Corals on the northeast coast suffer massive bleaching

publicado: 26/04/2020 00h00, última modificação: 14/05/2020 10h42

Corals of Seixas



Marcia Dementshuk

In the first days of March this year, before the registration of cases for coronavirus in João Pessoa, marine biologist Karina Massei made a technical dive in the corals of Seixas, in the Paraíba capital, as she did almost daily. Karina was surprised by a known but unusual phenomenon on the Paraiban coast: the massive bleaching of the corals. Since she began diving frequently in Seixas, five years ago, the biologist has never seen a whitening in such a comprehensive way, as it happened this year. In contact with the network of monitoring of corals in the Northeast she found, with apprehension, that the same occurred in all states.

"We know that the main cause of the accelerated whitening of the corals was the high temperatures of this summer, because even those corals that were far from the usual tourism appeared whitish", says Karina Massei, excluding the hypothesis of degradation by tourism. Behind it is global warming - a natural event in the various phases of Planet Earth's existence, but currently accelerated by unsustainable human activity. "Situations that were supposed to happen over 25 or 50 years, we are seeing now", says Massei.

The fact is a warning, it indicates that something is wrong and if normal conditions do not return, the corals die. And if they die, what happens? Several species are compromised. These reef environments not only shelter the corals, but also support an endless variety of lives - calcareous algae, polycarbonates, sponges, crustaceans, molluscs, fish, turtles, even mammals.

"And we humans are also connected, we do tourism, we remove food and even pharmaceuticals - some animals have toxins that serve us as vaccines and other medicines", adds Karina Massei. And also, the corals protect the continent, because they help to reduce the force of the waves by minimizing coastal erosion.

Among the causes of bleaching is global warming

However much everyone thinks that global warming is something natural and uncontrollable, if at that moment the world stopped cutting down forests 100%, even then, providence would not be enough to stop the rapid rate of temperature increase. This would only be possible if countries also stopped burning fossil fuels such as gasoline or diesel immediately.

In the case of corals, the global heat that hits the oceans causes stress and causes the coral to expel microscopic algae that live in symbiosis with it. These algae, called zooxanthas, are the main source of food for the coral; malnourished, they begin to lose their color and bleach, becoming more susceptible to disease. This is one of the hypotheses.

When it reaches this stage the choir still has life, but it shows that something is wrong and if there is no correction, it will not resist. "If the water temperature returns to normal conditions soon, the corals may survive a bleaching event, the zooxants may repopulate the small number left in the coral tissue, returning the nutrients and therefore the normal color. The problem is that some corals do not survive for more than 10 days without the microalgae. Others are able to survive for weeks or even months in a bleached state by feeding on plankton. But they will probably grow less, decrease their reproductive capacity and be more susceptible to disease," stresses Karina Massei.

Other local factors can cause the microalgae to detach from the corals. The researchers presented studies based on increased coastal pollution, intense flow of human activities, predatory fishing, making the algae no longer feel comfortable with the corals and release. But, according to Massei, there is a lack of research to better understand the complex relationship of this environment.

Event was registered all along the northeast coast

This whitening has occurred on a large scale in the last 20 years, although it is not always complete and does not always lead to the death of the colony. The perplexity of researchers today is the amount of corals affected. "All the species of coral we have here in Seixas have suffered," adds Karina Massei.

The monitoring network gathers projects from several states around the #DeOlhoNosCorais program. The Recifal Conservation Project, from Pernambuco, detected moments when the temperature is out of the historical average from satellite data. Since the beginning of 2020 the sea is warmer.

In Rio Grande do Norte, the monitoring of the ReefBank Project pointed out, this April, that more than 80% of the corals in the monitored area are in these conditions. It is an impressive aerial image to see the completely white animals under the crystal clear waters of the sea. Worse: mass whitening has been recorded by groups of researchers in each northeastern state.

Corals are ancient animals, but little researched

"Although they look like a lot of rocks, on the sea reefs lives an animal known as coral. It is considered one of the oldest inhabitants of the Planet Earth. This fossil animal has resisted several events and because it inhabits very restricted environments, in tropical warm seas, they are excellent indicators of environmental conditions. Through them, it is possible to understand the history of the Earth", explains Karina Massei.

This animal is adapted to live in colonies and produces a skeleton around it throughout its life. They form layers and layers that are bioconstructed by aggregating other marine organisms that also produce calcium carbonate, such as calcareous algae and shells. When corals die, and the conditions for life are favourable, new ones appear and give rise to more skeletons.

The largest of these reefs in the world is the Great Barrier Reef in Queensland, Australia, which consists of some 2,900 reefs and 300 atolls. In Brazil, the coral reefs occupy about 3,000 km of coast and oceanic islands. They are the only existing formations in the South Atlantic. There are 8 species of corals living only in Brazilian seas. In Paraíba most are very close to the beaches.

The coral reefs of Seixas are the object of research by marine biologist Karina Massei, whose PhD thesis at the Federal University of Paraíba (UFPB/Prodema) sought to understand how and when these reefs were formed (geology), how they function and interact (bioecology), and how they are used. "It's important to know in order to preserve and promote citizen science," Massei stresses. The researchwassupportedbythe Fundação de Apoio à Pesquisa da Paraíba (Fapesq-PB), in partnershipwiththe Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Capes). For its scope, it also had the support of researchers from the Laboratory of Studies in Water and Territory Management (LEGAT/UFPB), renowned professors and several laboratories from UFPB and UFPE, in addition to AquárioParaíba and the Extreme Eastern Nautical Association (ANEO). Currently, it depends on resources for continuity.

The United Nations has declared the International Decade of Oceanography for Sustainable Development for the period 2021 to 2030. The initiative aims to expand international cooperation in research to promote the preservation of the oceans and the management of the natural resources of coastal areas. Activities of the decade will be led by Unesco. We hope it is not too late