Coral restoration : how and why corals are being grown

During your dive or snorkel trips, you might have come across some weird man-made structures underwater with little corals growing on them. These are usually part of coral restoration projects that are happening all over the world. Pollution and changes in ocean temperatures are the main threats to coral reefs worldwide.

Coral restoration is one of the ways to help conserving or regrowing coral reefs. They are a key factor in balancing the eco system, providing shelter and nutrition for thousands of species, but also supporting the livelihood of millions of people.

What are corals?

There are over 6,000 species known today of corals, that are usually split into soft and hard corals. Contrary to popular belief, corals are animals, not plants. Many of them grow in “colonies”, meaning each tiny individual organism depend on each other for survival and grow as a group. Corals support the rest of the ocean ecosystem by providing habitat, protection or food to a lot of other species.

Healthy coral reef with various species

How do corals grow and reproduce?

Corals reproduce mainly through asexual means, so in the right conditions small fragments can easily spread out (coral propagation). Some species of corals will produce eggs that are released into the water. In some areas you can witness mass coral spawnings, when several colonies of different species release eggs at the same time. Some of these eggs will end up securing on a rock or bottom and grow into a new coral.

Once settled, coral colonies expand more or less fast depending on the species and their growth rate, as well as environmental factors.

An artificial reef structure designed to host new corals

What are different restoration techniques?

Corals can be secured on a structure by different means like straps, glue or other techniques. Each method basically aims at settling coral fragments in a favourable environment so they can grow and propagate. Coral fragments need to be installed with good light and depth, water movement and other conditions that are helping the success of the new fragments.

One method to help coral growth is artificial reefs: installing in the water man-made structures such as cement structures give baby corals an environment on which to attach to and grow on. They can then become a living environment for other marine species and can grow into lively reefs. Cement is the most popular material to create these as it is resistant to various water conditions and offers stability. You might come across different structures or smaller ones like “Reef balls” that offer protection to some species.

Other methods can involve smaller net structures either made of metal or strings, on which small coral fragments are attached with glue or strings. If the transplant is successful, these can grow and create new coral colonies, that attach to the ocean floor and then grow into new reefs.

Coral restoration project in Nusa Penida, Indonesia - courtesy of IndoOceanProject Top row after 5 months, bottom row photos after 18 months.

Where can you see coral restoration projects?

There are plenty of coral restoration projects all over the world that you might come across while snorkelling or scuba diving. Some famous artificial reefs include Neptune Memorial Reef in Florida, The Silent Evolution in Mexico, Pyramids Reef in Bali.

In a lot of popular snorkelling and scuba diving destinations, you will be able to visit smaller restoration projects, such as those created with Reef Balls or Biorocks.

How can you get involved?

There are plenty of NGO supporting coral restoration projects, such as Coral Reef Alliance or Reef Check. These types of organisations rely a lot on private funding to deploy projects. A lot of them also offer courses and volunteering programs in order to learn restoration techniques and help on projects. During your snorkelling trips you can also help conservation efforts!

Now with this new knowledge on corals, maybe you will look at them differently next time you go snorkelling or scuba diving. If you come across a restoration project, your local guide or dive operator will certainly be able to give more information about it!