RRS Discovery Cruise DY032, 20 Jun - 07 Jul 2014. Cruise to the Porcupine Abyssal Plain sustained observatory

The Porcupine Abyssal Plain Observatory is a sustained, multidisciplinary observatory in the North Atlantic coordinated by the National Oceanography Centre, Southampton. For over 20 years the observatory has provided key time-series datasets for analysing the effect of climate change on the open ocean and deep-sea ecosystems. As is normally the case during cruises which are needed to refurbish the observatory, a wide range of other activities were carried out during the cruise. The main mooring Ocean Data Acquisition System (ODAS) buoy had ceased transmitting data in March 2015, so a high priority was to recover the buoy and its stored data and this was successfully achieved. In addition, we recovered a set of sediment traps which had been collecting sinking material in the lower part of the water column for the previous 12 months and deployed a new set. These are the autonomous systems, but as is usually the case with our trips to PAP, we carried out various other activities and in this case we investigated the degradation of particles as they sink. Our colleagues from MIO in France carry out sophisticated interrogation using radiolabelling. The Bathysnap time-lapse camera system which had been taking photos of the seabed at 4800m was recovered to give an assessment of the behaviour of the benthic animals and how the seabed appearance changes in response to deposition of material. A new module was deployed. Temporal variability of the water column and seabed fauna - a task which is difficult or impossible to do autonomously was assessed using nets and cores