Polar opposites; bacterioplankton susceptibility and mycoplankton resistance to ocean acidification

• Main Authors: de Scally, Storme Zaviar, Chaffron, Samuel, Makhalanyane, Thulani Peter
• Other Authors: Laboratoire des Sciences du Numérique de Nantes (LS2N), IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom Paris (IMT)-Institut Mines-Télécom Paris (IMT)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-École Centrale de Nantes (ECN)-Centre National de la Recherche Scientifique (CNRS), Combinatoire et Bioinformatique (COMBI), Université de Nantes (UN)-Université de Nantes (UN)-École Centrale de Nantes (ECN)-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique)
• Format: Report
• Language: English
• Published: HAL CCSD 2020
• Subjects: envir; geo; Southern Ocean; Ocean acidification
• Online Access: https://doi.org/10.1101/2020.02.03.933325; https://hal.archives-ouvertes.fr/hal-02946889/file/2020.02.03.933325v1.full.pdf; https://hal.archives-ouvertes.fr/hal-02946889

Microorganisms form the basis of ocean ecosystems yet the effects of perturbations such as decreasing pH on microbial community structure, interactions and functionality remain compared to multicellular organisms. Using an experimental manipulation of Southern Ocean seawater, we subjected bacterioplankton and mycoplankton to artificial pH decreases, which are predicted to occur in the future. We show that acidification led to substantial increases of bacterioplankton diversity, while in contrast it had no effect on mycoplankton diversity. Our analyses revealed a loss of putative keystone taxa and a decrease in predicted community interactions as a response to lower pH levels. Bacterioplankton shifted from generalist to specialist community members, suggesting a specific stress response to unfavourable conditions. In addition, enzyme activities involved in nitrogen acquisition were lower at reduced pH levels, suggesting altered organic matter cycling in a more acidic ocean. Our findings suggest that bacterioplankton and mycoplankton may respond differentially to future ocean acidification, with potentially negative impacts on community structure and biogeochemical cycling in the Southern Ocean.