Saturday, January 7, 2017
It seemed simple: There are deposits of valuable minerals just lying on the sea floor for collecting—why not do it?
Now, researchers in Hawai`i are finding there are ecosystems that seem entirely dependent on these deposits—not the least of them a ghostly cute little white octopus relative nicknamed “Casper.”
(Image: The newly described octopod nicknamed Casper, photographed in 2011 near Ka`ena Ridge. Credit: Woods Hole Oceanographic Institute and the University of Hawaiʻi.)
It turns out that manganese nodules nearly a mile deep around the Islands grow a specific kind of sponge, and that Casper lays its eggs on those sponges.
Marcie Grabowski of the University of Hawai`i, wrote about this little biological-geological community on December 27, 2016.
The eight-legged Casper was spotted for the first time during a submersible dive in the Ka`ie`ie channel between Kaua`i and O`ahu. Geologists were trying to determine whether a submarine ridge that extends beyond Ka`ena Point on O`ahu was part of the Wai`anae volcanic range or a separate volcano.
Raising Islands covered that issue in 2014 here. It's O`ahu's third volcano.
The rock hounds saw this cut little white octopus, although they did not immediately realize that they may have been the first people to ever see it.
“Being a team of geologists, not cephalopod experts, we didn’t realize it was a previously unrecognized species,” said geologist Deborah Eason, of the University of Hawai`i at Mānoa’s School of Ocean and Earth Science and Technology.
Since them, new research has shown that Casper and related species inhabit seafloor habitats across the Pacific. A new paper in the journal Current Biology discusses that.
It shows that at least two species of octopods are active in water nearly a mile deep—they’ve been seen at more than 4,000 feet. And that they seem to be particularly linked to manganese rich nodules and crusts, where they attach their eggs to the stalks of dead sponges.
The sponges may be using the manganese-rich rocks, not so much for the manganese, but simply because they’re the only hard anchoring points in an otherwise muddy seafloor.
“This is the first time such a specific mineral-biota association has been observed for incirrate octopods. ... broods consisted of approximately 30 large (2.0–2.7 cm) eggs. Given the low annual water temperature of 1.5 degees C, it is likely that egg development, and hence brooding, takes years,” wrote the authors of that paper.
They clearly made the point that if you start mining the seafloor, it’s going to have an impact on the sponges and the octopi.
“The brooding behavior of the octopods we observed suggests that, like the sponges, they may also be susceptible to habitat loss following the removal of nodule fields and crusts by commercial exploitation,” said the authors, who are led by Autun Purser, of the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, in Bremerhaven, Germany. Eason is a co-author on that paper.
Casper the octopod has, since its discovery, gone viral for its similarity in appearance to the cartoon character, Casper the Friendly Ghost. The deep-sea critter now gets millions of hits on internet searches for news sites, television reports, magazines, newspapers and blogs. Scientific American had a piece here.
© Jan TenBruggencate 2017