Gojira, algae emit oxygen, they take up CO2. When a large amount die simultaneously and sink to depth, it is possible that they could stimulate bacterial growth to such an extent that a localized low oxygen area develops. This happens every summer in subsurface water off the mouth of the Mississippi and other places due to high nutrient runoff. I doubt this would be a problem for 2 reasons. First, the deep ocean area is not nearly as nutrient rich as the Mississippi river, and second the flow of bottom water to the surface would not come close to that produced by the Mississippi. On top of that the areas where this is being proposed are deep ocean areas where there is typically little life at the surface. At best the life would be stimulated to a level on par with shallower areas.
Cod costs a lot because they have been severely over-fished.

Fred, I think you overstate things. Both Lovelock and I mentioned that this scheme has possible downfalls, so to say “We totaly ignore the consequences of such experiment and can be very dangerous.” is really uncalled for. Similar experiments to this have actually already been accomplished and others are on going. The difference between this idea and those is in the method of fertilization. Besides no one is talking about building a lot of these things without long term studies.
Asking “how many will it take” is a relevant question. No doubt to completely neutralize the human carbon emissions it will take more than we could ever build. That is why I titled this thread “Deep ocean pipes to
help mitigate the effects of CO2?”. At best this method could help somewhat. Like turning off that light I left on in the other room, but on a much larger scale. As I mentioned before some previous researchers have doubted the effectiveness of similar techniques. This is obviously not meant to be a panacea.
We are all playing the
accidental apprentice wizard by adding so much CO2 so quickly to the atmosphere before the earth’s geosphere and biosphere can stabilize it. All the scientists that propose these ideas say we would be better off not emitting the CO2 to begin with rather than trying schemes to try to control it after the fact.
The upper layers of the ocean are absorbing CO2 as levels rise in the atmosphere. It will be centuries before much of it reaches the bottom of the deepest parts ocean. The beauty of this plan (if it works as they hope) is that the CO2 removed from the atmosphere is converted to organ forms like by the algae and other life, so CO2 levels at the bottom will not will not immediately increased as the dead algae sink to the bottom. At least that is the theory. Whether or not it will get there before being eaten and reconverted back to CO2 remains to be seen.