Relación entre la producción primaria y bacteriana pelágicas en dos lagunas húmicas vegetadas

Alex Aguilar Zurita,Patricia Rodríguez

doi:10.25260/ea.16.26.3.0.223

Abstract

In this study, we show that depth-integrated pelagic primary production (PP) can exceed bacterioplankton production (BP) in vegetated humic shallow lakes, giving as a result an autotrophic water column, despite light restrictions and availability of organic carbon for lake bacteria. Intuitively, these conditions should favor the development of a heterotrophic water column. Instead, during our survey, BP represented between 1.3 to 5% of PP most of the time. Only once, during late summer, BP was ~71% of PP. Although we cannot conclude about the mechanisms behind the observed results, previous surveys and experimentation in the wetland allow us to hypothesize that autotrophic conditions were favored by: i) the shallow nature of the lakes, which compensates for light attenuation by organic matter when integrating production in the water column, ii) the presence of anaerobic anoxygenic photosynthetic bacteria below the macrophyte cover, and iii) high predation rates on bacterioplankton by heterotrophic flagellates below the floating plants.

Highlights

At the global scale, shallow lakes are among the most abundant type of aquatic ecosystems (Downing et al 2006) and are recognized as important sources of carbon dioxide (CO2) to the atmosphere (Battin et al 2009)
We show that depth-integrated pelagic primary production (PP) can exceed bacterioplankton production (BP) in vegetated humic shallow lakes, giving as a result an autotrophic water column, despite light restrictions and availability of organic carbon for lake bacteria
We cannot conclude about the mechanisms behind the observed results, previous surveys and experimentation in the wetland allow us to hypothesize that autotrophic conditions were favored by: i) the shallow nature of the lakes, which compensates for light attenuation by organic matter when integrating production in the water column, ii) the presence of anaerobic anoxygenic photosynthetic bacteria below the macrophyte cover, and iii) high predation rates on bacterioplankton by heterotrophic flagellates below the floating plants

Summary

Introduction

Shallow lakes are among the most abundant type of aquatic ecosystems (Downing et al 2006) and are recognized as important sources of carbon dioxide (CO2) to the atmosphere (Battin et al 2009). One of most significant processes that consume CO2 is primary production (PP), which, in turn, is counteracted by respiration (R) of organic substrata in the entire water body (Falkowski and Raven 2007). This is generally the case for nutrient-poor ecosystems, which are net sources of CO2 to the atmosphere since respiration is higher than the production of autochthonous organic matter (R>PP) (del Giorgio et al 1997; Cole et al 2000). Recibido: 11 de diciembre de 2015 Aceptado: 5 de abril de 2016

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Conclusion