Volume 17, Number 1: 1 January 2014
In a report describing their intriguing study, which was published in the Latin American Journal of Aquatic Research, Miranda et al. (2013) write that sub-lethal bleaching effects "occur when corals do not experience mortality after bleaching, but rather undergo a temporary loss of zooxanthellae and/or of their photosynthetic pigments, with later recovery," which implies, in their words, that "corals have an adaptive capacity or resistance to seasonal changes in environmental conditions," as suggested by Buddemeir and Fautin (1993), Hennige et al. (2010) and Hughes et al. (2011).
Focusing on their homeland, the three Brazilian researchers note that "thermal anomalies on the Brazilian coast have been monitored by NOAA satellite imaging since 1998." And they say that "there have been many reports of bleaching events occurring in association with ocean warming events," but that "only Dutra et al. (2000) reported observations of the reefs after the occurrence of the beaching phenomenon." Therefore, to help bridge this knowledge gap, they studied the effects of bleaching in the corals of Caramuanas reef - which is comprised of three main flat reef banks (13°07'S, 38°43'W; 13°07'S, 38°44'W; 13°08'S, 38°44'W) - by comparing them during and immediately after the thermal anomalies related to the ENSO of 2010 in terms of "frequency and severity of bleaching, live coral cover, number of colonies, class size, disease occurrence and mortality rate," based on samples that were taken at 12 fixed transects in three reef locations.
As a result of their several observations, Miranda et al. determined that "after this bleaching event, neither the rate of mortality nor the number of colonies with disease increased; the size class structure of the most abundant species did not vary; and the number of live colonies and live coral cover also remained the same." Therefore, they were able to report that "the reef showed certain resilience to the perturbations caused by the 2010 ENSO event." And in further support of their findings, they state that "the sub-lethal effects of bleaching in Brazilian corals have been observed previously," noting that "in 1998, the northern littoral of Bahia experienced a bleaching event that affected up to 60% of the coral community, which after one year have completely recovered," as reported by Dutra et al. (2000).
In thinking about reasons for the great resiliency of the corals they studied, Miranda et al. say that "the Brazilian zooxanthellate coral fauna is characterized by endemic species, with some reminiscent of a Tertiary coral fauna that may be adapted to these inhospitable environment conditions," citing Leao et al. (2003). And they indicate, in this regard, that some examples are various species of the genus Mussismilia; for they say these species had "the lowest percent of bleached colonies" and that "those that bleached completely recovered during this investigation."
Last of all, in regard to potential policy implications of their findings, the Brazilian biologists suggest that "eliminating or reducing anthropogenic effects on this reef may increase its [already significant] resistance and resilience to bleaching, allowing its maintenance," so that "the Caramuanas reef could then act as a reserve of species and genes for this geographic region."
Sounds like an idea well worth considering.
Sherwood, Keith and Craig Idso
References
Buddemeier, R.W. and Fautin, D.G. 1993. Coral bleaching as an adaptive mechanism. Bioscience 43: 320-326.
Dutra, L.X.C., Kikuchi, R.K.P. and Leao, Z.M.A.N. 2000. Thirteen months monitoring coral bleaching on Bahia's north coast, Brazil. Proceedings of the International Coral Reef Symposium. Indonesian Institute of Sciences, Bali, p. 373.
Hennige, S.J., Smith, D.J., Walsh, S., Mcginley, M.P., Warner, M.E. and Suggett, D.J. 2010. Acclimation and adaptation of scleractinian coral communities along environmental gradients within an Indonesian reef system. Journal of Experimental Marine Biology and Ecology 391: 143-152.
Hughes, T.P., Baird, A.H., Bellwood, M., Card, S.R., Connolly, C., Folke, R., Grosberg, O., Hoegh-Guldberg, J., Jackson, B.C., Kleypas, J., Lough, J.M., Marshall, P., Nystrom, M., Palumbi, S.R., Pandolfi, J.M., Rosen, B. and Roughgarden, J. 2011. Climate change, human impacts, and the resilience of coral reefs. Science 301: 929-933.
Leao, Z.M.A.N., Kikuchi, R.K.P. and Testa, V. 2003. Corals and coral reefs of Brazil. In: Cortes, J. (Ed.). Latin America Coral Reefs. Elsevier, Amsterdam, The Netherlands, pp. 9-52.
Miranda, R.J., Cruz, I.C.S. and Leao, Z.M.A.N. 2013. Coral bleaching in the Caramuanas reef (Todos os Santos Bay, Brazil) during the 2010 El Niņo event. Latin American Journal of Aquatic Research 41: 351-360.