But if we are interested in mass carbon capture, there may be more value per dollar invested in pumping surface water down to very deep ocean depths. Such pumps could be driven directly by floating wind turbines, maybe without need for expensive electrical components, and could also raise deep, cold, neutral water to the surface to help mediate acidification and high-temperature coral bleaching.
Probably we should be seeding both, along with lots of others, and see which ones achieve more. We will probably be surprised by the results.
Edit: To be clear, there may be much more value here in the other things they are doing than in increased carbon capture, and we should be evaluating the work more on the other things. If they capture carbon, too, that is good.