Natural nutrient enrichment 8 million years ago caused today's largest ocean 'dead zone'

What is it about?

Oxygen-starved ocean "dead zones", where fish and animals cannot survive, have been expanding in the open ocean and coastal waters for several decades as a result of human industrial and agricultural activity. Trying to predict the scale and location of future dead zones, this study has looked to the past for historical clues. It was found that, today’s largest open ocean dead zone, located in the eastern Pacific Ocean, emerged eight million years ago as a result of increasing nutrient content in the ocean. This mechanism is similar to the formation of dead zones in today’s coastal waters, except that humans are responsible for the current nutrient enrichment.

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Photo by Cristian Palmer on Unsplash

Photo by Cristian Palmer on Unsplash

Why is it important?

Oxygen is critical to marine ecosystems. In order to better protect marine ecosystems and manage fisheries, it is critical to predict how the oxygen-starved ocean "dead zones" will evolve in the future. The new findings about the history of today's largest ocean dead zone may help better predict the future behavior of open ocean dead zones. For example, human activities have been adding a large amount of nitrogen to the ocean annually. The impact of anthropogenic nitrogen on the deoxygenation processes in the open ocean needs to be better assessed in the future.