Impact of Underwater Eruption: How Ash-Laden Coral Reefs and Marine Life are Affected

In 2022, something remarkable happened beneath the ocean. The Hunga volcano erupted, sending ash 37 miles into the sky. It was the biggest volcanic plume ever recorded by satellites. This colossal event offered scientists a unique opportunity to study the underwater ecosystem and its response to such a massive disturbance.

Months later, a research team, including undergraduate student Marcus Chaknova, ventured to the eruption site. They were surprised to find the seafloor covered in thick layers of ash, which had smothered delicate deep-sea life that depends on intricate chemical exchanges for survival.

Chaknova, now a graduate student at the University of Oregon, highlighted how rare this event was. “Observing how sediment shifts underwater hasn’t been studied much,” he noted. Working alongside Professor Thomas Giachetti and 16 other experts from various fields, Chaknova led a study to understand how this volcanic ash was distributed and its impact on marine life.

One of their first tasks was confirming the ash’s origin. The Hunga volcano, located about 40 miles from Tonga, was indeed the source. After an eruption, ash takes weeks to settle on the ocean floor, often drifting far from its point of origin due to currents. Professor Giachetti likened it to a leaf falling from a tree—its path can be unpredictable.

In the lab, Chaknova analyzed ash samples. They found various shapes, from sharp grains to smooth ones. In some spots, the sediment was over a meter thick, composed mainly of fine particles the size of human hair.

The eruption’s aftermath extended beyond geological changes. It disrupted entire ecosystems in the deep sea, where organisms typically rely on chemosynthesis for energy since sunlight doesn’t reach them. A staggering 90% of marine life resides on the ocean floor, according to the World Wildlife Fund. The sudden layer of ash buried much of this life, which couldn’t cope with such an abrupt change.

Many deep-sea creatures are filter feeders, relying on tiny particles in the water for sustenance. “With all the ash, these organisms end up sifting through sediment rather than food,” Chaknova explained. This could have severe consequences for their health and survival.

Interestingly, the ash also reached Tonga’s coral reefs. Initially, it caused a brief spike in plankton blooms; however, as the ash settled, it posed a significant threat to coral ecosystems. Coral health is crucial since it supports larger marine life and, consequently, local fishing industries. Approximately 82% of Tongan households depend on fishing, making it vital for their food security and economy. The World Bank reports that marine tourism also contributes significantly to Tonga’s GDP.

Chaknova’s findings carry important lessons. As interest in deep-sea mining grows—especially for metals vital for clean energy—the potential dangers of sediment plumes created by mining could mirror those from natural eruptions. This research provides invaluable insights, allowing scientists and policymakers to weigh the environmental risks against economic benefits.

Ultimately, the study, published in the journal Geochemistry, Geophysics, Geosystems, sheds light on the complex interplay between geological events and marine ecosystems, emphasizing the need for careful consideration in future mining endeavors.

For those looking for more information, you can check out the full study here.

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