Hypoxia is common in temperate headwaters and driven by hydrological extremes
Hypoxia is common in temperate headwaters and driven by hydrological extremes
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DOI：
10.1016/j.ecolind.2023.109987
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发表时间：
2023-02-10
影响因子：
6.9
通讯作者：
Pinay，Gilles
中科院分区：
文献类型：
--
作者：
Diamond，Jacob S.;Moatar，Florentina;Pinay，Gilles
缺氧，或溶解氧（DO）在低到足以损害生物体的水平，是淡水生态系统健康的一个特别有用的指标。然而，由于有限的采样在源头网络，缺氧事件的程度，分布和时间是不知道在绝大多数的河流网络。因此，我们试图澄清缺氧的程度，通过三年的仪器在8个温带，农业流域的78个站点的水源网络。我们观察到广泛分布的缺氧，在20个月内，78个部位中的51个部位发生率为4%。缺氧由三种机制驱动：风暴事件、干燥和再润湿，其中干燥是缺氧最常见的驱动因素（占所有缺氧事件类型的55%）。干燥引起的缺氧在较小的溪流中最为严重（Strahler级数≤ 3），而风暴事件优先引起较大溪流中的缺氧（Strahler级数3-5）。一个大的多样性在DO的轨迹缺氧依赖于水文事件类型，随后的预期差异的敏感物种的死亡率曲线。预测模型表明，最容易受到缺氧的网站是小溪流与低坡度，特别是在炎热，低流量期间。尽管低氧事件之间存在差异，但低氧事件期间DO下降速率具有显著的相似性（约100%）。1 mg O2 L −1d−1）。这种下降的相似性可能是一个有用的经验法则的管理人员，我们假设，这是一个信号，增加低溶解氧水的横向流入或下游需氧量增加的信号。总体而言，我们认为缺氧可能是大多数水源网络的共同特征，通常未被发现。在与气候和水资源管理变化相关的日益干旱的条件下，水源缺氧可能变得更加普遍，对生物群落和生物地球化学过程产生重要影响。
Hypoxia, or dissolved oxygen (DO) at low enough levels to impair organisms, is a particularly useful indicator of the health of freshwater ecosystems. However, due to limited sampling in headwater networks, the degree, distribution, and timing of hypoxia events are not known across the vast majority of most river networks. We thus sought to clarify the extent of hypoxia in headwater networks through three years of instrumentation of 78 sites across eight temperate, agricultural watersheds. We observed broadly distributed hypoxia, occurring 4 % of the time across 51 of the 78 sites over 20 months. The hypoxia was driven by three mechanisms: storm events, drying, and rewetting, with drying as the most common driver of hypoxia (55 % of all hypoxic event types). Drying induced hypoxia was most severe in smaller streams (Strahler orders ≤ 3), whereas storm events preferentially induced hypoxia in the larger streams (Strahler orders 3–5). A large diversity in DO trajectories towards hypoxia depended on hydrologic event type, with subsequent expected differences in mortality profiles of a sensitive species. Predictive models showed the most vulnerable sites to hypoxia were small streams with low slope, particularly during hot, low discharge periods. Despite variation among hypoxic events, there was remarkable similarity in the rate of DO drawdown during hypoxia events (ca. 1 mg O2L−1d−1). This drawdown similarity may be a useful rule-of-thumb for managers, and we hypothesize that it is either a signal of increasing lateral inflow of low DO water or a signal of increasing downstream oxygen demand. Overall, we posit that hypoxia is likely a common feature of most headwater networks that often goes undetected. Headwater hypoxia may become more common under increasingly dry conditions associated with climate and water resource management changes, with important implications for biological communities and biogeochemical processes.