Scientists Warn of Seafloor Mining Impact on Vital Marine Ecosystems

by | May 16, 2024

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As global metal demand increases, the attention on deep-sea mineral resources intensifies. Seafloor massive sulfide (SMS) deposits along the Mid-Atlantic Ridge are gaining economic interest for their rich metal content. However, exploiting these deposits presents significant environmental challenges, particularly for deep-sea sponge ecosystems. A recent study exploring the ecological impact of SMS mining underscores the need for careful management of these operations.

Plume Risks to Sponge Grounds

Deep-sea sponge grounds, particularly those dominated by the Geodia barretti species in the North Atlantic Ocean, serve as vital components of marine ecosystems. They cycle nutrients and create habitats for various marine life. Mining-related sediment plumes from extracting SMS deposits could devastate these sponge populations and associated organisms.

Researchers exposed these sponges and brittle stars to suspended SMS particles at a concentration of 30 mg/L for 21 days, mimicking the conditions near a mining site. After three days of exposure, sponges showed visible signs of particle accumulation in their tissue and exhibited significant discoloration and necrosis by the end of the 21-day exposure period. Brittle stars associated with the sponges shed their spines, lost all their arms, and died within ten days. The elevated concentrations of heavy metals, particularly copper and iron, further compromised the physiological performance of the sponges, resulting in a 100% increase in oxygen consumption and a 130% decrease in clearance rates. These physiological changes were paired with increased necrosis, leading to a dramatic decline in the health and survival of both sponges and brittle stars.

Disrupting the Deep-Sea Food Web

These findings highlight the potential long-term ecological disruptions that SMS mining could cause. Deep-sea sponge grounds are integral to the oceanic food web, providing essential habitats for various marine species. A decrease in the filtering capacity of these sponges may have widespread effects on the ecosystem, negatively impacting nutrient cycling and the availability of food resources. The research points to alterations in the microbial communities that sponges depend on, indicating that contact with SMS deposits could reduce populations of beneficial bacteria while increasing those of potentially harmful ones, further hindering nutrient processes.

Precautionary Management is Critical

The study’s findings emphasize the need for a precautionary approach to deep-sea mining. Further research is clearly needed to understand the varying impacts of SMS deposits based on concentration, particle size, and species. This data will be crucial in developing management strategies that minimize the adverse impacts on deep-sea sponge ecosystems and establish safe exposure levels. Working with deep-sea species presents inherent challenges, and future research should expand to include a wider range of marine life under realistic environmental conditions.

Understanding the potential ecological disruptions from SMS mining will be essential for balancing the growing demand for metals with preserving the ocean’s most fragile ecosystems. A careful approach will help protect deep-sea sponge grounds and their associated species from indirect mining effects.

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