Baffico Gustavo D, Diaz Mónica M, Wenzel M Teresa, Koschorreck Matthias, Schimmele Michael, Neu Thomas R, Pedrozo Fernando
Centro Regional Universitario Bariloche, Universidad Nacional del Comahue, Quintral 1250, 8400 San Carlos de Bariloche, Río Negro, Argentina.
Extremophiles. 2004 Dec;8(6):463-73. doi: 10.1007/s00792-004-0408-1. Epub 2004 Aug 5.
We explored a benthic community living on stones in an acidic (pH< or =2) stream of active volcanic origin from Patagonia, Argentina, by combining in situ measurements (temperature, pH, conductivity, dissolved oxygen), photosynthesis of intact biofilms (measured with microsensors by the light-dark shift method), pure-culture experiments on isolated algae, and confocal laser scanning microscopy on the biofilms. The epilithon of the Agrio River was dominated (99% of total biomass) by one species: Gloeochrysis (Chrysophyceae). This species was observed as brown, mucilaginous, 200-microm-thick films on stones, growing in clumps in a dense matrix of fungal hyphae, bacteria, and inorganic particles held together by extracellular polymeric substances. Gloeochrysis was isolated and cultivated. The photosynthetic rate measured at saturation irradiance was 120 micromol oxygen (mg chlorophyll a)(-1) h(-1) under laboratory conditions, and the saturation rate of photosynthesis by carbon dioxide was 90 micromol oxygen (mg chlorophyll a)(-1) h(-1) for oxygen evolution. Photosynthetic activity of the biofilm was light-dependent and saturated above 200 micromol photons m(-2) s(-1). In the dark, the stone surface became anoxic. Our data suggest that primary production in the Agrio River was not limited by light, carbon, or phosphorus but instead, nitrogen-limited.
我们通过结合原位测量（温度、pH值、电导率、溶解氧）、完整生物膜的光合作用（采用光暗转换法用微传感器测量）、对分离藻类的纯培养实验以及对生物膜的共聚焦激光扫描显微镜观察，研究了生活在阿根廷巴塔哥尼亚活跃火山源酸性（pH≤2）溪流中石头上的底栖生物群落。阿格里奥河的石上生物群落主要由一个物种（金球藻属（金藻纲））主导（占总生物量的99%）。该物种在石头上呈现为棕色、黏液状、200微米厚的薄膜，在由真菌菌丝、细菌和通过细胞外聚合物聚集在一起的无机颗粒组成的致密基质中呈团块状生长。金球藻被分离并培养。在实验室条件下，饱和辐照度下测得的光合速率为120微摩尔氧气（毫克叶绿素a）⁻¹小时⁻¹，二氧化碳光合饱和速率为90微摩尔氧气（毫克叶绿素a）⁻¹小时⁻¹用于放氧。生物膜的光合活性依赖于光照，在200微摩尔光子 米⁻² 秒⁻¹以上达到饱和。在黑暗中，石头表面变为缺氧状态。我们的数据表明，阿格里奥河的初级生产不受光照、碳或磷的限制，而是受氮的限制。
