Wednesday, 17 Oct 2018

Corals: the announced hecatomb takes place

The famous Great Barrier Reef, Australia, goes bad. About 30% of its reefs died in the course of 2016 due to global warming. Its future seems compromised as well as that of other coral reefs in the world. The event had been predicted for the 2020 horizon by 2000 by an Australian expert, Professor Ove Hoegh-Guldberg.

Over the last fifty years, the Earth lost between 40 and 50% of his Coral reefs . True “lungs of the oceans”, these vast structures are as vital to the planet as virgin forests. Even if they represent only 0.1% of the surface of the oceans (which produce 50% of the oxygen we breathe), the Coral reefs host 25% of all existing marine life. Above all, they allow more than 500 million people to live.

The announcement made recently by a team of researchers in an article published by the famous newspaper Nature is particularly worrying: it shows a real slaughter in the famous Great Barrier Reef (GBC), off Australia. It formalizes, through a scientific publication, what was already known for almost a year, namely that 30% of the corals of the GBC died in the course of 2016 following a heat wave directly related to global warming global.

That’s what healthy coral reefs look like. These are pictures of Ribbon Reefs , a chain of ten large reefs forming the outer edge of the Great Barrier Reef, Australia. These reefs are home to some of the most popular dive sites: Steve’s Bommie, Lighthouse Bommie and Cod Hole . © Undersea Productions

The disturbing bleaching of corals

These deaths are produced by coral bleaching. These are animals living in symbiosis with an alga responsible for their color and a large part of their food. However, this alga leaves them under the effect of heat stress. Some parts of the affected reefs can recover, but this is not obvious and it takes time. As there were two severe bleaching episodes in 2016, damaged GBC reefs have no chance of recovery. The loss occurred over a nine-month period between March and November 2016.

This is what has become of some reefs of the Great Barrier Reef. The bleaching that led in November 2016 to the death of corals is spectacular to Zenith Reef (north of the Great Barrier Reef). © ARC Center of Excellence for Coral Reef Studies

“The Great Barrier Reef coral is certainly threatened by the climate change but it is not condemned if we react very quickly to gas Greenhouse effect. Our study shows that coral reefs are already changing dramatically in response to unprecedented heat waves, ” said Professor Terry Hughes, director of the ARC Center of Excellence for Coral Reef Studies , one of the authors of the article of Nature .

Unfortunately, there may be good reasons to be pessimistic. A few years ago, Futura had devoted several articles to Catlin Seaview Survey . One of the world’s leading coral specialists worked closely with members of the Catlin Seaview Survey as scientific leader: this is the teacher Ove Hoegh-Guldberg (see article below). He had predicted a catastrophe by 2020.

What you must remember

Catlin Seaview Survey : corals are precious but threatened

Article published by Laurent Sacco on 21/02/2014

Coral reefs are present in all the tropical regions of the world. But what exactly are corals and how do they make reefs? Scientific Officer Catlin Seaview Survey and director of Global Change Institute Professor Ove Hoegh-Guldberg answers these questions, while explaining that their preservation concerns us directly.

The importance and beauty of coral reefs are generally unknown to the general public, who do not have the opportunity to dive across the world to fringing reefs, barrier reefs or atolls . Yet the future of hundreds of millions of people is threatened in the very short term if we do nothing to preserve them. As Futura-Sciences explained in a previous article, members of the Catlin Seaview Survey have begun to move things forward using modern means of communication and the essential medium that is now the World Wide Web.

The team is currently producing an extraordinary database of visual data for all the coral reefs on the planet. Available to all members of the global village, it is also valuable for marine biologists concerned with better understanding and better preservation of these ecosystems which contain one third of cash about 100,000. One of the world’s leading coral specialists works closely with the members of the Catlin Seaview Survey, as its scientific lead. This is the teacher Ove Hoegh-Guldberg .

In a report broadcast on France 3 from November 28, 2000, Professor Ove Hoegh-Guldberg joined a member of Greenpeace to announce that, as a result of global warming, the Pacific Ocean could lose most of its barriers. by the end of the century and that the damage will devastate the fishing and tourism industries of the region. The most vulnerable islands are Tuvalu and Kiribati, French Polynesia, Cook Islands, New Caledonia, Vanuatu and Fiji. ©

As shown in the video above, in the early 2000s, this Australian biologist was already drawing the bell alarm with Greenpeace members. It foresaw an ecological disaster by 2020 leading to an economic disaster. The very survival of coral reefs at the end of the XXI e century could be questioned.

Futura-Sciences has chosen to accompany the members of the Catlin Seaview Survey during their adventures around the globe to help the global awareness necessary for the preservation of corals for future generations. We will regularly give news of this project (you can also follow the adventures of the Catlin Seaview Survey sure Google+ , Twitter and Facebook ). But to understand the issues, it is essential to become familiar with coral reefs. That’s what we suggest you do with Ove Hoegh-Guldberg.

