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

寄生现象最近被确定为在生态学上极为成功的，可能是世界海洋水层中生物相互作用和营养最丰富的模式，而极地地区和底栖生境基本上仍未得到研究。壶菌是一种真的动物孢子真菌，在水生食物网中起着重要的生态作用，如控制浮游植物的大量繁殖，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起着营养联系的作用。底栖硅藻-即所谓的微型植物底栖群落-在海洋软底浅水沃茨中占主导地位，因为它们是：一）高初级生产者;二）控制沉积物/水界面处氧气和营养物通量的屏障;三）稳定沉积物表面，防止水动力侵蚀。然而，寄生壶菌是否以及在多大程度上影响极地地区的海洋底栖硅藻，还有待研究，以及在海洋环境中的真菌的存在。因此，本提案的主要问题是：极地底栖硅藻中的寄生相互作用有多大的相关性，全球变暖是否有可能改变这些相互作用？这一根本性的知识空白将通过首次重点研究以下目标来弥补：㈠利用单细胞和Illumina Amplicon测序等各种显微镜和分子工具，调查Potter Cove（南极洲）和Kongsfjorden（北极）的底栖硅藻，以了解寄生壶菌的存在和多样性。(ii)采用田间鉴定、培养和非培养方法相结合的方法评价特定壶菌的未知感染率，以通过分子检测工具（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。这些数据对于理解功能机制并将其与关键的生物相互作用联系起来至关重要。(iii)评估气候变化条件（变暖）是否可能促进或抑制极地底栖硅藻的寄生，并对微植物底栖结构和功能产生影响; ㈣建立寄生-宿主系统，宿主识别，生物化学/分子寄生虫-宿主相互作用）可以在受控和操纵的环境条件下进行研究;我们假设壶菌在底栖食物网，特别是极地地区与硅藻的生物相互作用中发挥着重要的生态作用，但迄今为止在很大程度上被忽视了。

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.