How are the coral reefs formed?

To understand how coral reefs are formed, we must first learn what a coral is.

Corals are living organisms that can be found in tropical warm waters (more than 20ºC), with high salt concentration. Together they form a massive calcareous structure which are known as reefs. They are the communities with the biggest and greatest biodiversity in the world.

These organisms live in a symbiotic relationship with an algae called Zooxantela, an unicellular algae capable of photosynthesis that is able to reproduce and live inside the coral tentacles. The corals ability of building their own calcium skeleton is because of this algae, it provides the necessary carbon. The corals are modular animals called polyps.

Soft Coral

Grupo de pólipos corales individuales que conforman una colonia

de corales pétreos. Crédito de la foto: Charles LoBue/EPA.

What’s a reef? 

The term reef refers to the biological use that is given to a three-dimensional structure that rises from the seabed. It has not been built exclusively by coral, but also by sponges, algae and marine worms.

What’s a coral reef?

The coral reef ecosystem consists of a group of corals that segregate rigid calcareous skeletons and live in colonies of the most diverse shapes and sizes that interact, along with other species, as a functional unit.

The coral reefs are one of the most productive and complex ecosystems in the world. In the entire reef structure, the living part of the reefs is a layer of one millimeter of tissue that is found on top of it, everything else is a skeleton that serves as habitat and food for other species.

The reef is the most diverse marine system. The coral reefs have so much diversity that are often compared to a tropical forest.

Coral Reef

The formation of coral reefs

The coral reefs of the tropical seas are a typical example, forming the greatest living community that populates the seas; built by tiny and primitive animals belonging to the group of coelenterates or Cnidaria known by the name of corals.
There are approximately 2,500 different species of coral that have the ability to extract calcium carbonate from seawater and make limestone skeletons from it for their own protection. As polyps multiply in one place and add layer upon layer of their calcareous skeletons, large reefs are formed inhabited by millions of animals and plant and animal organisms.

The coral reef being the most prosperous vital community known, it is home to the greatest wealth and variety of plant and animal creatures, ways of life and relationships of conduct.

By way of differentiation, it can be said that the coral is the one who builds the reef. Coral is the engineering species, it creates an environment and allows other species to live in it.

NOAA Coral Reef Conservation Program

What’s happening to the Corals?

Out of approximately 248,00 square kilometers of coral reef ecosystems around the world, a vast amount grows in the Americas. Specifically, Costa Rica has 970 kilometres of coral reef and together with Panama, Colombia and Ecuador they make up 1% of the world’s coral reef and 10% of America.

In the Caribbean coast, you can find coral reefs mostly in the south (from Limón to Manzanillo) and they grow better and in extensive areas than in the pacific coast. Cahuita has the most expressive area of coral reef (with a total of 5 km) that unfortunately in 2006 had its percentage of live coral reduced from 40% to 15%. The corals of Costa Rica are under a serious threat.

Drone photography by Juandi Gutierrez

What is killing our corals?

In general, the most common causes that have negative effects on the health and coral reefs survival are:

• Sedimentation.

• The contamination ( Fertilizers, hydrocarbons, pesticides, among others..)

• The excessive and unauthorized fishing.

• The fast coastal development without proper planning.

• Excessive tourism.

• Big storms, hurricanes, climate changes and other natural events.

• The excessively low tides that expose the upper part of the corals to air.

• Extreme saturation of carbon dioxide in the water that makes it more acidic.

• Fishing with with dynamite and cyanide.

•  Diseases of the corals itself.

•  The introduction of exotic species in the environment. Like the lionfish.

Lion Fish

What can we do to help with coral conservation?

• Save water: The less water you use, the less contaminated water ends up in the sea.

• Help reduce water contamination: Emissions from cars and industry contribute to the rise of oceans temperatures, which is the main cause of the fast coral.

• Use organic fertilizers: Chemical products travel through the rivers and subterranean water and end up contaminating the oceans, causing irreversible damage.

•  Recycle and use less plastic.

• Support organizations that have an active role on coral reef conservation.

• Plant a tree: Trees help prevent contaminated water and other elements from reaching the ocean. Also, you will be helping the planet on the climate change issue.

• Practice water sports with responsibility: Don’t touch the corals. Always try to reach an area with sand to walk on far from the reefs.

• Be active on beach cleaning: Every year there’s dozens of organizations that get together to collect trash from the beaches around here. Join and participate.

• Pressure the government to take action and create more protected areas to prevent ocean’s contamination. Let them know the importance of these incredible ecosystems and the need to protect them. Fight for our natural resources and support our natural reserves.

• Have an active voice on coral conservation: Share your causes with as many people as you can. People have to realize the importance coral reefs have on our ecosystems, there’s a lot of organisms depending on coral to live and a lot of biodiversity will be lost if we don’t do anything about it.

CORAL BLEACH

Corals are living organisms that can be found in tropical warm waters (more than 20ºC), with high salt concentration. Together they form a massive calcareous structure which are known as reefs.

The reefs are home to a large number of species of fish and invertebrates and together they constitute communities with the biggest and greatest biodiversity in the world.

These organisms live in a symbiotic relationship with an algae called Zooxantela, an unicellular algae capable of photosynthesis that is able to reproduce and live inside the coral tentacles. The corals ability of building their own calcium skeleton is because of this algae, it provides the necessary carbon. The corals are modular animals called polyps.

Unfortunately these incredible animals are under a serious and deadly threat in our oceans. THe corals are suffering from mass bleaching events that turn their vivid colors to white and the skeleton is exposed. This happens because the corals polyps get stressed and they end up expelling the algae, therefore losing their main food resource. A bleached coral is not a dead coral and can recover from it. However if the bleaching event keeps going until they are left out of nutrients to survive they can die.

Why are bleaching events happening?

• Rising ocean temperatures

Because of climate change, the water temperatures are rising at an alarming rate. And this is the main reason why corals from all over the world are turning white. 

• Sedimentation

Because of deforestation there’s a lot of areas by the rivers margins without structure. In the rainy season and without the much needed support provided by the trees the land ends up crumbling into the sea. It will later cover the corals and the algae will not be able to catch the light it needs to make the photosynthesis. The algae dies and the corals lose their main food resource.

• Contamination

The currents provoked by heavy rainfalls can bring pollutants to the ocean that will contribute to coral bleaching. We have to keep in mind that corals are super sensitive animals that react to minor changes of the environment around them. The majority of the products we use at home, chemicals used in the industry and agriculture, have a big impact on sea life and the reefs.

• Sunlight overexposure

When the temperatures are higher than normal, the sunlight irradiation will heat up the water temperature significantly and that will have a direct impact on the corals that are on shallow waters.

• Extreme low tides

Exposure of corals to air during extreme low tides can cause coral bleaching.