Ocean Fe fertilization
The idea is relatively simple: dump massive amounts of iron in the surface oceans in high latitudes, where there are many nutrients in the water, but little chlorophyll. The iron would act as "fertilizer", stimulating the growth of algae. These algae would then make photosynthesis by removing carbon dioxide from the water and produce oxygen. When they die and are deposited on the seabed, they help to maintain the carbon locked up. With less dissolved CO2, the ocean could absorb excess carbon into the atmosphere by humans.
The theoretical iron fertilization of large areas of the oceans was first made in 1990 by the American scientist John Martin, but was tested in field only ten times. In all these tests the iron in the water actually stimulated the multiplication of algae and photosynthesis, but the actual "burial" of carbon and how much CO2 could be absorbed each year could not be measured.
The Lohafex, an experiment for two months in the stormy South Atlantic by a group of the Alfred Wegener Institute, Germany, and the National Institute of Oceanography in Goa. The region was chosen because of its greater potential for carbon sequestration in the southern ocean areas where other similar experiments were performed, and for different types of algae. On board the icebreaker ship Polarstern, the research team turned 6 tons of iron in the sea over 300 square kilometers. As expected, the "fertilization" actually stimulated the growth of algae (or phytoplankton), which doubled their biomass in a period of two weeks.
And that was the shot literally began to backfire. Excess phytoplankton soon attracted the attention of copepods, micro-crustaceans that feed on algae. With food to spare, the copepods were increased, which in turn attracted amphipods. After 39 days, the concentrations of chlorophyll in the fertilized area went into decline and all that remains was a group of amphipods well-nourished. Carbon sequestration obtained from the experiment was negligible. The problem was that the "wrong" algae was multiplied and not the diatoms, which have a calcareous shell that protects them from predators and could sink after death. But in that region, the sea is low in silicon, an element that diatoms use to make its shell.