High light intensity mediates a shift from allochthonous to autochthonous carbon use in phototrophic stream biofilms
High light intensity mediates a shift from allochthonous to autochthonous carbon use in phototrophic stream biofilms
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DOI：
10.1002/2016jg003727
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发表时间：
2017-07
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通讯作者：
K. Wagner;M. Bengtsson;R. Findlay;T. Battin;A. Ulseth
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作者：
K. Wagner;M. Bengtsson;R. Findlay;T. Battin;A. Ulseth
河岸植被的变化沿着流通道，昼夜光的可用性，并在流中的本地光制度的纵向波动影响初级生产和碳（C）循环底栖流生物膜。为了研究光照对底栖生物膜中原生和外来溶解有机碳（DOC）吸收动力学的影响，我们实验性地将13 C标记的外来DOC添加到在5至152 μmol光子m−2 s−1的光照强度下生长的生物膜中。我们计算的净碳通量，这表明底栖生物膜释放本地DOC在整个光梯度。光的有效性和昼夜光模式影响底栖生物膜的C吸收。更多的外来DOC低光可用性和夜间呼吸，而在高光可用性和白天主要是本地C的底栖生物膜群落呼吸。此外，苯酚氧化酶活性（指示外来DOC吸收）在低光可用性下更高，而β-葡萄糖苷酶活性（指示本地DOC使用）随光强度增加。总的来说，我们的研究结果表明，暴露于高光输入的生物膜优先使用本地DOC，而在衰减水平下培养的生物膜显示出更大的使用外来DOC。这对溪流中DOC吸收的空间动态有影响，并反对藻类占主导地位的溪流生物膜中发生引发效应。
Changes in the riparian vegetation along stream channels, diurnal light availability, and longitudinal fluctuations in the local light regime in streams influence primary production and carbon (C) cycling in benthic stream biofilms. To investigate the influence of light availability on the uptake dynamics of autochthonous and allochthonous dissolved organic carbon (DOC) in benthic biofilms, we experimentally added 13C‐labeled allochthonous DOC to biofilms grown under light intensities ranging from 5 to 152 μmol photons m−2 s−1. We calculated the net C flux, which showed that benthic biofilms released autochthonous DOC across the entire light gradient. Light availability and diurnal light patterns influenced C uptake by benthic biofilms. More allochthonous DOC was respired under low light availability and at night, whereas under high light availability and during the day mainly autochthonous C was respired by the benthic biofilm community. Furthermore, phenol oxidase activity (indicative of allochthonous DOC uptake) was more elevated under low light availability, whereas beta‐glucosidase activity (indicative of autochthonous DOC use) increased with light intensity. Collectively, our results suggest that biofilms exposed to high light inputs preferentially used autochthonous DOC, whereas biofilms incubated at attenuated levels showed greater use of allochthonous DOC. This has implications for the spatial dynamics of DOC uptake in streams and speaks against the occurrence of priming effects in algal‐dominated stream biofilms.