Global Impact: Here's What's Actually Happening To The Coral Reefs
There’s so much going on under the ocean that we don’t think about. Clownfish, eels and parrotfish are making their homes among the corals. Jellyfish and sea stars are clinging to its surface. Crabs, shrimp, and lobsters are maneuvering through the cracks. Sea snakes and octopuses are blending into the coral in efforts to sneak up on their prey. Coral Reefs create an insanely diverse ecosystem. A system that covers less than one percent of the earth’s surface and less than two percent of the ocean's floor, yet is essential for 25 percent of ocean species. Its colors are so vibrant and inviting with the reds, purples and yellows. It really gives you a glimpse into a realm in which we are only visitors. The “rainforest of the sea" many have called it and for good reasons.
But just like our rainforest on land, these sea rainforests and in a bit of trouble. They’re not ‘dead’ by any means as some social media has implied. They’re simply a bit sick and becoming sick more often then they can recover from it. Corals are closely related to the sea anemone; they have a simple body structure called a polyp which has an open part, the mouth, surrounded by tentacles. The tentacles have stinging cells called nematocysts which sting organisms when they get too close stunning them so that the polyp can eat them. The coral has digestive and reproductive tissues inside of it and is surrounded by a mineral-like skeleton made of calcium carbonate. The same thing that makes up crustacean shells.
The shallow water corals get their vibrant colors from zooxanthellae, single-celled algae, which live on the corals forming a symbiotic relationship. In this relationship, the photosynthesizing algae give the coral some of its sugars that it produces from that process and the coral gives the algae nutrients as well as a home. This relationship allows the coral to grow fast and form the reef structures we’re most familiar with. Coral reefs are defined as many coral species together and can stretch for miles. Some of these colonies have lived over 4,000 years. Scientists can determine this because coral actually forms ring structures just like trees on the inside, yeah you have to cut into it to see them but that’s beside the point.
So in order for this relationship between the coral and the algae to stay productive, conditions have to stay relatively stable. Since these reef-building corals only live in tropical and subtropical waters it generally works out. The algae need the warmth and the sunlight to grow and photosynthesize and the coral does its thing. Well, when the conditions do change dramatically, and the ocean becomes way too hot or acidic the algae become more like poison to the coral. The algae stop photosynthesizing and begin to die. The coral expels the algae to get rid of the toxins and is left to fend for itself.
Coral ‘bleaching’ is a term used when the coral loses its algae. The vibrant color is only from the algae, once it’s gone it leaves the coral looking white and malnourished. After long the fish go because the coral is sick and no longer very useful to them and this creates a barren graveyard. The coral becomes vulnerable and weak. With recent rises in carbon dioxide levels, the oceans really take the hit. The ocean dissolves excess carbon dioxide and it changes the whole pH, lowering it, creating on the insanely acidic environment. Not only does this high acidity kill the algae, it also breaks down the coral's skeleton and makes it harder for them to build more. Their calcium carbonate levels can drop down so low that coral can literally break down and dissolve away into the ocean.
Now water chemistry differs widely from place to place, so not all corals are going to drop dead at once, dissolving into the sea, but we have lost about 27 percent of the world’s corals since 1980. At the rate that our carbon dioxide levels are rising, and our oceans are warming, it is predicted that in 30 years it will become more like 60 percent of all corals. In Hawai'i particularly corals are dissolving faster than they can rebuild themselves. Florida’s Reef Tract, which is the third largest barrier reef ecosystem in the world, is eroding away the fastest in the fall and winter months. Bleaching events are known to be seasonal sometimes and then the algae returns, but what is different about it in recent years is that these events are becoming so frequent that they no longer have time to recover.
When a coral loses its algae it’s like a disease. Let’s say the flu, a really really bad case of the flu. When people have the flu they are weak, susceptible to further infection, and fatigued. The same happens with coral. They’re used to obtaining this disease maybe once every 25-30 years but now its more like 1-6 years. That’s like if you usually get the flu once every 2 years, but now it’s more like almost every month. Corals need at least 10-15 years to fully recover from a bleaching event, larger reefs need decades even.
The largest reef system in the world, the Great Barrier Reef, isn’t ‘dead’ but very sick. The 1,600 mile stretch of corals had two bleaching events back to back in 2016 and 2017 for the first time ever recorded in history. It killed about two-thirds of the coral along one stretch of the reef. Humans are one of the main causes for these bleaching events. Overfishing, destructive fishing that damages reefs, changing ocean chemistry with fertilizers, introducing invasive species such as lionfish and plastic microparticle pollution are proving to be increasing threats. Plastic particles especially. They're toxic and deprive the coral of light and oxygen, suffocating it. The corals have an 89 percent chance of becoming diseased when they’ve come in contact with plastic. It has been reported recently that by 2050 there may be more plastic in the ocean than there are fish.
These coral reef ecosystems are not only beautiful while simultaneously supporting a great degree of diversity, they also hold a lot of value to humans. They are worth around 172 billion dollars per year by providing food, protecting shorelines, providing jobs biased on tourism, and medicines. Conservation relies on knowledge and slowing harmful practices. You wouldn't like it if someone gave you the flu every month, neither do the corals.