Coral Bleaching: A Death that is not as Black and White as it seems by: Arianna Bowley
Tital image: A before and after image of coral bleaching and later dying in March / May 2016, at Lizard Island on the Great Barrier Reef, captured by The Ocean Agency / XL Catlin Seaview Survey / Richard Vevers & Christophe Bailhache.
A Closer Look A coral structure consists of many individual animals that are the size of an ant, these are called polyps. Polyps are closely related to jellyfish and are extremely small benthic marine animals that feed using stinging tentacles. These polyps form colonies that when put together, construct a calcium carbonate structure for protection; they live stationary here for the rest of their life. When looking at coral the structure of calcium carbonate is what we really see and the soft bodied polyps live inside of it. (Trujillo https://www.dkfindout.com/uk/animals-and-nature/jellyfish-corals-and-anemones/corals/
Coral is a unique animal because it is able to adapt in many different environments. According to NOAA not all species of coral are found in shallow, warm costal water. It has been discovered that over half of the known corals live “…in deep, dark waters where temperatures range from 4-12° C…” and these can be found all over the world. The coral that live here have no sunlight and live off of the food that drifts by them. Like shallow water coral, they also provide a diverse environment for organisms to live in. Deep water coral are some of the oldest animals known on earth and date back thousands of years. Despite how long they have been here, there is very little documented about these coral. (NOAA) The more commonly known coral are the types that form reefs. They are found in tropical, warm water which typically has low productivity and is hard for organisms to survive there. However, coral reefs thrive in tropical water and that is due to their symbiotic relationship with photosynthetic algae called zooxanthellae. This relationship is what allows coral reefs to thrive in their warm environments. The zooxanthellae live inside the tissue of coral where it is protected and able to freely photosynthesis. In return the zooxanthellae produce oxygen and chemicals to make the coral’s protective calcium carbonate structure. This accounts for why some corals have vibrant colors. The NOAA Ocean Service Education says that “…as much as 90 percent of the organic material photosynthetically produced by the zooxanthellae is transferred to the host coral tissue.” This is why coral reefs need to be in clear water so zooxanthellae can constantly provide energy. Even though the water coral reefs are in have low productivity they are considered one of the most productive and diverse marine environments. (Zooxanthellae) Besides the mutually beneficial relationship coral and zooxanthellae share, there are a few factors needed to form a reef. First and foremost, coral is very temperature sensitive and needs water that is an average of 18°C (64°F) throughout the year, which is mainly in the topics. They also need a strong and constantly supply of sunlight to feed the zooxanthellae that live inside of them. The water surrounding them must also be clear so the sunlight can reach the zooxanthellae. Coral themselves do not necessarily need sunlight to live as the deep ocean coral has proven. The wave or current activity that surrounds the reef must be strong so that new nutrients and oxygen can be brought to the coral. Furthermore, coral will only grow in salt water; they would die in fresh water. The last thing a coral reef needs to thrive is a hard surface to attach to. Since coral are stationary animals that live in one place their entire, life they need a safe place to attach. (Trujillo) “Although coral reefs cover less than half of the ocean’s surface area, they are home to 25% of all marine species including almost a third of the worlds estimated 20,000 species of marine fish”( Trujillo). As many as a 500 million people depend on the reef for their job and food; some of these include tourism, fisheries or scientific research. People are naturally drawn to reefs for their beauty and the rich ecosystems they provide. A Short History of Coral Bleaching Coral bleaching is a process that causes coral to lose their coloration and turn white. This is a response to elevated water temperatures and causes conflict to the relationship they have with zooxanthellae. Coral and zooxanthellae cannot survive in water that exceeds 30°C (86°F). When temperatures become too hot zooxanthellae will die, become toxic in the coral and have to be flushed out. The coral cannot live without the zooxanthellae’s nutrients and if it is not replenished in the coral, they will eventually die. This process can happen overnight or over several weeks. (Trujillo) This phenomenon is something that has only been mass recorded starting in the 80s. The warming of oceanic water during an El Niño can cause coral to bleach. The El Niño event from 1997-1998 raised water temperatures many degrees and has been blamed for the most worldwide coral bleaching event recorded in history; killing 16% of the world’s coral. El Niño’s have been recorded to cause coral bleaching all throughout the 1900s. In the years 1982-1983, 70% of the corals across the Pacific Central America coast died due to coral bleaching. El Niño’s can cause severe coral bleaching depending on how much they warm up the ocean (Trujillo). A rise in sea temperature has been named as the most common factor to be responsible for large scale coral bleaching. Recovery from coral bleaching is extremely slow and will not happen if water temperatures continue to remain elevated. In the movie, “Chasing Coral,” they explained that in the last thirty years we have lost fifty percent of the world’s coral. It was confirmed that the early 1980s was the first mass bleaching event of coral and 2010 was the second. In the film they predicted that in about 25 years the average ocean temperature will rise too much for coral to survive and the entire class will disappear. The history of coral bleaching so far has been short and devastating. More bleaching events have been recorded in the past two years than any other times. In Australia, the Great Barrier Reef Suffered the worst bleaching even recorded between 2016 and 2017. It has been estimated that about half of its coral died due to bleaching. Mark Eakin, coordinator of Noaa’s coral reef watch program quotes, “At this point I’d say any El Niño, even moderate ones, will probably result in widespread, if not global, bleaching.” Coral reefs need between ten to fifteen years to recover and at the rate water temperatures are raising it may not happen. Besides bleaching coral reefs are destroyed by fishing, pollution from onshore chemicals and reduction in population size from human