Darwin Mounds Settlement Study

Study Extent

The Darwin Mounds are located in the NE Rockall Trough, approximately 190 km northwest of Scotland

Sampling

Two moorings were deployed in the western and two in the eastern Darwin Mound fields. Each mooring comprised a steel plate anchor (35 kg) and a single glass sphere with a polyethylene cover (as typically employed in deep-sea mooring designs), connected by a mooring line of 25 mm diameter polypropylene rope. The moorings deployed in the western field were approximately 4.5 m in length and 6 m in the eastern field. The original purpose for the moorings was to mark the start point of ROV transects. Moorings for this purpose were deployed in the western field. However, at the eastern field, the opportunity to augment the mooring was ceased and the length of the mooring rope was increased to accommodate two settlement panels (concrete roof tiles), located at 0.5 and 1 m above the sea bed.

Method steps

1. Upon recovery, all colonized surfaces were photographed before the scleractinian corals on the settlement panels were carefully removed, photographed, and preserved in 96% ethanol. The recovered settlement panel (lower panel) from the JC060-050 (eastern area) mooring was also preserved in ethanol. The upper panel had been lost upon recovery. Because the mooring at JC060-030 did not include any settlement panels, all fauna from an area of 659 cm2 of the surface of the buoy (matching the area of one side of the settlement panel) was preserved by freezing. One eighth subsample of the fouling community of both moorings was removed and preserved in ethanol. Given the homogeneity and high density of the encrustation (Fig. 1), this proportion was considered sufficient to provide a representative sub-sample of the majority community on each buoy. All remaining fouling was weighed (wet). All taxa from the representative mooring surface area were identified directly from specimens (i.e. not from photographs) to species level (where possible), counted, and the wet mass of the larger and most abundant taxa was measured. Specimens have been retained in the Discovery Collections at the National Oceanography Centre, United Kingdom (http://grscicoll.org/institution/national-oceanography-centresouthampton).

Marine invertebrate macrofauna, megafauna, and epifauna. All taxa identified to the lowest taxonomic level possible (e.g. Family, genus or species). Some taxa are retained at phylum level.

1. Echinodermata
   rank: phylum
2. Mollusca
   rank: phylum
3. Crustacea
   rank: phylum
4. Annelida
   rank: phylum
5. Cnidaria
   rank: phylum
6. Nemertea
   rank: phylum
7. Nematoda
   rank: phylum

The Darwin Mounds are located in the NE Atlantic in the Rockall Trough, approximately 190 km northwest of Scotland. There are hundreds of small cold water coral mounds, c. 75 m across and 5 m high, in water depths of 950–1,050 m.