Can Dark Oxygen Save the Ocean?

Maybe, but not in the way that you think.

Photo from eos.org

A new paper, published in Nature Ecology & Evolution, shows that in the ocean, oxygen-deficient waters have increased fourfold since 1960. There have been significant decreases in many freshwater and coastal areas as well. Some scientists and researchers want the ocean’s oxygen levels to be classified as the tenth planetary boundary.

Living organisms in the ocean need oxygen to change food into energy and to breathe. Dramatic drops in oxygen in the ocean will have profound and detrimental effects on the ocean food web.

The physics of the problem is simple. Warm water holds less oxygen but is also more buoyant than colder water. The warmer the water is, the less warm water near the surface of the ocean mixes with the cooler water lower down and the less oxygen ocean life gets deeper down in the ocean.

Scientists know this is a problem and have established the cleverly acronymed GO2NE (Global Ocean Oxygen Network) to study the problem of ocean deoxygenation. GO2NE is a working group of scientists that provides scientific advice to policymakers and stakeholders. Here are some of the highlights of GO2NE research:

1.        Deoxygenation occurs when oxygen is used up faster than it can be replenished

2.        Over 500 low-oxygen sites have been identified in estuaries and coastal waterways.

3.        Dense aquaculture contributes to deoxygenation

4.        Deoxygenation reduces growth, increases disease, and increases mortality of marine animals.

5.        With less oxygen to use, ocean microbes conduct denitrification to get energy. This produces N20 – a powerful greenhouse gas.

6.        With global warming and phosphorus and nitrogen pollution increasing, so will deoxygenation, making survival of marine life more challenging.

7.        Overfishing, ocean warming, phosphorus and nitrogen pollution, and ocean acidification are exacerbating the problem.

8.        Steps such as sewage treatment, reversing global warming, and limiting phosphorus and nitrogen pollution are needed.

Can dark oxygen save us?

A new development has complicated the talk about the ocean’s deoxygenation. Scientists discovered oxygen production at the bottom of the ocean that isn’t supposed to be there.

Metallic nodules, about the size of potatoes, have been forming for millions of years on the bottom of the ocean. The largest known concentration of these nodules is in the Clarion-Clipperton Zone (CCZ) in the Pacific Ocean between Mexico and Hawaii. These nodules contain high levels of nickel cobalt, copper, manganese, and other metals needed in batteries that will be a big part of the energy transition away from fossil fuels.

These mineral and metal-rich nodules have captured the attention of the mining industry, and companies like the Metals Company, which plans on mining them from the ocean floor, starting in the CCZ.

There is a great deal of pushback from environmental groups and others about the plans of those looking to mine the ocean floor. Mining the ocean floor will undoubtedly destroy habitat for many marine animals, and upset an ecosystem about which we know very little.

But now we also know that such mining activity might be robbing the ocean of oxygen at a moment when the ocean can least afford to lose it.

In 2013, Andrew Sweetman, a deep-sea ecologist discovered increased oxygen levels in the CCZ that shouldn’t have been there. He originally thought that his equipment was faulty. He went back a number of times and always found similar readings. In 2021, on an expedition sponsored by The Metals Company, Sweetman found the same high oxygen readings using different methods and different equipment. A year later he realized that the metals in the nodules might be acting as batteries, splitting the oxygen and hydrogen in the ocean water, producing “dark oxygen”.

The phenomena of dark oxygen in the ocean have likely been going on for hundreds of millions of years, if not longer. But our understanding of the process and just how much oxygen it produces is just beginning. It is likely that “dark oxygen” only makes up a fraction of the oxygen in the ocean. However, efforts to mine the ocean for precious metals may have hit another hurdle.

The International Seabed Authority (ISA), which governs the seafloor in international waters, is currently discussing rules and regulations for mining the nodules and other deep-sea targets. Twenty-seven nations, including 26 member states of the ISA, have called for a moratorium, precautionary pause, or ban on deep-sea mining.

Will the decision to mine these ocean nodules be based on scientific advice after research can be conducted to estimate the impact on ocean life and human life, or do we go ahead with the mining and worry about cleaning up the mess later? Human history says the latter, but there is a growing push against deep-sea mining.

What to do?

More than 800 marine scientists from 44 countries have signed a petition highlighting the environmental risks and calling for a pause on mining activity. Several organizations are also working to halt deep-sea mining, or at least delay the practice until an adequate scientific study can be done to ensure the safety of deep-sea ecosystems.

People looking to do something could support organizations The Deep-Sea Conservation Coalition (DSCC). The DSCC aims to remove and mitigate the threats to life in the deep sea and to safeguard the long-term health of deep-sea ecosystems. The Deep-Sea Conservation Coalition (DSCC) was founded in 2004 in response to international concerns over the harmful impacts of deep-sea bottom trawling.

More than 120 non-governmental organizations (NGOs), fishers’ associations, and law and policy institutes worldwide are working together through the DSCC to ensure the protection of deep-sea ecosystems.

You can read the DSCC factsheet on why the deep-sea nodules are not needed.

I’ll end with the DSCC recommendations for policy and industry to ensure the health of deep-sea ecosystems.

DSCC Recommendations:

·        Develop legislative frameworks that require manufacturers to produce technologies that can be fully recycled at end-of-life.

·        Increase and upscale recycling rates by establishing effective infrastructure for waste management and recycling and developing innovative industries such as urban mining.

·        Incentivize extended product life cycles and intelligent product design.

·        Research and develop substitutes for high-demand metals currently considered critical for renewable technologies.

·        Combine circular economy policies with policies aimed at reducing overall demand for resource-intensive products and energy, for example through improving energy efficiency, investing in shared economy models, and redesigning towns and mobility in cities.

·        Introduce policies and incentives aimed towards a reduction in demand for minerals and metals globally.

·        Develop legislative frameworks and standards that require terrestrial extractive industries to improve processes to maximize the capture of minerals, reduce waste, and minimize social and environmental impacts.