https://www.newscientist.com/a…ill-dump-iron-in-the-sea/
Unfortunately paywalled, it looks as if Sir David King has re-started the push to test this idea again.
A former UK chief scientific adviser is planning experiments to drop sand naturally containing iron in oceans to tackle climate change and restore marine life, in a major geoengineering project that is likely to prove controversial.
Ships will be sent to three locations across the world’s oceans in the next four years to trial the technique – known as ocean iron fertilisation – David King at the Centre for Climate Repair at Cambridge (CCRC), UK, tells New Scientist.
ETA- for those who are interested in the topic, there's an online presentation on this by DK and colleagues tomorrow.