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Coral reefs are not dead... Yet.

I thought I would write something different on my blog anniversary and sort of go back to my chemistry roots and the reason why I did my third-year research project... to find a way to prevent the exploitation of coral.  Albeit this blog post will be discussing the degradation of coral reefs and how we are very close to losing the beautiful coral structures under the sea. 

Coral reefs are undergoing severe bleaching. This has been reported over several years, not just in 2017. Starting from 1998, reports started to talk about coral bleaching, increasing in severity in 2010 and reaching its highest degree in 2017.

Corals, which build reefs, are made up of hundreds of thousands of polyps, living in colonies. These polyps build a skeleton made of calcium carbonate in layers, where the polyps live on top (visible to the naked eye if you're close enough) and the coral reef lives on top of old coral reefs a.k.a limestone.  
But coral cannot grow or flourish on their own, they live in harmony with a type of single-celled algae called zooxanthellae. Zooxanthellae (Zoox) give the polyps their significant green/brown colour and they absorb their energy from sunlight, hence why coral reefs grow closest to the sunlight on the sea floor. Via photosynthesis, the Zoox convert the sunlight they absorb to energy, in harmony with the polyps.  Under heat stress, this harmony is broken, even it's only 1-3 degrees Celsius increase of temperature over the optimal temperature. Instead of normal photosynthesis, Zoox start to produce harmful byproducts such as hydrogen peroxide which start to leak into the polyps. In turn, the polyps start to kick out the Zoox from them, leaving them bare and the significant white colour of bleached coral. 

(A) A normal cell with distinct subcellular organelles. (B) A cell undergoing degradation with indistinct subcellular organelles and a thick coral cell. (C) A degraded cell with an enlarged accumulation body and shrunken morphology. 
However, we have to take note that heat stress is not the only factor in coral bleaching. Since corals and algae possess a very fragile eco-system and need specific conditions to thrive, factors such as salinity, the opacity of the water, oxygen levels and temperature can all affect the growth of coral. The increase of salinity, high influx of sediments and/or pollutants or changes in the sea level and in temperature can degrade coral. 

In this blog post, we'll only be looking at heat stress which is caused by the increasing sea temperatures due to global warming.

Coral bleaching does not necessarily mean the death of the coral, if the temperature of the sea decreases, zooxanthellae can return back to the polyps and grow. however if they don't, and the polyps can die from starvation or disease. So although the coral reef isn't dead yet, the increase in sea temperatures which continue to rise will eventually affect the reefs and deplete them. It's also been predicted that this will more noticeable every coming summer if we do not provide a solution to global warming and lower greenhouse emissions. 

What's currently causing global warming?

You've probably already heard of the reasons why global warming is occurring but I'll quickly explain it for people who have not. Global warming is the increase of the temperature of the Earth and it is caused by the increase of greenhouse gasses in the atmosphere such as carbon dioxide, methane and nitrous oxide. The most prevalent greenhouse gas is carbon dioxide which causes the greenhouse effect. Living up to its name, the greenhouse effect is like a greenhouse which traps heat inside it whilst the atmosphere around it is cooler.  The earth's atmosphere acts as a gigantic greenhouse, trapping heat from the sun. Greenhouse gases such as carbon dioxide and methane accumulate in the atmosphere and create a "barrier" that traps sunlight, warming up the planet. This warming gives off heat energy of a longer wavelength infrared radiation, which radiates out toward space. However, a portion of this outgoing radiation doesn't pass through the atmosphere but is reflected back down to Earth, effectively trapping heat and keeping the planet about 33 degrees Celsius - the natural greenhouse effect which is required to provide life on earth. With the increase in gas emissions from car engines, for example, and the mass-scale burning of fossil fuels there has been a spike in carbon dioxide emissions, making the greenhouse "layer" thicker, therefore trapping in more heat. It's predicted that just within a century, the Earth's atmosphere could heat up an extra 2-5 degree Celsius over the norm. Although it doesn't sound like the big difference it's already having a big impact on the earth and in our case, the coral reefs. 

To prevent global warming we need to stop using fossil fuels and switch to more efficient means of energy. A difficult solution, but it has to be done...


My journey on this blog is now three years old!🎉 I want to thank you all, again, for reading my blog. Thank you, thank you, thank you!

Here's to many more years to come!


References and further reading/watching:

  1. Vox
  11. NBC 1970
  12. Guillaume Debever
  13. Martin Lalonde