ABSTRACT: Agricultural land use is known to adversely affect freshwater ecosystems, and recent studies have shown that it can significantly alter dissolved organic matter (DOM) concentrations and quality. DOM quantity and quality are key determinants of microbial community structure in streams and have been linked to changes in community abundance and composition. Considering the vital ecological role sediment microbes play in stream ecosystems, it is important to understand how agricultural land use changes affect stream microbial community structure. This study was conducted to determine if variation in sediment microbial biomass community structure could be attributed to differences in agricultural land use. Microbial biomass, microbial community structure, and stream water parameters were compared on 2 dates from 6 sites representing a gradient of agricultural land use from 18 to 64% within the Bear Creek Watershed in northwest Alabama, USA. Total microbial biomass, determined as phospholipid phosphate, was strongly influenced by sediment surface area and, to a lesser extent, correlated with sampling date and land use. Sediment microbial community structure, determined by phospholipid fatty acid analysis, was significantly correlated to percent agricultural land use in the watershed, as well as stream water DOM humification index, and sediment δ¹⁵N values and surface area. Microbial community structure also differed between sampling dates. These findings demonstrate that agricultural land use is linked via alteration of stream water and sediment organic matter to changes in sediment microbial structure which may, at least in part, account for widely observed changes in stream ecosystem functioning associated with agricultural activities.

中文翻译：

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农业土地利用影响河床沉积物的微生物群落结构

摘要：众所周知，农业土地利用会对淡水生态系统产生不利影响，最近的研究表明，它可以显着改变溶解性有机物（DOM）的浓度和质量。DOM的数量和质量是决定河流中微生物群落结构的关键因素，并与群落丰度和组成的变化相关。考虑到沉积物微生物在河流生态系统中的重要生态作用，了解农业用地变化如何影响河流微生物群落结构非常重要。进行这项研究来确定沉积物微生物生物量群落结构的变化是否可以归因于农业土地利用的差异。微生物生物量，微生物群落结构，在美国阿拉巴马州西北部Bear Creek流域内6个地点的2个日期的2个日期比较了河流和河流的水质参数，代表了从18％到64％的农业用地梯度。微生物总生物量，被确定为磷脂磷酸盐，受到沉积物表面积的强烈影响，并在较小程度上与采样日期和土地利用相关。通过磷脂脂肪酸分析确定的沉积物微生物群落结构与流域农业土地利用百分比，溪流水DOM增湿指数和沉积物δ显着相关 与采样日期和土地利用相关。通过磷脂脂肪酸分析确定的沉积物微生物群落结构与流域农业土地利用百分比，溪流水DOM增湿指数和沉积物δ显着相关 与采样日期和土地利用相关。通过磷脂脂肪酸分析确定的沉积物微生物群落结构与流域农业土地利用百分比，溪流水DOM增湿指数和沉积物δ显着相关¹⁵ N值和表面积。采样日期之间的微生物群落结构也不同。这些发现表明，农业土地利用通过溪流水和沉积物有机物的变化与泥沙微生物结构的变化联系在一起，这可能至少部分解释了与农业活动有关的溪流生态系统功能变化的广泛观察。