Cashel SERPENT visit report

This report presents the initial results from the SERPENT project collaborative research with StatoilHydro at the Cashel exploration oil well, drilled from the Ocean Vangaurd semisubmersible rig in the North-East Atlantic off the north-western coast of Ireland. The study was designed to investigate seabed disturbance resulting from the drilling activities at Cashel and the effects of these activities on the benthic megafaunal invertebrates. The Remotely Operated Vehicle (ROV) Magnum 085, was used to take video transects of approximately 100m in length after two phases of drilling. These showed the visible the extent of drill cuttings extended to 60m but megafaunal density was not significantly reduced. The ROV was also used to carry out in-situ experiments to investigate sublethal effects of exposure to drill cuttings on Porania pulvillus, the dominant echinoderm at the site. Specimens of P. pulvillus were placed in chambers within and outside the zone disturbed by cuttings. Following recovery of the specimens tissue samples were taken for biochemical (glycogen) analysis and histology. The results of these analyses are reported elsewhere.