Scientists have only really started to explore cold-water coral ecosystems in the last decade. Cold-water corals create intricate structures that enhance the complexity of the seabed, providing a unique 3D habitat for mobile organisms and a stable substrate that sedentary animals may colonise. However, these types of coral are slowgrowing and highly susceptible to damage from anthropogenic activities, and are considered to be threatened or declining in a number of regions worldwide. Accordingly, government bodies regulating the offshore industry increasingly require accurate mapping and assessment of coral reefs, so that potential detrimental impacts on these valuable structures may be minimised. This paper presents a practical and cost-effective approach to identifying and delineating coral reefs formed by Lophelia pertusa, using standard geophysical survey methods (i.e. sidescan sonar and multibeam echosounder (MBES)) and high-resolution underwater photography. Comparison is made with other mapping techniques, and the potential use of slope and aspect analysis is discussed.

1. Introduction

Contrary to popular belief, coral reef ecosystems are not found solely in shallow tropical waters. However, the remoteness of the majority of these structures, at depths of between 50m and 7000m (Freiwald et al., 2004), has limited research into the distribution and ecological functioning of these habitats until the last decade (Freiwald and Roberts, 2005). There are thought to be 622 species of true scleractinian cold-water corals, including 17 species known to form reefs (Roberts et al., 2009a). While six of these species are considered to be more significant due to their widespread distributions, they typically form small bushy colonies of less than 2m in diameter. In contrast, Lophelia pertusa – the most common reef-building coral - forms colonies up to several metres wide and is capable of forming extensive reefs composed of live and dead coral skeleton.

This content is only available via PDF.
You can access this article if you purchase or spend a download.