Submarine Robot Reveals the Life that Beats in the Depths of Rapa Nui

For the first-time scientists explored the Easter Island environment beyond where professional divers arrive. They found possible new species of fish and molluscs, but also evidence of contamination.

Although the waters of Rapa Nui up to 50 meters deep are well known by professional fishermen and professional divers, the world below is almost a mystery.

To know what is hidden there, since 2016 the Millennium Nucleus of Ecology and Sustainable Management of the Oceanic Islands (ESMOI) of the U. Católica del Norte and Oceana, with the support of the local community, have made a series of expeditions, covering the island on its three sides with the help of ROV submarine robotic vehicle.

“Between the ancestor and last year, we mainly explored its western flank, while this year we are dedicated to working more on the north and southeast sides,” says Javier Sellanés, ESMOI biologist and UCN.

They worked between 100 and 360 meters deep, where the panorama is very different from that of surface water. “At that level the environmental variables change, the light practically dies out and the temperature decreases, which is why the fauna has had to adapt to these conditions”, explains Sellanés.

This is how some fish have large eyes because they adapt to capture little light and are also more resistant to pressure than those that live in the waters above.

The landscape also changes. Unlike the classic coral, the one that abounds there is the coral called lash, because of its elongated and thin shape. “We have found extensive fields of whip corals more abundant than we thought and also of another smaller species, the mushroom,” he says.

Among the biggest surprises of the expedition was the discovery of a shark 330 meters deep. “It was probably about 3 to 4 meters and it was not of the species that are normally reported in the area, the Galapagos.” They determined that it was a specimen of the genus Hexanchus, which had not been described before for Chile.

In the video obtained by the robotic vehicle the shark appears suddenly in the middle of the penumbra and advances directly towards the camera and then pass over it. “These are highly migratory species, and their main threat is spinning,” says Matthias Gorny, director of science at Oceana and remote operator of the ROV.

The presence of a snail of a size larger than those usually found on the island and used for necklaces also attracted attention. “He was very particular, as he ‘collects’ other snails, because as he grows smaller shells stick around him,” says Sellanés.

At about 200 meters deep they had to see a unique fish. “Her head was transparent, similar to jelly, it was quite strange,” Gorny recalls, and she explains that there are about 13 registered of this type in the world. The closest relatives of other fish that he had to observe live in Hawaii. “It would be the first record for this part of the Pacific,” he says.

They determined a specimen of the genus Hexanchus

Another novelty for Rapa Nui was the green sea cucumbers, which remind Sellanés of the elongated balloons with which dogs and other figures are assembled. They are relatives of the hedgehogs and starfish. Of these they also saw in particular some specimens that would be related to those living in the Pukao seamount, 60 miles away. It is proof of the biological exchange that exists between the two points, says Gorny.

A not so positive aspect is that they found that plastic waste and organic remains still arrive at 300 meters of depth.

The funds also do not look as healthy as you would expect. This is how from a certain depth they saw how bacterial tapestries have begun to cover the coral reefs. “There are many nutrients coming from the discharge of sewage that enter from the island and favor the proliferation of these microbial communities. The key thing is to rethink the management of wastewater and rainwater, says Sellanés.


Source: Economia y Negocios