Chevron Rosebank SERPENT final report

Abstract

This report presents the results from the SERPENT project collaborative research with Chevron at the
Rosebank deep-water exploration site. SERPENT visited the Stena Carron drill ship in the Faroe Shetland
Channel (FSC) to investigate megafaunal diversity at the seabed (1124m depth) and determine the effects of
disturbance 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 100m
in length which were used to assess visually the extent of drill cuttings and to determine megafaunal
densities. Sediment samples were also collected using ROV operated push cores at 250 and 400m from the
well to determine heavy metal concentrations, total organic matter and particle size distribution.
These methods suggested disturbance was variable depending on heading but drill cuttings completely
covered the seabed 70m from the well and there was partial coverage to approximately 100m. Analysis of
the sediment showed elevated Barium concentration in surface sediments close to 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 60m radius of the well.
In addition, specimens of the characteristic megafauna were collected and physical data from the water
column was logged. An experiment was carried out to investigate bioturbation rate in disturbed and
undisturbed sediment. Luminophore tracer particles were added to the sediment surface in corrals which
were either controls or treated with a sedimentation disturbance event. The sediment was later sampled and
sectioned for subsequent analysis.

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