The SyMonS_MoM research cruise took place in September/October 2020 on board the RV Celtic Explorer in the North East Atlantic Ocean. The cruise (CE20011) had 5 objectives: Task 1.1 - ROV-mounted multibeam echosounder (Kongsberg EM2040). An EM2040 was integrated with a sound velocity probe, interital navigation system and mounted on the Holland 1 ROV. The objective of the survey was to acquire mulitbeam data (400 kHz) at each of the study areas in order to identify suitable lander deployment sites. Furthermore, multibeam data (.all and .wcd) will be acquired at 200 kHz and 400 kHz within the Downslope area. These data will be used to examine the potential usefulness of multfrequency watercolumn data for particle flux characterisation. Task 1.2 - ROV Photogrammetry. The Holland 1 ROV will be mounted with a downward-facing 1080i HD video camera. It will be equipped with a USBL beacon and inertial navigation system, laser scalers (10 cm) and lights. Data will be acquired in a 0.5 m gridded survey design, imagine a coral mound within each of the survey areas. Data acquisition will be managed within SIS, where the ROV will remain approx. 1 m above the seabed. This data will be used for: a) characterisation of the survey sites and; b) to complete a time series analysis of the Piddington Mound (2011; 2015; 2020). Task 1.3 - Hull-mounted multibeam echsounder (Kongsberg EM302). The vessel mounted Kongsberg EM302 acquired data during ROV reconfiguration periods. The survey lines will be set up to acquire water column (*.wcd). Data acquisition will be managed within SIS. EM302 bathymetric and backscatter data will be used to characterise the survey areas, to compare against previously acquired data in the area (e.g. Beyer et al., 2003; INSS, 2005) and to contextualise ROV-mounted water column data. Task 1.4 - ROV Lander systems 8 Lander frames, each equipped with an upward-facing Acoustic Doppler Current Profiler (ADCP) and Sediment Trap have been adapted specifically for deployment via the Holland 1 ROV. The landers have each been programmed to collect to trap particle flux binned into 14 day periods for approx. 1 year. Likewise, each ADCP was programmed to acquire 25 m current profiles for a period of 60 s every hour for 1 year. We aim to deploy 2 landers in each of the survey areas, 1 to the north of a coral mound and 1 to the south of the same coral mound. Deployment via ROV allowed to sample and image the area around the lander deployment site. Further, ROV pilots were able to exact the bottom position of the Lander to record on and around smaller seabed targets (small reefs, scour pits, mound summits and flanks, gullies etc.) in deep water. Landers will be retrieved on a follow up survey next year. Task 1.5 - ROV Vibrocores The Holland 1 ROV will be mounted with a vibro-core rig. The vibrocore rig will be used to acquire sediment cores from the survey areas. In particular, cores will be taken from coral mounds and adjacent areas. A maximum of 5 cores can be retrieved during a single ROV dive. On recovery to deck, all cores were removed, labelled and stored within a refrigerated space. Systematic Monitoring of the Moira Mound Chain for advancing seabed mapping of deep-water habitat classification in Submarine Canyons.
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