Ecological role of fungal parasites on benthic diatoms of polar coastal waters

寄生性最近被认为是生态学上非常成功的，并且可能是世界海洋中上层区域最丰富的生物相互作用和营养模式，而极地和底栖生物栖息地仍未得到广泛研究。壶菌是一种游动孢真（基底）真菌，在水生食物网中扮演着致命寄生虫的生态关键角色，如控制浮游植物的繁殖，并通过所谓的“菌圈”在不可食用的浮游植物和浮游动物之间充当营养纽带。底栖硅藻作为所谓的微底栖植物群落在海洋软底浅水中占主导地位，它们是i)高初级生产者，ii)控制沉积物/水界面上氧气和养分流动的屏障，以及iii)沉积物表面防止水动力侵蚀的稳定器。然而，寄生壶菌是否以及在多大程度上影响了极地地区的海洋底栖硅藻，以及海洋环境中菌圈的存在，还有待研究。因此，本提案的主要问题是：寄生相互作用在极地底栖硅藻中的相关性如何？全球变暖是否有可能改变这些相互作用？这一基本的知识差距将被缩小，重点放在以下目标上进行首次研究：(i)使用各种显微镜和分子工具，如单细胞和Illumina Amplicon测序，调查波特湾（南极洲）和Kongsfjorden（北极）的底栖硅藻寄生壶菌的存在和多样性。（ii）采用野外鉴定、培养和非培养相结合的方法评估特定壶菌的未知感染率，通过分子检测工具（包括FISH和RT qPCR）解决这些寄生虫及其宿主的相对感染率和身份问题。这些数据对于理解和连接关键生物相互作用的功能机制至关重要。（三）评价气候变化条件（变暖）作为刺激或抑制极地底栖硅藻寄生及其对底栖微植物结构和功能影响的潜在驱动因素；（四）建立寄生物-寄主系统，使生物相互作用（如寄主识别、寄主-寄主生物化学/分子相互作用）可以在受控和操纵的环境条件下进行研究；我们假设壶菌在生态上起着重要的作用，但到目前为止，它在与底栖食物网底部的硅藻的生物相互作用中起着很大的作用，特别是在极地地区。

Parasitism was recently identified as an ecologically immensely successful, and probably the most abundant mode of biotic interactions and nutrition in the world ocean’s pelagic zone, while the Polar Regions and benthic habitats remain largely unstudied. Chytrids are zoosporic true (basal) fungi that play an ecological key role as lethal parasites in the aquatic food web such as controlling phytoplankton blooms, and serving as trophic link between inedible phytoplankton and zooplankton via the so-called “mycoloop”. Benthic diatoms dominate - as so called microphytobenthic communities - marine soft bottom shallow waters as i) high primary producers, ii) control barrier for oxygen and nutrient fluxes at the sediment/water interface, and iii) stabilizer of sediment surfaces against hydrodynamic erosion. However, whether and to what degree parasitic chytrids affect marine benthic diatoms in Polar Regions, yet, have to be studied, as well as the presence of the mycoloop in marine environments. Therefore, the main questions of the present proposal are: How relevant are parasitic interactions in polar benthic diatoms, and does global warming has the potential to change these interactions? This fundamental gap of knowledge will be closed with a focus on the following goals to be studied for the first time: (i) to survey benthic diatoms in Potter Cove (Antarctica) and Kongsfjorden (Arctic) for the presence and diversity of parasitic chytrids using a variety of microscopic and molecular tools such as single cell and Illumina Amplicon sequencing. (ii) To evaluate the unknown infection rate by specific chytrids using a combination of field identification, culture and culture-independent methods to address the relative infection rate and identity of these parasites as well as their hosts via molecular detection tools (including FISH and RT qPCR). These data are essential for understanding and linking functional mechanisms to key biotic interactions. (iii) To evaluate climatic change conditions (warming) as potential driver for stimulation or inhibition of parasitism in Polar benthic diatoms with consequences for microphytobenthic structure and function; (iv) To establish parasite-host systems by which biotic interactions (e.g., host recognition, biochemical/molecular parasite-host interactions) can be studied under controlled and manipulated environmental conditions; We hypothesize that chytrids play an ecologically important, but so far largely overlooked role in biotic interactions with diatoms at the base of benthic food webs, in particular of the Polar Regions.