GBR - Coral mass bleaching extent in 1998 and 2002 by aerial surveys (MTSRF 1.1.5, AIMS)

The purpose of this study was to provide a large-scale documentation of the extent of bleaching, for comparison against SST and other bleaching events. The data record the large-scale bleaching event on the GBR in 1998, mapped by aerial survey method. Surveys were conducted at a flying height of 160 m and covered a total of 654 reefs. Data are estimated bleaching status of whole reefs, conducted by one experienced observer (RB). The surveys were conducted soon after the hottest period was over, a compromise between ensuring that bleaching on reefs was as advanced as possible but before major mortality had set in. Approximately 42% of reefs bleached to some extent in 1998, with ~18% strongly bleached. Aerial surveys of the 2002 large-scale (2,000 km) bleaching event on the GBR. Surveys were conducted at a flying height of 160 m over 11 days between 3 March and 20 March 2002 and covered a total of 641 reefs. Data are bleaching status of whole reefs. The surveys were conducted soon after the hottest period was over, a compromise between ensuring that bleaching on reefs was as advanced but before major mortality had set in. The data allowed to compare GBR-wide spatial patterns of bleaching between 1998 and 2002. In both events, more inshore than offshore reefs bleached. In 2002, ~54% of reefs bleached to some extent with 18% strongly bleached (compared with ~42% of reefs bleached to some extent in 1998 with ~18% strongly bleached). These statistics and the fact that nearly twice as many offshore reefs bleached in 2002 compared to 1998 (41 vs. 21%, respectively) makes the 2002 event the worst bleaching event on record for the GBR. The data is presented with five-point rating: 5 (<1% bleached) 4 (1–10% bleached) 3 (10–30% bleached) 2 (30–60% bleached) 1 (>60% bleached). As part of the Reef Atlas project (now the eAtlas) the bleaching observations were interpolated over the whole GBR by Glenn De'ath using Generalized Additive Models with a Quasibinomial fit. This produced a gridded version of the dataset and is available as a KML. Data format: As part of the Reef Atlas project (now the eAtlas) the bleaching observations were interpolated over the whole GBR by Glenn De'ath using Generalized Additive Models with a Quasibinomial fit. This produced a gridded version of the dataset and is available as a KML. Also available is the original bleaching observation data as a shapefile. References: - Berkelmans R, De’ath G, Kininmonth S, Skirving WJ (2004) A comparison of the 1998 and 2002 coral bleaching events on the Great Barrier Reef: spatial correlation, patterns, and predictions. Coral Reefs 23: 74–83

Principal Investigator
Berkelmans, Ray, Dr Australian Institute of Marine Science (AIMS)
Co Investigator
De'ath, Glenn, Dr Australian Institute of Marine Science (AIMS)
Point Of Contact
Berkelmans, Ray, Dr Australian Institute of Marine Science (AIMS) H.Sweatman@aims.gov.au

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