Acidification diminishes diatom silica production in the Southern Ocean

Abstract

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 CO2 levels 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.

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Fig. 1: Silicification and diatom community composition on day 12.
Fig. 2: Single-celled silicification with [H+].
Fig. 3: Silicification as a function of growth, cell surface area and abundance.
Fig. 4: Diatom response to [H+].

Data availability

The data that support these findings are available from the Australian Antarctic Data Centre (https://doi.org/10.26179/5c3e745a9b071)69.

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Acknowledgements

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.

Author information

K.P. conceptualized the study. K.P., K.G.B., D.A.N., A.M.H., K.G.S. and A.T.D. carried out the investigations. K.P. and K.G.B. developed the methodology. K.P. and D.A.N. conducted the formal analysis and visualization. K.P. prepared the original draft. K.P., K.G.B., D.A.N., A.M.H., K.G.S. and A.T.D. reviewed and edited it. K.P. and A.T.D. obtained the funding and provided resources.

Correspondence to Katherina Petrou.

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The authors declare no competing interests.

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Peer review information: Nature Climate Change thanks Phillipp Assmy, Paul Treguer and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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