Greening of retreating glaciers: storage versus export of autochthonous organic matter

有水就有生命，冰川也不例外。事实上，冰川是生物细胞和碎片的巨大储存库。碎片可以覆盖全球冰川表面的1-10%，它由无机和有机颗粒组成，比周围的白色冰面更暗，因此比冰更好地吸收太阳辐射。碎片对太阳辐射的吸收促进了冰的融化，这反过来又通过创造独特和理想的生命栖息地促进了微生物活动的增加。栖息地被各种微生物殖民，包括病毒，细菌和微观植物。在最近的NERC小额赠款中，我们测量了与格陵兰岛，斯瓦尔巴特群岛和阿尔卑斯山冰川表面碎片相关的微生物活性，我们发现它与温暖地区非常丰富的生态系统中发现的微生物活性相当。事实上，一克残骸中的微生物活性与地中海一克土壤中的微生物活性大致相同。微生物在碎片上的定居随后导致冰面进一步变暗。这是因为我们还发现，光合作用的量（即，其中二氧化碳被植物转化为生物质，释放氧气的过程）比呼吸作用的量（即，其中氧气被消耗并且有机物被生物转化回二氧化碳的过程）。光合作用高于呼吸作用的结果是，冰川表面是一个自我维持的生态系统，有机物质可以在其中积累。其结果是更强的太阳辐射吸收，促进进一步融化，并为微生物提供更多的水，然后分散到冰面的其他部分。这种扩散将微生物、有机物和碎片转移到邻近的生态系统，包括有可能维持其他生态系统生命的前田和冰下环境。我们假设，冰川变得越来越生物，因为他们腐烂，冰川融化是，在某种程度上，生物介导的过程，启动生态演替之前，冰已经消失。该项目旨在量化这些对冰川物质平衡的生物影响，并通过检查因夏季融化而明显退缩的北极山谷冰川表面，确定冰川消退期间输出到下游环境的有机物质的通量和质量。在这样做的过程中，我们的目标是产生第一个量化和表征的生物物理效应的冰量消耗在冰川消退。

Life exists whatever there is water and glaciers are no exception. Indeed glaciers are vast reservoirs of biological cells and debris. The debris can cover ca 1-10% of the surface of glaciers worldwide, and it is composed of inorganic and organic particles that are darker than the surrounding white icy surface and thus absorb the solar radiation better than the ice. The absorption of the solar radiation by the debris promotes melting of the ice which in turn promotes increased levels of microbial activity via the creation of unique and ideal life-habitats. The habitats are colonised by a diverse range of microorganisms, including viruses, bacteria and microscopic plants. In a recent NERC small grant, we measured the microbial activity associated with the debris at the surface of glaciers in Greenland, Svalbard and the Alps and we found that it was comparable to that found in very rich ecosystems from warmer regions. In fact, microbial activity in one gram of debris was roughly the same as in one gram of soil from the Mediterranean. The colonisation of the debris by microbes subsequently leads to further darkening of the ice surface. This is because we also found that the amount of photosynthesis (i.e., the process in which carbon dioxide is converted by plants to biomass, releasing oxygen) is much higher than the amount of respiration (i.e., the process in which oxygen is consumed and organic matter is biologically converted back to carbon dioxide). The consequence of higher photosynthesis than respiration is that the surface of glaciers is a self-sustained ecosystem in which organic matter can be accumulated. The result is even more enhanced absorption of solar radiation, promoting further melt and providing yet more water for microorganisms, which are then dispersed to other parts of the ice surface. This dispersal transfers the microbes, organic matter and debris to adjacent ecosystems, including those of the forefield and subglacial environments with the potential to sustaining life in other ecosystems. We hypothesise that glaciers become increasingly biological as they decay, and that glacier melting is, in part, a biologically-mediated process that initiates ecological succession long before the ice has disappeared. This project aims to quantify these biological effects on glacier mass balance, and to determine fluxes and quality of organic matter exported to downstream environments during deglaciation, by examining the surfaces of Arctic valley glaciers that are retreating markedly in response to summer melt. In doing so, we aim to produce the first quantification and characterisation of bio-physical effects on ice mass wastage during deglaciation.