Research

Coral Reef Mapping: Mapping Coral Reef Habitat from Space

Principal Investigator: Samuel J. Purkis, Ph.D.

Issue

IKONOS true-color satellite image of the Smith Bank reef system, Roatan, HondurasSpanning many political boundaries and frequently situated in isolated oceanographic areas, mapping coral reefs using traditional ground-based methods is notoriously inefficient. However, satellite remote sensing has emerged as a technology with the potential to accurately quantify the distribution and ecological status of coral reef systems at landscape scale.

On the basis that different reef substrates have distinctive optical properties, the spatial composition of the reef can be delineated using passive optical satellite sensors. Considering the rapid demise of coral reef diversity over the last decade, the need for an accurate audit of reef distribution at scales ranging from meters to thousands of kilometers is now overdue. Satellite remote sensing is both cost effective and offers quantitative information at ecologically meaningful scales. When combined with traditional field-based techniques, satellite imagery can provide the link between individual coral communities and the functional dynamics of the coral reef system.

Project and Findings

Benthic facies distribution from IKONOS multi-spectral satellite imagery, Jebel Ali, U.A.E. Arabian GulfSuccessful delineation of reef substrates from satellite imagery depends primarily on the development of algorithms capable of routinely differentiating between dominant submerged coral habitats. Our research is focused on the development of algorithms that can effectively correct for the disruptive influence of the water column on the spectral signature of the seabed and to facilitate reliable prediction of benthic character, regardless of varying bathymetry.

To aid this process, the potential of novel classifiers that operate on the textural as well as the spectral content of the imagery, are presently being investigated. Having successfully mapped the reef ecosystem at landscape scale, geospatial analysis is employed to investigate the spatial dynamics between reef substrates. The work aids in the comparison between the architecture of different reef systems and is moving forward to describe whether large-scale reef patterns are ordered and deterministic, or essentially stochastic.

Implications for Management

Quantitative and spatially explicit information on reef distribution is an invaluable resource for habitat management. Providing both a baseline from which to evaluate degradation of sensitive reef ecosystems and an audit of the condition of the reef at a snap-shot in time, remote sensing has the capacity to guide environmental decision making and revolutionize the management strategy for coral habitats at global scale.

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