Surprising ‘dark oxygen’ discovery could ensnarl deep-sea mining

Sub: Geo

Sec: Eco geo

Context:

A study published in Nature Geoscience on July 22 revealed an unknown process producing oxygen in the deep ocean, where photosynthesis is not possible.
This discovery suggests the existence of previously unknown ecosystems in the abyssal zone, a deep-sea region.

Abyssal zone:

The abyssal zone or abyssopelagic zone is a layer of the pelagic zone of the ocean.
The word abyss comes from the Greek word ἄβυσσος (ábussos), meaning “bottomless”.
At depths of 4,000–6,000 m (13,000–20,000 ft), this zone remains in perpetual darkness.
It covers 83% of the total area of the ocean and 60% of Earth’s surface.
The abyssal zone has temperatures around 2–3 °C (36–37 °F) through the large majority of its mass. The water pressure can reach up to 76 MPa (750 atm; 11,000 psi).

Presence of oxygen in Abyssal zone:

When the scientists were conducting experiments at a depth of 4 km, they noticed the oxygen concentration in some places rapidly increased instead of decreasing.
This underwater region is called the abyssal zone. It receives too little sunlight for photosynthesis to be feasible. Instead, life-forms here get oxygen from water carried in by a global circulation called the ‘Great Conveyor Belt’.
Still, the amount of oxygen is low and without any local production, the device should have measured the oxygen levels dropping as small animals consumed it.
But the scientists found the opposite: it increased, sometimes tripling in just two days.

Possible Mechanism: Polymetallic Nodules:

Polymetallic nodules, rich in iron, manganese, copper, and nickel, may play a role in producing oxygen by splitting water molecules through electric charges.
These nodules are found on the ocean floor, particularly in the Clarion-Clipperton Zone off Mexico’s west coast.
- Covering an area larger than India, the Zone is considered to have the world’s highest concentration of polymetallic nodules, including 6 billion tonnes of manganese and more than 200 million tonnes each of copper and nickel.

India’s Involvement and Deep-Sea Mining

India plans to explore and mine deep-sea minerals in the Pacific Ocean, as part of its ‘Deep Ocean Mission.’
The International Seabed Authority has issued 15-year contracts for deep-sea mining, with at least 22 contractors, including India and China.

Environmental Concerns and ‘Dark Oxygen’:

The study’s findings raise concerns about the impact of deep-sea mining on ecosystems dependent on ‘dark oxygen’ produced by the nodules.
Previous experiments, such as the Disturbance and Recolonisation (DISCOL) Experiment, showed long-term environmental impacts from simulated mining activities.
- DISCOL is conducted by Germany in Peru basin as the world’s “first large-scale impact assessment”.
Deep-sea mining could lead to irreversible loss of ecosystem functions and harm marine life, including deep-sea jellyfish.

Implications for Deep-Sea Mining and Conservation:

The discovery of ‘dark oxygen’ complicates the potential impacts of deep-sea mining on marine ecosystems.
Scientists and insurers are increasingly concerned about the sustainability and environmental consequences of such activities, with some insurers excluding deep-sea mining from their coverage.

Source: TH