Functional ecology of interactome-predicted key ciliates in deep temperate lakes

揭示水生食物网中关键参与者之间异常复杂的关系是淡水生态学的一个中心议题。这些关键参与者是在浮游生物群落中具有重要功能的物种，当它们因气候压力等原因而消失时，可能导致相互作用组网络的崩溃。水生食物网由微生物组成，包括细菌和原生生物，以及在季节循环中共存的小型后生动物。从浮游生物样本中获得的环境DNA元条形码的分析，以及随后将这些大规模序列数据集整合到相互作用组网络分析中，成为一个非常强大的工具，可以揭示这些复杂的水生食物网中生物和非生物相互作用的整体。除其他外，网络特性的统计分析可以检测关键物种。在以往的研究中，在两个高山湖泊中，纤毛虫是最重要的类群之一。不幸的是，由于核苷酸数据库的不完整性，许多纤毛虫，在相互作用组网络的关键物种的序列不能在分类学上分配超出门水平。这一失败阻碍了进一步的研究和网络成果的利用。例如，没有文化可以建立进行autecological实验，以揭示功能性状，生活方式和生态的重要性，提出的相互作用组结构。此外，在自然环境中的形态种的原位观察，以推断生态信息是不可能的。因此，拟议的扩展项目的目标是利用最先进的分子和显微镜技术、培养技术、实验室实验（微观世界）和实地观察，调查隐藏在两个深温带湖泊（蒙德湖和苏黎世湖）浮游生物相互作用组中的先前未识别的关键纤毛虫的功能作用。预期结果将有助于更好地预测湖泊生态系统功能的变化，以及这些湖泊在压力（气候和其他压力因素）下的恢复力和反应。

Revealing the extraordinarily complex relationships among the involved key players in aquatic food webs is a central topic in freshwater ecology. Such key players are species with important functions in the plankton community and which, when lost because of e.g. climate stressors, could cause the collapse of the interactome networks. Aquatic food webs consist of microscopic organisms, including bacteria and protists, and small metazoans that co-occur in seasonal cycles. The analyses of environmental DNA metabarcodes, obtained from plankton samples, and subsequent integration of these massive sequence datasets into interactome network analyses emerged as a very powerful tool to uncovered the entirety of interactions, biotic and abiotic, in these complex aquatic food webs. Among others, statistical analyses of network properties allow for the detection of key species. In such DNA-based networks obtained from two deep alpine lakes in previous project, especially ciliates emerged as a most important taxon group. Unfortunately, due to the incompleteness of nucleotide databases, the sequences of numerous ciliates which are key species in interactome networks cannot be taxonomically assigned beyond phylum level. This failure hampers further research and the exploitation of network results. For example, no cultures can be established to conduct autecological experiments to reveal the functional traits, lifestyle and ecological importance as proposed by the interactome structures. Also, in situ observations of the morphospecies in their natural environments to infer ecological information is not possible. Therefore, the goal of the proposed extension project is to investigate the functional role of previously unidentified key ciliates hiding in the plankton interactome of two deep temperate lakes (Lake Mondsee and Lake Zurich) using state-of-the-art molecular and microscopy techniques, cultivation techniques, lab-based experiments (microcosms) and also field observations. The expected results will help to better predict changes in lake ecosystem function, as well as the resilience and response of these lakes under stress (climatic and other stressors).