Deep-Sea Mining Effects on Marine Life Might Be More Significant Than Predicted

The impact of deep-sea cobalt mining on marine fauna was thoroughly analyzed in a research study based on Japan’s 2020 pilot experiment. The study documented a notable decline in marine life due to sediment pollution. Even though less mobile species appeared less affected, the investigation emphasized the potential lasting effects of deep-sea mining and called for broader and more comprehensive investigations. (Conceptual illustration.)

Marine species retreat from areas in the vicinity and beyond where deep-sea mining activities occur.

In 2020, Japan conducted its first successful test to extract cobalt crusts from deep-sea mountaintops, a process undertaken to mine cobalt, a mineral crucial for electric vehicle batteries. Areas directly affected by mining become less conducive for marine life, but the mining also generates a sediment plume that can disperse into surrounding waters. A research paper published in the Current Biology journal on July 14th scrutinized the environmental aftermath of this initial test, revealing a decline in marine life both within and around the mining area.

The International Seabed Authority (ISA), responsible for managing seabed resources beyond national jurisdictions, is yet to finalize a comprehensive deep-sea mining regulatory framework. Meanwhile, for businesses interested in extracting minerals like cobalt, copper, and manganese from the ocean floor, the ISA must either implement a set of exploitation rules or evaluate mining under the current international laws, effective from July 9.

“The urgency to disseminate this data cannot be overstated,” asserts lead author Travis Washburn, a benthic ecologist collaborating closely with the Geological Survey of Japan. “Regulations are expected to be finalized imminently, meaning a lot of these crucial decisions are being made presently.”

Japan’s 2020 experiment on deep-sea cobalt mining and its ensuing impact on marine life has been scrutinized in a recent study. The mining activity generated a sediment plume, which consequently led to a reduction in marine fauna in and around the mining area. (Conceptual illustration.)

The team examined data from three of Japan’s trips to the Takuyo-Daigo seamount: a month pre-mining, a month post-mining, and a year after the mining test. After a week-long boat journey from the port, a remotely controlled vehicle visited the seafloor and captured videos of the impacted zones. A year following the mining test, a drop of 43% in fish and shrimp density was observed in areas directly affected by sediment pollution. In contrast, a more significant decrease of 56% was reported in the surrounding areas. While there could be multiple reasons for this decline, the team posits that contamination of the fish food chain due to the mining experiment could be a factor.

The study did not find any substantial alteration in less mobile marine species like corals and sponges. However, even after a mere two-hour test, researchers warn that these species could still suffer from long-term mining activities.

“I was under the impression that we wouldn’t observe any changes because the mining experiment was rather minimal. They operated the machinery for just two hours, and the sediment plume only moved a few hundred meters,” Washburn explains. “Yet, this was sufficient to cause a shift.”

The researchers emphasize the need to replicate this study to gain a more precise understanding of the influence of deep-sea mining on the ocean floor. Ideally, several years of data should be gathered before conducting a mining test to account for natural variability in marine communities.

“We will undoubtedly require more data, but this research underscores one area requiring further attention,” Washburn observes. “We must examine this matter on a broader scale, as these results hint at the possibility that the ramifications of deep-sea mining could be much more extensive than we initially thought.”

Reference: “Seamount mining test provides evidence of ecological impacts beyond deposition” by Travis W. Washburn, Erik Simon-Lledó, Giun Yee Soong and Atsushi Suzuki, 14 July 2023, Current Biology. DOI: 10.1016/j.cub.2023.06.032

This research was facilitated by the Agency for Natural Resources and Energy of Japan, the Research Laboratory on Environmentally-Conscious Developments and Technologies, and the UK Natural Environment Research Council. The authors affirm that they have no conflicts of interest.

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• International Seabed Authority
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• Effects of Mining on Marine Life