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Acidification diminishes diatom silica production in the Southern Ocean


Diatoms, large bloom-forming marine microorganisms, build frustules out of silicate, which ballasts the cells and aids their export to the deep ocean. This unique physiology forges an important link between the marine silicon and carbon cycles. However, the effect of ocean acidification on the silicification of diatoms is unclear. Here we show that diatom silicification strongly diminishes with increased acidity in a natural Antarctic community. Analyses of single cells from within the community reveal that the effect of reduced pH on silicification differs among taxa, with several species having significantly reduced silica incorporation at CO2levels equivalent to those projected for 2100. These findings suggest that, before the end of this century, ocean acidification may influence the carbon and silicon cycle by both altering the composition of the diatom assemblages and reducing cell ballasting, which will probably alter vertical flux of these elements to the deep ocean.

Data availability

The data that support these findings are available from the Australian Antarctic Data Centre (


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The work was supported by Australian Antarctic Science project AAS 4026 from the Australian Antarctic Division (AAD); samples were imported under permit no. IP13019928. We are grateful to AAD technical support for their assistance and support in designing and equipping the mesocosm facility and to the Davis Station expeditioners in the summer of 2014/2015.

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About the author

Dr. Howard Dryden

Dr. Howard Dryden

Dr. Dryden has unique knowledge combination of biology, chemistry and technology and is the inventor of the activated, bio-resistant filter media AFM®. Dr. Dryden is one of the world`s leading experts in sustainable water treatment.

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