Biodiversity and biogeography of marine benthic diatoms in Antarctic and Arctic shallow water coastal zones to evaluate the degree of endemism using fine-grained taxonomy and eDNA metabarcoding

长期以来，南极海洋生物多样性一直被认为是物种贫乏的植物群和动物群，受到恶劣环境的限制。然而，最近的许多研究清楚地证明，南极的生物多样性比以前认为的要广泛得多，生态多样性和地理结构。这种生物多样性如何在海洋环境中分布，以及其空间变化的机制是尚未解决的问题。特别是南极微生物的研究还处于空白状态，全球环境变化对南极生物多样性及其相关生态功能（如食物网结构）的研究提出了新的挑战。在全球范围内，底栖硅藻是底栖微植物群落的关键生物，是浅水区最具生产力的微生物生物量。这些光养组合是已知的许多海洋软底区域。由于其高初级生产力，它们为底栖悬浮物或沉积物饲养者提供了主要食物来源，并作为沉积物/水界面垂直氧气和营养物通量的控制屏障，以及通过分泌粘性细胞外聚合物来稳定沉积物表面。虽然海洋底栖硅藻是沿海地区食物网的重要组成部分，但对它们在极地地区的生物多样性和生物地理学的了解却很少。与低纬度的联系，二。应对环境变化，三。提高对极地过程和机制的理解。为了解决这些问题，我们计划：1。在Potter Cove（南极洲）和Kongsfjorden（北极）采样的群落中，使用实地、培养和非培养的表型和基因型鉴定方法相结合，精确鉴定几乎未知的底栖硅藻生物多样性的细粒分类深度; 2.）建立一个经过分类学验证的极地底栖硅藻参考文库，提供有关栖息地、形态学的全面信息，并为不同物种的分配提供DNA参考序列; 3.）利用这一新的海洋底栖硅藻分类参考库进行环境DNA元编码，以获取南极和北极不同硅藻群的隐藏生物多样性和分类覆盖状况，以及4.）提供迄今为止最全面的生物多样性数据集，作为重建极地沿海地区古环境和未来变化（海岸侵蚀等）的基线。这一方法将首次澄清南极和北极浅水沿海沃茨的海洋底栖硅藻是否和如何不同（特有程度），哪些因素影响这一生态关键原生生物群体的空间分布，以及这些数据如何有助于发现和反映全球变化的情景。

Antarctic marine biodiversity has been considered for long time as species-poor flora and fauna constrained by a harsh environment. However, many recent studies clearly proved that Antarctic biodiversity is much more extensive, ecologically diverse and biogeographically structured than previously thought. How this biodiversity is distributed in the marine environment, and which mechanisms underlie its spatial variation are unresolved questions. Particularly Antarctic microorganisms are still not explored at all and hence the impacts of on-going global environmental change, pose challenges to the present and future understanding of Antarctic biodiversity and related ecological functions (e.g. food web structure).On a global scale, benthic diatoms form as key organisms of microphytobenthic communities the most productive microbial biomass in shallow water coastal zones. These phototrophic assemblages are known from many marine soft bottom regions. Due to their high primary production they provide a major food source for benthic suspension- or deposit-feeders, and act as control barrier for vertical oxygen and nutrient fluxes at the sediment/water interface as well as stabilizer of sediment surfaces by the excretion of sticky extracellular polymeric substances. Although marine benthic diatoms are a key component in the food web of coastal areas, knowledge on their biodiversity and biogeography in Polar Regions is mostly poor.The goals of this project contribute to 3 overarching questions of SPP 1158: I. Linkages to lower latitudes, II. response to environmental change and III. improved understanding of polar processes and mechanisms. To tackle these questions we plan: 1.) to precisely identify the almost unknown benthic diatom biodiversity in fine-grained taxonomic depth in communities sampled in Potter Cove (Antarctica) and Kongsfjorden (Arctic) using a combination of field, culture and culture-independent methods for phenotypic and genotypic identification; 2.) to establish a taxonomically validated reference library for Polar benthic diatoms with comprehensive information on habitat, morphology and providing DNA reference sequences for distinct species assignment; 3.) to utilise this new taxonomic reference library for marine benthic diatoms in environmental DNA metabarcoding to access the concealed biodiversity and the status of the taxonomic coverage of different diatom groups in Antarctica and the Arctic, and 4.) to provide the hitherto most comprehensive biodiversity data set as a baseline for reconstructing paleo-environments and future changes of Polar coastal regions (coastal erosion etc.).This approach will for the first time clarify if and how marine benthic diatoms of the shallow coastal waters of Antarctica and the Arctic are different (degree of endemism), which factors influence the spatial distribution of this ecological key protist group and how these data could help to detect and reflect scenarios of global change.