Abstract. The influence of human activities on the role of inland waters in the global carbon (C) cycle is poorly constrained. In this study, we investigated the impact of human land use on the degradation of terrestrial dissolved organic matter (DOM) and its potential impact on bacterial respiration in ten independent catchments of the Lake Geneva Basin. Sites were selected along a gradient of human disturbance (agriculture and urbanization), and we monitored bacterial respiration in parallel to DOM bioavailability. Fluorescence spectroscopy was used to determine the influence of human land uses on DOM sources and composition as well as the dynamic of degradation or production of the fluorophores identified in our study sites. Higher bacterial respiration measured in agro-urban streams related to a short-term bioreactive pool (0–6 days of incubation) from autochthonous origin, whose the size increased with human disturbance. On the other hand, the degradation of terrestrial DOM was not impacted by human activities and was not found to contribute substantially to aquatic bacterial respiration. Although human land uses controlled DOM sources, composition and bioavailability at the basin scale, our results showed that human activities in the Lake Geneva Basin had a limited impact on the net C exchanges between inland waters and the atmosphere related to DOM mineralization. Considering that greater proportion of autochthonous-DOM signature is a common feature in human-impacted catchments, the implications of our results likely apply more widely. Yet, on a global scale, the influence of human activities remains to be determine given the large diversity of effects of agriculture and urbanization on freshwater DOM depending on the local environmental context.

中文翻译：

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没有证据表明人类对高山河流网络中陆地溶解有机质 (DOM) 的矿化产生影响

摘要。人类活动对内陆水域在全球碳 (C) 循环中的作用的影响很少受到限制。在这项研究中，我们调查了人类土地利用对陆地溶解有机物 (DOM) 降解的影响及其对日内瓦湖盆地 10 个独立流域中细菌呼吸的潜在影响。沿着人类干扰（农业和城市化）的梯度选择地点，我们在监测 DOM 生物利用度的同时监测细菌呼吸。荧光光谱用于确定人类土地利用对 DOM 来源和组成的影响，以及我们研究地点确定的荧光团降解或产生的动态。在与来自本地来源的短期生物反应池（孵化 0-6 天）相关的农业城市河流中测量到的较高细菌呼吸，其大小随人为干扰而增加。另一方面，陆地 DOM 的降解不受人类活动的影响，也未发现对水生细菌呼吸有实质性影响。尽管人类土地在流域尺度上使用受控的 DOM 来源、组成和生物有效性，但我们的研究结果表明，日内瓦湖盆地的人类活动对内陆水域和大气之间与 DOM 矿化相关的净碳交换的影响有限。考虑到更大比例的本土 DOM 签名是受人类影响的集水区的一个共同特征，我们的结果的含义可能更广泛地适用。然而，在全球范围内，