ABSTRACT: Suspended particulate matter (SPM) samples collected in the Rhône River were incubated in vitro at different salinities, and the degradation of terrestrial vascular plant material was monitored using specific lipid tracers (triterpenes, cuticular waxes and phenolic acids). Two samplings were compared, i.e. during and after a phytoplankton bloom in the river (potamoplankton). Degradation was observed at a salinity close to that of seawater. Changes in salinity allow for the establishment of specific bacterial communities comprising bacteria possessing a capacity to degrade algal and vascular plant components more efficiently than those initially present within the river. The presence of potamoplankton clearly enhanced the mineralization of vascular plant material. The potamoplankton algal material was intensively degraded during the incubations and could thus act as a co-substrate or induce the appearance of a bacterial community efficiently degrading terrestrial vascular plants. In SPM samples collected in the salinity gradient of the Rhône Estuary, bacterial degradation of vascular plant material increased with the proportion of algal sterols, strongly suggesting the involvement of a priming effect. Bacterial diversity analyses showed the dominance of Betaproteobacteria in freshwater and Alphaproteobacteria and Gammaproteobacteria in seawater. These results revealed the importance of potamoplankton and of the structure of bacterial communities during the degradation of terrestrial vascular plant material in estuaries.

中文翻译：

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在河口盐度梯度中增强的陆地POM生物降解：有机物质池和细菌群落变化的相互作用

摘要：将在罗纳河中收集的悬浮颗粒物（SPM）样品进行体外培养在不同的盐度下，使用特定的脂质示踪剂（三萜，表皮蜡和酚酸）监测陆地维管植物的降解。比较了两个采样，即河中浮游植物开花期间（浮游植物）。在接近海水的盐度下观察到降解。盐度的变化允许建立特定的细菌群落，该细菌群落包括比河中最初存在的细菌更有效地降解藻类和维管植物成分的细菌。浮游植物的存在明显增强了维管植物材料的矿化作用。在培养过程中，浮游藻的藻类物质被强烈降解，因此可以作为共底物或诱导细菌群落的出现，从而有效地降解陆地维管植物。在罗纳河口盐度梯度中收集的SPM样品中，维管植物物质的细菌降解随藻类固醇的比例增加而增加，这强烈暗示了引发作用的参与。细菌多样性分析表明β-变形菌在淡水和α-变形菌和γ-变形菌在海水中。这些结果表明，在河口陆生维管束植物降解过程中，浮游生物和细菌群落结构的重要性。