Modelling Coral Bleaching Events Using a Fuzzy Logic Technique

A fuzzy logic algorithm was used to model coral bleaching events around Magnetic Island, North Queensland, Australia. Most events during the 80’s and 90’s did not coincide with the strong ENSO (El-Nino Southern Oscillation) phenomenon. The model uses monthly Air Temperature (AT) data obtained from the Townsville Bureau of Meteorology and monthly IGOSS-NMC and Geoffrey Bay Sea Surface Temperature (SST) data sets. Four separate model inputs were considered. They were: (a) raw temperature, (b) a temperature for a particular year is taken by subtracting the value of one year before from the value of that year, (c) a temperature for a particular year is taken by subtracting the 2-year running average from the value of that year, and (d) a temperature for a particular year is taken by subtracting the 3-year running average from the value of that year. Using the difference in seawater temperature with that of the previous year as a model input (case b) gave a better fit to bleaching events than using seawater temperature alone. This indicates that some form of acclimatisation may influence the response of corals to some form of bleaching event. It was also found that when the maximum sea temperature in a particular year exceeds 0.37 °C of the previous one year, coral bleaching occurs.

[1]  A. Huppert,et al.  Chaos in the Pacific's Coral Reef Bleaching Cycle , 1998, The American Naturalist.

[2]  Barbara E. Brown,et al.  Adaptations of Reef Corals to Physical Environmental Stress , 1997 .

[3]  H. Lasker,et al.  Coral mortality outside of the eastern Pacific during 1982-1983 : relationship to El Niño , 1990 .

[4]  S. Coles,et al.  Response of Hawaiian and other Indo-Pacific reef corals to elevated temperature , 1990, Coral Reefs.

[5]  S. Coles,et al.  Synergistic effects of temperature, salinity and light on the hermatypic coral Montipora verrucosa , 1978 .

[6]  R. Pielke,et al.  La Niña, El Niño, and Atlantic Hurricane Damages in the United States , 1999 .

[7]  R. Berkelmans,et al.  Large-scale bleaching of corals on the Great Barrier Reef , 1999, Coral Reefs.

[8]  R. Berkelmans,et al.  Recurrent bleaching of corals at Magnetic Island (Australia) relative to air and seawater temperature , 1997 .

[9]  B. Willis,et al.  Seasonal and local spatial patterns in the upper thermal limits of corals on the inshore Central Great Barrier Reef , 1999, Coral Reefs.

[10]  P. W. Glynn,et al.  Experimental evidence for high temperature stress as the cause of El Niño-coincident coral mortality , 1990, Coral Reefs.

[11]  Michio Sugeno,et al.  A fuzzy-logic-based approach to qualitative modeling , 1993, IEEE Trans. Fuzzy Syst..

[12]  S. Coles,et al.  Effects of temperature on the mortality and growth of Hawaiian reef corals , 1977 .

[13]  Lotfi A. Zadeh,et al.  Fuzzy logic = computing with words , 1996, IEEE Trans. Fuzzy Syst..

[14]  Sankar K. Pal,et al.  Fuzzy models for pattern recognition : methods that search for structures in data , 1992 .

[15]  Mark Ridgley,et al.  A Fuzzy Logic Model to Predict Coral Reef Development under Nutrient and Sediment Stress , 1998 .

[16]  J. Lough.  Sea surface temperatures on the Great Barrier Reef : a contribution to the study of coral bleaching , 1998 .

[17]  E. Williams,et al.  The World-Wide Coral Reef Bleaching Cycle and Related Sources of Coral Mortality , 1990 .

[18]  M. Ridgley,et al.  Optimization of economic policies and investment projects using a fuzzy logic based cost-effectiveness model of coral reef quality: empirical results for Montego Bay, Jamaica , 1999, Coral Reefs.

[19]  Lotfi A. Zadeh,et al.  Fuzzy Sets , 1996, Inf. Control..

[20]  P. W. Glynn,et al.  Coral reef bleaching: ecological perspectives , 1993, Coral Reefs.

[21]  Witold Pedrycz,et al.  OPTIMIZATION OF FUZZY MODELS FOR SYSTEM ANALYSIS, PATTERN RECOGNITION AND KNOWLEDGE ENGINEERING , 1994 .

[22]  R. S. Appeldoorn,et al.  Sea surface temperatures and coral reef bleaching off La Parguera, Puerto Rico (northeastern Caribbean Sea) , 1998, Coral Reefs.

[23]  John Lygeros.  A formal approach to fuzzy modeling , 1997, IEEE Trans. Fuzzy Syst..

[24]  R. Gates,et al.  Temperature Stress Causes Host Cell Detachment in Symbiotic Cnidarians: Implications for Coral Bleaching. , 1992, The Biological bulletin.

[25]  J. Lough.  Climate variation and El Niño-Southern Oscillation events on the Great Barrier Reef: 1958 to 1987 , 1994, Coral Reefs.

[26]  Kevin E. Trenberth,et al.  The Definition of El Niño. , 1997 .