'Casper octopod under threat from deep sea mining'
A deep sea octopod, dubbed "Casper" after the film ghost because of its appearance, could be at risk from mining, scientists say.
The animal, possibly a new species, was discovered last spring at depths of more than 4,000 metres (2.5 miles).
Studies suggest females nurture their eggs for several years on parts of the seabed that contain valuable metals.
Commercial companies are interested in harvesting metals and minerals from the bottom of the ocean.
There are growing concerns about the future impact of mining on life in the deep sea, much of which has yet to be discovered and categorised.
The octopus lays its eggs on the dead stalks of sponges, attached to rocky crusts which are rich in metals like manganese.
The female then protects the eggs as they grow, perhaps for a number of years.
"The brooding observation is important as these sponges only grow in some areas on small, hard nodules or rocky crusts of interest to mining companies because of the metal they contain," said Autun Purser, of the Alfred Wegener Institute's Helmholtz Centre for Polar and Marine Research in Germany.
"The removal of these nodules may therefore put the lifecycle of these octopods at risk."
The "Casper" octopod was spotted last year by the camera of a submersible vessel remotely operated by NOAA off Necker Island near Hawaii.
A type of octopus without fins, it crawls along the seafloor.
Jon Copley of the University of Southampton, who is not connected with the new research, said the record for octopus mothers keeping vigil over their eggs is four years, by another deep-sea species in the Pacific.
If this species is similar, then it could be particularly vulnerable to disturbance by deep-sea mining, he said.
"This discovery shows how we need far greater understanding of fundamental ecology - and far greater knowledge of the natural history of individual species - in deep-sea environments being targeted for future mining, before its potential impacts can really be assessed," Dr Copley told BBC News.
The German and US researchers investigated deep sea environments using remotely operated vehicles, and towed camera surveys, between 2011 and 2016.
They observed 29 octopods from two distinct species on the bottom of the Pacific Ocean off the Hawaiian Archipelago and in part of the Peru Basin.
Two octopods were seen to be brooding clutches of eggs that were laid on stalks of dead sponges, which require manganese to grow and stay attached to these rocky crusts or nodules.
"These nodules look a bit like a potato, and are made up of rings of different shells of metal-rich layers," said Dr Purser.
"They are interesting to companies as many of the metals contained are "high-tech" metals, useful in producing mobile phones and other modern computing equipment, and most of the land sources of these metals have already been found and are becoming more expensive to buy."
The scientists say the future of octopods and other animals, large and small, must be considered when managing "commercially attractive, yet bio-diverse and poorly understood deep sea ecosystems".
The research is published in the journal, Current Biology.
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