Ocean Fertilization

Many geoengineering projects have been proposed to address climate change, including ocean fertilization. Ocean fertilization was first proposed by an oceanographer called John Martin. He suspects that iron was the limiting factor for phytoplankton growth in the high-nutrients, low chlorophyll area. His research indicate that we can intensify phytoplankton growth by dumping iron into the ocean into those area. This process could decrease the amount of carbon dioxide in the atmosphere and mitigate the climate change. Scientists have been carrying out this experiment in Pacific Ocean and Gulf of Alaska. Although the results show the increase in phytoplankton populations and carbon dioxide uptake, they can cause many negative effects. 

Many side effects include disruption of food chain. If we manually shift the phytoplankton community composition, the other species might not be able to adapt to this rapid bloom. Ocean fertilization can also worsen ocean acidification problem and cause oxygen depletion in the deep ocean. Some scientists suspect that ocean fertilization can provoke harmful algae bloom that produce ammonia toxic to many marine species. These toxins are brought up the food chain through the consumption of primary, secondary and tertiary consumers. This could cause implications to food security and human health because we consume seafood as food. 

Harmful Algae Bloom
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Recent experiments are carried out to test the idea of inducing phytoplankton bloom but not so much about the side effects. To get a better understanding on impacts of ocean fertilization, more extensive research and actual experiments are required.