Deep-sea divers have discovered a completely new ecosystem 1,640 feet (500 meters) beneath the water’s surface in the Indian Ocean, and it’s filled with hungry sharks.
Scientists described the region — named the "Trapping Zone" and located near the Maldives’ deep-sea volcano Satho Rahaa — as an "oasis of life" in a "very large ocean desert" where swarms of fish and sharks descend to gorge themselves on a cloud of tiny sea creatures.
The creatures are called micronekton and are classified as being from 0.8 to 7.8 inches (2 to 20 centimeters) long, ranging from krill to larger organisms such as fish. Micronekton can move independently of ocean currents; they swim to the ocean surface at night to hunt plankton before diving back to the relative safety of the depths at dawn.
But in the Trapping Zone, steep cliffs below the ocean surface, fossilized reefs, and volcanic rock conspire to deter the micronekton from diving any deeper than 1,640 feet (500 meters). Instead, their lives play out in a nightmarish marathon as they are chased around an endless loop by a train of ravenous sharks.
"This has all the hallmarks of a distinct new ecosystem," Alex Rogers, a marine ecologist at Oxford University, said in a statement. "The Trapping Zone is creating an oasis of life in the Maldives and it is highly likely to exist in other oceanic islands and also on the slopes of continents."
The strange new ecosystem was discovered as part of the The Nekton Maldives Mission, which is sending submarines to around 3,300 feet (1,000 m) below the ocean surface near the Maldives’ 20 natural atolls to systematically survey and document their largely unexplored depths. Satho Rahaa is a roughly 15 nautical mile (28 kilometer) circumference seamount, an ancient extinct volcano which during its formation suddenly rose 4921 feet (1,500 m) from the ocean floor.
The predators that hunt the micronekton and each other during the vertical migration are schools of tuna, large deep-water fish such as the spiky oreo (Neocyttus rhomboidalis) and alfonsino (Beryx decadactylus) as well as sharks. By beaming the lights of their Omega Seamaster II submarine onto the thronging fish, the divers spotted tiger sharks (Galeocerdo cuvier), sixgill sharks (Hexanchus griseus), sand tiger sharks (Carcharias taurus), dog fish, gulper sharks (Centrophorus granulosus) , scalloped hammerhead sharks (Sphyrna lewini), silky sharks (Carcharhinus falciformis) and rarely seen bramble sharks (Echinorhinus brucus). The scientists captured footage of the ocean creatures, collected biological samples and scanned the region’s underwater topography with sonar.
“We’ve observed sharks in shallower waters quite extensively in the Maldives before, but for the first time we’ve been able to document an immense diversity of sharks in the deep sea,” Shafiya Naeem, director general of the Maldives Marine Research Institute, which partnered with The Nekton Maldives Mission for the expedition, said in a statement from the mission.
The scientists believe that by studying the murky region in detail, they can learn how it developed its weird yet durable ecosystem, and figure out how to better preserve micronekton, whose plankton food source is threatened by climate change. The survival of the micronekton is crucial for the Maldives, for whom fishing makes up the second biggest industry besides tourism. If global warming continues at its current pace, almost 80% of the Maldives will become uninhabitable by 2050, according to the U.S. geological survey.
"The evolutionary history of this beautiful coral atoll nation is written as a record on the bedrock, deposits and the fauna of the deep,” Hussain Rasheed Hassan, the minister of Environment for the Maldives, said in the statement. This Mission is shedding light on how we may use the science to survive as a nation."
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Ben Turner is a U.K. based staff writer at Live Science. He covers physics and astronomy, among other topics like tech and climate change. He graduated from University College London with a degree in particle physics before training as a journalist. When he's not writing, Ben enjoys reading literature, playing the guitar and embarrassing himself with chess.