El Nino-Southern Oscillation 1982-83 and 1997-98 Impacted Coral Reefs in the Equatorial Eastern Pacific Region: Effects, Recovery and Inter-ENSO Comparisons

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This project will occur over a five year period to continue and conclude a long-term study that has focused on ecological disturbances, causes, responses and recovery of eastern tropical Pacific (ETP) reef?building coral populations and reef communities in relation to the severe 1982?1983 El Nino?Southern Oscillation (ENSO) event. With the occurrence of the very strong 1997?1998 ENSO, two "one hundred year events" only 15 years apart, an unprecedented opportunity is at hand to study and compare the effects of consecutive major perturbations on community responses and recovery. This study involves strong international collaboration with host?country research teams working at several field sites in Costa Rica, Panam.6, and Ecuador (including the Gal6pagos Islands), all areas that were severely affected during the ENSO disturbances of 1982?83 and 1997?98. Several aspects of this study will be continued, namely (a) monitoring the physical and biological conditions of eastern Pacific coral reefs initiated in the early?to?mid 1970s~ (b) investigating the responses of selected zooxanthellate coral species to ENSO stressors (chiefly positive sea temperature anomalies), (c) retrospective climate studies from coral skeletal isotopic signatures, (d) coral reproductive ecology as it relates to recruitment success in disturbed communities, (e) coral community recovery or changes leading to alternate, non?reef building communities, (f) the linking of coral bleaching/mortality with local and global-scale sea surface temperature (SST) anomalies, including both high and low temperature extremes, and (g) modeling the size structure of coral populations and coral community dynamics based on mechanistic relationships between temperature, predation, coral growth and survivorship derived from field monitoring and experimental results. Additionally, studies initiated in 1997 will also be continued, namely (h) analysis of the molecular genetic structure of zooxanthella taxa symbiotic with eastern Pacific corals to assess the importance of zooxanthella diversity in explaining the variability in patterns of coral bleaching and mortality/survivorship of host corals, and (i) assessment of the genetic structure and diversity of recovering and recently stressed coral populations in relation to stress resistance, population size and distance from source populations. New initiatives will include (j) coral?algal?herbivore interactions, and (k) trophodynamic/benthic community structure modeling in high SST?stressed upwelling and non-upwelling environments in order to assess the effects of ENSO perturbations and recovery processes on coral reef framework growth.