Let’s go to Professor Ove Hoegh-Guldberg himself for the rest of the article.

“Corals, which are at the heart of coral reefs, are simple organisms related to sea anemones and jellyfish , but who have developed an intimate symbiosis with micro-algae called zooxanthellae . Together, the coral and the zooxanthellae trap the energy of the light of Sun and convert it to sugars and other organic compounds, which provide an important source of nutrition and energy for corals. This symbiosis between animals and microalgae is so successful that corals are also able to precipitate large amounts of calcium carbonate .

This one forms a material limestone, like those that many other tropical organisms produce, and which accumulates over time in the familiar structures associated with coral reefs. In addition to corals, many other organisms, including jellyfish , clams, nudibranchs, worms, kelp and tiny creatures called foraminifera have also developed symbiotic relationships with zooxanthellae.

In this video, Professor Hoegh-Guldberg explains that corals are essential to coral reefs. They grow from generation to generation on the limestone remains built by their predecessors by exploiting sunlight. These structures then allow other species, such as fish, to proliferate. © Catlin Seaview Survey, YouTube

Coral reefs, complex and rich ecosystems

While coral reefs are the only living structures visible from space, they occupy only a tiny fraction of the oceans (less than 0.1%). Despite this small size, coral reefs are the most diverse ecosystems in the oceans. Some scientists estimate that at least one million species live in and around coral reefs. In the Great Barrier Reef Australia, for example, there are more than 500 species of coral, nearly 1,500 species of Pisces and nearly 3,000 species of shellfish .

Although these charismatic creatures are the most visible coral reef organisms, the list of species found on the Great Barrier Reef contains hundreds of thousands more if we take into account the many cryptic organisms such as crabs. , shrimps, worms, echinoderms, algae , Ce terme englobe une variété d’espèces très différentes, qu’elles soient procaryotes (bactéries) ou eucaryotes (levures, algues)….” data-image=”” data-url=”/sante/definitions/biologie-micro-organisme-6183/” data-more=”Lire la suite”>microbes and the bacteria marine. At one end of this complex ecosystem are the primary producers that trap the energy of the sun, while at the other end we find predators such as sharks. Together, these organisms constitute a dynamic and interdependent ecosystem. Coral reefs have been a persistent feature of the tropical regions of our planet for hundreds of millions of years.

While some organisms have subtly changed over time, evidence of coral reef ecosystem activity has been frozen over time in the form of huge deposits of limestone across the planet. Throughout this period, coral reefs have dominated the warm, shallow seas, extending or regressing in response to slow changes in their environment. The Great Barrier Reef, for example, formed during warm periods and disappeared during ice ages when the sea level was 180 m lower than today. These flows and reflux Coral reefs along the world’s coasts are part of a natural cycle in which the distance from Earth to the sun varies slightly due to an oscillation of the eccentricity of his orbit over the course of thousands of years.

Coral reefs, vital actors of the economy

Although occupying only a small fraction of the Earth’s surface, coral reefs are extremely important to humanity. More than 500 million people derive their food and income from the coral reefs that line the shores of many tropical countries. This contribution to the subsistence of these populations is essential, when there is little alternative to find food and income. In developed countries, coral reefs also play important economic roles. For example, Australia’s Great Barrier Reef annually generates about € 4 billion and provides employment for 63,000 people, and in a sustainable way from tourism and seafood. Globally, the reefs Corallians bring hundreds of billions of euros each year to national economies. In this respect, coral reefs are not only beautiful and valuable from a biological point of view, they make an important contribution to the well-being of hundreds of millions of people around the world.

The Great Barrier Reef stretches over hundreds of thousands of square kilometers along the east coast of Australia. As this video explains, its existence is threatened in the very short term. © Euronews, YouTube

Despite their importance, Coral reefs Degrade rapidly under the pressure of human activities. At the local level, the destruction of coastal vegetation by mining, deforestation and Agriculture pollute coastal waters with sediment , toxins and nutrients. In many countries, coral reefs are also overexploited, leaving fish species and other key organisms to disappear, leading to large-scale ecological change. The reefs then regress, giving way to other organisms such as kelp and cyanobacteria , which become dominant.

On a global scale, the increase in atmosphere concentrations of effect gases such as the carbon dioxide leads to rapid changes in sea temperatures and to ocean acidification . The change in the product environment is hundreds of times faster than the transitions of glacial ages of the past, which are fundamentally different from all that we know in the last 40 million years. These large-scale changes have already had impacts on coral reefs: coral bleaching, disease occurrence and slowing down the ability of corals to form their calcium carbonate skeleton.

As for the future, the planned changes concerning the temperature of the sea and its chemistry suggest that coral reefs may well disappear before the end of this century if we do not take emergency measures to regulate the use of coral reefs. fuels fossils and the release of carbon dioxide into the Earth’s atmosphere that their combustion leads “.

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