Nuclear techniques to combat ocean acidification

Marine organisms such as corals and molluscs are under threat from ocean acidification. The sea is becoming more acidic as it absorbs 30% of the carbon dioxide produced by humans. This phenomenon limits the availability and quality of food from the seas.

As acidity levels increase and carbonate concentrations decrease, environmental conditions become corrosive to organisms that use calcium carbonate to produce their shells and skeletons, and the energy expended to overcome increasingly acidic conditions can reduce the energy for other physiological processes such as reproduction or growth.

Nuclear and isotopic techniques are effective tools for investigating ocean acidification, studying and predicting its effects, and supporting policies to combat this problem that contributes to climate change.

Some of these techniques are:

  • Use of the calcium isotope calcium-45 and carbon-14. As a tracer to study the growth rate of calcifying organisms such as corals or mussels and other molluscs, in whose skeletons and shells calcium carbonate is found, and to determine how ocean acidification affects the physiology of other marine organisms, as well as the consequences of a combination of stress factors such as acidification, temperature and the presence of pollutants.
  • Using the boron-11 isotope. Scientists can assess the pH of the oceans in the past from corals and fossilised organisms and identify previous ‘acidification events’ that could be related to mass extinctions and changes in ecosystem structure.
  • Use of X-rays. To study the annual growth bands of corals.
  • Use of uranium and thorium isotopes. To determine the age of corals.

There are other core techniques for assessing the ocean's carbon storage capacity that involve understanding the capacity itself and how it might be affected by changing climatic conditions.

The ocean stores carbon primarily through two mechanisms:

Solubility pump

In this pump, carbon dioxide is transported from the atmosphere to the deep ocean by physical and chemical processes, such as gas exchange, dissolution, and ocean circulation.

Biological carbon pump

Through this pump, phytoplankton, i.e. microscopic marine plants at the bottom of the oceanic food chain, take up carbon dioxide at the ocean surface as part of photosynthesis and convert it into dissolved organic carbon particles (carbon-containing molecules usually produced by living organisms).

Some of this carbon reaches the deep ocean, where it is recycled back into inorganic carbon and stored, isolated from the atmosphere.

If this pump were to stop operating, carbon dioxide in the atmosphere could increase in the order of 200-400 parts per million (ppm) above the current level of 400 ppm, which was first reached in 2015.

The flux of carbon into the deep ocean can be measured directly by capturing sinking particles (microscopic living and dead organisms, faecal matter) in sediment traps and indirectly by natural radioisotopes thorium and polonium. These radioisotopes, whose decay rates are known, are used as ‘clocks’ to determine the rate at which carbon-containing particles sink.

The Marine-Coastal Stressors Research Network in Latin America and the Caribbean (REMARCO) employs nuclear and isotopic techniques for peaceful use to address environmental problems in the marine-coastal ecosystems of Latin America and the Caribbean, including ocean acidity. To this end, they have produced a manual of technical procedures accompanied by explanatory videos that can be viewed here.

Tipos:
Access to the best

educational
resources

on Energy and Environment
Go to resources