Revisiting Squires' Coral Coppice, Campbell Plateau, New Zealand

Abstract

A ridge-like structure on the Campbell Plateau southeast of New Zealand, previously identified by Squires as a coral coppice, has been relocated (50° 41.46′S, 167° 41.45′E) and its extent and morphology mapped using multibeam and backscatter data obtained during an opportunistic survey. There are at least three other similar features at this location on a seafloor bank, although only two were fully mapped. ‘Squires’ Coral Coppice' is extensive, measuring 6700 m long, 900 m wide and up to 50 m high relative to the surrounding seafloor, in water depths of 273–325 m. Bathymetric profiles, backscatter data and historical samples of deep-sea coral (mainly Goniocorella dumosa) were used to infer that the ridge-like structures are coral reefs. The presence of deep-water coral reefs in the area could be due to the unique combination of geological (hard substrata), biological (high productivity) and oceanographic (relatively strong eastward flowing currents, seasonal vertical mixing) conditions east of Auckland Island. Squires' Coral Coppice covers an area of 9.2 km2 which makes it similar in size to some of the deep-water reefs and mounds in the North Atlantic, and it could represent the only known large coral reef (> 1 km maximum continuous extent) in the Southern Hemisphere. Further surveys are required to visually confirm that the relocated features are coral reefs, and to determine if similar features/coral reefs occur elsewhere on the Campbell Plateau. Deep-water coral reefs can support high levels of biodiversity and are vulnerable marine ecosystems that should be considered for protection in the region.