Dissolved and particulate organic matter (DOM and POM) distribution, lignin phenol signatures, bulk elemental compositions, fluorescence indices and microbial plankton (algae, bacteria, viruses) in a temperate river floodplain system were monitored from January to November 2003. We aimed to elucidate the sources and compositions of allochthonous and autochthonous organic matter (OM) in the main channel and a representative backwater in relation to the hydrological regime. Additionally, bacterial secondary production was measured to evaluate the impact of organic carbon source on heterotrophic prokaryotic productivity. OM properties in the backwater tended to diverge from those in the main channel during phases without surface water connectivity; this was likely enhanced due to the exceptionally low river discharge in 2003. The terrestrial OM in this river floodplain system was largely derived from angiosperm leaves and grasses, as indicated by the lignin phenol composition. The lignin signatures exhibited significant seasonal changes, comparable to the seasonality of plankton-derived material. Microbially-derived material contributed significantly to POM and DOM, especially during periods of low discharge. High rates of bacterial secondary production (up to 135 μg C L(-1) d(-1)) followed algal blooms and suggested that autochthonous OM significantly supported heterotrophic microbial productivity.

中文翻译：

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欧洲大型河流洪泛区系统（多瑙河，奥地利）中细菌生长的有机物来源和组成

2003 年 1 月至 2003 年 11 月，对温带河流漫滩系统中的溶解和颗粒有机物（DOM 和 POM）分布、木质素苯酚特征、整体元素组成、荧光指数和微生物浮游生物（藻类、细菌、病毒）进行了监测。我们旨在阐明主要渠道中异地和本土有机物（OM）的来源和组成，以及与水文状况相关的代表性回水。此外，还测量了细菌的二次生产，以评估有机碳源对异养原核生产力的影响。在没有地表水连通性的阶段，回水的 OM 属性往往与主河道中的那些不同；由于 2003 年河流排放量异常低，这种情况可能会得到加强。如木质素酚组成所示，该河流漫滩系统中的陆地 OM 主要来源于被子植物的叶子和草。木质素特征表现出显着的季节性变化，与浮游生物衍生材料的季节性相当。微生物衍生材料对 POM 和 DOM 的贡献显着，尤其是在低排放期间。藻类大量繁殖后细菌二次生产率高（高达 135 μg CL(-1) d(-1)），表明本土 OM 显着支持异养微生物的生产力。微生物衍生材料对 POM 和 DOM 的贡献显着，尤其是在低排放期间。藻类大量繁殖后细菌二次生产率高（高达 135 μg CL(-1) d(-1)），表明本土 OM 显着支持异养微生物的生产力。微生物衍生材料对 POM 和 DOM 的贡献显着，尤其是在低排放期间。藻类大量繁殖后细菌二次生产率高（高达 135 μg CL(-1) d(-1)），表明本土 OM 显着支持异养微生物的生产力。