WP 2 – Benthic Diversity and Recolonization Potential

Work package 2 will investigate the biodiversity and community structure of all size classes of benthic organisms from microbiota to megafauna at disturbed and undisturbed sites in the DISCOL area as well as in several areas of the CCZ. The sediment-inhabiting and noduleattached fauna will be characterized morphologically and genetically, and the biodiversity (including turnover) will be assessed at different spatial scales for microbiota, protists and metazoans.
The recolonization potential of benthic deep-sea fauna after anthropogenic impact will be studied at three sites: the well documented DISCOL site 26 years after disturbance, and in the CCZ  the IOM Benthic Impact Experiment, and the OMCO pilot mining tracks in the French License area 20 years and 37 years after disturbance, respectively. Additionally, the fauna at seamounts and nodule fields will be compared in ISA designated Areas of Particular Environmental Interest (APEIs) and in the western German License Area to assess the possible role of seamounts as source populations for the recolonization of disturbed nodule fields, but equally to assess the uniqueness of the nodule-associated fauna. Connectivity between sites across the CCZ (APEIs, French, Belgian, IOM and German License Areas) and between CCZ and DISCOL will be studied using population genetic methods, dispersal mechanism and reproduction of selected species. Advanced biophysical modeling will be performed to quantify larval dispersal, i.e. to estimate and assess population connectivity. This work will be complemented by isotope tracer studies and toxicology studies (see WP3) of the benthic food web in the DISCOL area, including bacterial productivity, to enable numerical simulations of the deep-sea ecosystem response to a mining impact.

Overall the following hypotheses will be tested:

  1. Disturbance effects are still present many years after disturbance in terms of benthic community structure and biodiversity, but differ according to disturbance type and intensity, and regional processes.
  2. Nodule fauna differs from the sediment fauna, resulting in an elevated local diversity in nodule-bearing areas.
  3. Sediment and nodule communities show a high spatial turnover on small spatial scales of a few km, and contain a high fraction of rare taxa.
  4. Elevated turnover rates in species composition with increasing spatial scales lead to high regional diversity.
  5. Reduced gene flow over long distances limits connectivity over large spatial scales, hence the DISCOL and CCZ share a low percentage of similar species.
  6. Different taxonomical groups representing different ecological groups show different distribution patterns.