Marine remote sensing toolkit

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BRG The University of Queensland
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# Cyclone, coral bleaching, and coral recovery

### St.Leu Reef, la Réunion: aerial photography and high spatial-resolution satellite images

Saint-Leu Reef, la Reunion, Indian Ocean was affected by two major cyclones and a major bleaching event in the last decades. A 35-year time series of coral community maps was obtained from visual analysis and manual delineation of patterns identified on the time series of high spatial resolution images. Both time series highlight the impact of the successive disturbances that affected the reef across the decades and cycles of coral degradation and coral recovery were retraced from the maps.

Time series of high-spatial resolution remote sensing images of Saint-Leu Reef. Digital aerial photographs scanned at 2.4m resolution: 1973, 1978, 1989, 1997, aerial photograph 2003 at 0.1m resolution, satellite Quickbird image 2002 at 2.4m resolution, and satellite Quickbird pan-sharpened image at 0.6 m resolution. Disturbances that affected the reef are indicated with black arrows: Cyclone Firinga (Jan 1989), post-cyclone Dina (Jan 2002) bleaching event (Mar 2002).

Multi-temporal series (1973 to 2006) of coral community maps on Saint-Leu Reef obtained from the images presented above. Coral communities were mapped on all images using manual delineation of polygons identified according to colour and texture contrasts on the images presented above. The maximum breaking wave zone is masked in white. Succession of degradation and recovery phases in response to the cyclones (1989, 2002) and bleaching event (2002) are highlighted below the maps for illustration only, with no indication of scale.

## Reference:

Scopélitits J., Andréfouët S., Phinn S., Chabanet P., Naim O. , Tourrand C., Done T. (2009) 35 years of coral community change on Saint-Leu Reef (la Réunion, Indian Ocean) from in situ and remote sensing assessment. Estuarine and Coastal Shelf Science, 84: 342-352.