Easter Bleaching

Coral Bleaching is caused by various environmental factors; pollution being one (Japp and Wheaton 1979), lowered salinity (Egana andDiSalvo 1982), but most commonly and talked about in previous blogs – increased seawater temperatures.

Easter Island lies at the South East part of the Indo Pacific region. It has no structural reefs and hosts a desperate amount of fauna, demonstrated by its few species of corals (Wells 1972).

There have been records of mass expulsion of zooxanthellae (algae which live symbiotically in the cells of marine invertebrates) in corals around the mid-1980 (Egana and DiSalvo 1982). Heavy rainfall on 16th June 1980, divers who looked for corals for exportation noticed that the corals had begun to turn white on an island wide basis (Egana and DiSalvo 1982). The corals recovered gradually, it would take 2-3 months (Egana and DiSalvo 1982). It is thought that increased rainfall will decrease water salinity, sharp reduction of water salinity induces osmotic stress which brings on symbiont expulsion (Egana andDiSalvo 1982). Generally, such bleaching events are rare and confined to relatively small, near shore areas, however with El Nino set to increase in severity and occurrence due to climate change may alter this (Glynn 1996). Climate change is set to increase rainfall and therefore lower salinity in waters causing coral bleaching.

As there is clear evidence that climate change, ENSO, sea temperature rise, and UVR are destroying corals, Glynn predicts a scenario where more or less continued warming with no return to optimal temperatures that would allow coral reef recovery. Threats also related to climate change (e.g. sea-level rise, increased solar irradiance, higher CO2 concentrations of ocean waters, changing patterns of rainfall, cyclonic storms and ocean circulation) are possible, and likely would interact with temperature rise (Glynn 1996). So depending on how we limit climate change and how the corals adapt to it, we could see a mass extinction of corals (Glynn 1996).

Easter Island is dependent on tourism and trade of Pacific goods such as corals (Egana and DiSalvo 1982). This makes them vulnerable as both of these things are becoming harder as climate change persists. The sea level rise and harsher storms are causing tourist boats not board Easter Island, as the choppy and high seas can make it dangerous for ships to go near its rocky shores (National Geographic 2012). This means tourism is decreasing and therefore creating a decline in its economy. Bleaching corals mean the quality of it decreases and is not suitable for export, also hitting the economy, it is suggested that Chile should invest more in its port to encourage tourism (National Geographic 2012).

If you want to read more about Easter Island, a blog I would recommend would be ‘Paradise Loss’, blogs 29.11.12 and 8.11.12 may be of interest to you.

Also if you have problems using my links for references:

Egana, A. DiSalvo, L. (1982) ‘Mass Expulsion of Zooxanthellae by Easter Island Corals’ Pacific Science, 36, 1, 61-3

Gylnn, P. (1996) ‘Coral reef bleaching: facts, hypotheses and implications’ Global Change Biology, 2, 6, 495-509

Japp, W. (1979) ‘Observations on Zooxanthellae Expulsion at Middle Sambo Reef, Florida Keys’, Bulletin of Marine Science, 29, 3, 414-22

Wells, J. (1972) ‘Notes on the IndoPacific scleractinian corals. Part 8.

Scleractinian corals from Easter Island’, Pac Sci 26: 183-190