Could be a practical way to slow CO2
Phytoplankton carbon sequestration would seem to hold promise. At reasonable expense, carbon is extracted from the air, and sequestered as carbon snow on the deep sea bed.
Of course there are real risks, so we need to be really sure of the effects of a given amount of iron seeding. My thinking is that, spread over a large expanse of ocean, the negative effects of such seeding might be minimised and acceptable.
Safeguards would need to be in place - monitoring of effects, and capping the level of seeding in any given area of ocean.
Given the potential benefit in slowing the growth of CO2 concentration in the atmosphere, I hope this is given serious consideration.