Temperature effects on carbon and nitrogen metabolism in some Maritime Antarctic freshwater phototrophic communities
Temperature effects on carbon and nitrogen metabolism in some Maritime Antarctic freshwater phototrophic communities
复制标题
温度对一些南极海洋淡水光养群落碳氮代谢的影响
作者：
D. Velázquez;C. Rochera;A. Camacho;A. Quesada
生长在冰和底栖垫上的生物膜是南极景观中最引人注目的生物群落之一，并拥有高度多样性的生物。这些群落是对南极非海洋生态系统的碳和氮输入作出重要贡献的联合体。在这里，我们研究了温度升高对拜尔斯半岛（利文斯顿岛，海洋南极洲）的两个底栖生物群落的碳和氮代谢的影响：一个生物膜占主导地位的绿色藻类生长在季节性的冰，和陆地微生物垫主要由蓝藻。无机碳的光合作用，尿素和硝酸盐的吸收和N2固定（乙炔还原活性）率在五个不同的温度（0，5，10，15，25°C），使用恒温水浴平行测定原位。蓝藻垫的结果表明，光合作用和N2固定积极响应温度升高，但尿素和NO3−吸收率没有显示出与温度相关的显着变化。该微生物垫在0°C下表现出相对低的活性，而在较高温度（高达15°C）下，N2固定速率显著增加。类似地，最大光合活性随温度增加而增加，并且在25°C之前没有显示出饱和。相比之下，冰生物膜在0°C下比在其他温度下显示出更高的光合活性，并且在较温暖的温度下显示出升高的光抑制。
Biofilms growing on ice and benthic mats are among the most conspicuous biological communities in Antarctic landscapes and harbour a high diversity of organisms. These communities are consortia that make important contributions to carbon and nitrogen input in non-marine Antarctic ecosystems. Here, we study the effect of increasing temperatures on the carbon and nitrogen metabolism of two benthic communities on Byers Peninsula (Livingston Island, Maritime Antarctica): a biofilm dominated by green algae growing on seasonal ice, and a land-based microbial mat composed mainly of cyanobacteria. Inorganic carbon photoassimilation, urea and nitrate uptake and N2-fixation (acetylene reduction activity) rates were determined in situ in parallel at five different temperatures (0, 5, 10, 15, 25°C) using thermostatic baths. The results for the cyanobacterial mat showed that photosynthesis and N2-fixation responded positively to increased temperatures, but urea and NO3− uptake rates did not show a significant variation related to temperature. This microbial mat exhibits relatively low activity at 0°C whereas at higher temperatures (up to 15°C), N2-fixation rate increased significantly. Similarly, the maximum photosynthetic activity increased in parallel with temperature and showed no saturation up to 25°C. In contrast, the ice biofilm displayed higher photosynthetic activity at 0°C than at the other temperatures assayed, and it showed elevated photoinhibition at warmer temperatures.