Oil-Burning Ships May be Fertilizing the Oceans

Oil-Burning ships may be unintentionally fertilizing the oceans with iron, New Scientist reports.

New research shows that the ships are dumping about 1100 tons of soluble iron every year, coving 6 million square kilometers of ocean. Dumping iron in the ocean has been proposed as a way to removing carbon dioxide out of the atmosphere, to slow global warming. The idea is controversial, but some geoengineers claim that the iron will stimulate plankton growth, which will absorb carbon.

"Experiments suggest you change the population of algae, causing a shift from fish-dominated to jellyfish-dominated ecosystems," Alex Baker of the University of East Anglia, UK told New Scientist. Because of this worry, the UN Convention of Biological Diversity imposed a moratorium on geoengineering experiments in 2010.

These shipping vessels deposit much more iron into the ocean than an experiment would, but in a much less concentrated area. A new study at the Japan Agency for Marine-Earth Science and Technology, led by Akinori Ito, seeks to determine how the iron is deposited in the ocean. Formerly, it was believed that only one to two percent of iron contained in aerosols (which includes shipping emissions) is soluble in seawater, which means the rest would sink to the ocean floor. Ito's research found that as much as 80 percent of shipping related soot is soluble, and therefore useful in fertilizing the ocean.

Because the shipping soot deposits are not scientifically controlled, meaningful conclusions can't really be drawn about the effects on the ocean. "Given the uncertainties, I just don't know how much these iron emissions would have to increase before there was demonstrable harm to any ecosystem, or benefit in terms of carbon uptake," said Baker.

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