Chevron Rosebank SERPENT final report

This report presents the results from the SERPENT project collaborative research with Chevron at theRosebank deep-water exploration site. SERPENT visited the Stena Carron drill ship in the Faroe ShetlandChannel (FSC) to investigate megafaunal diversity at the seabed (1124m depth) and determine the effects ofdisturbance resulting from the drilling activities on the seabed and benthic organisms.The Magnum 156 remotely operated vehicle (ROV), was used to take eight video transects of at least 100min length which were used to assess visually the extent of drill cuttings and to determine megafaunaldensities. Sediment samples were also collected using ROV operated push cores at 250 and 400m from thewell to determine heavy metal concentrations, total organic matter and particle size distribution.These methods suggested disturbance was variable depending on heading but drill cuttings completelycovered the seabed 70m from the well and there was partial coverage to approximately 100m. Analysis ofthe sediment showed elevated Barium concentration in surface sediments close to the well. These physicalchanges were associated with significant reductions in megafaunal abundance and changes in themegafaunal community structure, with very few animals observed in a 60m radius of the well.In addition, specimens of the characteristic megafauna were collected and physical data from the watercolumn was logged. An experiment was carried out to investigate bioturbation rate in disturbed andundisturbed sediment. Luminophore tracer particles were added to the sediment surface in corrals whichwere either controls or treated with a sedimentation disturbance event. The sediment was later sampled andsectioned for subsequent analysis