Climate Change and Coral Reefs: An Introduction

This blog will attempt to cover the main impacts of a changing climate on coral reefs, through a discussion of key academic papers and a look at issues that hit the headlines and social media. Whilst many would perceive climate change to be a contemporary issue, coral reefs have been affected by the impact of a changing climate throughout their history. Not only does this allow the investigation of past changes to sea surface temperatures and sea levels, but will enable the simulation of future changes.

My own experience of coral reefs is fairly classic of anyone who has been to Australia! In the time I was there I spent the odd day snorkelling off the coast of Queensland, exploring reefs by boat on organised trips and under my own steam at the many islands scattered across the Great Barrier Reef. Although I'm told the best reefs are far out to sea, and many are protected from the likes of people on their gap year, the areas I went to were fairly disappointing. Especially having seen other traveller's photos of the Ningaloo Reef in Western Australia, where the coral seemed to incorporate every colour of the rainbow, reef sharks and loggerheads were plentiful and shoals of fish were vast. It appeared evident that the dual blow being dealt to these fragile ecosystems by tourism and, more significantly, climate change was having a severe impact.

Ove Hoegh-Guldberg's (1999) paper is a good place to start, as it considers the primary impact of a warming climate on coral reefs - coral bleaching. Rising sea temperatures result in the required temperature for corals, and the photosynthetic single celled organisms (zooxanthellae) that have a symbiotic relationship with them, to be exceeded. This can cause mass coral bleaching events due to the zooxanthellae, that give the coral its colour, being expelled or dying. As well as allowing the development of coral bleaching knowledge, this paper also models future changes, unfortunately painting a fairly grim picture. It suggests that mass coral bleaching events will become much more commonplace and that current warming cannot continue without the global loss and degradation of coral reef. Although sea surface temperatures have increased in the past, the speed at which change is currently occurring prevents the marine ecosystem from adapting to change.
DOI: 10.1071/MF99078