Coral reefs are among the richest ecosystems on our planet. Covering approximately 284,300 kilometres squared, these reefs occupy less than 0.2% of the ocean’s surface, while still providing a home to almost a quarter of the fish species worldwide. Often, they are referred to as the ‘Rainforests of the Oceans’. |
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What is a Coral Reef?
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A Coral Reef is made up of millions of small animals living in colonies called Coral Polyps. During mating season, coral polyps release eggs and sperm into the water, which come together and combine to form Larva. This ‘Baby Coral’ looks like a jellyfish and floats in the water until it finds a place to which it can attach itself. After landing, the Larva builds itself a limestone shell, shaped like a round vase and the coral polyp lives inside. The Polyp is nocturnal and at night, it will stick its tentacles out of the shell to catch and feed on passing plankton.
When the Polyp dies, it leaves a hard branching Limestone structure to which more coral polyps can attach and the reef continues to grow, providing shelter for many species of aquatic life including fish, turtles, sponges and starfish. |
The optimum conditions for the coral reefs are; shallow, sunny clear waters, preferably salt, where the temperature is maintained between 20 and 30 degrees centigrade. There are exceptions. For example, there are reefs in the Persian Gulf which have adapted to the temperatures in that region (13 degrees centigrade in the winter and 38 degrees centigrade in the summer). Also, deep water coral can exist at greater depths and colder temperatures and can form reefs but very little is known about them.
There are two types of coral; hard and soft. Hard coral is the kind described above. It has the hard limestone skeletons and forms the basis of the reefs.
Soft corals, although animals, appear to be more like underwater plants. They still secrete limestone like hard corals and this gives them the needed support to gain their vertical structure. However, their inner core is comprised of Gorgonic protein. This is a flexible, fibrous wood like protein that allows the coral to flex with the waves.
Coral Reefs can grow up to 1 centimetre/ half an inch each year, but much of this is eroded by waves and boring organisms that make their homes on the reef so the growth rate seen is usually a couple of millimetres per year. If left undisturbed, they can grow quite large. |
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Why are Coral Reefs Important?
As stated before the reefs provide shelter for almost 25% of the world’s aquatic life. Without these coral reefs, the fish would be homeless with nowhere to breed and the balance of life in the oceans would be upset.
It is not only the fish and aquatic life that are protected by the coral reefs. The Barrier Reefs that tend to form between shallow and deeper waters also protect us on land. As the waves come in to shore from the oceans, the reefs act as a barrier, slowing the currents and waves and limiting coastal erosion. Equally, the reef benefits, as the breaking wave clean the surfaces of the reef and remove sediment and waste.
We are also finding new vaccines and medicines created from the organisms that live on our coral reefs. This means if we do not protect our reefs, we may lose valuable medical resources for our future.
 Zooxanthellae in Soft Coral
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A big problem in today’s society is the abundance of Carbon Dioxide in our atmospheres and waters and coral reefs have a role to play in this too. The Coral polyps live symbiotically (a mutually beneficial relationship) with a single celled algae called, zooxanthellae. Through a process known as photosynthesis, the Algae absorbs Carbon Dioxide and other waste products and releases Oxygen and other nutrients required by the Coral Polyp. In return, the coral polyp uses the Oxygen and nutrients and releases Carbon Dioxide and other waste products that the Algae needs for photosynthesis. |
The reason that these reefs are able, not only to survive, but to thrive in nutrient poor habitats is the diversity of species that occupy the nooks and crannies of the reef, each with their own complex food chains which efficiently recycle essential nutrients in similar ways to the coral polyps and algae. However, this also means that our reefs are susceptible to any process that can upset this balance.
The sensitivity of our reefs to climate and other external forces makes them an excellent early warning system for all other ecosystems on the Earth. They are the ‘canary in the mineshaft’, that gives us an indication towards the health of the planet.
According to the National Oceanic and Atmospheric Association, nearly 500 million people worldwide have some level of dependency on coral reefs, as food, income or coastal protection.30 million of those are completely dependent on the reefs as their livelihood or the land they live on (Atolls). Global DIVERSITAS biodiversity conference in Capetown, 2009 estimates the worldwide value of Coral reefs to be approximately $172Billion US.
So, if the health of our coral reefs gives an indication of our planet’s health, what is the diagnosis?
The answer is not good. Studies have shown that 10% of the world’s reefs have already been destroyed, while 58% are currently at risk. In the Philippines, where there is a high concentration of coral reefs, 70% have been destroyed and only 5% are in a good condition.
Natural threats to our coral reefs have always been present. For example, population explosions of crown of thorn starfish, which prey upon coral polyps, can cause natural stresses. Also, other factors such as earthquakes, storms and hurricanes can devastate the reefs which can take decades to recover. |
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Currently, the biggest threat that coral reefs have to face is HUMANS. There are a number of ways that we are destroying our reefs and it is imperative that we find ways to limit and reverse the damage being done.
Firstly, inexcusable damage is caused through negligence and ignorance. Swimmers and divers touching and handling coral, breaking pieces off the reef to keep as a memento of a great holiday can damage the ecosystem. Equally boats and anchors, if care is not taken, can do much harm.
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Overfishing and using harmful fishing techniques also takes its toll on the coral reefs. Overfishing, for food or for aquariums, upsets the balance of the complex food chains, leaving some life (predators) to perish through lack of food and others, the prey to flourish. The effect of removing certain species is visible on multiple trophic levels
Although mentioned earlier that coral polyps have a symbiotic relationship with zooxanthellae, there are other types of algae which can be detrimental. Fish usually eat these harmful algae but when an area is overfished and the populations dwindle, the algae can thrive, growing on the surface of the coral, blocking sunlight and nutrients and killing the coral. |
The Fishing techniques used in some regions are also a problem. Some fishermen trawl and dredge the bottom, snagging their nets on the reefs and breaking it. Equally damaging methods of fishing include; explosives (for obvious reasons) and cyanide fishing. When the fishermen drop cyanide into the seas, the fish become stunned and slow. This makes it easier to catch them. However, the toxins are damaging to the environment and the fishermen often have no qualms about ripping open the reef with a crow bar to get to that fish that is hiding in there.
