Lake Vanda is a permanently ice‐covered lake in the McMurdo Dry Valleys of Antarctica. Its bottom waters remain stratified year‐round because of a strong salinity‐driven density gradient. We have assessed spatial patterns in and relationships between major biogeochemical processes in the water column of Lake Vanda. Samples were collected in the austral summers of 2008 and 2011 to measure concentrations of metabolites associated with a suite of biogeochemical processes across the deep salinity gradient. The shapes of the resulting geochemical profiles were consistent between 2008 and 2011. Metabolite production and consumption rates were estimated using a reactive transport model based on the assumption that vertical diffusion was the only active physical transport process. We validated this model for nitrification by using stable isotope incubations to show that this process was only active at depths predicted by the model. No nitrification activity was observed at 68 m depth in spite of overlapping oxygen and ammonium gradients. We attribute this lack of activity to the competitive inhibition of ammonia monooxygenase by methane. Net nitrous oxide and nitrate consumption were observed in the oxic water column, providing evidence of aerobic denitrification. The depth of maximum net oxygen production did not coincide with the deep chlorophyll maxima (at 59.3, 63, and 68.2 m) measured in the same profile. Finally, the integrated sulfide oxidation rate was high compared with other oxidation processes, indicating that sulfide was an important electron donor for the water column microbial community.

中文翻译：

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南极万达湖深盐水中的垂直分层和生物地球化学过程的稳定性

万达湖是南极麦克默多干旱谷的永久覆冰湖泊。由于强烈的盐度驱动的密度梯度，其底部水全年仍保持分层状态。我们评估了万达湖水柱中主要生物地球化学过程的空间格局及其之间的关系。在2008年和2011年的南半球夏季采集了样品，以测量与整个深盐度梯度相关的一系列生物地球化学过程相关的代谢物浓度。最终的地球化学分布图的形状在2008年至2011年之间是一致的。代谢物的产生和消耗速度是根据垂直扩散是唯一的主动物理运输过程的假设，使用反应性运输模型估算的。我们通过使用稳定的同位素孵育验证了该模型的硝化作用，表明该过程仅在模型预测的深度有效。尽管氧气和铵的梯度重叠，但在68 m深度未观察到硝化活性。我们将这种缺乏活性归因于甲烷对氨单加氧酶的竞争性抑制。在含氧水塔中观察到净一氧化二氮和硝酸盐消耗量，为有氧反硝化提供了证据。最大净氧产量的深度与在同一剖面中测得的深叶绿素最大值（59.3、63和68.2 m）不一致。最后，与其他氧化过程相比，硫化物的综合氧化速率高，表明硫化物是水柱微生物群落的重要电子供体。