Earlier this year, oceanographer Brennan Phillips led a team of scientists on an expedition to Kavachi, an underwater volcano known to be one of the most active in the southwest Pacific. Located approximately 60 feet (18 m) beneath the surface near the Solomon Islands, Kavachi is prone to regular eruptions, the most recent of which took place in January 2014. Phillips’ team embarked on their expedition to learn more about Kavachi’s geology, but discovered something quite unexpected in the process.
Even when Kavachi is not erupting, the underwater volcano is an inhospitable place. Due to bubbling chemical plumes of methane and carbon dioxide, the water within the crater is highly acidic, to the point where divers who have tried to approach the crater have suffered acid burns. The water is also incredibly hot, and yet, when Phillips and his team reviewed footage of Kavachi filmed by National Geographic’s remote deep-sea Drop Cam, they were astounded to see evidence of life within the crater itself.
The scientists watched incredulously as the footage revealed first a sixgill stingray, then significant numbers of scalloped hammerhead and silky sharks, all of which appeared to be flourishing in water discolored by chemical fluctuations. Phillips summed up the enormity of the discovery, saying “these large animals are living in what you have to assume is much hotter and much more acidic water, and they’re just hanging out. It makes you question what type of extreme environment these animals are adapted to. What sort of changes have they undergone? Are there only certain animals that can withstand it?”
The discovery of the sharks within Kavachi’s crater also raises questions about how the animals cope when the volcano erupts. Since the volcano’s first recorded eruption in 1939, Kavachi has undergone several periods of major activity, many of which have lasted for several months. Since it’s highly unlikely that the sharks living in the volcano could survive an eruption, Phillips is anxious to find out whether they “get an early warning and escape the caldera before it gets explosive, or do they become trapped and perish?”
Apparently, eruptions are preceded by an audible rumbling sound, so perhaps the sharks have learned to associate that sound with imminent activity and abandon the area. Phillips hopes to launch another project to find out, by pairing observations of the sharks’ behavior with actual eruptions of Kavachi’s main peak. To do this, the team would need to monitor seismic activity while deploying underwater cameras capable of producing long-term footage of the volcano’s sharks.
In a time when ocean acidification as a result of climate change threatens the health of marine environments all over the world, understanding how the Kavachi sharks have adapted to survive in highly acidic conditions is of particular interest. The discovery demonstrates the incredible aptitude for adaptation and survival that has enabled shark species to thrive for millions of years, while highlighting how much we still have to learn about our oceans.