CO2 effects on diatoms: a synthesis of more than a decade of ocean acidification experiments with natural communities

• Published in: Ocean Science
• Main Authors: Bach, LT, Taucher, J
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus GmbH 2019
• Subjects: ocean acidification; primary production; phytoplankton; diatom; Ocean acidification
• Online Access: https://eprints.utas.edu.au/31315/; https://eprints.utas.edu.au/31315/1/134710%20-%20CO2%20effects%20on%20diatoms%20-%20a%20synthesis%20of%20more%20than%20a%20decade.pdf

Diatoms account for up to 50 % of marine primary production and areconsidered to be key players in the biological carbon pump. Oceanacidification (OA) is expected to affect diatoms primarily by changing theavailability of CO2 as a substrate for photosynthesis or throughaltered ecological interactions within the marine food web. Yet, there islittle consensus how entire diatom communities will respond to increasingCO2. To address this question, we synthesized the literature from overa decade of OA-experiments with natural diatom communities to uncover the following: (1) ifand how bulk diatom communities respond to elevated CO2 with respectto abundance or biomass and (2) if shifts within the diatom communities could beexpected and how they are expressed with respect to taxonomic affiliationand size structure. We found that bulk diatom communities responded to highCO2 in ∼60 % of the experiments and in this case moreoften positively (56 %) than negatively (32 %) (12 % did not reportthe direction of change). Shifts among different diatom species wereobserved in 65 % of the experiments. Our synthesis supports thehypothesis that high CO2 particularly favours larger species as 12 outof 13 experiments which investigated cell size found a shift towards largerspecies. Unravelling winners and losers with respect to taxonomic affiliationwas difficult due to a limited database. The OA-induced changes in diatomcompetitiveness and assemblage structure may alter key ecosystem servicesdue to the pivotal role diatoms play in trophic transfer and biogeochemicalcycles.