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Warming ocean makes bacteria smaller

Published online 12 July 2015

A decade of warming waters may be causing bacteria to shrink.

Biplab Das

An international research team has discovered that a warming ocean may reduce the cell size of two dominant groups of sea bacteria — bacteria with low nucleic acid (LNA) and high nucleic acid (HNA) content, confirming suspicions that climate change could lead to smaller organisms1

Xosé Anxelu  G. Morán and his colleagues from the Red Sea Research Center of King Abdullah University of Science and Technology (KAUST) in Saudi Arabia and the Oceanographic Center of Xixón of the Spanish Institute of Oceanography (IEO) collected seawater samples from the southern Bay of Biscay off Asturias in northern Spain. They then analysed LNA and HNA and correlated their cell sizes and abundance with sea temperatures. 

They found that size of LNA and HNA cells decreased consistently from 2002 to 2012 by roughly 1% per year in response to an average temperature rise of 0.5 °C during the decade — reaching 1.5 °C in springtime. In artificial setups with a temperature rise of 4 °C, the researchers found that the size of the bacterial cells also decreased.

While their size decrease, LNA cells’ abundance increased significantly between 2002 and 2012. In a separate ongoing study in the Red Sea, the same researchers detected that LNA cells clearly dominated surface seawaters in abundance.  

“This study adds to evidence from recent and geological times to strongly support that a shift towards lower sizes can be a widespread response of marine organisms to global climate change,” says Morán.


Moran, X. A. G. et al. More, smaller bacteria in response to ocean's warming? Proc. R. Soc. B. (2015).