Coral reefs are part of ancient underwater longevity forests that create more important ecological communities than we realize. The merit of these colorful structures is really given by some very small animals that live all together and are commonly called corals.
They form a kind of skeleton that over hundreds and hundreds of years is deposited in the funds and grows from generation to generation. In this way, those typical underwater landscapes so recommendable to visit, the reefs, are created.
The areas where the reefs are located are known as the underwater rainforests, since a truly amazing amount of marine life congregates there.
Coral reef, on one of the islands between Lombok and Komodo. Indonesia.
The Underwater Amazon
The reefs are like real underwater forests where a lot of different species meet. Some seek refuge in them for their entire lives and make them their home. Others use them as a passage zone forming an important part of their life cycle, for example to feed or reproduce.
The origin of these majestic natural infrastructures is found in those small animals that resemble flowers and that are capable of captivating anyone who discovers their existence.
And the interesting thing about them is that they are interconnected, which makes them a huge living structure. That’s why it’s said to be the only living structure visible from the moon.
The Great Barrier Reef off the coast of Queensland, Australia, is said to be visible from the moon.
And… what is a coral?
If you immerse yourself in the life of these little sea creatures you will discover why they are so special.
Its appearance simulates that of flowers, but it also releases gametes into the water, just as flowers release pollen into the wind.
This is not their only way of spreading, they are also capable of forming two new individuals from the fragmentation of a previous one. Certain evolutionary advantages like these have allowed them to get this far.
Behind their spectacular colors and diverse forms, they are actually a group of animals called polyps, all the same.
Each one of them with its tentacles, without heart, without lungs, without gonads, but capable of coordinating to do exactly the same as any other animal: to feed, to breathe, to relate to its environment and to reproduce.
These small animals – the polyps – by living in groups of hundreds and even thousands that are genetically identical, form a colony and together they are known as coral.
They are invertebrate animals, that is, they lack an internal articulated skeleton. They belong to that great Phylum of the Cnidarians, to this group also belong the jellyfish or the anemones, so that you can have an idea. And of course, hence the similarity.
Xenia or Coral Pom Pom, belongs to the soft corals. It serves as an example of the shape of a polyp.
These animals exhibit a wide range of shapes, colors, and sizes, but all share the same common characteristic which is a bunch of stinging tentacles surrounding a mouth.
They are animals apparently and relatively simple, but I warn you that even the greatest coral expert may have difficulty in identifying them, as these creatures can vary their coloration and shape depending on the environment around them and their environmental conditions.
They’re real living fossils!
These animals have been on Earth for more than 200 million years with hardly any major changes. We, the so-called Homo sapiens, began to form the culture that would be called history only about 70,000 years ago, and only 12,000 years ago we began to settle. Thousands of years compared to the millions of years they’ve been here.
Corals have always been able to adapt to the environmental conditions around them.
It is said that the most unique characteristic of them is the highly evolved relationship of symbiosis with unicellular algae, which most of them host in their bodies.
The polyps and this single-celled algae, called Zooxanthellae, have created a mutually beneficial relationship. So they share space, exchange gases and nutrients to survive.
Algae need light to carry out photosynthesis, which is why light is so important for corals, even competing for space on the sea floor.
There are slow-motion battles down there we haven’t even noticed. Just as we haven’t come to perceive which is the melody that leads them to make delicate movements beyond the sound of the currents.
Competition for space in search of light. More than 10 different species of coral can be counted in just one photo.
They really have a worldwide distribution, although the tropical coastal areas are where their greatest abundance is found.
Without this algae that lives in the tissues of the polyp, tropical corals would grow too slowly, would be transparent and could not create that calcium carbonate protection and, ultimately, the reefs would never have existed.
Although there are many other corals that do not have this strong symbiotic relationship with algae and can live in deeper waters, and even at lower temperatures. But of course, in a lonely way.
It’s interesting to know that not all corals form reefs
There is such a variety of different species that sometimes divers pass by them without noticing their presence. Some of them are often confused with anemones, bubble mounds or flowers because of their similarity.
