Inorganic N and P dynamics of Antarctic glacial meltwater streams as controlled by hyporheic exchange and benthic autotrophic communities
Inorganic N and P dynamics of Antarctic glacial meltwater streams as controlled by hyporheic exchange and benthic autotrophic communities
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受潜流交换和底栖自养群落控制的南极冰川融水流的无机氮和磷动态
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发表时间：
2004
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通讯作者：
D. Moorhead
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作者：
D. McKnight;R. Runkel;C. Tate;J. Duff;D. Moorhead
摘要 南极洲南维多利亚州的麦克默多干谷包含大量冰川融水溪流，这些溪流流入谷底的湖泊。许多溪流都有丰富的多年生丝状蓝细菌丛。藻丛在南半球夏季的水流中生长，并在一年中的其余时间处于休眠冻干状态。藻丛丰富的溪流中的 NO3 和可溶性活性磷 (SRP) 浓度低于藻丛稀疏的溪流。在藻丛丰富的河流的潜流带中，NO3 和 SRP 浓度高于河流本身。在绿溪 (Green Creek) 进行了一次注入 LiCl、NaNO3 和 K3PO4 的实验，那里有丰富的藻丛。发生大量的漏液交换。实验过程中，注入点下方 50 m 处的 NO3 和 PO4 浓度分别为 55 μM 和 18 μM。在 Cl 示踪剂到达期间，注入点下方 497 m 处的 NO3 和 PO4 浓度低于 1 至 2 μM 的检测限，表明藻类群落具有较高的养分吸收能力。 NO2 和 NH4 存在于注入点下方 226 和 327 m 的位置，表明除了反硝化和藻类吸收之外，NO3 异化还原为 NO2 和 NH4 可能是运输过程中的 NO3 汇。将养分吸收表示为一阶过程的运输模型产生的 NO3 和 PO4 吸收的范围参数分别为 4.3 × 10−5 至 3.9 × 10−4/s 和 1.4 × 10−4 至 3.8 × 10−4/s。与观测数据最匹配的是 PO4 吸收仅发生在主河道中而 NO3 吸收发生在主河道和潜流区的模型。不同河段的次流NO3 吸收量占总吸收量的7% 至16%。这些结果表明，流入湖泊的养分通量是由干谷溪流中藻垫的潜流交换和养分吸收控制的。没有藻垫的溪流比有藻垫的溪流为湖泊提供更多的养分。
Abstract The McMurdo Dry Valleys of South Victoria Land, Antarctica, contain numerous glacial meltwater streams that drain into lakes on the valley floors. Many of the streams have abundant perennial mats of filamentous cyanobacteria. The algal mats grow during streamflow in the austral summer and are in a dormant freeze-dried state during the rest of the year. NO3 and soluble reactive P (SRP) concentrations were lower in streams with abundant algal mats than in streams with sparse algal mats. NO3 and SRP concentrations were higher in the hyporheic zone of a stream with abundant algal mats than in the stream itself. An experimental injection of LiCl, NaNO3, and K3PO4 was conducted in Green Creek, which has abundant algal mats. Substantial hyporheic exchange occurred. The NO3 and PO4 concentrations at 50 m below the injection were 55 μM and 18 μM, respectively, during the experiment. NO3 and PO4 concentrations were below the detection limit of 1 to 2 μM at a site 497 m below the injection during the Cl tracer arrival, indicating a high capacity for nutrient uptake by algal communities. NO2 and NH4 were present at sites 226 and 327 m below the injection, indicating that, in addition to denitrification and algal uptake, dissimilatory NO3 reduction to NO2 and NH4 may be a NO3 sink during transport. Transport modelling with nutrient uptake represented as a 1st-order process yielded reach-scale parameters of 4.3 × 10−5 to 3.9 × 10−4/s and 1.4 × 10−4 to 3.8 × 10−4/s for uptake of NO3 and PO4, respectively. The best match with the observed data was a model in which PO4 uptake occurred only in the main channel and NO3 uptake occurred in the main channel and in the hyporheic zone. Hyporheic NO3 uptake was 7 to 16% of the total uptake for the different stream reaches. These results demonstrate that nutrient flux to the lakes is controlled by hyporheic exchange and nutrient uptake by algal mats in dry valley streams. Streams without algal mats contribute more nutrients to the lakes than streams with algal mats.