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

Data Location:

This dataset is filed in the eAtlas enduring data repository at: data\MTSRF\GBR_MTSRF-1-1-5_AIMS_Death-G_e-Atlas-maps-code\geomap\reef-data-eric\Coral_Bleaching