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

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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.