Understanding causes and consequences of increased levels of biodiversity. A case study based on nematodes from different bathyal habitats under contrasting productivity regimes
Contrasting hydrodynamic regimes and disturbance frequencies, as well as availability and quality of food resources between seafloor features have been shown to shape communities notably differently and result in variable biodiversity. High heterogeneity between different habitats is assumed to be linked to a high turnover in benthic community structure and can maintain the local and regional diversity of deep-sea environments. However evidence is lacking so far. In addition, the great success of nematodes and their high biodiversity in deep-sea ecosystems is probably linked to their high trophic diversity, although this hypothesis has not yet been tested. Furthermore, it is unclear to what extent increased levels of biodiversity (morphological and functional) enhances the use of resources, and contributes to the food web efficiency in deep-sea ecosystems. In this study, we will use correlative and manipulative research strategies to identify patterns in nematode diversity for different habitats and to understand their trophic interactions in combination with the importance and role of their biodiversity for resource exploitation in deep-sea environments.
We identified the following hypotheses in order to understand the importance of habitat heterogeneity (including surface productivity) for nematode diversity (causes), and to unravel the importance of nematode diversity for trophic efficiency (consequences):
H1: Increased habitat heterogeneity, through the presence of canyons intercepting the continental slope, increases regional nematode diversity along continental margins.
H2: Areas of higher surface productivity and associated increased flux of OM to the deep sea are characterized by a higher local and regional diversity.
H3: A higher taxonomic diversity is linked to a higher trophic diversity.
H4: More diverse communities are characterized by a more efficient resource use