Harmful algal booms occur only in coastal areas, not out in the open ocean. Besides, if a coral reef dies but we manage to feed more hungry people, well, I for one could accept the trade-off. If you enrich the nutrients in the open ocean, you will have blooms there, too. And even if the blooms are not due to toxic species, not all species of algae favor copepod reproduction. My research shows that iron fertilization results in diatom bloom.
Copepods feeding on diatoms have lower counts of eggs.
And diatoms can clog the gills of marine animals. If we don't try, we'll never know. We've conducted experiments in the Gulf of Mexico to find the best Geritol mixes and the best delivery system. The next step is to try this out around the Marshall Islands. The recent New York Times report regarding the melting of the North Pole ice cap would support any measures to prevent global warming.