Scientists of Smithsonian Institution of Washington, USA, have discovered five new species of black corals living as deep as 760 metres or 2,500 feet, below the surface in the Great Barrier Reef and Coral Sea off the coast of Australia in November 2022. The scientists had used a remote-controlled submarine, named Su Bastian, for this task.
About Black Corals
Black corals could be found growing both in shallow and deep waters up to the depths of over 8000 metres (26,000 feet). Some individual corals have a life of over 4,000 years. They are presumed to have survived at least four mass extinction events. There are only 300 known species of black corals in the world till now. Now these five new species have been added to the list. Many of these black corals are branched and look like feathers, fans, or bushes while some are straight like a whip.
Contrary to colourful corals, black corals are filter feeders and eat tiny zooplankton that are abundant in deep waters. The colourful corals live in shallow-water and rely on the sun and photosynthesis for energy. Shallow-water corals build colourful reefs full of fish. Black corals act as important habitats where fish and invertebrates feed and hide from predators in what is otherwise a mostly barren seafloor, called seabed.
Methodology of Collecting Black Corals
In the past, corals from the deep parts of the region were collected using dredging and trawling methods. However, these methods would often destroy the corals. Therefore, this time the researchers first sent a robot down to these particular deep-water ecosystems. This allowed the researchers to actually see and safely collect deep sea corals in their natural habitats. Thus, the researchers were able to collect 60 black coral specimens over the course of 31 dives.
Thereafter, the researchers removed the corals from the sandy floor or coral wall using the rover’s robotic claws. The corals were then placed in a pressurised, temperature-controlled storage box and were brought up to the surface. The researchers examined the physical features of the corals and sequenced their DNA. Among the many interesting specimens were five new species—including one that was found growing on the shell of a nautilus which was 760 metres or over 2,500 feet below the ocean’s surface.
Threat and Significance
Many black corals are threatened by illegal harvesting for jewellery. So, these fascinating and hard-to-reach habitats must be conserved in order to know what species live at these depths and also the geographic ranges of individual species. As only a few specimens of deep-sea black corals have been collected, many undiscovered species and the evolutionary tree of corals are yet to be explored and learnt. So, the researchers must continue to explore the ocean’s floor and learn more about the black corals to protect their habitats.
Great Barrier Reef
The Great Barrier Reef, located in the Coral Sea, off the coast of Queensland, Australia, is the world’s largest coral reef system consisting of more than 2,900 individual reefs and 900 islands stretching for over 2,300 kilometres over an area of approximately 3,44,400 square kilometres (km2). The Great Barrier Reef can be seen from outer space. This reef structure is composed of billions of tiny organisms, known as coral polyps. This reef also supports a wide diversity of life and was selected as a World Heritage Site in 1981.
Since 2018, the percentage of baby corals has been dropping fast. Scientists describe it as the early stage of a ‘huge natural selection event unfolding’. Many of the mature breeding adults died in the bleaching events of 2016–17 resulting in low coral birth rates. In March 2022 also, another mass bleaching event was confirmed which raised further concerns about the future of this reef system, especially taking into consideration the possible effects of El Nino weather phenomenon.
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