In March 2016, the world met Casper, a milky-white deep-sea octopus that makes its home 2.5 miles beneath the ocean surface.

Now, a new study suggests that the newly discovered cephalopod could be under threat from deep sea mining.

In a paper published Monday in Current Biology, a team of researchers report that octopi such as Casper have been observed to lay their eggs on the stalks of dead sponges. These sponges in turn are attached to fist-sized clumps of metals that slowly precipitate out of the water column over millions of years. They are called manganese nodules.

An octopod broodis its eggs on the stalk of a dead deep-sea sponge. The sponge stalk is attached to a manganese nodule, a naturally forming rock containing commercially interesting metal deposits. (Alfred Wegener Institute )


The nodules aren’t much to look at (black, shaped like a potato), but the metals they contain are used in cellphones and computers, making them increasingly attractive to miners.

“Many of these metals are not available easily on land at a good price,” said lead author Autun Purser of the Alfred Wegener Institute for Polar and Marine Research in Germany. “This is driving research into how to get these metals out of the sea.”

The deep sea is hard to get to and expensive to explore, and marine scientists still don’t know much about it. Until recently, they’ve had little opportunity to learn how mining on this part of the planet will affect the plants and animals that live there.

There are a few research vessels that are equipped to explore the seafloor. For example, Casper was spotted in the Hawaiian archipelago by scientists aboard the National Oceanic and Atmospheric Administration’s Okeanos Explorer, which is tasked with exploring the deep sea.


In this new study, the researchers relied on observations of 29 deep sea octopi made over five years, from 2011 through 2016. All the observations were made with the help of ROVs — remotely operated vehicles that can descend to depths that would be impossible for any human to reach without a submarine.

Only two of the octopi included in the study were seen brooding over their eggs, but in both cases, the eggs were on dead sponge stalks. Although octopi have been known to lay hundreds of eggs, both of the observed broods consisted of approximately 30 large eggs between 2 centimeters and 2.7 centimeters.

Previous studies have shown that octopods are vigilant parents who watch over their eggs for as long as it takes until they hatch.

In the deep sea, where temperatures hover near freezing and the pace of life tends to move more slowly than in warmer waters, this process could take years.


The researchers suggest that if miners remove manganese nodules in deep sea areas such as the Peru Basin in the southern Pacific, the sponges will have nothing to attach themselves to and these deep sea octopods could lose an essential habitat for reproduction.

“The most important part of our study is the observation that these large, mobile animals can be impacted by nodule mining,” Purser said. “If the nodules are mined, there will be nowhere for the stalked sponge to grow and therefore nowhere for the octopods to lay their eggs.”

He added that there are likely other unexpected life stories that could be affected by nodule mining.

“If we are serious about protecting our deep sea heritage, further research work is needed before we can best reduce the impacts of resource collection in these remote regions of the world ocean,” he said.


deborah.netburn@latimes.com

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