Rapid macrofaunal colonization of water-based drill cuttings on different sediments

A field experiment was conducted to investigate how water-based drill cuttings and sediment type influence colonization of soft bottom communities. Bottom frames with trays containing defaunated sediments were placed at the seabed for 6 months to study colonization of macrofauna. Two different sediments (coarse and fine) were used, and 6 or 24 mm layer of water-based drill cuttings were added on top of these sediments. Some of the sediments were controls with no additions. In the end of the experiment, the oxygen availability in sediment porewater and macrofaunal abundance were reduced in treatments with 24 mm drill cuttings compared to controls. Tube-building annelids were particularly sensitive to drill cuttings. However, these responses were only minor, and notably, the drill cuttings initiated a weaker faunal response than sediment type and site of the bottom frame. Sediments capped with water-based drill cuttings thus showed a rapid colonization of macrofaunal communities.

Highlights► Twenty-four millimeter of water-based drill cuttings reduced O2-concentrations in sediment porewater. ► Twenty-four millimeter of water-based drill cuttings caused reduced and altered benthic colonization. ► Tube-building annelids were identified as particularly sensitive to drill cuttings. ► Significantly different macrofaunal communities colonized different sediment types. ► Significantly different macrofaunal communities colonized different depths/sites.