Seawater carbonate chemistry and microbial abundances, bacterial activity and extracellular enzyme activities

• Main Authors: Sala, M M, Aparicio, F L, Balagué, Vanessa, Boras, J A, Borrull, E, Cardelus, C, Cros, Lluisa, Gomes, Ana, Lopez-Sanz, Angel, Malits, A, Martinez, R A, Mestre, M, Movilla, Juancho, Sarmento, Hugo, Vazquez-Dominguez, E, Vaqué, Dolors, Pinhassi, Jarone, Calbet, Albert, Calvo, Eva, Gasol, Josep M, Pelejero, Carles, Marrasé, Celia
• Format: Dataset
• Language: English
• Published: PANGAEA 2016
• Subjects: Abundance per volume; Alkalinity; total; alpha-glucosidase activity; Aragonite saturation state; beta-glucosidase activity; Bicarbonate ion; Biomass/Abundance/Elemental composition; Blanes_Bay_Microbial_Observatory; Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chitobiase activity; Chlorophyll a; Coast and continental shelf; Community composition and diversity; Containers and aquaria (20-1000 L or < 1 m**2); Entire community; EXP; Experiment; Experiment day; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Laboratory experiment; Leucine aminopeptidase activity; Leucine incorporation rate; Macro-nutrients; Mediterranean Sea; OA-ICC; Ocean Acidification International Coordination Centre; Other metabolic rates; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pelagos; pH; Potentiometric titration; Replicate; Salinity; Spectrophotometric; Temperate; Temperature; water; Treatment; Type; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.934302; https://doi.org/10.1594/PANGAEA.934302

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.