The impact of precipitation intensity and vegetation in the catchment area on autochthonous and allochthonous carbon transfer in stream biofilm food webs

在河流和小溪中，生物膜是碳循环的主要场所。它们保留了大量的溶解有机碳（DOC），因此对更高营养水平的水生生物的发育至关重要。除了支持生物膜异养生产的原生初级生产外，大量的有机碳（OC）来自周围的集水区。由于气候变化，更多的降水和更频繁、更严重的洪水将增加物质进入河流的运输。此外，包括植被在内的流域特征影响了DOC在水生生态系统中的迁移和性质。因此，碳动态取决于河流如何嵌入其周围的陆地环境并与之相互作用。尽管其对碳循环很重要，但目前尚不清楚生物膜中使用的原生碳或外来碳的程度，以及外来碳添加量的增加如何决定两种碳源的相对使用。13C和14C分析在不同标记的DOC来源上的联合应用，旨在回答来自不同来源的DOC在多大程度上被生物膜中的细菌利用并最终转运到更高的营养水平。在碳化合物和生物标志物上使用13C和14C信号是确定微生物碳源和食物网中标记物质运输的一种极好的方法。

In rivers and streams, biofilms are major sites of carbon cycling. They retain large amounts of dissolved organic carbon (DOC) and consequently are most important for the development of aquatic organisms on higher trophic levels. Besides autochthonous primary production, which supports heterotrophic production in biofilms, large amounts of organic carbon (OC) are derived from the surrounding catchment areas. More precipitation and more frequent and severe floods due to climate change will increase the transport of material into streams. Moreover, catchment characteristics including vegetation affect the transport and nature of DOC into aquatic ecosystems. Thus, carbon dynamics depend on how a stream is embedded within and interacts with its surrounding terrestrial environment. Despite its importance for carbon cycling it is not understood to which extent autochthonous or allochthonous carbon is used in biofilms and how increased addition of allochthonous carbon determines the relative use of both carbon sources. The combined application of 13C and 14C analysis on differently labeled DOC sources intend to answer to which extent DOC from different sources is used by bacteria in biofilms and finally transported to higher trophic levels. The use of 13C and 14C signals on carbon compounds and biomarkers is an excellent method to determine carbon sources for microorganisms and the transport of labeled material within the food web.