In temperate lakes, eutrophication and warm temperatures can promote cyanobacteria blooms that reduce water quality and impair food-chain support. Although parasitic chytrids of phytoplankton might compete with zooplankton, they also indirectly support zooplankton populations through the “mycoloop”, which helps move energy and essential dietary molecules from inedible phytoplankton to zooplankton. Here, we consider how the mycoloop might fit into the biodiversity–ecosystem functioning (BEF) framework. BEF considers how more diverse communities can benefit ecosystem functions like zooplankton production. Chytrids are themselves part of pelagic food webs and they directly contribute to zooplankton diets through spore production and by increasing host edibility. The additional way that chytrids might support BEF is if they engage in “kill-the-winner” dynamics. In contrast to grazers, which result in “eat-the-edible” dynamics, kill-the-winner dynamics can occur for host-specific infectious diseases that control the abundance of dominant (in this case inedible) hosts and thus limit the competitive exclusion of poorer (in this case edible) competitors. Thus, if phytoplankton diversity provides functions, and chytrids support algal diversity, chytrids could indirectly favour edible phytoplankton. All three mechanisms are linked to diversity and therefore provide some “insurance” for zooplankton production against the impacts of eutrophication and warming. In our perspective piece, we explore evidence for the chytrid insurance hypothesis, identify exceptions and knowledge gaps, and outline future research directions.

在温带湖泊中，富营养化和温暖的气温会促进蓝藻大量繁殖，从而降低水质并损害食物链支持。尽管浮游植物的寄生壶菌可能与浮游动物竞争，但它们也通过“菌环”间接支持浮游动物种群，这有助于将能量和必需的膳食分子从不可食用的浮游植物转移到浮游动物。在这里，我们考虑 mycoloop 如何融入生物多样性-生态系统功能 (BEF) 框架。BEF 考虑更多样化的社区如何有利于浮游动物生产等生态系统功能。壶菌本身是远洋食物网的一部分，它们通过孢子产生和增加宿主的可食性直接为浮游动物的饮食做出贡献。壶菌可能支持 BEF 的另一种方式是它们参与“杀死胜利者”的动态。与导致“吃可食用”动态的食草动物相反，宿主特异性传染病可能会发生“杀死胜利者”动态，这些传染病控制了优势宿主（在这种情况下是不可食用的）宿主的丰度，从而限制了竞争排斥较差的（在本例中是可食用的）竞争对手。因此，如果浮游植物多样性提供功能，并且壶菌支持藻类多样性，那么壶菌可以间接支持可食用浮游植物。所有这三种机制都与多样性有关，因此为浮游动物的生产提供了一些“保险”，以抵御富营养化和变暖的影响。在我们的观点文章中，我们探索壶菌保险假说的证据，确定例外情况和知识差距，并概述未来的研究方向。