Dalsnuten SERPENT final report

Abstract

This report covers the work of the SERPENT project at the deep water exploration well Dalsnuten in the Norwegian Sea (1452 m depth). The study was designed to investigate the general benthic diversity (mega- and macrofauna) at the location and the disturbance on the seabed resulting from drilling activities and the effects of these activities on the benthic environment, the megafaunal and macrofaunal organisms.

The seabed at Dalsnuten experiences a low current regime with the sediment consisting of homogeneous fine silt. A total of 78 species, of which 35 are megafauna (<1 cm) and 43 are macrofaunal (? 0.5 mm) were recorded. The megafauna was present in low numbers but the species were typical for the deeper cold waters of the Norwegian. The macrofauna samples were dominated numerically by protozoan species such as foraminifera.

Disturbance appeared variable with complete coverage of the seabed with drill cuttings reaching as far as 60 m from the well and partial coverage as far as 100 m. Barium concentrations in surface sediments were elevated but decreased with distance. Megafaunal abundance was also significantly reduced and the community structure altered with very few animals observed in a 50 m radius of the well. Approximately 15,000 m2 of seabed were disturbed.

A possibly new species of the amphipod genus Neohela was discovered.

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