A laden with scientists has just returned from exploring the uncharted waters of the Indian Ocean, where they mapped gigantic seamounts and encountered a multitude of deep-sea animals decked out in glittering lights, with velvety black skin and mouths full of glassy tusks.
The team of biologists was the first to study the waters around the Cocos (Keeling) Islands, an Australian territory more than 600 miles off the coast of Sumatra. “It’s just a complete blank slate,” says the expedition’s lead scientist, Dr Tim O’Hara, of the Museum Victoria Research Institute.
“That area of the world is so rarely studied,” says Dr Michelle Taylor of the University of Essex and president of the Deep-Sea Biology Society, which was not involved in the expedition.
Few research expeditions make it to the Indian Ocean, mainly because it’s so remote. It took the team six days to reach the Cocos (Keeling) Islands from Darwin in Australia’s Northern Territory on the research vessel Investigator, operated by Australia’s national science agency, CSIRO.
“The real stars of the show are the fish,” says O’Hara, an invertebrate specialist. “There are glass eels and tripod fish and hatchet fish and dragon fish, with all these bioluminescent organs on them and bait coming out of their heads. They are simply extraordinary.
Among the huge variety of life they found, deep-sea batfish were a highlight. It sits on the seabed like a decorated pancake and struts around on two stubby fins that serve as its legs. It wiggles a tiny lure stuffed into a hollow on its snout, presumably hoping to trick its prey into thinking it’s a tasty worm.
They spotted tribute spiderfish, which have long lower fins that they use as stilts to perch above the seabed, catching morsels of food in passing. They found a previously unknown glass eel, caught from a depth of 5,000 meters, covered in a transparent, gelatinous skin. And they saw the free jaws of the semaphore, a type of dragon fish, which have huge open jaws with double hinges and the unusual habit of spying on other animals with bioluminescent red light, a color that most deep-sea animals can’t. see.
A sampling net dragged across the abyssal plain turned out to be full of ancient shark teeth. “They were gigantic sharks that lived millions of years ago,” O’Hara says. Based on the photographs, fossil experts think they came from “megalodon-like animals.” They’ll know more once they get their hands on the teeth, which are now being sent to museums along with everything else in the collections.
In addition to shedding light on the underwater life of this unstudied region, the team also uncovered a spectacular seascape, including huge submerged volcanoes, or seamounts, which at 5,000 meters (16,000 feet) are more than twice as tall as Earth’s tallest mountain. Australia. “From the surface you wouldn’t know it,” says O’Hara.
Using high-resolution sonar, the team created detailed 3D maps of the deep seabed and discovered several smaller seamounts that were previously unknown.
Not only are many deep seamounts covered in rich habitats of corals, sponges, and other wildlife, but they play a crucial role in mixing the ocean. Deep currents sweep up the sides of seamounts, bringing vital nutrients to the surface. “Some people call them the stirring rods of the oceans because they actually stir the water at different levels,” says O’Hara.
One of the reasons for traveling to the Cocos (Keeling) Islands was to provide background information to help manage and protect the newly established marine park, established in March 2022 with neighboring Christmas Island Marine Park, which the team visited the year last.
The area is not threatened by deep-sea mining because, as O’Hara says, geologists looked at the seabed minerals and decided they weren’t worth exploiting. The main threat, according to the team, was plastic pollution. “Even when you’re that far from the continent, four kilometers down, you’ll be dredging up the plastic,” he says. “You see it in the water, you see it above the water, and we’ve seen it in our collections.”
It will take years for experts to work their way through all of the specimens collected by the expedition, but O’Hara estimates that between 10% and 30% will be species new to science. “I’m really excited about what new future scientific discoveries will come of this in the years to come,” says Taylor.
One thing the team has already planned is to match the DNA from the samples with sieved DNA fragments from seawater, known as environmental or eDNA, which are shed by the organisms into slime and skin cells. The idea is that in the future, scientists will be able to identify which species are present in the deep sea just from the genetic calling cards left in the seawater.
“Who knows what will happen with those specimens in museums 100 years from now,” says Taylor. “Trying to maximize as much science as possible from each of the specimens is so important, because it’s such a rare privilege to be able to visit these deep-sea areas.”