in the eutrophic Lake Taihu across the bloom season. External environmental factors showed limited influence on denitrifying community structure, which were more strongly shaped by biotical factors. Network analysis revealed both monofunctional and multifunctional modules, with a small subset of linker OTUs playing a critical role in maintaining these multifunctional modules by mediating interactions among different functional communities. Biotic regulation was further demonstrated by coupling patterns among denitrifiers associated with specific microbial lineages, as well as niche partitioning driven by cyanobacterial composition. While the assembly of the total phycospheric communities was governed by stochastic processes, the denitrifying communities were predominantly shaped by homogeneous selection. These findings indicate biological processes, particularly synergistic relationships and autotroph-heterotroph interactions, were key drivers of the structure and dynamics of denitrifying communities within CAs. Moreover, the key taxa identified in this study may provide potential targets for regulating nitrogen cycling in the management of cyanobacterial blooms.
人类活动导致的富营养化已严重影响淡水生态系统，引发有害蓝藻水华，威胁水质和生态系统稳定性。在水华期间，反硝化作用是氮去除的关键过程，该过程可发生在沉积物中以及由蓝藻聚集体（CA）相关微生物介导的水体中。在本研究中，对富营养化的太湖整个水华季节中与CA相关的编码nirK、nirS和nosZ的反硝化群落的结构、动态和组装机制进行了研究。外部环境因素对反硝化群落结构的影响有限，生物因素对其影响更强。网络分析揭示了单功能和多功能模块，一小部分连接操作分类单元（OTU）通过介导不同功能群落之间的相互作用，在维持这些多功能模块方面发挥着关键作用。与特定微生物谱系相关的反硝化菌之间的耦合模式以及由蓝藻组成驱动的生态位划分进一步证明了生物调节作用。虽然整个藻际群落的组装受随机过程控制，但反硝化群落主要由同质选择塑造。这些发现表明，生物过程，特别是协同关系和自养生物 - 异养生物相互作用，是CA内反硝化群落结构和动态的关键驱动因素。此外，本研究中确定的关键分类群可能为在蓝藻水华管理中调节氮循环提供潜在目标。
