Saw this article at WTFUWT

Unexplored Possible Climate Balancing Mechanism

Even after chopping down 80% of the rainforest and removing over a megaton of iron from the core ocean every year, people blame fossil fuels for the CO2 rise.

If you want a better explanation - trying dumping iron sulfate in the ocean - there is an immediately algae bloom. This indicates the ocean is iron depleted. People who are surprised by the depletion of fishing stocks shouldn't be - if you have fewer nutrients and fewer plankton there are fewer fish. Why is iron so critical? Iron is 5% of the earth's crust. The concentration in seawater is only 0.00034 ppm (parts per million) - much less than one part in a billion.

Well - if there is so little, how much are we taking out each year? Doing the math:
1.34x10⁹ (sea volume in km*3) * 0.00034 (mg/l) * 10^-6 (tonnes/gm) * 10³ (l/m*3) * 10⁹ (m3/km3) * 10^-3 (gm/mg) = 455600000 tonnes of iron. We are removing at least 2.2% of the ocean's iron per decade.
The solution is obvious - we should be dumping the equivalent of several large ore carriers of iron and trace elements into the ocean every year to keep the ocean productive, and stop chopping down rainforest to produce palm oil biodiesel.

This is win/win - a more productive ocean means less CO2 and more fish. As for the rainforest - who can argue with more trees.