As coral populations rapidly decline, scientists are racing to find the most efficient methods of restoration while being cost savvy. Scientist have used everything floating farms to full submersible statues. Not only do reefs provide ecosystem services that benefit humans, but they are also a hotspot for other marine life. Even though corals occupy only 1% of the ocean floor, they support 25% of all marine life! Because of this amazing biodiversity, it is no surprise that they are a large ecotourism attraction According to the World Resources Institute, coral reefs bring in almost 30 billion dollars annually.
Humans also directly benefit from coral reefs. Reefs act as a wave barrier and protect shorelines from erosion. Reefs reduce wave energy by 97%, by breaking up large waves that could destroy coastal communities. Coral reefs 40% of the world live with 60 mile of the ocean, many of which benefit from reefs. We should conserve foundation species not only for their intrinsic value, but also because of their ecosystem services and economic benefit.
But what exactly is a coral reef? Often we think of pristine bright corals and tropical fish darting in and out of rocks. While this may be a snapshot image, at a detailed level it can get much more complicated. Technically, only hard corals are considered to be reef building corals, soft corals perform other ecosystem tasks, but alone do not constitute a reef. Corals are made up of a calcareous skeleton, with polyps that use sticky tentacles to feed. But corals have a secret
super power for additional help. Inside their tentacles are small photosynthetic unicellular organisms called zooxanthellae. Corals act as a hotel for zooxanthellae; in exchange for a place to live, the zooxanthellae will pay the coral back in nitrogen, an element that can be hard to come by in the ocean. Zooxanthellae
are what give corals their beautiful colors, like their terrestrial counterparts, plants, zooxanthellae use pigments to photosynthesis. While they may look more like plants than animals, there is more than what meets the eye. These foundational species are beautiful in their own right, but as climate change continues these ecosystems and
their services may be at risk.
Corals are just one species that are affected by climate change. Many organisms are sensitive to subtle change in the environment. For corals, rising temperatures and acidity are the leading issues that affect corals. When a coral is thermally stressed it can expel the zooxanthellae inside. Without the zooxanthellae, corals turn stark white, a process that is aptly called a bleaching event. After a bleaching event, there is a chance that the coral could survive by recruiting a new host of zooxanthellae. However, prolonged bad conditions can result in the death of a coral. Eventually, the coral can be overgrown by algae.
Unfortunately, bleaching is just one threat to corals. Another byproduct of climate change, ocean acidification, is also jeopardizing coral health. Ocean acidification, OA, occurs when carbon dioxide, CO2, interacts with the surface of the water and dissolves, raising the overall acidity of the ocean. Since the Industrial Revolution 250 years ago, CO2 levels have been building up at alarming rates, increasing the greenhouse effect. Gasses, like CO2, are trapped in the atmosphere and reflect solar heat and warm the atmosphere, creating a ‘greenhouse’ around the earth. Although vegetation absorbs some of the atmospheric CO2 during photosynthesis, most of the CO2 is sequestered into the ocean. In fact, , the ocean sequesters 30-40% of human caused CO2, which accounts to 525 billion tons since the industrial revolution!
At the dawn of marine chemical research, scientists believed that the ocean’s buffering ability had no limit or consequence. But over time and through new research, scientists realize that the ocean is acting as a safety net, but we’re nearing the max. Today, scientists use modeling software to predict the oceans chemistry if CO2 levels continue to rise and are concerned about secondary effects of rising CO2. The more difficult task is predicting how organisms like corals will react to these chemical changes.
When a CO2 molecule dissolves it reacts with a water molecule to create carbonic acid. Carbonic acid can further dissociate by removing hydrogen atoms. It is the addition of the hydrogen atoms which results in a lower pH, 1 being the most acidic, and 14 being the least. For example, a lemon has a pH around 2, and water is a neutral 7, currently, the ocean is around 7.6.
Because corals need a specific pH to grow, that is certain concentrations of carbonate, corals are at high risk as humans continue to increase CO2 levels. Future predictions of the ocean chemistry suggest that the ocean could be at a pH of 8! While a jump in acidity from say a pH of 8 to a pH of 7.6 may not seem significant, pH is measured on a log scale. This means that even a small increase or decrease actually has much larger implications. While the chemistry can get complicated, the take home is that as oceans become more acidic the harder it is for animals like corals to grow and maintain their structure.
Other circumstances, like warming water, pose additional threat to corals, adding to the rapid decrease in coral abundances. Because pH is directly related to carbon emissions by humans, widespread and long-term adjustments in policy need to be made to halt worsening conditions. However projects like the Green New Deal are a far way off. In the meantime there is a tremendous effort by scientists to find ways to restore corals reefs after extreme bleaching events.
The standard way of restoring reefs is through direct transplantation. Scientists harvest little pieces of healthy coral, and then glue it to an affected reef. Unfortunately, this process only works well with fast growing corals like staghorn corals. However many of the structural corals are slow growing corals, crusting corals. To increase the likelihood the transplant takes, scientists will sometimes grow them in nurseries until they are more established. Using floating tables of corals, scuba divers can tend to them in underground farms! Because these in situ nurseries are floating mechanisms, it limits predator access. It also allows for scientists to clear off pesky algae which can shade and kill small corals.
This process isn’t without its flaws, it can be slow growing while farming corals, new research suggests that microfragmenting may be the way to go. This process breaks up corals into tiny pieces using an electric saw into pieces about the size of a dime and gluing them together in a kind of mosaic. It’s important that each mosaic is made up of the same individual, or you might have a coral war on your hands. Corals are able to sense if their neighbor is a friend of foe, and in the world of a coral, space can be limited, so it’s advantageous to be territorial. Corals can undergo warfare using nematocysts, small venomous harpoons, to impale and sting their enemies. But if it is genetically the same individual, they recognize themselves and will eventually fuse together.
Scientists have dialed down how to get corals to repopulate well, but often times these methods are time consuming and costly, making it extremely hard to scale up. For areas like the Great Barrier Reef, which is over XX miles, that have undergone large bleaching events, current methods may not be sufficient enough. Scaling up restoration projects is on the forefront of coral research. The science community isn’t the only community involved. Through collaboration with researchers in the field, artists like Jason deCaires Taylor
combine their art to make living sculptures. The porous cement is a great substrate for swimming coral larva, a planula larva, to latch onto and grow.
The science community is not the only group concerned about reefs. Because coral reefs bring so much money to the tourist economy, there is some talk of insuring coral reefs. Hotels and waterfronts can take out an insurance policy for the reefs that run along their establishments. The hope is to link ecosystem services to a concrete value. In the event that a reef is damaged, companies can cash in on their insurance policies to repair the reef. While this may have good intentions, there is worry that this pushes the boundary of ownership. Although large hotels and companies may be able to afford these insurance policies, many coastal communities do not. Rather this could add to the economic disparities that affect island communities.
While these methods are indeed promising and exciting, it is important to not lose sight of the real culprit. CO2 emissions. Researches may argue about the best way to restore a reef, but all experts agree that the problem is much larger. Repairing a reef is dealing with the symptom of a greater issue. Decreasing emissions in a goal that many countries are making. While the right policy steps can take a long time, we can do our own part by opting to bike to work, or take public transport.
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