Fucking around with the ocean on a scale that's going to move the needle on CO2 in the atmosphere has a very high probability of serious unintended consequences.
Iron particles won't replicate, but the chemistry of the ocean could change dramatically. We don't know what happens at scale, and we probably don't want to find out.
Not doing anything has a certainty of turning the ocean to a mild acid, with disastrous effects that are already becoming visible in coral bleaching and shellfish die offs. And carbon that is already in the atmosphere and not yet dissolved is only going to make it worse.
We are at the point of choosing between what disasters we will suffer, rather than figuring out how to not have a disaster.
Why are we so concerned about ocean acidification from CO2, when past CO2 levels were far higher than now and all of the shellfish species that currently exist lived back then too? Wouldn't it be a good idea to consider the massive quantities of known toxins we pump into the oceans rather than fixating on a red herring?
Technically, seeding the ocean with iron particles is a suspension, not a solution. Luckily, the common technique is to use Iron(II) sulfate, which mixed with water does create a solution!