interference. (Slezak) Risk the Loss of an Entire Population or Reduce our Effect? It is known that if global temperatures continue to raise at their current rate the world population of coral reefs will eventually become extinct. The human population risks losing a multi-billion dollar industry and a provider for over 500 million people if nothing is done. Many scientific studies have proven that human-caused greenhouse gasses emissions have caused the overall planet temperature to rise. The ocean absorbs a majority of the heat in the atmosphere and has increased in temperature from bottom to top because of this. The global temperature rise that has impacted the ocean so much is called Global Warming. One suggestion to reduce the impact of the global warming is to remove the human caused greenhouse gasses and dispose of them elsewhere. The suggested location is to place it back into earth’s crust or into the deep ocean. The ocean already absorbs a third of the carbon dioxide in the air. The ocean acts as a “biological pump” and takes carbon dioxide from its surface and concentrates them into the deep sea floor. This theory would not work because too much carbon dioxide would increase the acidity in the ocean. If the ocean acidity was increased crustaceans would not be able to form their shells properly and coral would disintegrate. High levels of carbon dioxide also increase algae blooms which cause poisoning in shellfish and prevent other sea plants from receiving sunlight (Trujillo). Another theory to reduce carbon dioxide in atmosphere is the iron hypothesis. Oceanographer John Martin discovered that the areas of low productivity were also low in iron. In the 1980s he proposed that the regions of the ocean that are otherwise rich in nutrients but poor in iron be fertilized with iron and it would increase the productivity. By adding iron to the ocean it would stimulate the productivity of phytoplankton, who will remove carbon dioxide from the atmosphere through photosynthesis. His hypothesis was proven correct but has been studied in more depth over time and found that it is much more complicated than just adding iron. “James K. B. Bishop and Todd J. Wood of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory have measured the fate of carbon particles originating in plankton blooms in the Southern Ocean…” They have discovered that iron cannot just simply be added to high nutrient low productivity areas in the ocean. The phytoplankton would eventually become to abundant and the zooplankton, their predator, would not be able to keep up with the increase. It has been determined that adding iron to the ocean would have to be carefully observed constantly and the mixing of iron would need to be precise. In other words it is not a theory that is ready to be used on the entire ocean; it is also not healthy to have such a mass amount of iron wide spread for all species (Ocean Carbon). The iron would need to be used over areas of low productivity, that is mainly where coral grown. Dumping iron over coral reefs would cause numerous problems. The zooxanthellae would increase as well as phytoplankton and photosynthesis would become a competition. This would decrease coral nutrients and possibly cause bleaching. Iron in the coral would cause heavy metal poison to the animals that eat the coral and the sediment surrounding it. This would eventually come back to people since coral reefs feed mass amounts of the world population. Adding iron to the ocean is not a suggested theory at this time.
Do we have the moral ethics to restrain and rehabilitate In Kyoto, Japan on December 11, 1997 a protocol was made to help reduce carbon dioxide emissions. It was put into effect on February 16th, 2005. The Kyoto Protocol is an international agreement that has been made by the United Nations to help reduce climate change. The protocol “commits” the participating parties by setting emission limits and reduction targets. The protocol has commitment periods for countries to abide to and reduce their amount of carbon emissions. The first commitment period was from 2008 to 2012. The second commitment period started in 2013 and will end in 2020. The countries who have joined this protocol make up almost fifty percent of the world’s carbon dioxide emissions. This is one step forward in really reducing greenhouse gas emissions, but it is also a waiting period because the effects are not something seen immediately. (Kyoto Protocol) “With an annual global economic value of $375 billion, coral reefs provide food and resources for over 500 million people in 94 countries and territories.” (Losing Our Coral Reefs) Coral bleaching is the most prominent issue at the moment but there are so many other factors effecting coral at the moment as well. Overfishing, deep water trawling and aquarium harvesting are devastating coral fish populations. Pollution from land in forms of run off and chemical dumping cause algae blooms making zooxanthellae compete for photosynthesis. Coastal development and increased tourism disrupt the natural habitats of coral and stresses out the environment. Coral bleaching is not the only danger to completely wiping out their ecosystem and species. (Losing Our Coral Reefs) Conclusion In total it can be said that coral is a delicate and beautiful animal that needs to be protected. Through the intervention of human caused global warming and destruction one of the top wonders of the world, coral is being destroyed. The Great Barrier Reef, which can be seen from space, has lost half of its coral to bleaching in the past thirty years. The loss of coral would cause untold ecological damage to the ocean and it would cause a huge ecological shift in species within the ocean. People can make a difference individually as well as globally to help prevent this. If a massive change in decreasing carbon dioxide emission happens within the next few years the ocean temperature will only rise about 1°C. This could save a portion of the coral instead of taking it off the map for good. Reducing carbon emissions would require a great effort worldwide but it is something necessary to help our coral reefs survive.
Jeff Orlowski, director. Chasing Coal. Netflix, 2017.
“Kyoto Protocol.” United Nations Framework Convention on Climate Change. Kyoto Protocol, 30 May 2013, unfccc.int/kyoto_protocol/items/2830.php.
“Losing Our Coral Reefs.” State of the Planet, 3 Aug. 2011, blogs.ei.columbia.edu/2011/06/13/losing-our-coral-reefs/.
“NOAA Okeanos Explorer: Education: Deep-Sea Corals.” US Department of Commerce, National Oceanic and Atmospheric Administration. NOAA Ocean Explorer Podcast RSS, 11 Aug. 2014, oceanexplorer.noaa.gov/edu/themes/deep-sea-corals/welcome.html.
“Ocean Carbon: A Dent in the Iron Hypothesis | Berkeley Lab.” News Center, 6 May 2009, newscenter.lbl.gov/2009/05/06/ocean-carbon-iron/.