Biological effects 26 years after simulated deep-sea mining.

Area of Science:

• Deep-sea ecology
• Marine biology
• Environmental science

Background:

• Abyssal polymetallic nodule exploitation is imminent, raising concerns about ecosystem impacts.
• Deep-sea ecosystems, particularly nodule-sediment interfaces, host high biodiversity but remain poorly understood.
• The long-term effects and recovery potential of mining disturbances on these remote habitats are unclear.

Purpose of the Study:

• To assess the long-term effects of simulated mining disturbance on abyssal megabenthos.
• To understand the timescale of ecosystem recovery following deep-sea mining impacts.
• To infer potential consequences of polymetallic nodule mining in the Clarion-Clipperton Zone based on experimental data.

Main Methods:

• Analysis of seafloor photo-mosaics from the DISturbance and reCOLonization experiment (DISCOL) in the Peru Basin.
• Long-term monitoring (26 years post-disturbance) of megabenthos community structure.
• Comparison of disturbed versus undisturbed areas to evaluate ecological changes.

Main Results:

• Simulated mining impacts were still evident 26 years after the DISCOL experiment.
• Suspension-feeder abundance remained significantly reduced in disturbed areas.
• Deposit-feeder presence normalized, but heterogeneity diversity was lower, and faunal composition differed significantly across disturbance levels.

Conclusions:

• Deep-sea mining disturbances can have lasting impacts on abyssal ecosystems, persisting for over two decades.
• Recovery of some faunal groups may occur, but overall ecosystem function and biodiversity may be irreversibly altered.
• Potential impacts of polymetallic nodule mining in the Clarion-Clipperton Zone could be severe and long-lasting, potentially exceeding current expectations.