Land based Pollution is another big factor in the destruction of our coral reefs. This includes the use of fertilisers and pesticides along with other by-products of land based activities, including pollutants and sediments, which are transported in surface waters, run-off, and atmospheric deposition into the coastal waters leading to disease and death. The resulting excess nutrients and turbidity of the water promotes seaweed and algae growth, which in turn, destroys the coral. Deforestation and the resulting soil erosion, along with the lack of tertiary treatment for sewage are also contributing factors.
Finally, the most commonly known threat facing our coral reefs is climate change. As we have previously discussed, the coral are highly sensitive to the environment and the changes that are occurring in the oceans. Climate change and global warming caused, mainly by industry, is leading to the sea temperatures climbing and the acidification of our oceans. A change of just 1 degree can have dire consequences to the health of our coral reefs but scientists believe that if the current trend of warming continues, there is a strong possibility of a rise in sea temperatures of 4 degrees centigrade by the end of this century. This poses a very serious problem.
The increase in water temperatures can promote the growth of the harmful algae on top of the coral. The symbiotic algae, therefore, can no longer photosynthesise due to the light from the sun being blocked. This causes the symbiotic algae to leave the coral or to die and since it is the algae that give the coral its colour, we see a phenomenon known as CORAL BLEACHING.
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Simply put, the limestone shell can now be seen white through the transparent coral bodies. In extreme events, almost all the corals in the reef could die. Any survivors can take up to 10 months to recover and regain normal colour and growth but during this time, they are starving and unable to grow or reproduce.
The added carbon Dioxide also contributes to the acidification of our oceans. Approximately one third of this excess gas is absorbed into the seas, reducing its pH (scale used to measure acidity or alkalinity). The Oceans have a natural buffer to protect against this but to maintain a neutral pH requires using the Carbonate ions that would normally be used for limestone production. This means that the coral no longer has the tools to produce limestone needed for its shell and its growth is stunted.
What can we do to limit the damage?
We can reduce our emissions now but scientists suggest that the excess carbon Dioxide levels already in the atmosphere will continue to change the Earth’s climate over the course of this century. However, limits must be set now to limit future irreparable damage and runaway global warming similar to the Eocene period when all the ice at the poles disappeared.
There are many international legislation and policies being implemented to try and slow the rate of global warming. The Kyoto Protocol sets emission limits for the world’s economically developed nations. It has been suggested that the Carbon dioxide levels must be capped at 450 parts per million (ppm).
One method of sustaining the 450ppm limit is to allocate everyone an equal Carbon Footprint. Currently, the Carbon footprint is approximately 4 tonnes per person but to stay within the suggested limits, this would have to drop to 2 tonnes per person, possibly falling to 1.5 tonnes depending on the population increases. This should mean the temperature increase this century would be approximately 2 degrees centigrade, which is considered to be the level of temperature increase we would have reached without the industrial revolution. However, some scientists believe that coral reefs are not likely to survive unless the carbon dioxide emissions drop below 350ppm.
There are some steps that everyone can take to reduce their carbon footprint and protect the coral reefs and our planet.
Firstly, be knowledgeable. Ask questions and be informed as a consumer. If you own an aquarium, make sure the fish you have are from a sustainable source and check what method of collection is used. Equally, when eating sea food at a restaurant or from a supermarket, ensure that you are not eating endangered species and that the food is from a sustainable source in a method that is safe for the corals and other aquatic life (no by-catching).
Even if you live a long way from the ocean, avoid using chemically enhanced pesticides and fertilisers as these products often end up in the waters of rivers and run off and heading into the oceans to destroy the coral. Garbage and waste products on the beach and near the water can lead to similar problems so keep it clean and don’t litter.
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Recycling is available in most countries now, so take advantage of the recycling stations in your area.
Conserve water. Not only will you see a drop in your bills but the less water you use, the fewer run-offs and the less water finds its way back into the oceans carrying waste, chemicals and other detrimental by-products.
Of course, let us not forget, the simplest forms of protecting our reefs and environment. Limit the use of cars and vehicles by walking, running or riding a bike. It will keep you fit too. |
If you have a garden or a window box, plant trees, bushes and plants, which contribute to the fight against global warming through photosynthesis of carbon dioxide.
When buying food, look for local produce with minimum packaging and processing to maintain a low carbon diet.
For electronics, the energy star labels depict a low energy usage machine and be sure to turn electronics off when they are not in use. Even items left in standby mode use a lot of energy for no reason.
Support your conservation organisations such as project aware and reef aware and visit local reef friendly businesses. If you are visiting reefs, use a guide. Not only will you have the inside track on the area but they can assist you with information about moorings etc so you do not inadvertently damage the reefs. Also, if you go snorkelling over coral reefs, use a floatation device so that if you do get tired while swimming, you can simply float rather than standing on and killing the coral. As a diver, do not touch anything, leave only bubbles and stay off the bottom to prevent stirred up sediment from smothering the coral. Follow all the guidelines, regulations and customs. We must try and limit the external stresses on these bio-diverse ecosystems and reduce the changes to a rate within which, the reefs have the capacity to adapt.
These are all small steps in the fight to keep our planet healthy and they are very easy to implement in everyday life but if every single person took these actions on a daily basis, our world and in particular, our coral reefs would be in much better shape.
