@TimUpham @Phyl12 It is not growing rice in and of itself that is a problem, so much as using flood irrigation of rice fields to control weeds. Using flood irrigation once to get the baby rice plants off to a good wet start makes sense, but most of the growing season, it should be possible to hoe weeds instead of drowning them.
U S Navy has contracted since about 2006 with Algae Systems for engineering R&D to bring their now already CARBON_NEGATIVE bio-diesel from algae down in price to make it cost-competitive with petroleum. I believe they have every intention of licensing the technology to all the too big to fail American oil firms as soon as the cost of bi0-diesel comes down enough and/or the cost of petroleum toes up enough for the two prices to meet in the middle. Once this becomes a commercial product, it will be a big help in controlling the greenhouse gas content of both the atmosphere and the ocean.
The ocean's biggest problem seems to be CO2, the same as for the atmosphere. We really need to switch from fossil fuel to renewable energy. Buying most of the otherwise obsolete fossil fuel as reserves to keep them from being burned most likely needs to be part of the deal, given the enormous political power of the fossil fuel firms.