Alternative states drive the patterns in the bacterioplankton composition in shallow Pampean lakes (Argentina)

Authors

  • Maria E. Llames,

    Corresponding author
    • Laboratorio de Ecología y Fotobiología Acuática, Instituto de Investigaciones Biotecnológicas, Instituto Tecnológico Chascomús (IIB-INTECH), CONICET, UNSAM, Chascomús, pcia. de Buenos Aires, Argentina
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  • Paul A. del Giorgio,

    1. Groupe de Recherche Interuniversitaire en Limnologie (GRIL), Département des sciences biologiques, Université du Québec à Montrèal, Montreal, Quebec, Canada
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  • Horacio Zagarese,

    1. Laboratorio de Ecología y Fotobiología Acuática, Instituto de Investigaciones Biotecnológicas, Instituto Tecnológico Chascomús (IIB-INTECH), CONICET, UNSAM, Chascomús, pcia. de Buenos Aires, Argentina
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  • Marcela Ferraro,

    1. Laboratorio de Ecología y Fotobiología Acuática, Instituto de Investigaciones Biotecnológicas, Instituto Tecnológico Chascomús (IIB-INTECH), CONICET, UNSAM, Chascomús, pcia. de Buenos Aires, Argentina
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  • Irina Izaguirre

    1. Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, CONICET, Buenos Aires, Argentina
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For correspondence. E-mail mariaellames@intech.gov.ar; Tel. (+54) 2241 430323 ext 115; Fax (+54) 2241 424048.

Summary

We assessed the influence of environmental factors in shaping the free-living bacterial community structure in a set of shallow lakes characterized by contrasting stable state patterns (clear-vegetated, inorganic-turbid and phytoplankton-turbid). Six temperate shallow lakes from the Pampa Plain (Argentina) were sampled over an annual cycle, and two fingerprinting techniques were applied: a 16S rDNA analysis was performed using denaturing gradient gel electrophoresis (DGGE) profiles, and a 16S–23S internally transcribed spacer region analysis was conducted by means of automated ribosomal intergenic spacer analysis (ARISA) profiles. Our results show that the steady state that characterized the different shallow lakes played a major role in structuring the community: the composition of free-living bacteria differed significantly between clear-vegetated, inorganic-turbid and phytoplankton-turbid shallow lakes. The state of the system was more important in determining these patterns than seasonality, geographical location or degree of hydrological connectivity. Moreover, this strong environmental control was particularly evident in the pattern observed in one of the lakes, which shifted from a clear to a turbid state over the course of the study. This lake showed a directional selection of species from a typical clear-like to a turbid-like community. The combined DGGE/ARISA approach revealed not only broad patterns among different alternative steady states, but also more subtle differences within different regimes.

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