Higher thermal resistance of corals in the global marine biodiversity center
Cite this dataset
McClanahan, Tim (2022). Higher thermal resistance of corals in the global marine biodiversity center [Dataset]. Dryad. https://doi.org/10.5061/dryad.73n5tb2tc
Predictions for the future of coral reef are largely based on thermal exposure and poorly account for geographic variation in biological sensitivity and resistance to thermal stress. Based on the ratio of thermal exposure and sensitivity, geographic variability of coral resistance was estimated during the 2016 global-bleaching event. Exposure was estimated as historical cumulative excess summer heat (CTA) and a multivariate index of SST, light, and water flow (CE). Site sensitivity was estimated for 226 sites using coordinated bleaching observations. Site resistance was evaluated by 128 possible models for the influences of geography, historical SST variation, coral cover, and number of coral genera. Most factors were statistically significant but the strongest factor was geography - Coral Triangle having higher resistance than non-Coral Triangle sites. Consequently, future predictions of thermal stress will need to account for strong geographic differences in acclimation/adaptation.
The data are field observation on coral bleaching at the genus level and the associated environmental data at the time of the sampling. This is the raw data.
For each survey, we calculated two standard bleaching metrics: (1) the percentage of bleached coral colonies, and (2) bleaching intensity, a weighted average of the relative abundance of coral colonies within each category of bleaching severity (Fig. 1b):
〖Bleaching intensity〗_ = (((0×c0)+(1×c1)+(2×c2)+(3×c3)+(4×c5)+(5×c5)+(6×c6)))/7
Both metrics of bleaching produced similar results, and both provide simple, repeatable, and comparable methods to quantify bleaching. We chose the intensity metric for further analyses as it is separated sites across a wider bleaching gradient and resulted in better distinctions for modelling. On each survey, we evaluated total bleaching intensity across all coral colonies.
Between March and September 2016, we conducted 235 bleaching surveys in 12 countries across the Indian and Pacific Oceans using a standard rapid roving observer methodology. To evaluate how survey timing was related to accumulated temperature stress, we extracted daily 5 km Degree Heating Week time series from NOAA Coral Reef Watch for each site from 1 September 2015 to the date of survey and calculated the date of maximum observed DHWs for each site. Based on these satellite temperature time-series, 45 sites did not experience excess heating (i.e., 0 DHWs). For the remaining 190 sites, we calculated the number of days between the date of the bleaching survey and the date of maximum DHW. For 181 sites, bleaching surveys occurred within 21 days of maximum DHW, well within suggested timelines to assess bleaching-related stress and mortality for corals (~30 days31). Nine sites where bleaching surveys were assessed >21 days after maximum DHW were excluded from further analyses, leaving 226 sites across 11 countries for further analysis. Further details on study reefs and bleaching notes are provided in Supplementary Table 1.
The data are frequency information on the sites, the environmental variables, and the percentage of bleached corals in different bleaching categories.
John D. and Catherine T. MacArthur Foundation