Shell Gro SERPENT final report

This report presents the results from the SERPENT project collaborative research with Shell at the Gro deep-water exploration oil well, drilled from the Leiv Eiriksson in the Norwegian Sea. The study was designed to investigate seabed disturbance resulting from the drilling activities at Gro and the effects of these activities on the benthic environment and megafaunal organisms. The Magnum 105 remotely operated vehicle (ROV) was used to take nine video transects of at least 100m in length which were used to assess visually the extent of drill cuttings and to determine megafaunal densities. Also a series sediment samples were collected using ROV operated push cores at 25, 50, 75 and 100m from north of the well to determine heavy metal concentrations, total organic matter and particle size distribution. Comparison of these methods suggested disturbance was variable depending on heading but suggested complete coverage of the seabed up to 40m from the well and partial coverage to 90m. Barium concentration was elevated and total organic matter reduced in the area surrounding the well. These physical changes were associated with significant reductions in megafaunal abundance and changes in the megafaunal community structure; with very few animals observed in a 40m radius of the well. Small ophiuroids were extremely abundant at the site reaching up to 15m-2. Similar to the megafauna, their numbers were reduced by the disturbance event and density was significantly reduced within 70m of the well. Samples of an area of unidentified gelatinous material were also collected for future analysis.