Dissolved organic nutrients dominate melting surface ice of the Dark Zone (Greenland Ice Sheet)
Dissolved organic nutrients dominate melting surface ice of the Dark Zone (Greenland Ice Sheet)
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DOI：
10.5194/bg-16-3283-2019
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发表时间：
2019-08-30
期刊：
影响因子：
4.9
通讯作者：
Anesio, Alexandre M.
中科院分区：
文献类型：
--
作者：
Holland, Alexandra T.;Williamson, Christopher J.;Anesio, Alexandre M.
冰川和冰盖的冰表面（冰上环境）拥有丰富且动态的微生物群落。最近的研究表明，格陵兰冰盖西南海岸冰层表层上盛开的链藻冰川藻是造成15年来反照率显着下降的重要原因。目前，人们对这种大规模藻华的限制因素知之甚少，例如营养物质的可用性。在这项研究中，我们研究了这些变暗的表面冰环境中溶解的无机和溶解的有机大量营养素（N 和 P）的相对丰度。对三个不同的冰表面（具有低、中和高可见杂质含量）、冰上溪流水和冰石洞水进行了采样。我们的结果表明，在所有含有低、中、高可见杂质含量的冰面样品中，有机相明显占主导地位，其中有机相占总溶解氮的 93% 和总溶解磷的 67%。低、中、高可见杂质地表冰环境中溶解无机氮(DIN)平均浓度为0.91、0.62和1.0μM，溶解有机氮(DON)平均浓度为5.1、11和14μM，溶解无机磷(DIP)平均浓度为0.03、0.07和0.05μM，溶解有机磷平均浓度为0.10、0.15和0.12μM。 （DOP），分别。所有三个表面冰样本中的 DON 浓度均显着高于冰上溪流和冰石洞水中的 DON 浓度（分别为 0 和 0.7 μM）。与冰上溪流和冰石洞水相比，所有三个表面冰样本中的 DOP 浓度均较高（均为 0.07 μM）。溶解有机碳（DOC）浓度随着存在的可见杂质的量而增加（低：83μM，中：173μM，高：242μM），并且与冰上溪流和冰冰洞水（分别为30和50μM）相比有所升高。我们推测，风化壳的结构会影响融化的表面冰中的水流路径和储存和/或细胞外聚合物（EPS）的产生，其中含有N和P以及C，是导致DON和DOP暂时保留在融化的表面冰中的原因。在融化的表面冰环境中，可测量的 DIP 和 DIN（主要为 NH4+）的异常存在表明，除了宏量营养素限制之外的其他因素正在控制冰川藻类的范围和规模。
Glaciers and ice sheets host abundant and dynamic communities of microorganisms on the ice surface (supraglacial environments). Recently, it has been shown that Streptophyte glacier algae blooming on the surface ice of the south-western coast of the Greenland Ice Sheet are a significant contributor to the 15-year marked decrease in albedo. Currently, little is known about the constraints, such as nutrient availability, on this large-scale algal bloom. In this study, we investigate the relative abundances of dissolved inorganic and dissolved organic macronutrients (N and P) in these darkening surface ice environments. Three distinct ice surfaces, with low, medium and high visible impurity loadings, supraglacial stream water and cryoconite hole water, were sampled. Our results show a clear dominance of the organic phase in all ice surface samples containing low, medium and high visible impurity loadings, with 93% of the total dissolved nitrogen and 67% of the total dissolved phosphorus in the organic phase. Mean concentrations in low, medium and high visible impurity surface ice environments are 0.91, 0.62 and 1.0 mu M for dissolved inorganic nitrogen (DIN), 5.1, 11 and 14 mu M for dissolved organic nitrogen (DON), 0.03, 0.07 and 0.05 mu M for dissolved inorganic phosphorus (DIP) and 0.10, 0.15 and 0.12 mu M for dissolved organic phosphorus (DOP), respectively. DON concentrations in all three surface ice samples are significantly higher than DON concentrations in supraglacial streams and cryoconite hole water (0 and 0.7 mu M, respectively). DOP concentrations are higher in all three surface ice samples compared to supraglacial streams and cryoconite hole water (0.07 mu M for both). Dissolved organic carbon (DOC) concentrations increase with the amount of visible impurities present (low: 83 mu M, medium: 173 mu M and high: 242 mu M) and are elevated compared to supraglacial streams and cryoconite hole water (30 and 50 mu M, respectively). We speculate that the architecture of the weathering crust, which impacts on water flow paths and storage in the melting surface ice and/or the production of extracellular polymeric substances (EPS), containing both N and P in conjunction with C, is responsible for the temporary retention of DON and DOP in the melting surface ice. The unusual presence of measurable DIP and DIN, principally as NH4+, in the melting surface ice environments suggests that factors other than macronutrient limitation are controlling the extent and magnitude of the glacier algae.