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极其复杂的关系是淡水生态学的中心主题。这些关键角色是在浮游生物群落中具有重要功能的物种，当它们因为例如气候压力因素可能导致相互作用组网络崩溃。水生食物网由微生物（包括细菌和原生生物）以及季节性循环中共同出现的小型后生动物组成。对从浮游生物样本中获得的环境 DNA 元条形码进行分析，以及随后将这些大量序列数据集整合到相互作用组网络分析中，成为揭示这些复杂水生食物网中生物和非生物全部相互作用的非常强大的工具。除此之外，网络特性的统计分析可以检测关键物种。在之前的项目中从两个高山深湖获得的基于 DNA 的网络中，纤毛虫尤其成为最重要的分类群。不幸的是，由于核苷酸数据库的不完整，作为相互作用组网络中的关键物种的许多纤毛虫的序列不能在门水平之外进行分类学分配。这一失败阻碍了进一步的研究和网络结果的利用。例如，无法建立任何培养物来进行自生态实验来揭示相互作用组结构所提出的功能特征、生活方式和生态重要性。此外，通过对自然环境中的形态物种进行原位观察来推断生态信息也是不可能的。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）和现场观察，研究隐藏在两个温带深湖（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（气候和其他压力源）下的恢复力和响应。

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).