Quantifying the quality of coral bleaching predict

Authors: R van Hooidonk M Huber

Publish Date: 2009/05/02

Volume: 28, Issue: 3, Pages: 579-587

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Abstract

Techniques that utilize sea surface temperature SST observations to predict coral reef bleaching are in common use and form the foundation for predicted global coral reef ecosystem demise within this century Yet quality assessments of these methods are typically qualitative or anecdotal Quality is the correspondence of forecasts with observations and has standard quantitative measures Here a forecast verification method commonly used in meteorology is presented and used to measure the quality of the degree heating weeks DHW technique as an exploration of insights that can be gleaned from this methodology DHW values were calculated from NOAA Optimum Interpolation SST version 2 data and compared to a database of bleaching observations from 1990–2007 Quality is expressed with an objective measure the Peirce Skill Score PSS The quality at varying DHW thresholds above which bleaching was projected to occur is calculated By selecting the thresholds that maximize quality the predictive technique is objectively optimized This results in optimal threshold maps showing reefs more prone and more resistant to bleaching Optimization increases the quality of DHW as a predictor of bleaching from PSS = 055 to PSS = 083 in global average but the optimal PSS and corresponding DHW values vary significantly from location to location The coral reef research and management community are urged to adopt the simple but rigorous tools of forecast verification routinely used in other disciplines so that bleaching forecasts can be quantitatively compared and their quality improvedThe authors thank two anonymous reviewers D Manzello T McClanahan J Maina and M Baldwin for their comments and suggestions that improved the manuscript The high resolution coral reef location file was provided by Serge Andréfouët IRD UR CoRéUs Frank MullerKarger Univ Massachusetts Dartmouth Julie Robinson NASA Earth Sciences and Image Analysis Laboratory UNEP World Christine Kranenburg Damaris TorresPulliza and Brock Murch IMaRS University of South Florida The coral bleaching data was downloaded from reefbaseorg a project by “The WorldFish Center” The Optimal Interpolated SST data was obtained from NOAA/OAR/ESRL PSD Boulder Colorado USA from their Web site at http//wwwcdcnoaagov/ The authors like to acknowledge NCAR for the development of NCL R van Hooidonk was partly funded by a Fulbright/NetherlandAmerica Foundation scholarship The authors are grateful to Mark Eakin for conversations which helped guide the research This is PCCRC paper number 0833

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