How does rising atmospheric CO2 affect marine organisms?

Learn how plants respond to higher atmospheric CO2 concentrations

Click to locate material archived on our website by topic


Coral Responses to Recurring Disturbances on Saint-Leu Reef
Reference
Scopelitis, J., Andrefouet, S., Phinn, S., Chabanet, P., Naim, O., Tourrand, C. and Done, T. 2009. Changes of coral communities over 35 years: Integrating in situ and remote-sensing data on Saint-Leu Reef (la Reunion, Indian Ocean). Estuarine, Coastal and Shelf Science 84: 342-352.

Background
The authors sought to determine the responses of corals of Saint-Leu Reef on la Reunion (a mountainous volcanic island of the Mascarene Archipelago in the South West Indian Ocean) to major devastating events that had occurred there over the prior 35 years (between 1973 and 2007), including a category 5 cyclone (Firinga, of 29 January 1989) that "caused 99% coral cover loss (Naim et al., 1997)," a severe coral bleaching event in March 2002 that followed on the heels of cyclone Dina of January 2002, plus other bleaching episodes in 1983, March-April 1987 and February 2003.

What was done
Scopelitis et al. used vertical images of the reef provided by five aerial photographs taken in 1973, 1978, 1989, 1997 and 2003, along with two Quickbird satellite images taken in 2002 and 2006, as well as periodic quantitative in situ observations of parts of the reef-top that could be used to document ecological and substratum characteristics that produce the color and texture observable in the photos and satellite images, to ultimately construct a history of changes in the reef's coral community over a period of 35 years (1973-2007).

What was learned
"Despite the multiple disturbance events," in the words of the six scientists, "the coral community distribution and composition in 2006 on Saint-Leu Reef did not display major differences compared to 1973." This pattern of recurrent recovery is truly remarkable, especially in light of the fact that "in the wake of cyclone Firinga, Saint-Leu Reef phase-shifted and became algae-dominated for a period of five years," and even more amazing when one is informed that following an unnamed cyclone of 27 January 1948, no corals survived.

What it means
Once again quoting the Australian and French researchers, their findings suggest "a high degree of coral resilience at the site, led by rapid recovery of compact branching corals," which demonstrates the amazing ability of earth's corals, in the words of the old Timex watch commercials, to take a licking and keep on ticking.

But maybe it's not amazing at all. Maybe that's the way all of earth's corals would behave, if they were not so burdened by the host of local assaults upon their watery environment that are produced by the local impacts of mankind's modern activities. Destructive cyclones and high temperature excursions have always been a part of the coral reef environment. The intensive activities of modern human societies have not. And it is these newer activities that likely provide the greatest threat to the health of earth's corals. Mitigate them significantly, and the world's coral reefs would likely successfully cope with the vagaries of nature.

Reference
Naim, O., Cuet, P. and Letourneur, Y. 1997. Experimental shift in benthic community structure. In: Final Proceedings of the 8th International Coral Reef Symposium. Panama, pp. 1873-1878.

Reviewed 6 January 2010