TY - JOUR
T1 - Contribution of deep dark fixation processes to overall CO2 incorporation and large vertical changes of microbial populations in stratified karstic lakes
AU - Casamayor, Emilio O.
AU - Llirós, Marc
AU - Picazo, Antonio
AU - Barberán, Albert
AU - Borrego, Carles M.
AU - Camacho, Antonio
N1 - Funding Information:
Acknowledgments This research was supported by projects VIARC REN2003-08333 and CRENYC CGL2006-12058 to EOC and CBM, from the Spanish Ministerio de Ciencia e Innovación (MICINN), and CONSOLIDER-INGENIO 2010 project GRACCIE CSD2007-00067 from MICINN. We thank A. García, MC Gutiérrez, and MA Vich for excellent technical and field assistance. We also thank the constructive comments made by two anonymous reviewers and the editor.
PY - 2012/1
Y1 - 2012/1
N2 - We carried out a detailed study in five stratified lakes in the karstic regions of NE Spain along a redox gradient combining vertical profiles of inorganic carbon dioxide fixation and analysis of microbial (bacteria and archaea) community composition determined by 16S rRNA gene fingerprinting (DGGE), microscopic counts, and pigment analysis. High rates of non-photosynthetic (i.e., "dark") inorganic carbon incorporation were detected mostly at deeper layers after short-term in situ incubations at noon. Significant contribution of dark CO2 incorporation was observed at the whole lake level for the single time sampling, ranging between 4 and 19% of total carbon fixation measured, and up to 31% in the case of a meromictic basin. Good agreement was found between vertical patterns in redox conditions and the different microbial diversity descriptors (DGGE band sequencing, microscopic analysis, and pigment data), showing large vertical changes in microbial community composition covering a wide range of phylogenetic diversity. Cyanobacteria, Alpha and Beta-Proteobacteria, Actinobacteria, Flavobacteria and Flectobacillaceae were the most frequently recovered groups in the DGGE from oxygenated water masses. In anoxic waters, we found Beta-Proteobacteria mostly of the Rhodoferax group, Gamma-Proteobacteria (Chromatiaceae), Delta-Proteobacteria related to different sulfate reducing bacteria, Chlorobiaceae, and anaerobic Bacteroidetes spread among the Bacteroidales, Flavobacteriales and Saprospiraceae. However, as a whole, we did not find any significant correlation between dark fixation rates and either nutrient distribution and microbial community composition in the study lakes. All of this suggests that (1) different physiologies and ecologies are simultaneously contributing to the process (2) more sensitive methods are needed and more specific compounds measured and (3) some of the non-specialist microbial populations detected may carry out carbon dioxide assimilation in the dark under in situ conditions.
AB - We carried out a detailed study in five stratified lakes in the karstic regions of NE Spain along a redox gradient combining vertical profiles of inorganic carbon dioxide fixation and analysis of microbial (bacteria and archaea) community composition determined by 16S rRNA gene fingerprinting (DGGE), microscopic counts, and pigment analysis. High rates of non-photosynthetic (i.e., "dark") inorganic carbon incorporation were detected mostly at deeper layers after short-term in situ incubations at noon. Significant contribution of dark CO2 incorporation was observed at the whole lake level for the single time sampling, ranging between 4 and 19% of total carbon fixation measured, and up to 31% in the case of a meromictic basin. Good agreement was found between vertical patterns in redox conditions and the different microbial diversity descriptors (DGGE band sequencing, microscopic analysis, and pigment data), showing large vertical changes in microbial community composition covering a wide range of phylogenetic diversity. Cyanobacteria, Alpha and Beta-Proteobacteria, Actinobacteria, Flavobacteria and Flectobacillaceae were the most frequently recovered groups in the DGGE from oxygenated water masses. In anoxic waters, we found Beta-Proteobacteria mostly of the Rhodoferax group, Gamma-Proteobacteria (Chromatiaceae), Delta-Proteobacteria related to different sulfate reducing bacteria, Chlorobiaceae, and anaerobic Bacteroidetes spread among the Bacteroidales, Flavobacteriales and Saprospiraceae. However, as a whole, we did not find any significant correlation between dark fixation rates and either nutrient distribution and microbial community composition in the study lakes. All of this suggests that (1) different physiologies and ecologies are simultaneously contributing to the process (2) more sensitive methods are needed and more specific compounds measured and (3) some of the non-specialist microbial populations detected may carry out carbon dioxide assimilation in the dark under in situ conditions.
KW - 16S rRNA
KW - Archaea
KW - Bacteria
KW - DGGE
KW - Dark carbon fixation
KW - Karstic lakes
KW - Photosynthetic sulfur bacteria
KW - Primary production
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U2 - 10.1007/s00027-011-0196-5
DO - 10.1007/s00027-011-0196-5
M3 - Article
AN - SCOPUS:84855335873
SN - 1015-1621
VL - 74
SP - 61
EP - 75
JO - Aquatic Sciences
JF - Aquatic Sciences
IS - 1
ER -