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受到恶劣环境限制的物种贫乏的动植物。然而，最近的许多研究清楚地证明，南极生物多样性的范围、生态多样性和生物地理结构比以前认为的要广泛得多。这种生物多样性是如何在海洋环境中分布的，以及其空间变化背后的机制是什么，这些都是尚未解决的问题。特别是，南极微生物仍然没有被探索，因此，持续的全球环境变化的影响，对目前和未来对南极生物多样性和相关生态功能（如食物网结构）的理解构成挑战。在全球范围内，底栖硅藻是微底栖植物群落的关键生物，是浅水海岸带最多产的微生物生物量。这些光养组合在许多海洋软底地区都是已知的。由于初级产量高，它们为底栖悬浮物或沉积物食性动物提供了主要的食物来源，并在沉积物/水界面上作为控制垂直氧气和营养通量的屏障，以及通过排泄粘性细胞外聚合物物质作为沉积物表面的稳定剂。尽管海洋底栖硅藻是沿海地区食物网的关键组成部分，但对极地地区底栖硅藻的生物多样性和生物地理学的了解却很少。该项目的目标有助于SPP 1158的3个首要问题：1 .与低纬度地区的联系；对环境变化的响应；提高了对极性过程和机制的理解。为了解决这些问题，我们计划：1.利用野外、培养和非培养相结合的方法，在南极洲波特湾和北极Kongsfjorden取样的群落中精确识别几乎未知的底栖硅藻生物多样性；2.)建立一个分类上有效的极地底栖硅藻参考文库，提供完整的生境、形态信息，并为不同物种分配提供DNA参考序列；3)利用这一新的海洋底栖硅藻环境DNA元编码分类参考库，获取南极和北极地区不同硅藻类群的隐蔽生物多样性和分类覆盖状况；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。这一方法将首次阐明南极和北极浅海沿岸海域的海洋底栖硅藻是否以及如何不同（地方性程度），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探测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.