When you begin to investigate the subject you realize that their wide variety does not make them so easily recognized. In fact, there are so many different species that any scientific expedition ends up identifying a new one.
The simplest classification would be the one known to divide corals into soft and hard corals, depending on whether they have a skeleton or not. This is not really a scientific division, but it helps to explain how they are classified.
Soft corals would be sea fans, feathers and sea whips…
Alcyonaria. Dendronephthya. Soft coral near the island of Flores in Indonesia.
Mind-blowing organisms to be found underwater, but if you don’t know them your eyes won’t identify them. They do not have a calcareous skeleton and they look fleshy.
In addition, it is interesting to know them since many of them have a high concentration of toxins that they use to defend themselves from their predators. That’s why it’s important to know that you should never touch anything underwater, especially if you don’t know what it is.
It is always advisable to go with someone you know, because an underwater visit can be a thousand times more interesting.
Within hard corals, they are divided according to whether they have long or short tentacles. They are more impressive in terms of size, as they include the main reef builders, who belong to the order Scleratinia. They are special and important because their polyps have the ability to secrete calcium carbonate from the water.
Their feeding habits are also varied, hence their survival success. They usually combine the nutrients they get from the algae with active hunting of suspended particles. To do this, they use their tentacles where there are some organelles called nematocysts that, at the slightest touch, launch some harpoon-shaped filaments. And well, sometimes some people inject toxins, hence the reputation that they are somewhat stinging.
Infinity of corals of different species, forming underwater forests.
They form a tiny part of the ocean’s surface and are home to 25% of the ocean’s biodiversity.
Its importance is extremely essential. Without them, a quarter of the ocean’s biodiversity would not be sustained. It wouldn’t exist. It would disappear. So the loss of the reefs would put the survival of other species at risk.
Let us remember that we feed on many of these species that are bred or found there, with the consequences that this entails for our well-being. So…
What is a coral for?
We humans have that peculiar habit of thinking that in nature everything is created for our service. And that is why when we talk about what a coral is for, we only want to know what it is useful for us.
Indeed, this would be a small part of what their importance to the balance of life in the oceans actually means. In short, they are the basis of many ecosystems and marine life.
And as far as humans are concerned, I have to say that the structure of many of them, being located a few metres from the coast, as on the islands, serves as a kind of protection. They are built as a natural barrier that reduces the energy of the waves, often preventing disasters or material losses.
Around the coral structures, a lot of marine life is always found. Redang Island, Malaysia.
They’re real nurseries! They serve as home and hideout for a wide variety of marine animals, both large and those tiny ones that go unnoticed to our eyes.
In addition, reefs are like history books, as their calcium carbonate skeletons contain bands, like tree rings, which can tell us about the environmental changes they have witnessed. For scientists, these records are extremely useful, as they speak of times when we humans were not on Earth.
If the corals did not exist, the sand that forms on the seabed and ends up creating these paradisiacal places on tropical islands would not exist either.
It is actually a whole process involving many other organisms such as fish, sea worms, and even turtles. But to sum up, think about the parrot fish that has the habit of crushing corals. They obtain their food by digesting the living tissue of the corals and spitting out the remains of the hard skeleton. Those tiny fragments will be part of the sand. So you can say that they are part of the origin of the sand on the beaches.
And the most important thing, something that is not visible but is essential for our life, is that they produce oxygen and, in addition, they absorb CO2 thanks to those algae that live with them. Just like the rainforests.
And like the rainforests, they are subject to the threats of human activities.
Rising temperatures, fishing pressure and habitat destruction are some of the factors that are threatening them. The corals, incapable of protecting themselves or fleeing before our presence, only have to hurry to be able to adapt in time to the changes we are subjecting our world to.
Something they hadn’t had to face in their many years of existence.
So I recommend that when you visit these places, you enjoy to the maximum the satisfaction that it causes in our mind to contemplate the beauty of these creatures and also remember, that thanks to them, the ocean is kept in harmony.
The Natural Route, by María Marcos