Mussels surprisingly thrive in a small, harsh section of the western Pacific. The future of other molluscs? Not so certain.
North of Guam, along the Mariana arc in the western Pacific Ocean, corrosive liquid carbon dioxide droplets rise from the ocean floor to the surface like wobbly champagne bubbles as hydrothermal vents gush plumes of super-heated water and dissolved minerals.
Some organisms happily thrive in this extremely acidic environment — even more than scientists initially thought.
Prof. Verena Tunnicliffe and a multi-disciplinary team of colleagues have been monitoring the site and reported their latest findings in a recent issue of the journal Nature Geoscience.
“We found surprisingly rich populations of organisms that have adapted to life in the very challenging conditions on active, deep sea volcanoes,” says Tunnicliffe, “These populations have grown substantially in complexity and size since our last visit to the area in 2006 — despite a very intense cycle of eruptions.”
In particular, mussels practically carpet the crater of an active volcano 1.6 km below the surface, in temperatures of 100ºC. To protect themselves from the acidic environment, they have an outer organic layer that covers and insulates their shells.
“Without this protective layer, the acid in the water would eat away the mussel’s shell within a few hours,” says Tunnicliffe, “It’s a remarkable adaptation that has allowed this species to grow from just a few small groups of animals to a vast colony covering most of the volcano.”
It also helps that predators, such as crabs aren’t able to cope in the extreme conditions.
“It’s intriguing that the highly unpredictable nature of the environment is balanced by conditions that enhance survival for some species,” says Tunnicliffe. “What would mean certain death for one species means a quiet life with plenty of food and no predators, for another.”
In the related, broader context, Tunnicliffe is concerned as more carbon dioxide is absorbed from the atmosphere and the ocean acidifies, there will be a decrease in the carbonate used by molluscs to make shells.
“It’s happening so fast that the ocean cannot buffer it,” Tunnicliffe told CBC Radio’s Quirks and Quarks. “As our oceans acidify, many species won’t be able to change fast enough, and we’ll lose a lot of animals. Of course, some species will be able to move in and adapt, but it’s impossible to know exactly what changes will happen. The whole balance of the system will be perturbed and it’s hard to predict what adaptation will occur. We do know there will be a change.”