Kavachi and the Adapted Sharks: Life in an Underwater Volcano

The Kavachi volcano, located in the southwestern Pacific Ocean near the Solomon Islands, is considered one of the most active underwater volcanoes in the world. Nicknamed "Sharkcano", it is notable not only for its intense geological activity but also for sustaining unique life forms in an extreme environment. The Kavachi caldera, which periodically emerges above sea level during eruptions, creates conditions characterized by high temperatures, low oxygen levels, high acidity, and significant concentrations of volcanic gases (PHILLIPS et al., 2016).

In May 2022, NASA (National Aeronautics and Space Administration) satellite images recorded volcanic activity at Kavachi, detecting discolored water plumes above the volcano, indicating that it likely began erupting in October 2021 (NASA EARTH OBSERVATORY, 2022). Despite these harsh conditions, a surprising biodiversity has been documented in its waters, with sharks being the most remarkable presence.

Caption. Image of the Kavachi Volcano eruption. Credits: NASA EARTH OBSERVATORY.

Phillips et al. (2016) report that, following an expedition, it was possible to identify the presence of an ecosystem within the Kavachi crater, including gelatinous zooplankton, reef fish, and sharks. Among the shark species identified, the hammerhead shark (Sphyrna lewini) and the silky shark (Carcharhinus falciformis) stand out. These animals were filmed swimming inside the crater, displaying aggressive behavior toward bait placed by the cameras. The presence of large marine predators in such a hostile environment raises questions about the physiological and behavioral tolerance limits of these organisms.

Caption. (A) Scalloped hammerhead shark and (B) Silky shark recorded in the Kavachi crater. Credits: PHILLIPS et al., 2016.

The same study also reports that the environmental conditions observed in Kavachi are extreme, with warm and acidic waters due to the release of gases rich in carbon dioxide (CO₂) and sulfur. Measurements taken over the crater revealed a temperature increase of up to 13°C above the surrounding environment, reaching approximately 42°C. Additionally, the pH was estimated at around 6.1, characterizing a highly acidic environment. The observed hydrothermal plume was filled with suspended particles, creating an ideal habitat for adapted microbial populations, such as bacteria of the Sulfurimonas genus, which are capable of performing chemosynthesis using sulfur and CO₂.

Studying the Kavachi ecosystem not only expands our understanding of marine life adaptation to extreme conditions but also highlights the resilience of biodiversity in the face of climate change and ocean acidification. This fascinating interaction between geology and biology, explored in the Sharkcano documentary aired by National Geographic, demonstrates how inhospitable environments can sustain surprising forms of life, reinforcing the importance of investigating the limits of survival and adaptation in today's global scenario.

Author: Roberta Stopasolla Pinto - Director of Internal Communications at GEAS Brasil 

Review: Iago Junqueira - Partner of GEAS BRASIL at The Wild Place 

Painel Selvagem, January 2025

References:

GLOBAL VOLCANISM PROGRAM. Report on Kavachi (Solomon Islands). In: BENNIS, K. L.; ANDREWS, B. (ed.). Bulletin of the Global Volcanism Network, v. 48, n. 8, 2023. Smithsonian Institution. Available at: Global Volcanism Program | Kavachi. Accessed on: January 14, 2025.

PHILLIPS, B. T.; DUNBABIN, M.; HENNING, B.; HOWELL, C.; DECICCIO, A.; FLINDERS, A.; KELLEY, K. A.; SCOTT, J. J.; ALBERT, S.; CAREY, S.; TSADOK, R.; GRINHAM, A. Exploring the “Sharkcano”: Biogeochemical observations of the Kavachi submarine volcano (Solomon Islands). Oceanography, v. 29, n. 4, p. 160–169, 2016. Available at: https://doi.org/10.5670/oceanog.2016.85. Accessed on: January 14, 2025.

NASA EARTH OBSERVATORY. Submarine Eruption of Kavachi Volcano. Available at: NASA Earth Observatory. Accessed on: January 14, 2025.

REVISTA GALILEU. Famous shark habitat, submarine volcano erupts. Available at: Revista Galileu | Espaço. Accessed on: January 14, 2025.

025.