Incidence of phytoplankton and environmental conditions on the bacterial ammonium uptake in a subtropical coastal lagoon

  • Germán Pérez Instituto de Investigaciones Biológicas Clemente Estable, Uruguay.
  • Laura Farías Universidad de Concepción, Chile.
  • Camila Fernandez UPMC Univ. Paris 06 and CNRS, UMR 7621, France.
  • Daniel Conde Universidad de la República, Uruguay.
  • Claudia Piccini | cpiccini@iibce.edu.uy Instituto de Investigaciones Biológicas Clemente Estable, Uruguay.

Abstract

We analyzed the coupling between bacterioplankton and phytoplankton in Laguna de Rocha through an experimental approach. A freshwater zone of high turbidity and macrophytes growth and a brackish zone of higher light penetration and lower macrophytes biomass characterize this coastal lagoon. It has been shown that dissolved inorganic nitrogen, especially NH4+, has decreased to undetectable levels during the last decade. One hypothesis for this trend is the rapid removal by phytoplankton and bacterioplankton uptake. In an attempt to test this, we performed incubations using lagoon water from both zones split in two treatments (pre-filtered by 1.2 µm and unfiltered water) and amended with 15N-NH4+. After 4 h incubation we found that in both zones bacterioplankton showed significantly higher NH4+ uptake rates when incubated together with phytoplankton and that uptake rates of both microbial communities were higher in freshwater incubations. These results suggest that bacterial NH4+ uptake would be coupled to phytoplankton-derived exudates and hence that depletion of dissolved NH4+ in this system could be linked to rapid microbial uptake. The degree of this coupling would vary according to hydrological dynamics in this ecosystem.

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Author Biographies

Germán Pérez, Instituto de Investigaciones Biológicas Clemente Estable

Depto. Microbiología

Investigador Asistente

Laura Farías, Universidad de Concepción

Departamento de Oceanografía

Profesor Asistente

Camila Fernandez, UPMC Univ. Paris 06 and CNRS, UMR 7621
Researcher CNRS, Laboratory of Microbial Oceanography
Daniel Conde, Universidad de la República

Sección Limnología,  Facultad de Ciencias

Claudia Piccini, Instituto de Investigaciones Biológicas Clemente Estable

Departamento de Microbiología

Published
2014-03-13
Section
Original Articles
Supporting Agencies
ANII, PEDECIBA, AMSUD-Pasteur
Keywords:
ammonium uptake rates, coastal lagoon, microbial interactions.
Statistics
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How to Cite
1.
Pérez G, Farías L, Fernandez C, Conde D, Piccini C. Incidence of phytoplankton and environmental conditions on the bacterial ammonium uptake in a subtropical coastal lagoon. jlimnol [Internet]. 13Mar.2014 [cited 29Mar.2020];73(1). Available from: https://www.jlimnol.it/index.php/jlimnol/article/view/jlimnol.2014.829