Three quarters of the Earth is ocean, yet the ocean is home to only one-tenth of the Earth's photosynthesis, the first step in the production of all food. That leaves some room for improvement. This is intriguingly close to the 30 to 40-fold increase in chlorophyll noted by the iron experimenters. Implication for activists Phytoplankton have an interest in iron. Wee beasties have an interest in phytoplankton.
Fish have an interest in wee beasties.
Fishermen have an interest in fish. Oh, and don't worry about Martin's ice age forecast. Variations in the atmospheric CO2 level have little impact on global temperatures, which are mainly set by solar activity. Read CNN's story about it. Here's another account of the spectacular Galapagos experiment.