On the expansive abyssal plains of our oceans, stretches of sedimented habitat conceal treasures that have remained largely untouched for generations. Found at depths between 3,000 and 6,000 meters, polymetallic nodules emerge as the prominent mineral treasure, scattered across vast areas akin to potatoes scattered in a farmer’s field. These geological formations form over thousands of years through complex processes involving metals dissolved in ocean water and the remnants of organic material decomposed by microbes in the seabed. As technological advancements propel exploration further into these depths, there is an increasing call for the harvesting of these metals, including nickel, cobalt, and copper, essential for modern technologies.
However, the deep-sea environment isn’t simply a treasure trove. It houses an intricate ecosystem of high biodiversity, primarily composed of minute organisms residing in the sediment. These ecosystems are exceptionally delicate to any disturbance. Since the initiation of the European project known as MiningImpact in 2015, led by the GEOMAR Helmholtz Centre for Ocean Research Kiel, there has been a concentrated effort to study the environmental implications associated with deep-sea mining. The preliminary findings, particularly concerning the Clarion-Clipperton Zone and the Peru Basin, reveal a disconcerting long-term impact that mining activities could have on biodiversity and crucial ecosystem functions, effects that may last for centuries.
A significant yet underexplored risk linked to deep-sea mining is the disturbance of sediment plumes, which can spread and affect areas far removed from the mining site itself. To investigate this issue further, researchers have meticulously monitored trials involving a newly developed remotely operated pre-prototype nodule collector implemented by Global Sea Mineral Resources, a contractor from Belgium. The findings, which have recently been published in the esteemed journal Nature Communications, illustrate the extensive spatial footprint characterizing the dispersion and redeposition of sediment plumes generated by mining activities.
Lead researcher Iason-Zois Gazis, hailing from the DeepSea Monitoring Group at GEOMAR, notes an important observation: “While the predominant fraction of the sediment settles back within a few hundred meters from the source, we have detected nuances in sediment concentration extending as far as 4.5 kilometers away.” This observation underscores the extensive reach of mining activity, hinting at ecological consequences that may not be immediately apparent close to the mining zone.
On April 19, 2021, a notable experiment was undertaken, which saw the deployment of a nodule collector at an astonishing depth of 4,500 meters for a span of 41 hours. Over the course of this operation, the vehicle navigated approximately 20 kilometers, meticulously covering an astonishing 34,000 square meters of seafloor — an area roughly equivalent to five football pitches. Throughout this duration, a diverse array of calibrated sensors was employed to monitor the sediment plume generated by the collector, utilizing various stationary platforms positioned on the seafloor, alongside remotely operated and autonomous underwater vehicles.
The results from the study were revealing. Specifically, researchers documented the emergence of a gravity current composed of dense suspended particles trailing behind the collector as it traversed the seabed. This phenomenon presented a notably complex interaction between the mining apparatus and the unique geological features beneath the ocean, with the current propagating downslope through steeper sections of the seabed for nearly 500 meters. The subsequent spread of the sediment plume appeared to be predominantly driven by natural near-bottom currents, a dynamic interplay between human activity and the forces of nature.
Proximity to the mining site yielded staggering sediment concentrations, at times reaching levels up to 10,000 times higher than what could be deemed normal. Fortunately, this perturbation was temporary, with sediment concentrations returning to baseline levels within just 14 hours post-operation. Most of the suspended particles, noted the researchers, remained in the upper 5 meters of the water column above the seafloor. They settled back relatively quickly, a process facilitated by particle flocculation, an essential process that aids the natural remediation of disturbed environments.
Further analysis employed high-resolution 3D mapping techniques to accurately depict the marks left behind from the mining operation, revealing an astounding level of detail down to the millimeter. Researchers calculated the sediment extracted from the mining area and the amount that subsequently redeposited on the seafloor. Results indicated that substantial nodules were removed from the top five centimeters of the seafloor. Additionally, the redeposited sediment layer formed a thickness of approximately three centimeters, effectively obscuring the surrounding nodule habitat in proximity to the mining area, with the thickness tapering off the further away one moves from the mining site.
This study not only elucidates the immediate impact of mining activities on deep-sea ecosystems but also contributes essential data that can aid in shaping global regulatory frameworks for deep-sea mining. As the International Seabed Authority (ISA) continues to develop guidelines for these operations, findings from MiningImpact will serve as a pivotal resource. Researchers remain committed to ongoing assessments of environmental impacts, aiming to forge a connection between the physical disturbances caused by mining and the ecological consequences that follow.
The call for further understanding of these effects is more critical than ever. As the world increasingly turns to the ocean floor as a source for vital minerals, it is imperative that we weigh the immediate benefits against the potential long-term ecological fallout. A balance must be struck that ensures resource extraction does not irreversibly damage these vital marine ecosystems. The future of deep-sea mining lies not only in uncovering the seabed’s treasures but also in safeguarding the interconnected webs of life that have flourished in these depths for millennia.
Deep-sea mining remains a contentious topic on the global stage, evoking passionate debates among environmental scientists, policymakers, and industry stakeholders. As we advance into the depths, the lessons gleaned from projects like MiningImpact must illuminate responsible practices that embrace cautious exploration and sustainable management of our oceans. It is a shared responsibility to safeguard the abyss and ensure that even as we seek the riches hidden beneath the waves, we do so with the utmost respect for the marine ecosystems that harbor these precious resources.
With Earth’s demands ever-increasing, particularly for technologies reliant on rare earth elements, the relationship between society’s thirst for progress and environmental preservation must be navigated with diligence. The exploration for new resources should harmonize with a commitment to maintaining the ecological integrity of the world’s oceans, ensuring that we leave behind a vibrant and thriving marine environment for future generations.
Subject of Research: Environmental impacts of deep-sea mining
Article Title: Monitoring benthic plumes, sediment redeposition and seafloor imprints caused by deep-sea polymetallic nodule mining
News Publication Date: 31-Jan-2025
Web References: http://dx.doi.org/10.1038/s41467-025-56311-0
References: Nature Communications
Image Credits: GEOMAR Helmholtz Centre for Ocean Research Kiel
Keywords: deep-sea mining, sediment, sea floor, ocean policy, marine ecosystems, biodiversity threats, environmental monitoring, vehicles, materials testing, pattern formation, mineral resources, marine biodiversity
