Darcy John L, King Andrew J, Gendron Eli M S, Schmidt Steven K
Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, USA.
King Ecological Consulting, 2504 Scarlett Oak Ct, Knoxville, TN 37909, USA.
FEMS Microbiol Ecol. 2017 Aug 1;93(8). doi: 10.1093/femsec/fix095.
Although microbial communities from many glacial environments have been analyzed, microbes living in the debris atop debris-covered glaciers represent an understudied frontier in the cryosphere. The few previous molecular studies of microbes in supraglacial debris have either had limited phylogenetic resolution, limited spatial resolution (e.g. only one sample site on the glacier) or both. Here, we present the microbiome of a debris-covered glacier across all three domains of life, using a spatially-explicit sampling scheme to characterize the Middle Fork Toklat Glacier's microbiome from its terminus to sites high on the glacier. Our results show that microbial communities differ across the supraglacial transect, but surprisingly these communities are strongly spatially autocorrelated, suggesting the presence of a supraglacial chronosequence. This pattern is dominated by phototrophic microbes (both bacteria and eukaryotes) which are less abundant near the terminus and more abundant higher on the glacier. We use these data to refute the hypothesis that the inhabitants of the glacier are randomly deposited atmospheric microbes, and to provide evidence that succession from a predominantly photosynthetic to a more heterotrophic community is occurring on the glacier.
尽管已经对许多冰川环境中的微生物群落进行了分析，但生活在覆盖着碎屑的冰川顶部碎屑中的微生物却是冰冻圈中一个研究较少的前沿领域。此前对冰面碎屑中微生物的少数分子研究，要么系统发育分辨率有限，要么空间分辨率有限（例如，冰川上只有一个采样点），或者两者都有限。在这里，我们展示了一个覆盖着碎屑的冰川在生命的所有三个领域的微生物群落，使用一种空间明确的采样方案来描述托克拉特冰川中叉从其末端到冰川高处的微生物群落。我们的结果表明，冰面样带的微生物群落各不相同，但令人惊讶的是，这些群落具有很强的空间自相关性，这表明存在一个冰面年代序列。这种模式以光合微生物（细菌和真核生物）为主，它们在末端附近较少，在冰川高处较多。我们利用这些数据反驳了冰川居民是随机沉积的大气微生物这一假设，并提供证据表明冰川上正在发生从以光合作用为主的群落向更多样化的异养群落的演替。
