Cruise Report - REPORT PELAGIA CRUISE 64PE412 TREASURE (Towards Responsible ExtrAction of SUbmarine REsources) Horta - Horta 25 June – 13 July 2016

TREASURE (Towards Responsible ExtrAction of SUbmarine REsources) is a Dutch project funded by the Technology Foundation (STW) and industry with the aim to develop and test methodologies enabling the industry to properly monitor the impacts of deep-sea mining of SMS (Seafloor Massive Sulphide) deposits. SMS deposits contain a high percentage of metals like copper, zinc, gold as well as trace metals for industrial applications (e.g. electronics) (Hein et al. 2013), and are typically found near vent sites in seafloor spreading areas such as the Mid-Atlantic Ridge (MAR). The protected Rainbow Vent site (36o 13.8 N 33o 54.12’W) is an example of a vent on MAR outside the EEZ containing SMS deposits (Marques et al. 2006; Hannington et al. 2011). The TREASURE project has
selected Rainbow Vent as study area (Fig. 1) to test methodologies and approaches acknowledging that the area is protected under the OSPAR convention and is not a potential mining site. Moreover, the focus of TREASURE is on the background environment and fauna of the vent site and not on the active vents themselves as latter will be not be targeted by mining. In comparison to the active vents and their fauna, little to nothing is known of the background.

The TREASURE project covers 3 cruises (2014-2016) during which video-footage has been recorded, oceanographic measurements have been made using bottom moored instruments, and water and small sediment samples have been collected. The sampling is conducted in cooperation withcolleagues from the University of the Azores and various other European universities. The Dutch TREASURE project has strong links with the European MIDAS project (www.EU-Midas.net) through exchange of data and scientific crew.

For the 3rd TREASURE cruise (64PE412), the following primary activities were scheduled:
• recovery of moored equipment (2x landers, 1 x mooring) which had been deployed in spring 2015;
• collection of water (CTD) and seabed samples (boxcorer) at varying distances from Rainbow Vent;
• video surveys of the seafloor to supplement earlier recordings;
• deployment of 2 seafloor moorings with thermistors for the duration of the cruise.

Primary focus of the sampling program will be put on the background physical conditions and associated deep-water fauna at varying distances from the active Rainbow vent. As secondary target a seamount was chosen ca 10 nm N of Rainbow Vent with a contrasting rich fauna on its flanks and summit (see map in Fig 2). Video recordings of the seamount had already been made in 2014 and 2015 TREASURE cruises.