Novel and Unexplored Coral Reef Types of the Red Sea - A Synoptic Mapping Approach
2010 Ocean Sciences Meeting
Remote Sensing, Seafloor Morphology, Geology, and Geophysics, Instruments and Techniques, Ecosystems, Structure, Dynamics, and Modeling
Coral reef environments are esteemed for their biological, social and economic value. We present work from a number of research sites comprising much of the Saudi Arabian Red Sea reef tract. Lying sixth globally in terms of total reef area (UNEP statistics), the reefs of this region remain poorly explored and little understood. A variety of remote sensing techniques and technologies, along with post-processed data layers are the foundation of a basin-scale assessment. Calm and clear oligotrophic waters facilitate the use of optical sensors. Over 25,000 sq km of multispectral QuickBird satellite imagery and 3000 sq km of CASI hyperspectral imagery were acquired. Coupled to an exhaustive four year field survey, maps of benthic character comprising fifteen classes were generated to a depth of 25 m at exceptionally fine spatial resolution. Remotely Operated Vehicle (ROV) survey permitted assessment down to 150 m. Patterns of sediment infill and antecedent reef structures were evaluated using low-frequency bottom-penetrating acoustics at targeted locations. Spatially continuous bathymetry was retrieved for all mapped areas using a spectral derivation of the image data, trained using millions of acoustic soundings collected during field campaigns. Drawing on Airy wave theory, wind and wave exposure was modelled across the seascape by coupling external wind data with spatially accurate bathymetry. The Red Sea is known for its expansive fringing-reefs affixed to a narrow and steep coastal shelf, yet our investigation reveals a startling variety of additional reef environments significant in size and scope; these include bank-reefs, ribbon-reefs, patch-reefs, atolls, bounded lagoons, as well as vast sediment bank systems. The importance of the region in terms of global reef diversity has been severely underplayed. The distribution of these systems varies both along the latitudinal and longitudinal axis. In the central and northern Red Sea, reef systems are predominantly attached or close to the mainland while in the south, reef systems are more expansive in nature. Varieties of exposure and depth gradients are seen across these reef systems and account for much of the heterogeneity in habitat distribution. The richest coral habitat was found on exposed fringes. Interestingly, much of the reef resource is concentrated below 10 m depth, where less prolific, but more expansive, reef frameworks exist. Scrutiny of the data reveals the structural importance of tectonics, sea-level and climatic history, in shaping the distribution of modern habitats, even at fine scales. We highlight the advances that come with taking a synoptic approach to reef mapping; combining both direct and derived measurements of the seascape into a useful and adaptable framework.
Rowlands, Gwilym; Purkis, Samuel J.; Riegl, Bernhard; Bruckner, Andrew; and Renaud, Philip, "Novel and Unexplored Coral Reef Types of the Red Sea - A Synoptic Mapping Approach" (2010). Oceanography Faculty Proceedings, Presentations, Speeches, Lectures. 72.
0000-0002-6003-9324; F-8807-2011; B-8552-2013