Bringing coral reefs back from the brink

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Acropora coral species, Mauritius © Shashi Chumun

Lagon Bleu in Mauritius is one of several organisations around the world aiming to use coral farming as a way to rejuvenate their coral reefs. But can human intervention really save these delicate ecosystems from an ominous future?

The beauty of a healthy coral reef is matched only by its importance to oceans, wildlife and people. The stunning corals, fish and other animals it supports are magnets to tourists, that can bring a lot of money into a country – estimated at $700 million a year globally.

The corals themselves create the world’s famous white sandy beaches and clear blue waters, and act as barriers to protect coastlines from storm damage. They are also vital nurseries for a huge array of fish and other species, often acting as oases in otherwise nutrient-poor waters.

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Green turtles are just one of the many species that use Mauritius’ coral reefs © Skitterphoto (Pixabay)

Corals in crisis
Coral reefs are currently under threat from warming sea temperatures, ocean acidification, disease, pollution and overfishing. Besieged by these human -induced or -exacerbated issues, alarm bells are ringing all across the marine world. Only last year part of the Great Barrier Reef in Australia was pronounced biologically dead, and the health of the remaining section is worsening following another mass-bleaching event this year.

Reef-building corals are animals made up of two partners: a coral polyp and a photosynthetic algae. It is the algae that gives the coral its colour and produces food through photosynthesis, whereas the polyp scavenges other nutrients and creates the hard coral structure they both live in.

When under stress, from rising sea temperatures for example, coral polyps release their algal partners into the ocean, thus losing their colour and ‘bleaching’. If the coral remains stressed, does not take in another algal partner and remains bleached then it will die over time without the crucial extra nutrients the algae produces.

Melon butterflyfish swimming among healthy and bleached/dead corals in Blue Bay’s Marine Park © Kay Haw

Repairing the damage
In recent years, Mauritius’ coral reefs have suffered from serious bleaching events, resulting in a disturbing loss of 50-60% of their live coral cover – a situation mirrored in many other areas of the world. Despite its protected status, Blue Bay’s Marine Park has experienced some of the worst coral die-off in the Grand Port area. But coral farming may offer a way to repair some of the damage and rejuvenate the reef.

Lagon Bleu’s project aims to increase coral cover in the Grand Port lagoon through the transplantation of nursery-grown coral colonies. A site within the lagoon has been selected to locate special multi-layered rope nursery units, one that does not negatively affect the local ecosystem. These particular structures are less permanent and impactful than others, and can be removed at the end of the project or maintained if it is successful and further funding is secured for a second phase.

During September, the transition between Mauritius’ winter and summer, the team will collect 1,000 healthy coral fragments from the local reef to move into and propagate in the nurseries. Thermally tolerant and bleaching resistant species will be selected to help build habitat resilience. These fragments will be cared for by Lagon Bleu’s staff, interns and volunteers to help ensure they survive and flourish, until they have grown enough to be transplanted out to reinvigorate damaged areas of the reef.

A similar project in Jordon transplanted coral colonies into degraded reef sites in the Aqaba Marine Park, as well as establishing a coral nursery site. The survival and growth rates of the transplanted and nursery corals were monitored for two years, alongside growth rates at a non-transplanted control site. Their results showed an 87% survival rate for the transplanted corals and an 88% survival rate for nursery corals, and rates of growth that compared positively to those in the control site. This is strong evidence that coral farming and transplantation can be used to support damaged reefs.

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Fungia coral species, Mauritius © Shashi Chumun

Heroes or villains?
Humans are often seen as enemies of nature because of the widespread damage we cause, but can we also be its heroes or healers? There are many people around the world working hard to find solutions to some of the destruction – although there is always need for more energy and innovation if you have it! But only time will tell if we can help save Earth’s coral reefs and secure the future of these amazing ecosystems.

If you want to find out more or get involved with any of Lagon Bleu’s work, as a volunteer, intern or sponsor, then do go to their website and help support marine conservation.

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Lagon Bleu volunteers and interns about to go monitoring

 

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