By Fiona Hodge

Stressful environmental conditions can be the make or break of a species. The people in Christchurch have done a wonderful job of accepting, coping, and responding to the recent earthquake. Hopefully in the long run the relationships, skills, and new housing that result from this experience will strengthen their communities.

Corals also face stressful environmental conditions. The coastal waters they live in are warming, and increasingly being affected by runoff and sediments from coastal development. Coral reefs aren’t coping well with the stress… this year alone mass bleaching events have being reported in Sri Lanka, Thailand, Malaysia, Myanmar, the Phillipines, and Indonesia. Sixty percent of coral reefs in the Indonesian Aceh region are estimated to have bleached over the last few months.

Coral reefs are made up of millions of coral polyps, looking like tiny transparent anemones, sitting on a shared reef skeleton. These coral polyps spend their days charging their solar batteries and occasionally plucking at food particles. The solar batteries are actually tiny single-celled algae, invisible to the naked eye, providing the vast majority of coral’s energy.

When stressed the relationship between the corals and the algae breaks down. Stressed coral will kick the algae out, and lose their colour, hence the term ‘bleaching’. Corals can recover from being bleached, but long periods of bleaching are fatal. Scientists have predicted ‘regular and widespread catastrophic bleaching’ over the next 15 to 25 years as climate change drives water temperatures up.

Although the outlook doesn’t look good for corals, there is a small glimmer of hope. Researchers are now investigating whether the bleaching response to environmental stress could strengthen some coral communities. The idea is that the algal solar batteries come in a variety of types with some coping better with warmer seas then others. Bleaching may allow some corals to pick up solar batteries more suited to the environmental conditions. 

Unfortunately even if there are benefits to bleaching, these benefits are limited. Only a quarter of the world’s corals are able to host more than one type of algal solar battery over their lifetime. Additionally picking up more suitable algal batteries may be a good way to acclimatise to warming sea temperatures, but it doesn’t help species adapt. Adaptation requires the traits to be passed on to offspring, allowing them to be more suited to their environments.

Rising sea temperatures, unlike earthquakes, are preventable. The loss of corals is more than the loss of an amazing group of species, it’s the loss of habitat for countless other valued and valuable species, it’s the loss of erosion and storm protection for coastlines, it’s the loss of undiscovered medicines and other biochemicals.