Coral reefs only occupy 0,07% of the ocean floor, yet they are the oldest and most productive ecosystem in the ocean. They are breeding grounds and home to more than 25% of all marine species. These vital ecosystems are facing serious threats causing them to degrade faster than they can rebuild. This blog will explain some of the reasons why and provide useful information on how you can help to conserve coral.
Have you ever questioned yourself what coral really is? Maybe you imagine corals as underwater forests or simply as rocks providing shelter for aquatic life. That would be partly correct, partly a big misconception which sadly causes some people to have a damaging behaviour towards reefs. In truth, corals are a unique and fascinating mix of animal, plant and mineral. They are actually relatives of jellyfish and sea anemones, and their evolution clearly places them in the category of animals.
The animal parts of corals are called polyps. Polyps are able to build mineral skeletons by secreting calcium carbonate. Some corals, like the mushroom coral, exist of only one polyp but most corals make colonies. Colonies develop asexually, meaning that all the small polyps making up a big coral are clones.
Hot-spots of life and energy
Coral reefs are life-giving environments. They provide a base of energy for other species in the reef community to thrive, in otherwise very nutrient-poor areas. Energy is generally produced in two different ways; food capture and photosynthesis.
Food capture; Corals; Corals are extremely sufficient predators. The polyp has a central opening which is surrounded by tentacles tipped with stinging cells.
These are called nematocysts and they are used to capture plankton from the surrounding seawater.
Photosynthesis (primary production); The polyps live in a mutualistic symbiosis with a small plant cell called zooxanthellae, which gives the corals their beautiful colour.
These small dinoflagellates use photosynthesis, using sunlight to produce sugars and oxygen. The sugar feeds the polyp and in return zoox has safe place to live, inside the polyps’ tissue.
The Zooxanthellae are an essential key factor in coral reefs health, as the photosynthesis raises corals growth-rate up to 10 times.
The importance of diversity
So reefs are the hot-spots of life in the ocean and a key factor for the oceanic ecosystem. This high concentration of life leads to a constant competition for space which keeps the reef diverse. The slow growing massive coral will for example detect when the faster growing branching coral gets too close, and the massive coral will eat a piece of its competitor, in order to keep its territory. Some aquatic species are consuming coral but at the same time they also remove algae which would otherwise overgrow the reef. These very important species are called grazers and include sea urchins, damselfish, surgeonfish and parrotfish. Other species, like sharks, prey on smaller fish, keeping the different populations on the reef in balance. Every species on the reef fulfil its role and if one is diminished, it will have consequences.
Once, people believed that reefs were characterized by stability and consistency. Now we know that it is rather natural disturbances from things like wave activity or predators that keep reefs healthy, diverse and balanced. Basically, the higher the diversity is, the stronger the ecosystem is. Food chains in the sea are generally longer and more complex than the ones for terrestrial life. Changing one level can quickly create an unbalance in the whole ecosystem. An example of this is found in Jamaica where sea urchins and parrotfish became extinct in one area. Consequently, algae overgrew and killed the whole reef. Or take for example fish feeding; when fish are fed by people, they no longer carry out their important role of cleaning the coral.
One thing is feeding, another is killing. 98-99% of the energy produced (primary production) on reefs, is consumed again by the reef community itself. Therefore, reefs are basically closed systems that very quickly will collapse if energy goes lost; for example due to fishing. It is a bit of a scary paradox, that at many dive destinations, you can have reef fish served at your table every night. Especially industrial fishing has shown to be a bigger threat to reefs than first imagined, as it results in species declining faster than they can reproduce. In 55 years, humans have managed to wipe out 90% of the ocean’s top predators. These include different species of sharks, Bluefin tuna, swordfish, marlin and King maquerel. From the earlier explained reef ecology, it should now be clear that a decline in species can have disastrous effects on coral reefs ecological balance.
As 40% of what is fished in the sea is ground up into pellets, to feed terrestrial animals, eating meat is indirectly consuming fish. As crazy as it may sound, cows, pigs and chickens have become the main oceanic predators. Furthermore, nutrient-loaded runoff from terrestrial animal farming, especially cattle, have created huge dead zones in our ocean.
Talking about pollution; as most products we use will one day end up in the sea, choose natural products rather than chemical ones. This is especially true for sunscreen as the chemical type is directly harmful to the reef. Plastic pollution poses a big threat to aquatic wildlife. Species like turtles and whales are often found dead due to plastic within their digestive system.
In addition to the importance of diversity, coral reefs also live within the extremes of their environment. This is mainly in relation to salinity, temperature and sedimentation. Are any of these factors changed, corals will be affected immediately. This is unfortunately happening right now, and the main reason is human-caused stress. An estimated 70%-90% of the worlds coral reefs could be dead by 2025 and as you are reading this 10% are already degraded beyond recovery. It is shown that human activity has significantly destroyed reefs in 93 out of the 109 countries where they occurred.
The meat and fishing industries are the leading producers of greenhouse gases causing global warming. Global warming causes reefs to be stressed because of rising water temperatures. Stressed coral will expel zoox, phenomena also called coral bleaching. Without the energy production from zoox, coral will slow its growth-rate, making it even more vulnerable to degradation.
Ambassadors of the Ocean
As an eco-dive centre, The Adventure Club have focus on responsible dive practices minimizing environmental impact and is in addition also participating in a Coral Nursery– and Artificial Reef project. Divers are said to be the underwater ambassadors, and dive activity is not what is causing the real damage to the worlds coral reefs. When that said, corals are very delicate and touch from humans has the potential to kill them, so it is important to be an aware and respectful diver. Corals produce a protective layer of mucus which helps them to avoid sedimentation. Mucus is easily removed from corals and it requires a great deal of energy to reproduce. Kicking up sand is similarly damaging if the sand ends up on corals, so good buoyancy and a horizontal position is a must for a good diver. Continuously train your skills and remember to refresh them whenever needed.
Knowledge and awareness are equally important. If we as divers do not understand the world that we observe, we can cause undesired damage to what we love. Learning more about the underwater realm will enable you, as a diver, to act in the least harmful way based on awareness and understanding. This can be gained by doing your Naturalist and Aware fish-ID courses as part of you PADI Advanced Open Water Diver Course.
Least but not last is our attitude. Being an experienced and aware diver does not necessarily means being a non-destructive diver. Some studies on Marine Resource Management found that experienced divers are just as likely to make contact with the reef as inexperienced divers. They tend to be less cautious about approaching the bottom and spend more time close to the reef, bumping into it as a result. Coming from terrestrial life and relating to that when we go diving, we often fail to intuitively make the distinction between what is alive and what is not. Keep in mind that on the reef, there is life everywhere, so you should generally keep a distance of approx. 1 meter to the bottom while diving, and never interact with marine life. Passive observation is the respectful way to dive.
It is our attitude towards the reef and how respectful we choose to be that matters. Training buoyancy and positioning will make this easier, but divers still need the right attitude and respect towards the reef and its community, to not cause damage by ignorant and careless behaviour.
If we want reefs to survive, it’s the whole ocean that we have to care for better than we do now. Take a step further and be a responsible diver/snorkeler out of the water as well.
You have power through your actions and there are plenty of things you can do to help corals; for example by limiting your use of plastic and chemical products.
As described, the key-factors causing coral reefs to degrade faster than they can rebuild include the fishing and meat industry. Together, they are responsible for ocean dead-zones, species decline or extinction and also main-contributors to global warming. Consequently, choosing a plant based diet is the most efficient way you can help to conserve our precious ocean and its coral reefs.