I've been reading a bit about the idea of fertilization the oceans to increase plankton production, with the hopes that this might provide a carbon "sink" to pull more CO2 out of the atmosphere. There's currently a lot of doubt that this would work, at least permanently; the eventual fate of most carbon in any new biomass will perhaps be to return to the ocean, which readily exchanges CO2 with the atmosphere, rather than sinking into deeper waters where it might stay a longer time.
However, given the enormous mass of the oceans, and the fact that so much of it is effectively devoid of surface life because it lacks a few essential ingredients for plankton growth, it seems there's potential for enormously increasing fish production through fertilization. It's pretty much like land fertilization: add some key missing ingredients, growth takes off. We can't eat plankton; but we can eat the fish who will eventually follow it in its wake. So forget about CO2 sequestration, we may need another approach to address that problem; but we might be able to address our food needs better by making better use of much of the 71% of our planet covered in water, most of which is relatively lifeless.
Of course, we have to be concerned about disrupting ecosystems. But most of the ocean surface has no ecosystem: very little grows there. We might just be increasing the size of the ecosystem, like if we could water land deserts. Perhaps the main obstacle is political: nobody owns the open oceans, so we'd need some world treaty whereby anyone who fished in the fertilized waters would have to contribute to the fertilization efforts; the costs of that might be relatively small compared to the benefits, but some mechanism is needed to prevent free- riders from fishing in oceans that others have fertilized. In a few years, we might restore some of the oceans's historical fisheries, while actually getting more fish out of previously unused areas; imagine large swaths of ocean becoming as productive as the Georges Bank used to be before overfishing. We might even be able to reduce our use of land for livestock somewhat, by farming the oceans instead. Fishburger, anyone?-- scottinmn, Mar 21 2012 More fertilizer Fertilizing_20the_20Open_20Ocean [bungston, Mar 21 2012] I'm having a hard time finding the halfbake here; it seems like you're just suggesting that we step up the effort on things that are already being done.-- Alterother, Mar 21 2012 Can be abbreviated to "Dump iron in ocean".-- marklar, Mar 21 2012 Oceanic acidification would probably not be a good thing.-- RayfordSteele, Mar 21 2012 random, halfbakery