PEECE II mesocosm experiment: Dynamics of extracellular enzyme activities in seawater under changed atmospheric pCO2, 2011

• Main Authors: Arnosti, Carol, Grossart, Hans-Peter, Mühling, M, Joint, Ian, Passow, Uta
• Format: Dataset
• Language: English
• Published: PANGAEA 2011
• Subjects: 14C-leucine incorporation; Alkalinity; total; Aragonite saturation state; Bacteria; production as carbon; Bacterial cell multiplication; Bicarbonate ion; BIOACID; Biological Impacts of Ocean Acidification; Biomass/Abundance/Elemental composition; Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Cell density; standard deviation; Chondroitin sulfate hydrolysis; Coast and continental shelf; EPOCA; EUR-OCEANS; European network of excellence for Ocean Ecosystems Analysis; European Project on Ocean Acidification; Experimental treatment; Experiment day; Field experiment; Fucoidan hydrolysis; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Identification; Laminarin hydrolysis; Measured; Mesocosm or benthocosm; North Atlantic; OA-ICC; Ocean Acidification International Coordination Centre; Other metabolic rates; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pelagos; pH; Proportion of total bacteria attached to particles; Salinity; Sample ID; see reference(s); Temperate; Temperature; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.778190; https://doi.org/10.1594/PANGAEA.778190

As part of the PeECE II mesocosm project, we investigated the effects of pCO2 levels on the initial step of heterotrophic carbon cycling in the surface ocean. The activities of microbial extracellular enzymes hydrolyzing 4 polysaccharides were measured during the development of a natural phytoplankton bloom under pCO2 conditions representing glacial (190 µatm) and future (750 µatm) atmospheric pCO2. We observed that (1) chondroitin hydrolysis was variable throughout the pre-, early- and late-bloom phases, (2) fucoidanase activity was measurable only in the glacial mesocosm as the bloom developed, (3) laminarinase activity was low and constant, and (4) xylanase activity declined as the bloom progressed. Concurrent measurements of microbial community composition, using denaturing-gradient gel electrophoresis (DGGE), showed that the 2 mesocosms diverged temporally, and from one another, especially in the late-bloom phase. Enzyme activities correlated with bloom phase and pCO2, suggesting functional as well as compositional changes in microbial communities in the different pCO2 environments. These changes, however, may be a response to temporal changes in the development of phytoplankton communities that differed with the pCO2 environment. We hypothesize that the phytoplankton communities produced dissolved organic carbon (DOC) differing in composition, a hypothesis supported by changing amino acid composition of the DOC, and that enzyme activities responded to changes in substrates. Enzyme activities observed under different pCO2 conditions likely reflect both genetic and population-level responses to changes occurring among multiple components of the microbial loop.