Impacts of an industrial deep-sea mining trial on macrofaunal biodiversity | Nature Ecology & Evolution
A large-scale trial of a commercial deep-sea mining machine in 2022 on an abyssal plain at 4,280 m depth extracted over 3,000 tonnes of polymetallic nodules — prompting researchers to assess the impact on sediment-dwelling macrofauna. By comparing species-level data collected for two years before and two months after the mining test, they separated mining effects from natural background variation. Within the mining tracks they observed a 37% drop in animal density and a 32% loss in species richness. Although overall diversity metrics (when adjusted for sample size) appeared stable, the structure of the community shifted: rarefaction shows many species remain undiscovered, and dominance patterns changed, hinting at long-term disruption. Meanwhile, areas impacted only by sediment plumes showed altered species dominance but no clear change in total abundance. The findings demonstrate deep-sea mining’s capacity to rapidly degrade seabed biodiversity and underscore the need for rigorous baseline and impact monitoring before commercial exploitation.
The Key points
- A 2022 deep-sea mining trial removed over 3,000 tonnes of polymetallic nodules from the ocean floor at ~4,280 m depth.
- Two-year pre-mining and two-month post-mining sampling allowed distinguishing mining impacts from natural variation.
- Within the mining tracks, macrofaunal density fell by 37%.
- Species richness dropped by about 32% inside the mined area.
- Sample-size–independent diversity metrics did not show a clear drop, masking community structure changes.
- Species dominance patterns shifted — some species declined, others became more dominant — reducing overall biodiversity.
- Regions adjacent to mining tracks but affected only by sediment plumes showed no decline in abundance, though community composition changed.
- In total, 788 macrofaunal species were identified in the study area, with many more estimated to remain undiscovered.
- The results highlight the importance of detailed, species-level baseline surveys for deep-sea environments before mining.
- The study warns that commercial-scale seabed mining could cause substantial, rapid losses of deep-sea biodiversity.
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