Devey, Colin W., ed. and Shipboard scientific party (2015) RV SONNE Fahrtbericht / Cruise Report SO237 Vema-TRANSIT : bathymetry of the Vema-Fracture-Zone and Puerto Rico TRench and Abyssal AtlaNtic BiodiverSITy Study, Las Palmas (Spain) - Santo Domingo (Dom. Rep.) 14.12.14 - 26.01.15. . GEOMAR Report, N. Ser. 023 . GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel, Kiel, Germany, 130 pp. DOI 10.3289/GEOMAR_REP_NS_23_2015.

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Abstract

The abyssal seafloor makes up > 60% of our planet´s surface, it is nevertheless
largely unexplored. We know very little about how the processes which created it have
varied through time, about life on the deep seafloor or about how the hydrosphere,
biosphere and lithosphere interact over this vast area. In the Atlantic, transform faults
and fracture zones characterize most of the seafloor bathymetry and the volcanic and
tectonic process which create and modify the crust can be deduced from their
bathymetric signature. During the cruise SO-237 we surveyed and sampled the entire
length of one of the major offsets of the Mid-Atlantic Ridge, the Vema Fracture Zone,
looking at a history of plate creation and modification over 120Ma. Variations in benthic
communities along this transect will be investigated using samples recovered from
corers and towed gear as well as detailed photographic mapping of the benthic
megafauna using AUV. The results will be used to test the hypothesis that the Mid-
Atlantic Ridge serves as a barrier limiting benthic species distribution in the abyssal
basins on both sides of the ridge. The Puerto Rico Trench is much deeper than the
surrounding abyssal West Atlantic and so we also took samples there to determine
whether the biodiversity of its hadal meio-, macro-, and megabenthic fauna differs from
that of the abyssal Atlantic due to isolation of the trench. The cruise yielded important
information for the Transregio proposal "Maturing oceanic plates: Earth’s hidden
reactors" and has provided the first high-resolution bathymetric survey along an entire fracture zone trace and one of the world’s best surveyed seafloor features.

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