Vulnerable marine ecosystems at the Tropic Seamount in the High Seas (NE Atlantic)

ATLAS work package 3 presentation at ATLAS 3rd General Assembly

The 2016 Marine E-Tech JC142 cruise mission to the Tropic Seamount in the High Seas, 300 nm SW off the Canary Islands, was to understand what controls the formation and precipitation of cobalt-rich crusts on seamounts, and to study the potential impact of deep-sea mining on seamount ecosystems. The autonomous underwater vehicle (AUV) Autosub6000 conducted high-resolution multibeam swathe bathymetry surveys across the seamount, while the Remotely Operated Vehicle (ROV) Isis made the first ever visual observations across 24 dives from the seamount flank (4,200 m) to its summit (1,000 m). Analysis of >18,000 high-definition ROV still images revealed areas with high densities of VME indicator taxa including deep-sea sponges, octocorals, and reef framework-forming scleractinian corals. An area with dense octocoral gardens also harboured high densities of deep-sea squid eggs. Coral and sponge specimens sampled by the ROV are being identified using both classical morphological taxonomy and DNA barcoding (COI and 18S). Very high densities of the glass sponge Poliopogon amadou Thomson, 1878 (>6/m2) were tightly constrained to steeply sloping ridges along the seamount axes and to a particular water mass. The new VME indicator records at the Tropic Seamount provide much needed data to the Ecological and Biologically Significant Area process and particularly to the Fishery Committee for the Eastern Central Atlantic by improving our understanding of the biodiversity and biogeography of seamount ecosystems in the High Seas.