Abstract Increased temperature in the epilimnion and hypoxia in the metalimnion of a lake would result in an increase of positive-size-selective fish predation on zooplankton and in turn in a decrease of mean body size in zooplankton populations and communities. We tested this hypothesis in four types of experiments with juvenile rudd (Scardinius erythrophthalmus) foraging on Daphnia longispina in an indoor twin column tank system. In each experiment of the first three types, one column contained one of three types of experimental treatments differing from the control treatment (in the other column) by the following: (i) elevated temperature in the epilimnion, (ii) hypoxia in the metalimnion and (iii) simultaneous elevated temperature in the epilimnion and hypoxia in the metalimnion. In the fourth type of experiment, the gradients of temperature and oxygen concentration in both columns were the same, but prior to the experiments, Daphnia and fish in the control treatment were acclimated to normoxia and, in the experimental treatment, to hypoxia. The results confirmed our hypothesis, since the predation rate of fish was greater in each of the first three experimental treatments than in the control. We did not detect an effect of the acclimation to hypoxia on the predation rate of the fish.

中文翻译：

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浮游温度升高和金属浮游缺氧对浮游鱼类捕食率的综合影响

摘要 湖泊表层温度升高和金属层缺氧会导致正大小选择性鱼类对浮游动物的捕食增加，进而导致浮游动物种群和群落的平均体型减小。我们在四种类型的实验中测试了这一假设，即在室内双柱水箱系统中，幼鱼（Scardinius erythrophthalmus）在 Daphnia longispina 上觅食。在前三种类型的每个实验中，一个柱子包含三种类型的实验处理中的一种，与对照处理（在另一列中）的不同之处在于：（i）表层温度升高，（ii）金属层缺氧(iii) 表层温度同时升高和金属层缺氧。在第四类实验中，两列中温度和氧气浓度的梯度相同，但在实验之前，对照处理中的水蚤和鱼适应了常氧，而在实验处理中，则适应了缺氧。结果证实了我们的假设，因为在前三个实验处理中的每一个中鱼的捕食率都高于对照。我们没有检测到适应缺氧对鱼的捕食率的影响。