Climate change has the potential to shape the future of infectious diseases, both directly and indirectly. In aquatic systems, for example, elevated temperatures can modulate the infectivity of waterborne parasites and affect the immune response of zooplanktonic hosts. Moreover, lake warming causes shifts in the communities of primary producers towards cyanobacterial dominance, thus lowering the quality of zooplankton diet. This may further affect host fitness, resulting in suboptimal resources available for parasite growth. Previous experimental studies have demonstrated the respective effects of temperature and host diet on infection outcomes, using the zooplankter Daphnia and its microparasites as model systems. Although cyanobacteria blooms and heat waves are concurrent events in nature, few attempts have been made to combine both stressors in experimental settings. Here, we raised the zooplankter Daphnia (two genotypes) under a full factorial design with varying levels of temperature (the standard 19°C and elevated 23°C), food quality (Scenedesmus obliquus as high‐quality green algae, Microcystis aeruginosa and Planktothrix agardhii as low‐quality cyanobacteria) and exposed them to the parasitic yeast Metschnikowia bicuspidata. We recorded life history parameters of the host as well as parasite traits related to transmission. The combination of low‐quality cyanobacterial diets and elevated temperature resulted in additive detrimental effects on host fecundity. Low‐quality diets reduced parasite output, while temperature effects were context dependent. Overall, we argue that the combined effects of elevated water temperature and poor‐quality diets may decrease epidemics of a common fungal parasite under a climate change scenario.

中文翻译：

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温度和宿主饮食共同影响水蚤-真菌寄生虫系统中的感染结果

气候变化有可能直接或间接影响传染病的未来。例如，在水生系统中，升高的温度可以调节水生寄生虫的传染性并影响浮游动物宿主的免疫反应。此外，湖泊变暖导致初级生产者群落向蓝藻优势转变，从而降低了浮游动物饮食的质量。这可能会进一步影响宿主的健康，导致可用于寄生虫生长的次优资源。以前的实验研究已经证明了温度和宿主饮食对感染结果的各自影响，使用浮游动物水蚤及其微寄生虫作为模型系统。虽然蓝藻大量繁殖和热浪在自然界中是同时发生的，很少有人尝试在实验环境中结合这两种压力源。在这里，我们在具有不同温度水平（标准 19°C 和升高的 23°C）、食物质量（Scenedesmus biliquus 作为优质绿藻、铜绿微囊藻和浮游生物）的全因子设计下饲养浮游动物水蚤（两种基因型） agardhii 作为低质量的蓝藻）并将它们暴露于寄生酵母 Metschnikowia bicuspidata。我们记录了宿主的生活史参数以及与传播相关的寄生虫特征。低质量的蓝藻饮食和高温相结合导致对宿主繁殖力的额外不利影响。低质量的饮食会减少寄生虫的产量，而温度的影响则取决于环境。全面的，