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Deep-sea mining has deadly consequences for marine life

The ocean’s abyssal depths, a realm of perpetual darkness and immense pressure, harbor unique ecosystems still shrouded in mystery. This remote world, once seemingly devoid of life, is now of heightened interest due to extensive mineral deposits on the seafloor – prompting the rise of deep-sea mining. Yet, a critical tension exists between the potential economic gains and the largely unknown environmental risks to these vast, unexplored habitats of marine world.

Deep-sea mining and marine life

To understand the potential impacts of deep-sea mining, scientists often turn to filter-feeding organisms like sponges and brittle stars. These animals play important roles in deep-sea ecosystems and are uniquely vulnerable to the effects of mining-related pollution.

Sponges act as powerful “living filters,” processing large volumes of water to extract tiny food particles and dissolved nutrients. This filtering activity makes them susceptible to ingesting any contaminants suspended in the water column.

Brittle stars, closely related to starfish, play a different yet equally vital role. As they move across the seafloor, they ingest and redistribute sediment, playing a key role in nutrient cycling within the deep-sea ecosystem. Close interaction with the seafloor means they could accumulate pollutants released from disturbed sediment.

Because these organisms rely on filtering the surrounding environment for sustenance, they are particularly susceptible to pollutants introduced by mining activities. This sensitivity makes them valuable indicators for scientists. By monitoring changes in their health, behavior, or tissue chemistry, researchers can gain insights into the spread and ecological effects of mining-related contamination.

Seafloor massive sulfide

A recent study by researchers at Wageningen University & Research and the University of Bergen underscores the cause for concern about the impacts of deep-sea mining. To understand the potential effects of mining activities, they carefully simulated the sediment plumes that would likely be generated during operations.

The researchers exposed the common deep-sea sponge Geodia barretti and its associated brittle stars to crushed seafloor massive sulfide (SMS) deposits. SMS deposits are naturally occurring mineral formations found on the seafloor that contain high concentrations of commercially valuable metals like copper, zinc, and gold.

The potential economic value of SMS deposits makes them prime targets for deep-sea mining operations. However, disturbing these deposits would release large clouds of sediment into the surrounding water, impacting marine life.

“The adverse effects observed on Geodia barretti and associated species signal potential disruptions in benthic-pelagic coupling processes, necessitating further research and to establish guidelines for protection of this deep-sea fauna,” stated research leader and marine biologist Erik Wurz.

Troubling life of marine animals by deep-sea mining

The study revealed concerning results regarding the potential impact of deep-sea mining on marine life. Sponges exposed to the simulated mining plume exhibited a tenfold increase in tissue death compared to the control group. This dramatic rise in mortality suggests a significant negative impact on the health of these organisms.

In addition, all of the brittle stars exposed to the crushed SMS deposits perished within ten days of the experiment. While the exact cause of death requires further investigation, the researchers believe it’s likely linked to exposure to toxic metals released by the crushed material. This rapid mortality rate raises serious concerns about the ability of deep-sea ecosystems to recover from mining activities.

To further investigate the impact of mining particles, the researchers analyzed the tissues of the exposed sponges. They found significantly higher concentrations of iron and copper compared to unexposed sponges.

This accumulation of metals within the filter feeders demonstrates their vulnerability to ingesting and retaining pollutants released during deep-sea mining operations. The study highlights the potential consequences of large-scale mining activities on the deep-sea ecosystem, particularly for filter-feeding organisms like sponges.

Why the disruption matters

Deep-sea ecosystems are unique in several ways that make them exceptionally vulnerable to disturbance. Unlike many land-based or shallow-water ecosystems, organisms in the deep sea are adapted to environments where food resources are scarce and temperatures are near freezing. This leads to extremely slow growth rates and long lifespans for many deep-sea species.

As a result, populations may take decades or even centuries to recover from even minor disruptions. Additionally, the various organisms within these ecosystems are often tightly interconnected in complex food webs. Removing or harming one species can have significant ripple effects for others that depend on it for food, shelter, or other ecological services.

Deep-sea mining operations pose a specific threat to these habitats. Large-scale mining activities could disrupt or alter the natural cycles of nutrients within the deep-sea environment.

The sediment plumes created by mining could also smother the seafloor, burying organisms vital to the food web and altering the physical environment that many deep-sea species rely on for survival.

These disruptions could have long-lasting and potentially irreversible consequences for the overall health of these delicate deep-sea habitats.

Urgent need for assessment

“[These results] underscore the urgent need for comprehensive assessments of deep-sea mining impacts on marine ecosystems,” said Wurz. Before large-scale mining becomes widespread, a thorough understanding of its potential consequences is crucial.

Researchers need more data on deep-sea biodiversity, the dispersal of mining plumes, and the resilience of these slow-growing ecosystems to disturbance. This information is essential for informed decision-making about both the scale and appropriate locations for mining activities.

The regulation of deep-sea mining falls under the International Seabed Authority, charged with balancing potential commercial interests with responsible environmental stewardship in areas beyond national jurisdiction. The scientific community, together with responsible industries and policymakers, have a duty to ensure the sustainable use of deep-sea resources.

The study is published in Deep Sea Research Part I: Oceanographic Research Papers.


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