Fool’s Gold - fertiliser for the oceans

Pyrite or Fools Gold is a rich source of iron in the deep sea say researchers from the University of Delaware.

Scientists thought pyrite – iron disulphide – spewed out by deep hydrothermal vents at the bottom of the ocean were solids that settled back onto the ocean floor. However, new research has shown the vents spew out significant amounts of microscopic pyrite particles which are dispersed into the ocean, rather than falling to the floor.

These nanoparticles are so small they have a diameter 1,000 times smaller than that of a human hair, and can stay suspended as iron disulphide for a lengthy time.

“These particles have long residence times in the ocean and can travel long distances from their sources, forming a potentially important food source for life in the deep sea,” said Barbara Ransom, program director in the National Science Foundation’s (NSF) division of ocean sciences.

The Fool’s Gold – which has a metallic lustre and brass-yellow colour leading to its nickname – doesn’t rapidly react with oxygen in seawater to form oxidised iron or rust. This allows it to stay intact and move through the ocean better than other forms of iron.

“As pyrite travels from vents to the ocean interior and towards the surface ocean, it oxidises gradually to release iron, which becomes available in areas where iron is depleted so that organisms can assimilate it, and then grow,” said George Luther from the University of Delaware.

“It’s an ongoing iron supplement for the ocean – as much as multivitamins are for humans.”

The research received funding from the NSF and the Experimental Program to Simulate Competitive Research (EPSCOR). It involved scientific cruises to the South Pacific and East Pacific Rise using Alvin – the manned deep-sea submersible – and Jason, a remotely operated vehicle.