Species identification using morphology is far from straightforward for deep-sea nematodes. The existing taxonomical knowledge is insufficient for identification to species level as most have yet to be comprehensively described. A high degree of phenotypic plasticity and cryptic speciation further complicate the delineation of species using morphological characteristics exclusively. Currently, the advent of Next Generation Sequencing (NGS) has the potential to further extend the application of DNA information for biodiversity assessment to an unprecedented scale. Whether through single-specimen or environmental samples, NGS of the commonly used mitochondrial barcode marker Cytochrome Oxidase I (COI) and the nuclear ribosomal small subunit (SSU or 18S rDNA) locus have proven effective for rapid estimation of nematode species diversity. The application of NGS technologies to deep-sea nematodes, however, is hindered by data deficiency in the same way as non-molecular approaches in that numerous DNA sequences in public databases are not correlated to reliably identified species. As such, deep-sea nematode diversity marks a yet unexplored component of molecular biology and ecological knowledge. The principle objective of the research is to provide insight regarding nematode diversity, ecology and biogeography in the Clarion-Clipperton Fracture Zone from local to regional scale. We aim to identify correlations between nematode assemblage structure and habitat geomorphology with distance taken into account (environment versus distance as drivers for spatial turn-over) . The molecular research is targeted at providing a comprehensive genetic baseline of deep-sea nematode biodiversity through barcoding as well as determining patterns of gene flow, i.e. movement of genes from one population to another, in the CCFZ at varying spatial scales. In addition, NGS methodologies will be evaluated as a rapid biodiversity assessment tool in the context of deep-sea mining impact.
