Data from: The jellification of north temperate lakes

Calcium (Ca) concentrations are decreasing in softwater lakes across eastern North America and western Europe. Using long-term contemporary and palaeo-environmental field data, we show that this is precipitating a dramatic change in Canadian lakes: the replacement of previously dominant pelagic herbivores (Ca-rich Daphnia species) by Holopedium glacialis, a jelly-clad, Ca-poor competitor. In some lakes, this transformation is being facilitated by increases in macro-invertebrate predation, both from native (Chaoborus spp.) and introduced (Bythotrephes longimanus) zooplanktivores, to which Holopedium, with its jelly coat, is relatively invulnerable. Greater representation by Holopedium within cladoceran zooplankton communities will reduce nutrient transfer through food webs, given their lower phosphorus content relative to daphniids, and greater absolute abundances may pose long-term problems to water users. The dominance of jelly-clad zooplankton will likely persist while lakewater Ca levels remain low.

北美东部与西欧地区的软水湖泊中，钙（Calcium, Ca）浓度正持续下降。本研究依托长期现代观测与古环境野外数据，证实该钙浓度降低现象正引发加拿大湖泊的剧烈生态转型：原本占据优势的远洋浮游植食动物——富钙溞属（Daphnia）物种——正被具胶被的贫钙竞争者透明薄皮溞（Holopedium glacialis）所取代。在部分湖泊中，本土幽蚊属（Chaoborus spp.）与外来的长肢溞（Bythotrephes longimanus）这类浮游动物食性生物所造成的大型无脊椎动物捕食压力上升，进一步推动了这一生态转型；而透明薄皮溞凭借其胶被结构，对这类捕食相对具备抵御能力。相较于溞科物种，透明薄皮溞的磷含量更低，因此其在枝角类浮游动物群落中占比的提升，会削弱食物网的营养传递效率；同时，透明薄皮溞种群绝对丰度的升高，还可能长期给水务使用者带来潜在隐患。当湖泊水体钙浓度持续维持低位时，具胶被浮游动物的优势地位或将长期保持。