Contrasting effects of ocean acidification on the microbial food web under different trophic conditions

• Published in: ICES Journal of Marine Science
• Main Authors: Sala, M. Montserrat, Aparicio, Francisco Luis, Balagué, Vanessa, Boras, Julia A., Borrull, Encarnación, Cardelús, Clara, Cros, Lluïsa, Gomes, Ana, López-Sanz, Àngel, Malits, Andrea, Martínez, Rodrigo Andrés, Mestre, Mireia, Movilla, Juan Ignacio, Sarmento, Hugo, Vázquez-Domínguez, Evaristo, Vaqué, Dolors, Calbet, Albert, Calvo, Eva María, Gasol, Josep M., Pelejero, Carles, Marrasé, Cèlia
• Other Authors: Ministerio de Economía y Competitividad (España), Generalitat de Catalunya
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: International Council for the Exploration of the Sea 2016
• Subjects: Acidification; Eutrophication; Mediterranean Sea; Mesocosm; Microorganisms; Ocean acidification
• Online Access: http://hdl.handle.net/10261/129671; https://doi.org/10.1093/icesjms/fsv130; https://doi.org/10.13039/501100003329; https://doi.org/10.13039/501100002809

Sala, M. Montserrat .et al.-- Special issue: Towards a Broader Perspective on Ocean Acidification Research.-- 10 pages, 2 figures, 3 tables, supplementary data http://icesjms.oxfordjournals.org/content/73/3/670/suppl/DC1 We investigated the effects of an increase in dissolved CO2 on the microbial communities of the Mediterranean Sea during two mesocosm experiments in two contrasting seasons: winter, at the peak of the annual phytoplankton bloom, and summer, under low nutrient conditions. The experiments included treatments with acidification and nutrient addition, and combinations of the two. We followed the effects of ocean acidification (OA) on the abundance of the main groups of microorganisms (diatoms, dinoflagellates, nanoeukaryotes, picoeukaryotes, cyanobacteria, and heterotrophic bacteria) and on bacterial activity, leucine incorporation, and extracellular enzyme activity. Our results showed a clear stimulation effect of OA on the abundance of small phytoplankton (pico- and nanoeukaryotes), independently of the season and nutrient availability. A large number of the measured variables showed significant positive effects of acidification in summer compared with winter, when the effects were sometimes negative. Effects of OA were more conspicuous when nutrient concentrations were low. Our results therefore suggest that microbial communities in oligotrophic waters are considerably affected by OA, whereas microbes in more productive waters are less affected. The overall enhancing effect of acidification on eukaryotic pico- and nanophytoplankton, in comparison with the non-significant or even negative response to nutrient-rich conditions of larger groups and autotrophic prokaryotes, suggests a shift towards medium-sized producers in a future acidified ocean Financial support from the Spanish Ministry of Economy and Competitiveness is acknowledged, specifically through the projects STORM(CTM2009–09352), DOREMI (CTM2012-34294), MANIFEST (CTM2012-32017), and PROTOS (CTM2009-08783) of the Spanish Ministry of ...