Sea Environment, unstoppable stress

Marine biologists call it “coral bleaching”, the whitening of corals, a calamity that is impacting tropical waters all around the world

by Clelia Pirazzini

Due to the rising sea temperatures caused by global warming, coral reefs are under stress with disastrous consequences for the corals, which experience fading colour in the initial stages of the problem, and then, if they do not recover, gradually end up dying.

Urgent measures are needed to counter the danger that is threatening corals more and more concretely.

Immeasurable damage to the submarine ecosystem, since corals host more than 30% of marine biodiversity and provide a rich and safe habitat for various kinds of organisms – fish, shellfish and crustaceans. It has been estimated that should the coral reef collapse entirely, more than 25% of the marine species living in the reef would become extinct and, obviously, also the presence of large edible fish would decrease, which would strongly jeopardize the practice of fishing. But that is not all. In many cases, the disappearance of the reef would provoke the reduction of the shorelines making them more vulnerable to attacks from violent waves and causing the erosion of the coasts. It is therefore urgent to seek refuge to avoid catastrophe, keeping in mind that this is about protecting the existence of one of the most surprising marine animal species on the planet. Because corals are constituted by tiny colourless polyps that unite in colonies and generate calcium carbonate in the form of calcite to shape protective calcareous skeletons of different types and sizes.

According to scientists, by 2035, 50 per cent of corals will be in an area considered unsuitable for their life.

But their existence is closely linked to microscopic unicellular algae – so-called zooxanthellae – with which they live in symbiosis: corals provide these algae with a safe shelter and favour photosynthesis, while the algae are not only responsible for the colour of coral reefs but also produce oxygen and nutrients for the polyps. But when the water temperature rises excessively, the algae are expelled and start to exit the calcareous skeleton, furthering the bleaching process, while the polyps of the corals slowly die out since they no longer receive any nutrients.

These concerning phenomena have been detected in the Australian Great Barrier Reef, the most impressive reef on the globe and one of the most monitored, as well as in other tropical areas, like the Caribbean, where, close to the island of Cuba, a very large madreporic formation can be found, which is considered the second-largest in the world. A very important sea, since it is studded with countless inhabited islands where the coral reefs are a crucial support for the local population in terms of food and economic activity, in particular, linked to seaside and nautical tourism.

THE STABILITY OF THE CORAL REEF, WHICH HAS BEEN INTACT
FOR HUNDREDS OF THOUSANDS OF YEARS, IS NOW IN DANGER DUE TO RISING SEA TEMPERATURES AND ACIDITY CAUSED
BY CLIMATE CHANGE.

To avoid any further stress on the seabeds, experts are now searching for new solutions to protect the marine flora and fauna. The island of Bonaire was declared a National Park in all its surrounding waters and has prohibited fishing or collecting any fragments found on its beaches. In addition to these, also the coral formations in Belize are being monitored, seven of which are strictly protected, as well as the ones in the Dominican Republic which has established the National Park of the East. Also, Cuba, where the area of Los Jardines de la Reina stands out, is highly surveyed and booming with biodiversity thanks to the surprising variety of corals that compose it, like the ones belonging to the Acropora species, which are highly eye-catching, the Cervicornis, commonly called Staghorn coral due to its highly elegant ramifications, or the Acropora digitifera which look like giant and rough fingers. And then there are the platform-shaped corals, nicknamed Table Corals, which present flat and compact calcium carbonate structures, or the characteristic and rounded Star Coral (Montastraea cavernosa). All formations are visited by myriads of large and small tropical fish who find refuge and nutrition here.

Thousands of species of fish, corals, sea turtles, whales, and dolphins are at risk due to the loss of their habitat.

The establishment of protected Marine Parks is certainly an important measure, but not sufficient to safeguard the seabeds from the recent maritime environmental disaster that is taking on increasingly concerning proportions in all tropical waters. This is why many nations lapped by the Caribbean Sea and the area of the Gulf of Mexico have enacted additional initiatives to preserve the reefs. Some time ago already, biologists in laboratories in the Florida Keys honed a cutting-edge technique to transplant corals previously grown in special greenhouses into the sea – greenhouses where the ideal conditions are generated to make them grow 25 faster than normal. The branches obtained with this technique are then transferred into the sea hanging from a sort of artificial tree or in suspended baskets to later be placed on pedestals on the seabed. The results are so positive that it is possible to conceive an increase in cultivation which currently provides 25,000 corals per year.

THE RED SEA, THE BAJA CALIFORNIA MEXICAN PENINSULA, WEST AFRICA, THE CARIBBEAN AND NORTHERN AUSTRALIA ARE THE AREAS POPULATED BY CORAL REEFS MOST AT RISK.

But also other areas of the Caribbean have implemented projects of these so-called Coral Gardens. Cuba’s National Aquarium, the ANC, is carrying out highly precise studies about the techniques to be followed for innovative transplants into the sea, which involve in particular four highly resistant species of corals that are grown in certain specialised “farms”. Also in this case, the coral fragments are grown in dedicated greenhouses and after accurate tests to determine their good health, they are transferred into the sea in four specific areas, two in the National Park of Guanahacabibes, one close to the coast of Havana, and lastly in the province of Matanzas in Playa Coral.

To monitor their health, divers have placed supports welded to floats that are easy to spot and are anchored close to the branches. Here, they can periodically and easily dive under the water to check the transplants since the water is not too deep. No doubt these are still small steps, but they are highly significant since they attract attention towards the decline that is taking place in one of the most complex and extraordinary ecosystems on the planet.

CORALS ARE FUNDAMENTAL FOR FISH BECAUSE THEY PROTECT THEM FROM PREDATORS AND REPRESENT A REPRODUCTION GROUND AND A NURSERY FOR MANY FISH SPECIES.

But if our Oceans’ fauna is under stress, the animals inhabiting the internal waters are doing no better. The biggest island in the Greater Antilles host, among other species, an endemic aquatic reptile, the Cuban crocodile (Crocodylus rhombifer), which is just under 2 metres long and weighs about 80 kg. Its survival is at risk, not only due to illegal hunting – since its meat is highly appreciated in the local cuisine – but also due to its hybridization with the more common American crocodile, and, above all, due to the rising temperature of the waters. In fact, the gender of its offspring is determined by the temperature of the nest where it lays its eggs since it is an oviparous animal. But if the temperature constantly exceeds 32 °C, generally only male hatchlings will be born, breaking the balance between the male and female genders. Also here, experts are studying innovative solutions, which for now consist in collecting the eggs as soon as they are laid to then place them in dedicated incubators where the temperature is constantly controlled. Once they are born, the young reptiles are set free in nature in the most suitable areas, which, in Cuba, are mainly swamps full of mangroves. The hope is that the introduction of these new techniques will at least in part restore the balance in the delicate world of waters in order not to lose the memory of the great beauty, but also the great importance, which it has always had for mankind.

(Sea Environment, unstoppable stress – Barchemagazine.com – August 2023)