Coral bleaching

Incredibly large amounts of coral have died in recent years, this is due to a process known as coral bleaching. But how does coral bleaching happen? How does it affect ecosystems? And how can this be prevented?

Coral bleaching is a process in which the algae on corals become ‘stressed’ and leaves the coral, this means that all the things that the coral previously relied on the algae for, cannot be supplied by the algae any more. So eventually the coral dies.

Half of the Great Barrier Reef has been bleached to death

Coral’s normally contain an important type of algae called zooxanthellae, this type of algae responsible for providing corals with food from photosynthesis and the corals provide the algae a protected environment and the products it needs for photosynthesis. This healthy two way relationship allows and supports life for both the coral and the algae.

If algae like zooxanthellae or many other algae become ‘stressed’ then the algae decides to leave the coral this means that the coral loses it’s energy supplies and many other functions that it once relied on. The corals also lose their colour and become white or ‘bleached’. Algae often provides up to 90% of corals energy.

After coral bleaching, corals are weak and often die however it is possible for corals to recover.

A factor that can cause algae to become stressed is low tides, low tides can cause algae to be exposed to air in the event of a hot summer. This exposure to air causes algae to become stressed. Pollution also causes causes algae to become stressed and a further factor is heavy rainfall, this causes material on the land like fertilisers to get washed into the sea. Over-exposure to the sun causes bleaching. The final and most common factor is warmer waters, sea water has heated up by about 1 degree Celsius. This is enough to stress ridiculous amounts of corals and it is a major contributor to coral bleaching.

This affects ecosystems massively, by killing off the corals many fish are left without a habitat and they often end up dying too. Many fish will die, and almost 50% of the fish on the planet need coral reefs. Not only will the reefs be damaged, but other members of the food chain will be affected. For example the predators of the fish will go hungry and will be forced to move to another reefs or die. if the predators move to another reef then that will cause an over-population of predators in that other reef and the predators prey will die causing a decrease in population of them, and the cycle will continue.

The factor that causes, warmer waters, more sun exposure, hotter summers (therefore lower tides due to evaporation) and heavy precipitation is global warming. Global warming is caused by greenhouse gases like carbon dioxide or methane being emitted into our atmosphere. these are emitted through things like farming, driving, flying, non-renewable power and oil refining.

To prevent coral bleaching we must cut down on these things through methods like using renewable power, reducing long distance holidays, cycling, CCS and reducing meat intake.

Post Author: Daniel McKean