RRS James Cook Cruise 165 19 May - 12 Jun 2018. Water column and seafloor time-series studies at the Porcupine Abyssal Plain Sustained Observatory

Abstract

RRS James Cook cruise 165 departed Southampton 19 May, operated in the Porcupine Abyssal Plain Sustained Observatory area (48°50´N 016°30´W) 22 May – 9 June, and returned to Southampton 12 June 2018. The overarching goal of the cruise was to continue various time-series observations of the surface ocean, water column, and seafloor at the site, as first studied by NOC (then the Institute of Oceanographic Sciences) in 1985. The specific objectives of the cruise were to recovery and redeploy, or service, three mooring systems (PAP1, PAP3, Bathysnap), and conduct a range of water column and seafloor observation and sampling operations. This cruise was a contribution to the Climate Linked Atlantic Section Science (CLASS) project supported by the UK Natural Environment Research Council (grant number NE/R015953/1).
The PAP 1 mooring, a Met Office (Balmoral ODAS) buoy and Autonomous Sensor Platform (ASP) suspended 30 m below the surface buoy, was successfully, fully serviced, including replacement of the full ocean depth mooring on this occasion. The PAP 3 mooring, a sediment trap and current meter string, was successfully recovered and redeployed, including colonisation substrates and larval traps for the on-going LO3CAted (Larval Occurrences in Open Ocean: Connectivity studies in NE Atlantic and Mediterranean Sea) project. Unfortunately, the Bathysnap seafloor time-lapse camera mooring, and associated LO3CAted samplers, could not be recovered and is presumed lost (manual recovery may be attempted on a subsequent cruise, RRS Discovery cruise 103). Nevertheless, a replacement Bathysnap mooring with LO3CAted samplers was deployed. Two short-term (2-4 day) amphipod trap mooring deployments were also successfully carried out during the cruise.
A series of water column observation and sampling operations were successfully carried out with a CTD instrument package and water bottle rosette, and vertically hauled zooplankton nets. The former including pre- and post-deployment calibrations of PAP 1 sensors. Seafloor sampling operations were successfully carried out with a Megacorer and otter trawl, yielding samples for a broad range of subsequent analyses (eDNA; prokaryotic and viral dynamics; biogeochemistry; microplastics; metazoan meiobenthos; macrobenthos; megabenthos; biochemistry and microbiome studies of selected megabenthic taxa). A programme of seafloor survey photography was also undertaken using the HyBIS vehicle, assessing the seafloor environment and associated fauna of the abyssal plain, a low abyssal hill, and the summit of a seamount ("Ben Billett"). A series of Megacorer samples were also succesfully recovered from the abyssal hill location.

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