Growing evidence suggests that global climate change promotes the dominance of mixotrophic algae especially in oligotrophic aquatic ecosystems. While theory predicts that mixotrophy increases trophic transfer efficiency in aquatic food webs, deleterious effects of some mixotrophs on consumers have also been reported. Here, using a widespread mixotrophic algal genus Dinobryon, we aimed to quantify how colonial taxa contribute to secondary production in lakes. We, therefore, studied the dietary effects of Dinobryon divergens on Cladocera (Daphnia longispina) and Copepoda (Eudiaptomus gracilis), representing two main taxonomic and functional groups of zooplankton. In feeding experiments, we showed that Dinobryon was largely grazing resistant and even inhibited the uptake of the high-quality reference food in Daphnia. Eudiaptomus could to some extent compensate with selective feeding, but a negative long-term food quality effect was also evident. Besides, Eudiaptomus was more sensitive to the pure diet of Dinobryon than Daphnia. Low lipid content and high C:P elemental ratio further supported the low nutritional value of the mixotroph. In a stable isotope approach analysing a natural plankton community, we found further evidence that carbon of Dinobryon was not conveyed efficiently to zooplankton. Our results show that the increasing dominance of colonial mixotrophs can result in reduced dietary energy transfer to consumers at higher trophic levels. In a wider perspective, global climate change favours the dominance of some detrimental mixotrophic algae which may constrain pelagic trophic transfer efficiency in oligotrophic systems, similarly to cyanobacteria in eutrophic lakes.

越来越多的证据表明，全球气候变化促进了混合营养藻类的优势，特别是在贫营养水生生态系统中。尽管理论预测混合营养增加了水生食物网中的营养传递效率，但也有一些混合营养对消费者的有害影响的报道。在这里，我们使用分布广泛的混合营养藻类Dinobryon来量化殖民地分类单元如何促进湖泊的次级生产。因此，我们研究了Dinobryon divergens对Cladocera（Daphnia longispina）和Copepoda（Eudiaptomus gracilis）的饮食影响，代表了浮游动物的两个主要分类和功能组。在喂养实验中，我们证明了Dinobryon高度耐草食，甚至抑制了水蚤对高质量参考食物的摄取。鹰嘴豆可以在一定程度上补偿选择性饲喂，但长期的食品质量负面影响也很明显。此外，Eudiaptomus对纯恐龙的饮食比水蚤更敏感。低脂质含量和高C：P元素比率进一步支持了混合营养的低营养价值。在分析天然浮游生物群落的稳定同位素方法中，我们发现了进一步的证据，证明狄诺布里昂的碳没有有效地转移到浮游动物。我们的结果表明，殖民混合营养动物的优势日益增强，可导致营养水平更高的饮食能量转移到消费者身上。从更广泛的角度来看，全球气候变化有利于某些有害的混合营养藻类的优势，这可能会限制富营养化系统中上层营养的转移效率，类似于富营养化湖泊中的蓝细菌。