Kajan Katarina, Osterholz Helena, Stegen James, Gligora Udovič Marija, Orlić Sandi
Division of Materials Chemistry, Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia; Center of Excellence for Science and Technology-Integration of Mediterranean Region (STIM), Split, Croatia.
Institute for Chemistry and Biology of the Marine Environment, University of Oldenburg, Oldenburg, Germany; Leibniz Institute for Baltic Sea Research Warnemünde, Rostock, Germany.
Water Res. 2023 Oct 15;245:120653. doi: 10.1016/j.watres.2023.120653. Epub 2023 Sep 19.
Lakes are active components of the global carbon cycle and host a range of processes that degrade and modify dissolved organic matter (DOM). Through the degradation of DOM molecules and the synthesis of new compounds, microbes in aquatic environments strongly and continuously influence chemodiversity, which can feedback to influence microbial diversity. Developing a better understanding of the biodiversity patterns that emerge along spatial and environmental gradients is one of the key objectives of community ecology. A changing climate may affect ecological feedback, including those that affect microbial communities. To maintain the function of a lake ecosystem and predict carbon cycling in the environment, it is increasingly important to understand the coupling between microbial and DOM diversity. To unravel the biotic and abiotic mechanisms that control the structure and patterns of DOM and microbial communities in lakes, we combined high-throughput sequencing and ultra-high resolution mass spectrometry together with a null modeling approach. The advantage of null models is their ability to evaluate the relative influences of stochastic and deterministic assembly processes in both DOM and microbial community assemblages. The present study includes spatiotemporal signatures of DOM and the microbial community in six temperate lakes contrasting continental and Mediterranean climates during the productive season. Different environmental conditions and nutrient sources characterized the studied lakes. Our results have shown high covariance between molecular-level DOM diversity and the diversity of individual microbial communities especially with diversity of microeukaryotes and free-living bacteria indicating their dynamic feedback. We found that the differences between lakes and climatic regions were mainly reflected in the diversity of DOM at the molecular formula-level and the microeukaryota community. Furthermore, using null models the DOM assembly was governed by deterministic variable selection operating consistently and strongly within and among lakes. In contrast, microbial community assembly processes were highly variable across lakes with different trophic status and climatic regions. Difference in the processes governing DOM and microbial composition does not indicate weak coupling between these components, rather it suggests that distinct factors may be influencing microbial communities and DOM assemblages separately. Further understanding of the DOM-microbe coupling (or lack thereof) is key to formulating predictive models of future lake ecology and function.
湖泊是全球碳循环的活跃组成部分，承载着一系列降解和改变溶解有机物（DOM）的过程。通过DOM分子的降解和新化合物的合成，水生环境中的微生物强烈且持续地影响化学多样性，而化学多样性又会反馈影响微生物多样性。深入了解沿空间和环境梯度出现的生物多样性模式是群落生态学的关键目标之一。气候变化可能会影响生态反馈，包括那些影响微生物群落的反馈。为了维持湖泊生态系统的功能并预测环境中的碳循环，了解微生物与DOM多样性之间的耦合变得越来越重要。为了揭示控制湖泊中DOM和微生物群落结构及模式的生物和非生物机制，我们将高通量测序、超高分辨率质谱与空模型方法结合起来。空模型的优势在于它们能够评估随机和确定性组装过程对DOM和微生物群落组装的相对影响。本研究包括六个温带湖泊在生长季节的DOM和微生物群落的时空特征，这些湖泊对比了大陆性气候和地中海气候。不同的环境条件和营养源是所研究湖泊的特征。我们的结果表明，分子水平的DOM多样性与单个微生物群落的多样性之间存在高度协方差，特别是与微型真核生物和自由生活细菌的多样性，这表明它们之间存在动态反馈。我们发现湖泊和气候区域之间的差异主要体现在分子式水平的DOM多样性和微型真核生物群落上。此外，使用空模型发现，DOM组装受确定性变量选择的支配，该选择在湖泊内部和湖泊之间持续且强烈地起作用。相比之下，微生物群落组装过程在不同营养状态和气候区域的湖泊之间变化很大。控制DOM和微生物组成的过程差异并不表明这些组分之间的耦合较弱，相反，这表明不同的因素可能分别影响微生物群落和DOM组装。进一步了解DOM与微生物的耦合（或缺乏耦合）是构建未来湖泊生态和功能预测模型的关键。
