I think they came up with the wrong use case though. What you'd really like is to have a gengeneered bacteria that extracts gold out of solution and can live in salt water. And some phytoplankton or arthropods that eat the bacteria and concentrate metallic salts in a kidney like organ. which are then collectable with drag nets. All new gold mining industry :-)

One wonders though if there are plants in the Sierras that would be similar processors of dissolved gold.