Global warming is burying huge amounts of silver beneath the South China Sea – and the same could be happening across the world's oceans. The amount of silver trapped in marine sediments off the coast of Vietnam has increased sharply since 1850, the new study shows. This coincides with the start of the Industrial Revolution, when humans began pumping greenhouse gases into the atmosphere on a large scale.

This is the first time research has highlighted a possible link between silver cycles in the ocean and global warming, told study lead author Liqiang Xu, an associate professor in the department of geosciences at the Hefei University of Technology in China. The discovery indicates global warming could have unknown impacts on other trace elements, too, Xu said.

Like other elements, silver originates on land and enters the oceans primarily through weathering, where rainwater leaches elements from rocks and carries them into rivers.

Certain regions of the ocean are enriched with silver due to heavy river inputs, atmospheric dust, human emissions and hydrothermal vents. Silver in its ionic form (Ag+) is toxic for marine creatures, Xu said, but very little is known about how it interacts with wider ocean ecosystems.

To find out more about how silver behaves in marine environments, Xu and his colleagues analyzed a sediment core from the Vietnam upwelling area in the eastern South China Sea.

Global warming boosts water temperatures and coastal winds, which combine to increase the intensity of upwelling. This leads to more nutrients rising to the surface, increasing the abundance of algae that feed the entire food chain. High levels of dissolved silver in these regions could mean organisms absorb more silver than elsewhere. When they eventually die and sink, this silver drops down to the seafloor.

If the silver doesn't escape back into the water, it will eventually find its way to land, the authors of the review said. "Nothing is truly lost, only relocated," they said.

Source: Live Science

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