Widespread methanotrophic primary production in lowland chalk rivers.
Widespread methanotrophic primary production in lowland chalk rivers.
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DOI：
10.1098/rspb.2013.2854
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发表时间：
2014-05-22
期刊：
影响因子：
--
通讯作者：
Trimmer M
中科院分区：
文献类型：
--
作者：
Shelley F;Grey J;Trimmer M
在许多河流中，甲烷相对于大气来说是过饱和的，但人们对它的循环和命运知之甚少。虽然光合作用是河流自养碳的主要来源，但化学合成，特别是甲烷氧化，可以在河床阴影严重或沉积物表面以下的深度提供初级生产的替代来源。在这里，我们强调地理上广泛的甲烷氧化碳固定在30多条白垩河流的砾石河床。在其中的15个中，还将甲烷氧化（甲烷营养）的潜力与光合作用进行了比较。此外，我们进行了详细的同步测量的光合作用和甲烷氧化在一个大的白垩河流在一个完整的年度周期，在那里我们发现甲烷氧化是活跃到至少15厘米到河床和强烈的基板限制。甲烷营养活动的季节性趋势反映了河流甲烷浓度的季节性趋势，因此在仲夏测得的最高比率。在沉积物表面，光合作用是有限的光的大部分时间与密集的水生植物床引起的沉重的阴影。在15条河流中，在夏末，我们保守地计算出净甲烷营养相当于砾石河床内底栖生物净光合生产的1%至46%，中值为4%。因此，河床化学合成，再加上甲烷的氧化，是广泛和显着的英国白垩河流。
Methane is oversaturated relative to the atmosphere in many rivers, yet its cycling and fate is poorly understood. While photosynthesis is the dominant source of autotrophic carbon to rivers, chemosynthesis and particularly methane oxidation could provide alternative sources of primary production where the riverbed is heavily shaded or at depth beneath the sediment surface. Here, we highlight geographically widespread methanotrophic carbon fixation within the gravel riverbeds of over 30 chalk rivers. In 15 of these, the potential for methane oxidation (methanotrophy) was also compared with photosynthesis. In addition, we performed detailed concurrent measurements of photosynthesis and methanotrophy in one large chalk river over a complete annual cycle, where we found methanotrophy to be active to at least 15 cm into the riverbed and to be strongly substrate limited. The seasonal trend in methanotrophic activity reflected that of the riverine methane concentrations, and thus the highest rates were measured in mid-summer. At the sediment surface, photosynthesis was limited by light for most of the year with heavy shading induced by dense beds of aquatic macrophytes. Across 15 rivers, in late summer, we conservatively calculated that net methanotrophy was equivalent to between 1% and 46% of benthic net photosynthetic production within the gravel riverbed, with a median value of 4%. Hence, riverbed chemosynthesis, coupled to the oxidation of methane, is widespread and significant in English chalk rivers.
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