If you’re like me, you may have found yourself scrolling down Facebook one day when you came across headlines exclaiming that “The Great Barrier Reef is Dead.” And if you’re like me you probably clicked on that article and saw pictures of white, lifeless stems of biological material—the remnants of what was once the most diverse and colorful ecosystem planet Earth had to boast—immediately followed by an explanation that, due to coral bleaching, the Great Barrier Reef has been killed. For the next few weeks, I’m sure many of your social media feeds were full, like mine, of articles about pollution. They debated how maybe, just maybe, we can still save what we have left of our coral reefs. But, what is coral bleaching, how are we causing it, and how bad is it, really?
To understand the significance of coral bleaching, it’s important to first look at a healthy ocean and identify what parts of its ecosystem are most vulnerable to climate change. The National Ocean Service says that an important characteristic of healthy coral is that the coral and its surrounding microorganisms live off each other in a mutually beneficial relationship. These microorganisms are what give the coral its beautiful color, but they are also extremely vulnerable in times of climate change. Dinoflagellate, a common species of protist that survives on coral, is a perfect example of an organism that is extremely vulnerable to climate change. These organisms cannot survive on coral when the temperature and pH of the ocean water changes; unfortunately, human action has altered exactly those things.
...an important characteristic of healthy coral is that the coral and its surrounding microorganisms live off each other in a mutually beneficial relationship. These microorganisms are actually what give the coral its beautiful color, but they are also extremely vulnerable in times of climate change.
Humans have increased the temperature of the oceans by polluting them with hot factory and reactor waste and by using ocean water as a coolant in nuclear processes. There has been a temperature increase in the oceans, but also the Earth in general, due to heat that is trapped in by our increasingly carbon-heavy atmosphere—of course, caused by carbon emissions. This temperature change is not beneficial to the survival of Dinoflagellate, and in fact, it makes a significant portion of these organisms either die or leave the coral.
Another reason Dinoflagellates and other microorganisms are leaving our coral reefs is because of the pH change in our oceans. As previously mentioned, our atmosphere is becoming more saturated with carbon dioxide due to the combustion of different types of fuels. So, as the composition of CO2 in our atmosphere increases, and as our atmosphere achieves equilibrium with our oceans, the composition of our oceans also becomes more CO2-heavy. This is significant to coral bleaching in our oceans because, when it is dissolved in water, CO2 reacts to create carbonic acid, then bicarbonate, and finally various carbonate compounds. This causes the production of hydronium ions, thus decreasing the pH of the water and making the ocean more acidic, causing the vital microorganisms to leave the stressed coral. In fact, researchers at the University of Queensland have demonstrated the direct correlative and causal relationship between the acidity of a body of water and the emigration of microorganisms, leaving the coral frail and exposed, which is otherwise known as coral bleaching.
So now for the all-important question: is the Great Barrier Reef too far gone? Well, the short answer is, no. Studies have shown that up to 75% of our coral population is threatened due to climate change and coral bleaching, but that doesn’t mean that we should call it a day and give up on this beautiful species: although 75% of our reefs are threatened, many parts are salvageable if humans reverse the trends that have been causing their destruction in the first place. In addition, other methods have been proposed to purge the oceans of excess carbons, which would help fight against the acidification and pollution that have contributed to bleaching.
Overall, what humans have done to coral species around the world has been destructive, and many coral reefs are already gone. But, there are also many coral reefs left alive that we can hope to save if we can change our ways and reverse our impact on the oceans. Coral bleaching is a serious threat to the species, and it should be treated as such; however, we cannot give up the fight to save the reefs yet—there’s still work to be done.