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Coral Bleaching: the causes, effects, and how we can stop it

Coral Bleaching: the causes, effects, and how we can stop it

We’ve all heard about coral bleaching over the last few years. Along with global warming and climate change, these are terms that tend to go together. But what is the meaning of coral bleaching? Is it something new? What causes coral bleaching and, what are the consequences of this event?

Many people may be under the impression that corals are “sea plants”, when, in fact, corals are animals with colonies of many identical individual polyps. Most of them are transparent and tend to be bright and colourful due to a microscopic algae called zooxanthellae. This type of algae lives in the coral as they help each other survive.

When coral is stressed by changes in their environmental conditions such as water temperature, the amount of light they receive or its nutrients, they expel the algae that gives them colour, causing them to turn white, this is the phenomenon we call Coral bleaching.

Does this mean that bleached coral reef is dead? Unlike the popular opinion, the answer is no. Coral can survive the bleaching if the conditions change back to what they were before, although of course, any coral that has been bleached are more stressed and have higher chances of mortality.

It can take decades for reefs to get back to their original state, so it’s crucial that these do not happen frequently.

What are the causes of coral bleaching?

As mentioned above, coral bleaching is caused by a change of conditions in the coral ecosystem. Water’s optimal temperature for coral growth is between 20 to 28°C. Ocean’s temperature is an important attribute; it varies with latitude as warmer waters are near the equator, whereas coldest ones are near the Arctic and the Antarctic.

Currently, the ocean takes in high quantities of heat due to an increased amount of greenhouse gases in the atmosphere, which cause are fossil fuels. According to a report published by the Intergovernmental Panel on Climate Change (IPPC) in 2013 showed that the ocean had absorbed more than 93% of greenhouse gas emissions. Other data from NOAA (the US National Oceanic and Atmospheric Administration showed that the average sea temperature has increased approximately by 0.13 degrees per decade over the last 100 years which could result in an increase of 1-4 degrees by 2100 if immediate action isn’t taken.

How does coral bleaching impact the environment?

Contrary to what many people may think, coral bleaching doesn’t just affect corals and the organisms that live in it; thousands of animals such as sea turtles, fish, crabs, jellyfish, sea birds, etc depend on reefs to survive.

Bleaching also impacts human life, food security and safety. Reefs are barriers that contain the force of waves and storms. It would also affect anyone relying on fishing for feed or economic purposes as bleached coral would remove links in the food chain and wouldn’t allow marine species to develop. Not to mention how the tourism industry would be affected as it moves millions on a yearly basis.

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How can we conserve coral reefs?

In order for corals to recover, there needs to be a reduction in the increasing ocean temperature. The most ambitious carbon reduction targets should be in place in order to stop global warming and the replacement of fossil fuels with sustainable energy should be in process.

What can we do?

Preservation work can start at a personal level; from raising awareness to choosing a reef-safe sunscreen, as well as adopting a “no-trace culture” meaning when visiting a coral reef, we do not interact with their ecosystem.

There are many coral restoration initiatives around the globe and Be ALAM has decided to partner with Indo Ocean projecta marine research and conservation program in the heart of the coral triangle, training the next generation of dive professionals through our conservation divemaster internship program. Would you like to learn more about the initiative? Check our website for more.

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