This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Little is known about the long-term effects of deep-sea mining on the organic matter that supports life on the seafloor. However, as interest in mining the deep sea for rare metals grows, there is concern that disturbing the seabed could affect the ecosystems of the deep ocean.
New research by the University of Liverpool published in Elementa: Science of the Anthropocene provides evidence that the effects of deep-sea mining on the organic matter that supports life on the seafloor can still be found more than four decades later. In 2023, a team of researchers from the SMARTEX (Seabed Mining and Resilience To EXperimental Impact) project investigated an area of seafloor in the Clarion-Clipperton Zone of the Pacific Ocean that had been used as a test site for deep-sea mining by the Ocean Minerals Company in 1979. The tracks of the 100-ton mining machine are still visible on the seafloor.
The team spent a month collecting sediment samples from the seabed at a depth of about 4,800 meters (15,750 feet), both within and around the historical mining disturbance and at an undisturbed control site. They analyzed the quantity and quality of particulate organic matter in the sediments. This organic matter is an important food source for organisms living on and within the seafloor and provides essential nutrients, such as omega-3 fatty acids, that support growth, development and reproduction.
The team assessed organic matter quality using a range of measurements, including carbon and nitrogen content, lipid biomarkers and stable isotope analysis. The study reveals differences in organic matter composition and particle size, coupled with lower quantity and quality of organic matter at the historic mining site more than four decades after completion of the test mining. Using still and video images from the area, the SMARTEX project identified lower abundances of both larger animals and single-celled organisms living in the sediments affected by the test mining.
This study linked these lower organism abundances to the depleted organic matter observed in the mined area, suggesting implications for the recovery and resilience of deep-sea animals to mining impacts. The Clarion-Clipperton Zone is a huge area of ocean located in the eastern and central Pacific Ocean between Hawaii and Mexico. There is significant interest in mining its polymetallic nodules, which contain rare and critical metals used in modern electronics, such as rechargeable batteries and touch screens, and in manufacturing.
The researchers say their findings demonstrate the importance of considering long-term changes to the availability and quality of organic matter when assessing the environmental impacts of deep-sea mining. Rachel Jeffreys is a marine biologist at the University of Liverpool and the lead author of this study. She said, "Deep-sea mining is likely to alter the seafloor by disturbing and moving sediments, but we still do not understand the full range of environmental impacts or how these disturbances will affect the species and ecosystems that live in the deep sea.
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