- Casper the octopod lays its eggs on stalks of dead sponges attached to nodules rich in manganese on the ocean floor.
- The stalked sponges require the presence of manganese nodules as a substrate for their survival, and the removal of nodules can cause a collapse of the sponge populations.
- This would suggest that, like the sponges, the octopods would also be vulnerable to the removal of nodules by commercial exploitation, the researchers say.
“Casper”, the ghost-like octopod discovered early this year, could be at risk from deep sea mining, scientists say.
The octopod was found at a depth of 4,290 meters (2.7 miles) during a deep ocean expedition near Hawaii’s Necker Island.
At such depths, the animal lays its eggs on stalks of dead sponges attached to nodules rich in metals like manganese, scientists report in a new study published in Current Biology. In fact, octopods like Casper seem to be abundant in manganese-rich areas, regions which are likely to attract future deep sea mining, researchers say.
“These nodules look a bit like a potato, and are made up of rings of different shells of metal-rich layers,” lead author Autun Purser of the Alfred Wegener Institute’s Helmholtz Centre for Polar and Marine Research in Germany, said in a statement. “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.”
Between 2011 and 2016, Purser and his colleagues examined three nodule-abundant regions of the deep Pacific using remote operated-vehicles, and observed 29 octopods of two distinct species. Two of these octopods laid broods of about 30 large eggs on stalks of dead sponges that were attached to rocky, metal-rich nodules on the sea floor.
The stalked sponges require the presence of manganese nodules as a substrate for their survival, the researchers say. They know this because the experimental removal of nodules has been shown to cause a collapse of the sponge populations.
This would suggest that, like the sponges, the octopods would also be vulnerable to the removal of nodules by commercial exploitation, the team adds. Moreover, these nodules can take millions of years to form, putting these octopods and other nodule-dependent animals at risk.
“As long-lived creatures, recovery will take a long time and may not be possible if all the hard seafloor is removed,” Purser said. “This would be a great loss to biodiversity in the deep sea and may also have important knock on effects. Octopods are sizable creatures, which eat a lot of other smaller creatures, so if the octopods are removed, the other populations will change in difficult to predict ways.”
- Autun Purser, Yann Marcon, Henk-Jan T. Hoving, Michael Vecchione, Uwe Piatkowski, Deborah Eason, Hartmut Bluhm, Antje Boetius. Association of deep-sea incirrate octopods with manganese crusts and nodule fields in the Pacific Ocean. Current Biology, 2016; 26 (24): R1268 DOI: 10.1016/j.cub.2016.10.052