In coastal marine ecosystems, the depletion of dissolved oxygen can cause behavioral and distributional shifts of organisms and thereby alter ecological processes. We used the spatiotemporal variation in the onset and intensity of low dissolved oxygen in Hood Canal, Washington, USA, to investigate consequences of seasonally reduced oxygen on fish–zooplankton predator–prey interactions. By simultaneously monitoring densities of zooplankton (primarily the euphausiid; Euphausia pacifica) and zooplanktivorous fish (Pacific herring, Clupea pallasii, and Pacific hake, Mercluccius productus), and the feeding of zooplanktivorous fish, we could separate the effects of dissolved oxygen on fish–zooplankton interactions from other seasonal changes. We expected that fish predators (especially Pacific herring) would be less abundant and have lower feeding rates when oxygen levels declined below biological thresholds, and that this would result in increased zooplankton abundance in areas with lowest dissolved oxygen. However, these expectations were not borne out. Overall, there was mixed evidence for an effect of dissolved oxygen on many of our response variables, and when effects were detected, they were frequently in the opposite direction of our expectations. Specifically, the pelagic fish community became more abundant (as measured by increasing acoustic backscatter), which was particularly pronounced for Pacific herring. Zooplankton had weak evidence for a response to dissolved oxygen, but the direction was negative instead of positive. Although predator feeding composition was unrelated to dissolved oxygen, stomach fullness (an index of feeding intensity) of Pacific herring declined, as per our expectations. These unexpected findings highlight the importance of in situ measurements of multiple aspects of predator–prey linkages in response to environmental stress to enhance our ability to predict ecological consequences of declining oxygen.

中文翻译：

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食物网对河口峡湾低溶解氧的反应。

在沿海海洋生态系统中，溶解氧的消耗会导致生物的行为和分布转移，从而改变生态过程。我们使用美国华盛顿胡德运河低溶解氧的发生和强度的时空变化来调查季节性减少的氧气对鱼-浮游生物-捕食者-猎物相互作用的影响。通过浮游动物的同时监测密度（主要是磷虾;磷虾茵）和zooplanktivorous鱼（太平洋鲱鱼，鲱pallasii，和太平洋无须鳕，Mercluccius productus）以及浮游动物的摄食，我们可以将溶解氧对鱼类与浮游动物相互作用的影响与其他季节变化区分开来。我们预计，当氧气水平降至生物阈值以下时，鱼类捕食者（尤其是太平洋鲱鱼）的数量将减少，摄食率降低，这将导致溶解氧最低的地区浮游动物的丰度增加。但是，这些期望并未得到证实。总体而言，有混合的证据表明溶解氧对我们许多响应变量的影响，并且当检测到影响时，它们常常与我们预期的方向相反。具体而言，中上层鱼类群落变得更加丰富（通过增加声学反向散射来衡量），这在太平洋鲱鱼中尤为明显。浮游动物缺乏对溶解氧作出反应的证据，但是方向是负的而不是正的。尽管捕食者的摄食成分与溶解氧无关，但根据我们的预期，太平洋鲱鱼的胃部饱满度（摄食强度指标）下降了。这些出乎意料的发现凸显了对捕食者与猎物之间联系的多个方面进行现场测量以响应环境压力的重要性，以增强我们预测氧气下降对生态后果的能力。