Limnology/Aquatic Geomicrobiology Research Group, Institute of Ecology, Friedrich Schiller University Jena, Jena, Germany.
FEMS Microbiol Ecol. 2012 Jan;79(1):118-31. doi: 10.1111/j.1574-6941.2011.01202.x.
Food webs in the rhithral zone rely mainly on allochthonous carbon from the riparian vegetation. However, autochthonous carbon might be more important in open canopy streams. In streams, most of the microbial activity occurs in biofilms, associated with the streambed. We followed the autochthonous carbon transfer toward bacteria and grazing protozoa within a stream biofilm food web. Biofilms that developed in a second-order stream (Thuringia, Germany) were incubated in flow channels under climate-controlled conditions. Six-week-old biofilms received either ¹³C- or ¹²C-labeled CO₂, and uptake into phospholipid fatty acids was followed. The dissolved inorganic carbon of the flow channel water became immediately labeled. In biofilms grown under 8-h light/16-h dark conditions, more than 50% of the labeled carbon was incorporated in biofilm algae, mainly filamentous cyanobacteria, pennate diatoms, and nonfilamentous green algae. A mean of 29% of the labeled carbon reached protozoan grazer. The testate amoeba Pseudodifflugia horrida was highly abundant in biofilms and seemed to be the most important grazer on biofilm bacteria and algae. Hence, stream biofilms dominated by cyanobacteria and algae seem to play an important role in the uptake of CO₂ and transfer of autochthonous carbon through the microbial food web.
底栖带食物网主要依赖于河岸植被的外源碳，但自源碳在开阔林冠溪流中可能更为重要。在溪流中，大部分微生物活动发生在与河床相关的生物膜中。我们跟踪了溪流生物膜食物网中自源碳向细菌和放牧原生动物的转移。在德国图林根的一条二级溪流中培养的生物膜在气候控制条件下的流动通道中进行孵育。将接受 ¹³C 或 ¹²C 标记的 CO₂ 的六周龄生物膜，并跟踪其进入磷脂脂肪酸的吸收情况。流动通道水中的溶解无机碳立即被标记。在 8 小时光照/16 小时黑暗条件下生长的生物膜中，超过 50%的标记碳被生物膜藻类吸收，主要是丝状蓝藻、有肋硅藻和非丝状绿藻。标记碳的平均 29%到达原生动物食草动物。测试有壳变形虫 Pseudodifflugia horrida 在生物膜中大量存在，似乎是生物膜细菌和藻类的最重要食草动物。因此，以蓝藻和藻类为主的溪流生物膜似乎在吸收 CO₂ 和通过微生物食物网转移自源碳方面发挥着重要作用。
