' Muddying The Waters ' : A warning from jellyfish about deep-sea mining : 

A trove of metal is hiding at the bottom of the oceans. Nodules of iron and manganese litter the seafloor, and metal-rich crusts cover underwater mountains.

Deep-sea mining companies want to use these minerals in batteries and electronics. But environmentalists warn that the mining and the plumes of sediment that such operations would dump back into the sea could affect marine life.

Shipboard experiments on Jellyfish in the Norwegian fjords, published in Nature Communications, offer insights into these warnings.

The scientists approximated the effects of mining by pumping sediment into the jellies' tanks, especially asking how the animals would cope with the muddy water. The answer? Not well.

Helmet jellyfish were selected as research subjects because of their ubiquity and hardiness. They are representative of the many soft-bodied animals living in the ocean that could be affected by mining and that are food for tuna and other fish consumed by humans.

They are found around the world at depths of 1,500 to 2,000 feet [ 450 to 600 meters] and are abundant in Norway's fjords.

The scientists exposed the jellyfish to plumes of sediment comparable to what they might encounter around deep-sea mining sites.

One response was visible to the naked eye : They tried to rid themselves of the sediment by producing excess mucus. Other stress responses were at the molecular level, but researchers feared they could add up to threats to the population. [ Kate Golembiewski ]


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