Integrated ecosystem assessment

Paper (pre-print): Integrated assessment identifies pathways for effects of deep-sea nodule mining across ocean and seafloor ecosystems

• The study developed the first integrated ecosystem model for the Clarion Clipperton Zone (CCZ), linking components from the ocean surface to the abyssal seafloor, to assess mining impacts on biodiversity, ecosystem functions, and services.
• A set of ecosystem indicators and management tools was proposed to support adaptive, ecosystem-based management of deep-sea mining activities.
• Deep-sea mining in the CCZ is predicted to potentially cause long-term impacts on seafloor ecosystems, but no pathways of effects from the seafloor to the upper ocean ecosystems were identified.

This study presents the first comprehensive ecosystem assessment of potential environmental impacts from deep-sea mining in the CCZ, a vast area of the Pacific Ocean rich in polymetallic nodules. The study uses a new ecosystem model that spans from the ocean surface to the abyssal seafloor to evaluate how mining could affect marine life, ecosystem functions, and services.

The model includes 38 ecosystem components and 97 interactions, capturing the complex relationships between organisms and their environment. It shows that while abyssal ecosystems depend on organic matter from the surface ocean, there are no feedback pathways from the seafloor back to upper ocean ecosystems. This means that seabed mining impacts are likely to remain localised to the seafloor and nearby waters.

The study identifies the contributions of ecosystem components to key functions and services, including biodiversity, carbon cycling, and habitat structure. Pressures from mining activities—such as nodule collection and seabed disturbance—are predicted to directly impact seafloor organisms and alter habitat conditions. Sessile (non-moving) organisms that rely on nodules for attachment are especially vulnerable. In contrast, some infaunal species (living inside the seafloor) may recover or even increase in abundance over time.

The study also highlights the importance of monitoring and adaptive management. It proposes a set of ecosystem indicators aligned with the DPSIR (Driver-Pressure-State-Impact-Response) framework to track changes and guide decision-making. These indicators can help determine when mining activities cause detectable, significant, or serious harm—each requiring different management responses.

Finally, the study emphasises the need for representative reference zones and long-term monitoring to distinguish mining impacts from natural variability. It provides a scientific foundation for ecosystem-based management in the CCZ and offers a model that can be adapted for other deep-sea mining regions.

This is a preprint of a manuscript submitted to a scientific journal. It has not been peer-reviewed through the journal publishing process.