Nuclear Techniques Unveil Ocean Change, Safeguard Seas

Our ocean is facing unprecedented pressure from a changing climate and human activity.

Invisible threats such as ocean acidification, chemical and microplastics pollution and oxygen depletion are changing the marine environment, placing coastal resources at risk. Because these environmental stressors cross national boundaries, understanding their long-term impact requires a globally coordinated scientific response.

To address these challenges, the IAEA launched a four-year Coordinated Research Project, Applied Radioecological Tracers to Assess Coastal and Marine Ecosystem Health , to support the development, improvement and application of nuclear techniques to assess environmental damage and better understand associated risks. Scientists from 11 laboratories in nine countries on five continents took part in the initiative.

The project used radioecological tracers - natural and fabricated substances containing small amounts of radioactive isotopes - to track the movement, exposure pathways and accumulation of contaminants in marine food webs.

By using these advanced techniques across different regions, scientists were able to show how ecosystems respond to external pressures and how marine organisms are affected by ocean change.

Research into the bioaccumulation of trace metals under climate change scenarios led by the University of La Rochelle in France revealed how ocean acidification influences mercury metabolism in marine life. Their findings showed that changing water chemistry affects how species like cuttlefish absorb and retain contaminants such as organic and inorganic mercury during early life stages. This highlights a direct link between ocean acidification and seafood safety.

"By providing countries with insights on contaminants in marine organisms using radiotracer techniques, we are enhancing the global scientific community's capacity to monitor contaminant pathways in the marine food web," said Jana Friedrich, Head of the IAEA Radioecology Laboratory in Monaco. "We are providing the rigorous data needed to inform environmental protection strategies worldwide."

The project also addressed the growing global threat of marine plastic pollution, revealing previously unquantified complex ecological interactions . Research coordinated through the Federal University of Paraná in Brazil investigated how floating plastic litter can act as an artificial vector, transporting toxic microalgae and harmful biotoxins across the ocean.

Using microscopic and advanced analytical techniques, researchers identified high-risk areas globally and found that floating microplastics can facilitate the dispersal of toxic benthic algae from tropical regions to higher latitudes. This bio-colonization means that dangerous toxins can enter marine food chains and reach marine animals in open waters that would otherwise never encounter them, presenting a novel threat to both marine life and human consumers of seafood.

"Our collaborative work under this framework helped us rethink the impact of marine litter," said Luiz Mafra, Jr., a researcher at the Federal University of Paraná in Brazil. "The data shows that more than one third of coastal waters globally are at risk of plastics acting as vectors for harmful algal blooms, creating a pressing need for integrated monitoring."

In addition to demonstrating the relevance of nuclear techniques for assessing ocean health, the project has generated critical information that can support several major international environmental frameworks, including the Minamata Convention on Mercury.

The project also identified new areas for future collaboration. Participating scientists agreed to produce a joint perspective paper on polonium, a powerful natural radiotracer in seawater. The forthcoming publication aims to broaden awareness among policymakers and non-experts about polonium's potential to map deep-sea vulnerability and organic carbon cycling.

Countries around the world are now better equipped to assess environmental risks and protect global marine ecosystems using refined nuclear techniques that have been tested, validated and are ready for deployment.