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

在河流和溪流中，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)，因此对营养水平较高的水生生物的发展至关重要。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。气候变化导致的更多降水和更频繁、更严重的洪水将增加进入溪流的物质运输。此外，包括植被在内的集水区特征会影响DOC向水生态系统的迁移和性质。因此，碳动力学取决于河流如何嵌入其周围的陆地环境并与其相互作用。尽管它对碳循环很重要，但生物膜在多大程度上使用了原生或异地碳，以及增加异地碳的添加如何决定了这两种碳源的相对使用，目前还不清楚。对不同标记的DOC来源的13C和14C分析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，并最终被输送到更高的营养水平。在碳化合物和生物标志物上使用13C和14C信号是确定微生物的碳源和食物网内标签材料运输的极好方法。

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.