Effect of Ocean Acidification on Iron Availability to Marine Phytoplankton

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Science  14 Jan 2010:
DOI: 10.1126/science.1183517


The acidification caused by dissolution of anthropogenic CO2 in the ocean changes the chemistry and, hence, the bioavailability of iron (Fe), a limiting nutrient in large oceanic regions. Here, we show that the bioavailability of dissolved Fe may decline due to ocean acidification. Acidification of media containing various Fe compounds decreases the Fe uptake rate of diatoms and coccolithophores to an extent predicted by the changes in Fe chemistry. A slower Fe uptake by a model diatom with decreasing pH is also seen in experiments with Atlantic surface water. The Fe requirement of model phytoplankton remains unchanged with increasing CO2. The ongoing acidification of seawater is likely to increase the Fe-stress of phytoplankton populations in some areas of the ocean.