The mystery of the mystical holes on the ocean floor has been revealed

Created by porpoises

Mysterious depressions discovered in the North Sea were previously thought to be the result of methane seeping from beneath sediments. But new research has shown that these mysterious phenomena are likely signs of life left behind by porpoises and sand eels that live in the region.

Photo: en.wikipedia.org

In a study conducted by geophysicist Jens Schneider von Deimling from the University of Kiel, it was proven that small depressions are the responsibility of representatives of underwater fauna. Porpoises (mammals similar to dolphins, but related to toothed whales) living in the North Sea forage on the bottom, and sand eels also nest there, which crawl out of their burrows, leaving holes behind them. The study was published in the journal Communications Earth & Environment.

“Our results show for the first time that these depressions arise in direct connection with the habitat and behavior of porpoises and sand eels and are not formed as a result of rising fluids, as previously thought,” says Schneider von Deimling. “Our high-resolution data provide new interpretation of the formation of tens of thousands of holes on the seafloor of the North Sea, and we predict that the underlying mechanisms occur globally.”

The previous interpretation of the holes was that fluid was escaping from the bottom. At the same time, many depressions—in fact, most—cannot be explained in this way.

The research team used a combination of high-resolution sonar mapping of the seafloor, behavioral biology, oceanographic analysis and satellite imagery to study the shape of the seafloor, look for traces of methane and find out what animals are active in the areas where the holes appear. Scientists have found that the depressions are often located in the foraging areas of porpoises, which are close to the habitat of sand eels.

New high-resolution data shows that the marine mammals leave shallow holes on the bottom that are only about 11 centimeters deep as they forage.

“The mechanism of formation of these pits, as we call them, likely also explains the existence of numerous crater-like depressions on the seafloor around the world that have been misinterpreted as the result of methane gas leaking,” says Jens Schneider von Deimling.

The study, the team says, suggests that humanity is significantly underestimating the impact of marine vertebrates on the ocean floor environment.