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

寄生最近被认为是一种在生态学上极为成功的方式，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，而极地区域和海底栖息地在很大程度上仍未得到研究。菊苣是游动孢子型真(基础)真菌，在水生食物网中扮演着致死寄生虫的生态关键角色，例如控制浮游植物的水华，并通过所谓的菌壳作为不可食用的浮游植物和浮游动物之间的营养纽带。底栖硅藻占主导地位--即所谓的微型底栖植物群落--海洋软底浅水：i)高初级生产者，ii)控制沉积物/水界面的氧气和营养物质通量的屏障，以及iii)防止水动力侵蚀的沉积物表面的稳定剂。然而，寄生脊椎动物是否以及在多大程度上影响极地地区的海洋底栖硅藻，以及海洋环境中真菌的存在还有待研究。因此，本提案的主要问题是：极地海底硅藻中的寄生相互作用有多大相关性，全球变暖是否有可能改变这些相互作用？将缩小这一根本知识差距，重点是首次研究的下列目标：(I)利用各种显微镜和分子工具，如单细胞和光镜下扩增子测序法，调查波特湾(南极洲)和Kongsfjorden(北极)的底栖硅藻，以了解寄生食蟹的存在和多样性。(Ii)使用现场鉴定、培养和非培养方法相结合的方法，通过分子检测工具(包括FISH和RT qPCR)确定这些寄生虫及其宿主的相对感染率和身份，以评估特定裂殖吸虫的未知感染率。这些数据对于理解和将功能机制与关键的生物相互作用联系起来是必不可少的。(3)评估气候变化条件(变暖)作为刺激或抑制极地底栖硅藻寄生的潜在驱动因素，从而对微型植物底栖动物的结构和功能产生影响；(4)建立寄生虫-宿主系统，借以在受控和操纵的环境条件下研究生物相互作用(例如，宿主识别、生化/分子寄生虫-宿主相互作用)；我们假设，脊椎动物在生态上很重要，但迄今在很大程度上被忽视了与底栖食物网底部，特别是极地地区的硅藻的生物相互作用。

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.