Shell Gro SERPENT final report

This report presents the results from the SERPENT project collaborative research with Shell at the Grodeep-water exploration oil well, drilled from the Leiv Eiriksson in the Norwegian Sea. The study wasdesigned to investigate seabed disturbance resulting from the drilling activities at Gro and the effects ofthese 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 100min length which were used to assess visually the extent of drill cuttings and to determine megafaunaldensities. Also a series sediment samples were collected using ROV operated push cores at 25, 50, 75 and100m from north of the well to determine heavy metal concentrations, total organic matter and particle sizedistribution.Comparison of these methods suggested disturbance was variable depending on heading but suggestedcomplete coverage of the seabed up to 40m from the well and partial coverage to 90m. Bariumconcentration was elevated and total organic matter reduced in the area surrounding the well. Thesephysical changes were associated with significant reductions in megafaunal abundance and changes in themegafaunal community structure; with very few animals observed in a 40m radius of the well. Smallophiuroids were extremely abundant at the site reaching up to 15m-2. Similar to the megafauna, theirnumbers were reduced by the disturbance event and density was significantly reduced within 70m of thewell.Samples of an area of unidentified gelatinous material were also collected for future analysis