Cold-water coral reefs in the Hola glacial trough off Vesterålen, North Norway

Abstract

Coral reefs, including cold-water coral reefs in deep water, grow most favourably in areas of firm seabed and strong ocean currents. Data collected by the MAREANO programme (www.mareano.no) from the Hola glacial trough off Vesteralen, North Norway, reveal a spectacular seafloor morphology. Features found include large clusters of coral reefs and sand-wave fields, and moraines from the last glacial period (Boe et al. 2009; Buhl-Mortensen et al. 2010). More than 300 coral reefs occur in water depths of 200–270 m, where measured bottom current speeds exceed 0.3 m s−1 and water temperature is about 7–8°C. The area offshore of Vesteralen, North Norway (Fig. 1a), comprises alternating shallow banks and deeper troughs formed during successive glaciations (Boe et al. 2009). The banks Vesteralsgrunnen and Eggagrunnen, NE and SW of the Hola trough, respectively, have water depths of 70–90 m, whereas the Hola trough is 200–270 m deep (Fig. 1b). A gentle moraine ridge (10–35 m high) crosses the central part of the Hola trough between the two banks. Water depth on this ridge increases from c. 170 m in the SW to c. 200 m in the NE. Several smaller moraine ridges are also …