“Unveiling the Impact: Lau Basin How a Volcanic Eruption Transformed Deep-Sea Ecosystems”
In April 2022, a team of scientists aboard a research vessel in the Lau Basin near Tonga embarked on a mission to study deep-sea animals living around hydrothermal vents. Their plans took an unexpected turn when they deployed a remotely operated vehicle (ROV) to explore these vents, only to find the seafloor, typically a hard basalt surface, covered in sediment resembling a snow-covered landscape.
Lau Basin
“It was like a snow-covered landscape,” described Roxanne Beinart, a marine microbial ecologist from the University of Rhode Island, who was part of the expedition. The team suspected the sediment was ash from the powerful eruption of the Hunga volcano in January 2022, which had profoundly impacted the ecosystem by killing off vulnerable mollusks.
Recognizing the unique opportunity to document the effects of such a large volcanic eruption on marine ecosystems, the scientists quickly began their survey. Their findings, published in Communications Earth and Environment, mark the initial phase of their investigation into how these ecosystems recover over time.
“This is a real opportunity to understand and study the impacts of a large eruption,” commented Isobel Yeo, a volcanologist from the UK’s National Oceanography Centre, highlighting the rarity of such events where processes and timescales are well-documented.
Over 24 days, the team surveyed six hydrothermal vent fields using the ROV, collecting sediment samples that revealed an abundance of volcanic glass—a hallmark of volcanic ash. They improvised methods to measure the ash depth, using a T-shaped metal rod with colored markers every 7.6 centimeters, revealing depths of up to 1.5 meters near the volcano and significant deposits even 96 kilometers away.
The ash had likely descended from the eruption, settling in the water and gaining density as it flowed down the volcano’s slopes, analogous to a snow avalanche on land. This rapid flow, termed “roaring into the deep sea” by marine geoscientist Mike Clare, underscores the powerful currents that carried the ash over varied seafloor terrain to reach the hydrothermal vents.
The impact on marine life was drastic. Comparing footage from a 2019 expedition to the same sites, the team observed stark contrasts: while some mobile species like lobsters and crabs appeared unaffected, the populations of snails and mussels, many of which are endangered, were devastated.
“These populations were decimated,” lamented Beinart, attributing the mollusks’ vulnerability to their limited mobility and their oxygen-intensive symbiotic relationships with bacteria. Covered by ash, they suffocated as their oxygen needs surpassed their ability to escape.
Looking ahead, the scientists plan to revisit the sites in 2026 to monitor recovery dynamics. Their research aims to understand how these ecosystems cope and regenerate after such a catastrophic event. While scientific precedent suggests recovery is possible, the timeframe and trajectory of recovery remain uncertain.
“This study provides a valuable baseline,” remarked Clare, emphasizing the study’s significance in tracking long-term changes in the seafloor ecosystem post-eruption. As they continue their research, the team hopes to uncover insights that will illuminate the resilience and adaptability of deep-sea ecosystems in the face of natural upheavals.
