Blue-Bay: Spectacular reproduction of corals

2 weeks ago - November 16, 2023
Blue-Bay: Spectacular reproduction of corals
The pink or red sea visible until the end of November

Like every year at this time, the reproduction of corals in the Blue Bay-Pointe d’Esny-Mahébourg region offers a beautiful spectacle. The sea takes on a pink or red hue which dominates the azure blue. This phenomenon will be visible until the end of November.

Those who have passed through Blue Bay and its surrounding areas in recent weeks have undoubtedly noticed that in certain places, the sea has changed color. This is not pollution, but a natural phenomenon that occurs once or twice a year. Vinayagen Munusami, Scientific Officer at Eco-Sud, explains: “During the reproductive period, male polyps release gametes, that is to say sperm, and female polyps release eggs. When the two meet in water, fertilization occurs. When the sea turns red, it means that fertilization has already taken place."

In Mauritius, the phenomenon is especially visible in the South-East region, particularly in Blue-Bay, with the marine park, but also in Pointe-d'Esny and Mahébourg, on the seafront side. also in other areas but are not visible due to the current.” Once fertilization is complete, a larva is formed. It will continue its journey in the water, until it clings to a support to grow. With pollution and global warming, can we ensure that they survive?

Vinayagen Munusami suggests that Eco-Sud scientific officers carry out surveillance on certain sites, but that it is difficult to comment on the entire territory. “We place pieces of marble underwater in the affected areas and follow up. You need special light to be able to observe them. In some places, we notice, in fact, that there are larvae which have clung and in others, there are none. But I believe that it is already a positive sign that we have them on certain sites,” he declares.

As for whether human activities have an impact on coral reproduction, the Scientific Officer concedes that the presence of certain pollutants such as diesel from boats can prove harmful to this natural process. “Fortunately, fertilization happens during the night, when there are no activities,” he said. The phenomenon actually occurs as the full moon and high tides approach.

The pink sea does not pose a danger to humans either. Vinayagen Munusami explains that you can swim without problem, avoiding areas where moss forms. “These moss come from the decomposition of organic matter. This is why a strong odor also emerges from the sites where the phenomenon can be observed. However, they do not represent anything dangerous,” he reassures.

Not all coral species are affected by this spectacular reproduction. “Branch-shaped and tabular corals are known for this. » He adds that for some time now, small episodes of Spawning have also been observed, outside of the main reproduction period.

The phenomenon will be visible until the end of November. Those who wish to see it can go to the public beach of Blue-Bay, on the seafront of Mahébourg or along the coast of Pointe-d’Esny, among others.

Apart from monitoring sexual reproduction, the NGO Eco-Sud also ensures the asexual reproduction of corals through Coral Farming. The objective is to restore 1.6 hectares of the coral ecosystem of the Blue-Bay marine park. Volunteers from communities in the Southeast were also trained in coral preservation. Two sites, at Trou-Capitaine and Pointe-d’Esny, are particularly affected by this project.

Text by Le Mauricien

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