Depression marks on seafloor suggest whales might be visiting prospective mining sites

Date: August 22, 2018

Source: Phys Org
Author: Bob Yirka

A trio of researchers with the National Oceanography Centre in the U.K. has found depression marks on the sea floor in a very deep part of the ocean—they suggest the marks may have been made by deep-diving whales. In their paper published in the journal Royal Society Open Science, Leigh Marsh, Veerle Huvenne and Daniel Jones describe how they found the marks, and why they believe they might have been made by whales.

In recent years, scientists have discovered that the seafloor is home to many rocky nodules that harbor valuable materials such as rare-earth elements and metals such as copper. Eager to cash in, companies have begun the process of sending machinery down to the bottom of the sea to set up mining operations. The researchers with this new effort suspected that such mining operations might cause problems for creatures that make use of the seafloor. They have been sending remotely controlled vehicles down below to study the ocean floor to find out. Past evidence has shown some creatures, such as starfish, live at very great depths. In this latest effort, they report that they might have found evidence of a type of whale making use of the seabed to forage for food—also at very great depths.

The researchers have been focusing on an area known as the Clarion-Clipperton Fracture Zone, a large swath of seafloor located between Mexico and Hawaii—past research has shown it is a region with a lot of rocky nodules. The remote vehicles they sent to the bottom of the ocean were outfitted with side-scan sonar, which can scan the seafloor looking for geographic features of the underwater terrain. The researchers report that they have found what they describe as a series of depressions resembling tracks made by beaked whales in other parts of the world. But what is unusual is the depth—from 3,999 to 4,258 meters. That is far deeper than any other observed tracks.

The researchers believe the depressions were caused by deep-diving whales sifting seafloor debris looking for food. They acknowledge that more research will need to be done to prove that the marks were made by whales—but if their suspicions turn out to be correct, it could impact licensing for mining in such areas.

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