Jimenez, C.E. and Cortes, J. 2003. Coral cover change associated to El Niņo, eastern Pacific, Costa Rica, 1992-2001. Marine Ecology 24: 179-192.
What was done
The authors document coral cover variability between 1992 and 2001, when the El Niņo warming events of 1991-1992 (weak) and 1997-1998 ("the strongest in recorded history") affected coral communities along the Costa Rican central Pacific coast, after which they report their observations, as well as those of other scientists pertaining to these and earlier warming events caused by the El Niņos of 1982-1983 (very strong) and 1986-1987 (moderate).
What was learned
Several things noted by Jimenez and Cortes are at odds with what climate alarmists typically claim about rising temperatures and coral bleaching.
First of all, they report a "paucity of bleaching and mortality in the study area in 1987 despite sea temperature anomalies similar to or higher than in other years in which bleaching and mortality occurred," saying that this situation "may have been the result of the higher cloud cover and runoff which, in combination, decreased solar radiation stress." Likewise, they suggest that "similar atmospheric conditions during 1998 may explain the considerably small number of corals that bleached that year in the upwelling area of [Costa Rica's] Golfo de Papagayo," where they report that "few corals bleached, even though sea temperature anomalies were higher than in autumn 1997."
In like manner, Jimenez and Cortes report that "Mumby et al. (2001) attribute the scarcity of bleaching at the Society Islands during the 1998 warming event to high cloud cover." And in explaining "the near absence of coral bleaching in the Andaman Sea during the 1998 warming," they note that Dunne and Brown (2001) have proposed that "elevated solar radiation prior to sea-temperature maxima may protect corals from bleaching by priming the coral and algae photoprotective defenses."
With respect to what is considered "the strongest event on record (McPhaden, 1999; Enfield, 2001)," the authors report that "mortality of entire colonies associated with this event was remarkably low in Costa Rica, less then 6% (Jimenez et al., 2001)," and that "only one coral species, Psammocora stellata, disappeared at one locality (Cambutal) after the 1997-1998 warming event." What is more, this disappearance "did not have an effect on the percent of total cover, which was not significantly dissimilar to previous years." In addition, they further report that "this species was not affected in Mexico by the 1997-1998 warming episode (Carriquiry et al., 2001)."
As for other potential explanations for these observations, Jimenez and Cortes note that conspecific corals "have shown differences in susceptibility to bleach, mortality rates and recovery capabilities (Brown, 1997; Hoegh-Guldberg, 1999; Marshall and Baird, 2000; Fitt et al., 2001; Glynn et al., 2001)," which they say may "reflect corals' adaptation to local conditions, different warming intensities at each locality, thermal acclimation, and presence of several clades of symbionts." In fact, they state that moderate warming events "may positively affect coral reef communities," noting that "increases in growth rates, reproductive activity and recruitment pulses have been observed after some El Niņo episodes (Glynn et al., 1991, 1994; Feingold, 1995; Guzman and Cortes, 2001; Vargas-Angel et al., 2001; Jimenez and Cortes, 2003)."
What it means
Adjeroud et al. (2002) say "it is generally believed that mortality rates following bleaching events are related to the intensity and duration of sea temperature anomalies," citing the paper of Hoegh-Guldberg (1999) as one of the primary origins of this favorite climate-alarmist concept. However, they report that their results "do not fit this general rule." Now, the observations of Jimenez and Cortes, as well as those of the many studies they cite, also suggest that this simplistic concept is rather far removed from reality.
Adjeroud, M., Augustin, D., Galzin, R. and Salvat, B. 2002. Natural disturbances and interannual variability of coral reef communities on the outer slope of Tiahura (Moorea, French Polynesia): 1991-1997. Marine Ecology Progress Series 237: 121-131.
Brown, B. 1997. Coral bleaching: causes and consequences. Coral Reefs 16: S129-S138.
Carriquiry, J., Cupul-Magaņa, A., Rodriguez-Zaragoza, F. and Medina-Rosas, P. 2001. Coral bleaching and mortality in the Mexican Pacific during the 1997-1998 El Niņo and prediction from a remote sensing approach. Bulletin of the Marine Sciences 69: 237-249.
Dunne, R. and Brown, B. 2001. The influence of solar radiation on bleaching of shallow water reef corals in the Andaman Sea, 1993-1998. Coral Reefs 20: 201-210.
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Feingold, J. 1995. Effects of Elevated Water Temperature on Coral Bleaching and Survival During El Niņo Disturbance Events. Ph.D. Dissertation. University of Miami, Coral Gables, Florida.
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Jimenez, C. and Cortes, J. 2003. Growth of seven species of scleractinian corals in an upwelling environment of the eastern Pacific (Golfo de Papagayo, Costa Rica). Bulletin of the Marine Sciences, in press.
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Vargas-Angel, B., Zapata, F., Hernandez, H. and Jimenez, J. 2001. Coral and coral reef responses to the 1997-1998 El Niņo event on the Pacific coast of Colombia. Bulletin of the Marine Sciences 69: 111-132.
Reviewed 21 January 2004