Bleaching has always happened

Is bleaching a new phenomenon due to recent climate change?

It is often claimed that bleaching is a new phenomenon caused by the modest increase in temperature during the twentieth century and that it did not start to occur until the 1980s. For example, Professor Terry Hughes, is a pre-eminent coral ecologist at James Cook University Coral Reef Centre in Townville, Australia, who has been responsible for much of the publicity about the 2016 bleaching event. He stated on ABC radio.[i]

a critical issue here is that these bleaching events are novel. When I was a PhD student 30 years ago regional scale bleaching events were completely unheard of. They are a human invention due to global warming.”

The records show that there were 26 records of coral bleaching events on the GBR before 1982;[ii] bleaching was observed on the first scientific expedition to the GBR, from England, in 1929.[iii]   It was not until the 1960s that the number of marine biologists exploded on the GBR and the phenomenon started to be documented. If a major bleaching event had occurred in 1925, who would have noticed, who would have cared?

Figure: Sir Maurice Yonge (right) was the first to observe bleaching on the GBR

The world-first “scientific” observation of bleaching, where a picture was recorded,  was in 1862 off the coast of the Sinai in Egypt. It was done by von Ransonnet using a diving bell. Those were the days when the underwater world was effectively hidden.

Bleaching is not new. It is a natural response that has evolved over a few hundred million years of evolution.

Lithograph of bleaching in 1862 by von Ransonnet.(see Cedhagen[iv]) The white coral is clearly bleached.

[i] ABC Radio National. (2016). Widespread coral bleaching detected on the Great Barrier Reef. [online] Available at:

[ii] Oliver, J.K., Berkelmans, R. and Eakin, C.M. (2018). Coral Bleaching in Space and Time. In: M.J.H. Van Oppen and J.M. Lough, eds., Coral bleaching : patterns, processes, causes and consequences. Springer-Verlag Berlin Heidelberg.

[iii] Yonge, C.M. and Nicholls, A.G. (1931). The Structure, Distribution and Physiology of the Zooxanthellæ. Great Barrier Reef Exped 1928-29 Sci Rep, 1, pp.135–176.

[iv] Cedhagen Phuket mar. biol. Cent. Res. Bull.78: 21–28 (2021) DOI: 10.14456/pmbcrb.2021.1

%d bloggers like this: