Molecular and physiological mechanisms of fungal parasitism and their ecological consequences in polar waters

作为极地水生生态系统的初级生产者，底栖硅藻发挥着重要的生态作用，因为它们为包括鱼类在内的较高营养水平提供食物。然而，人们对它们的生物量生产如何受到寄生虫的影响知之甚少，例如被称为chytrids的基础真菌。在之前的一个项目中，我们检测到南极洲和北极的龟裂频繁出现，并具有高度的多样性。然而，我们无法机械地研究它们对食物网动态和碳循环的生态作用，特别是在全球气候变化的情况下。因此，根据SPP 1158南极研究计划，我们的项目解决了两个主要问题：一、通往低纬度地区的通道；二、对环境变化的反应。将与SPP的其他成员一起在波特湾(南极洲卡里尼站的Dallmann Lab)和Kongsfjorden(AWIPEW站，纽约-奥勒苏德，斯瓦尔巴群岛)进行实地工作。我们的主要问题是：宿主-寄生虫(底栖藻类-chytrids)在不同环境条件下的动态和生理变化，环境变化将如何影响chytrid寄生虫的生态作用，以及它们如何在变暖的海洋中生存在完全黑暗的时期？将致力于四个目标：i)通过实地和实验研究，评估和比较波特湾(南极)和Kongsfjorden(北极)不同环境条件下宿主-寄生虫的动态(包括。显微镜和分子工具)。Ii)在两个研究地点，利用实地研究和实验研究(包括：代谢组学)。三)确定在不断变化的环境条件下宿主-寄生虫相互作用的生态作用，并比较南极和北极的研究地点。4)确定寄生虫在变暖的海洋中持续黑暗时期生存的策略，并通过结合实验室和田间孵化的代谢组学在细胞水平上描述宿主-寄生虫系统。我们将测试以下假设：H1：宿主-寄生虫(底栖生物藻类-chytrid)作为对不断变化的环境(即温度和光照的可获得性)的反应而发生的多样性变化。H2：预测的环境变化将影响寄主和寄生虫在极地沿海水域的“相互作用”，从而影响它们在极地沿海水域的生态作用，这可能会导致南极和北极地区海底食物网和碳循环的差异。H3：在完全黑暗和低温时期(1摄氏度；极地冬季)，寄生虫形成特殊的休眠阶段和/或切换到通用策略。我们的研究将从机制上深入了解气候变化对底栖硅藻-壶菌相互作用的生态作用的影响，以及它们对食物网动态的影响，从而实现碳循环。单细胞代谢组学和后转录组学的结合使得能够探索极地地区被很大程度上忽视的底栖原生动物-寄生虫相互作用的代谢后果。

Benthic diatoms play an ecologically important role as primary producers for polar aquatic ecosystems as they provide food for higher trophic levels including fish. Yet, little is known how their biomass production is affected by parasites, e.g. basal fungi called chytrids. In a previous project, we detected the frequent occurrence and a high diversity of chytrids in both Antarctica and the Arctic. Yet, we were not able to mechanistically study their ecological role for food web dynamics and C-cycling, in particular under global climate change scenarios. Thus, in accordance with SPP 1158 Antarctic Research, our project addresses the two major overarching questions: I. Gateways to Lower Latitudes and II. Response to Environmental Change. Field work will be performed with other SPP members at Potter Cove (Dallmann Lab, Carlini Station, Antarctica) and Kongsfjorden (AWIPEW Station, Ny-Ålesund, Svalbard). Our main questions are: How do host-parasite (benthic alga-chytrids) dynamics and physiology change under different environmental conditions, how will environmental change affect the ecological role of chytrid parasites, and how do they survive periods of complete darkness in a warming ocean? Four goals will be addressed: i) Evaluate and compare host-parasite dynamics under different environmental conditions in Potter Cove (Antarctica) vs. Kongsfjorden (Arctic) via field and experimental studies (incl. microscopic and molecular tools). ii) At both study sites, examine and compare changes in host-parasite physiology under changing environmental conditions using field and experimental studies (incl. metabolomics). iii) Determine the ecological role of host-parasite interactions under changing environmental conditions and compare both Antarctic vs. Arctic study sites. iv) Define parasite strategies to survive periods of continuous darkness in a warming ocean and describe the host-parasite system on the cellular level via metabolomics combined with lab and field incubations. We will test the following hypotheses: H1: Host-parasite (benthic alga-chytrid) “diversity” changes as a response to a changing environment (i.e. temperature and light availability). H2: Predicted environmental changes will affect host-parasite “interactions” with implications for their ecological role in polar coastal waters, which may lead to differences in benthic food webs and C-cycling at Antarctic vs. Arctic sites. H3: During periods of complete darkness and low temperatures (1°C; polar winter), parasites form special resting stages and/or switch to generalist strategies. Our study will provide a mechanistical insight into climate-change related impacts on the ecological role of benthic diatom-chytrid interactions and their consequences for food web dynamics and hence C-cycling. The combination of single cell metabolomics and metatranscriptomics enables to explore metabolic consequences of largely neglected benthic protist-parasites interactions in polar regions.