A Toxic Chemical in Marine Ecosystems Turns Out to Play a Beneficial Role, Study Funded by Ford Foundation Finds

Monday, July 22, 2019

A Toxic Chemical in Marine Ecosystems Turns Out to Play a Beneficial Role, Study Funded by Ford Foundation Finds

Advocates of healthy eating often extol the benefits of adding antioxidants to one's diet. These compounds are thought to suppress "free radical" molecules in the body that can age cells as a response to stress.

These destructive free radicals - known as reactive oxygen species - also exist in marine ecosystems and are thought to degrade the cells of phytoplankton and other organisms. A new paper, however, suggests that these molecules actually play a beneficial role, upending some conventional wisdom.

Julia Diaz, a newly hired marine biogeochemist at Scripps Institution of Oceanography at the University of California San Diego, and colleagues report that the reactive oxygen species produced by one type of phytoplankton, the diatom Thalassiosira oceanica, protects cells from overproduction of a compound that is used to power photosynthesis. In essence, that reactive oxygen species acts to protect cells' batteries from the effects of overcharging.

The study, "NADPH-dependent extracellular superoxide production is vital to photophysiology in the marine diatom Thalassiosira oceanica," appears July 22 in the journal Proceedings of the National Academy of Sciences.

"Our findings point to a new role for reactive oxygen species in the photosynthetic health of this diatom. The next challenge is to determine whether this process also exists in other phytoplankton species," said Diaz.

The findings could have implications for marine organisms and their chemical environment. The type of reactive oxygen species studied by Diaz is known as superoxide, which is a charged oxygen atom. Superoxide has been identified as a probable culprit in die-offs of fish and marine animals when toxic algae blooms spread in the ocean, suggesting a need for scientists to better understand how and why it is produced in certain circumstances. The varying positive and negative roles of superoxide could be a critical factor in how marine ecosystems respond to climate change. It is possible, Diaz said, that superoxide production could mitigate stress, which is a form of ocean resilience to changing climate that has not been understood previously...

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