The Effects of Coral Bleaching
Coral itself is an amazing creature. An upside down jellyfish that has learned how to not only fix itself to the seafloor and secrete a hard, calcareous limestone skeleton, but over millions of years it has recruited tenants.
Symbiotic algae called zooxanthellae live inside the coral’s tissue. They photosynthesize sunlight which create sugars that the coral feed on. In some cases up to 90% or more of the coral’s food.
When the temperature rises and the water becomes too warm, or UV radiation intensifies too much, these symbionts over metabolise, causing tissue damage.
Consequently the coral needs to expel the algae. It doesn’t want to, but it needs to so it can survive in the short term.
This causes the coral to turn white. If the water temperature cools down in a few weeks, the algae will return. However, if the temperature remains high, the coral bleaching will persist and the corals will die.
Research has shown that coral reefs are particularly sensitive to increases in ocean temperature and bleaching events are happening more regularly over the past 20 years and on a much wider scale.
Historical Coral Bleaching Effects
Around the warm, tropical waters of Koh Tao we experienced a severe bleaching event in 2010.
Parts of Shark Bay have not recovered from this event as can be seen in areas of the bay itself.
Since then, much of the world’s coral reefs have experienced widespread bleaching, with a global mass bleaching event recorded between 2015 – 2017.
During this bleaching event, Koh Tao was relatively unaffected in comparison to other areas around the world and we hope that we don’t see another event for a long time.
Recovery from a Coral Bleaching Event
Unfortunately, scientific evidence points to bleaching events becoming more regular and possibly more serious in nature.
With shorter timeframes between bleaching events, the challenge is for coral reefs to be granted enough time to recover.
A number of other factors, including water pollution and disease can also affect corals, also causing them to expel the zooxanthellae.
It only takes a sustained increase in the water temperature of 1°C above average to upset coral reef’s, which can lead to them bleaching.
Reef Check Survey Monitoring of Coral Reefs
As part of Reef Check reef monitoring protocols, researchers measure the effect of coral bleaching and other factors on reefs around the world.
This helps reef managers learn how to manage the effects of climate change and implement ways to help reduce its impact.