Cruise report 64PE454 – Rainbow2019, Terceira - Terceira June 24th – July 4th 2019

Abstract

The Rainbow 2019 cruise on board of R/V Pelagia allocated 2 days of work to explore 2 different deepsea areas of the Azores region using the Hopper tow-cam system: the Rainbow hydrothermal vent site and Sarda seamount. Overall, 6 successful video transects were carried out, generating more than 18 hours of seafloor images. These dives provided information along 17.8 km of seabed, at depths that ranged between 430 and 2,500 meters (Table 13). One of the main objectives of the cruise was to contribute to the understanding of the spatial distribution patterns of benthic megafauna species around the Rainbow hydrothermal vent site, located south of the Azores EEZ (Fig. 16). Two high-definition video transects of 1.5 km long were performed at the hydrothermal vent site (Table 13), starting and ending at a distance larger than 500 m off the main active chimneys. Spatial changes in the structure of the benthic community will be visually evaluated to understand the potential effect of vent plumes on deep-sea megafauna. The total amount of bottom time recorded at Rainbow site was above 3 hours and 20 minutes, with all footage considered valid for annotation purposes. Another main objective of the Rainbow 2019 cruise was to explore Sarda seamount, located on the western side of the MAR (Fig. 16). This geological structure stretches for more than 120 kilometres in length, and its summit can reach depths as shallow as 300 m. The 4 Hopper dives carried out at Sarda seamount aimed to obtain video footage from a wide bathymetric range, starting down to 1000 m depth all the way up to the summit. The 4 dives covered 14.8 km of seabed, generating over 15 hours of bottom time (Table 13)