No, iron fertilization and geoengineering are not consequences of algae blooms, because it is the other way around. Algae blooms are the consequences of geoengineering. Scientists were brilliant when they figured out that iron fertilization and the increase in algae blooms can combat global warming. One is not a consequence of the other.
Alga blooms would occur naturally, without the influence of geoengineering, iron fertilization of alga blooms. However, it does not help the situation, in regards to the resulting increase in bacteria levels in water sources, which further leads to depleting oxygen-levels in the waters, along with killing fish and sea creatures.