Hydrological pulse regulating the bacterial heterotrophic metabolism between Amazonian mainstems and floodplain lakes.
We evaluated in situ rates of bacterial carbon processing in Amazonian floodplain lakes and mainstems, during both high water (HW) and low water (LW) phases (p < 0.05). Our results showed that bacterial production (BP) was lower and more variable than bacterial respiration, determined as total respiration. Bacterial carbon demand was mostly accounted by BR and presented the same pattern that BR in both water phases. Bacterial growth efficiency (BGE) showed a wide range (0.2-23%) and low mean value of 3 and 6%, (in HW and LW, respectively) suggesting that dissolved organic carbon was mostly allocated to catabolic metabolism. However, BGE was regulated by BP in LW phase. Consequently, changes in BGE showed the same pattern that BP. In addition, the hydrological pulse effects on mainstems and floodplains lakes connectivity were found for BP and BGE in LW. Multiple correlation analyses revealed that indexes of organic matter (OM) quality (chlorophyll-a, N stable isotopes and C/N ratios) were the strongest seasonal drivers of bacterial carbon metabolism. Our work indicated that: (i) the bacterial metabolism was mostly driven by respiration in Amazonian aquatic ecosystems resulting in low BGE in either high or LW phase; (ii) the hydrological pulse regulated the bacterial heterotrophic metabolism between Amazonian mainstems and floodplain lakes mostly driven by OM quality.
Laboratório de Ciências Ambientais, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense Rio de Janeiro, Brazil.
Luciana O
LO
Vidal
Laboratoire Environnements et Paléoenvironnements Océaniques, Université Bordeaux 1 Bordeaux, France ; Departamento de Geoquímica, Universidade Federal Fluminense Rio de Janeiro, Brazil.
Gwenäel
G
Abril
Laboratoire d'Océanologie et Géosciences, Université du Littoral Côte d'Opale Wimereux, France.
Luiz F
LF
Artigas
Departamento de Hidrobiologia, Universidade Federal de São Carlos São Carlos, Brazil.
Michaela L
ML
Melo
Departamento de Geoquímica, Universidade Federal Fluminense Rio de Janeiro, Brazil.
Marcelo C
MC
Bernardes
Departamento de Biologia, Instituto de Ciências Biológicas, Universidade Federal de Juiz de Fora Juiz de Fora, Brazil.
Lúcia M
LM
Lobão
Departamento de Hidrobiologia, Universidade Federal de São Carlos São Carlos, Brazil.
Mariana C
MC
Reis
Institut de Recherche pour le Développement, Géosciences Environnement Toulouse Lima, Peru.
Patrícia
P
Moreira-Turcq
Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot Paris, France.
Marc
M
Benedetti
Laboratório de Ecotoxicologia, Centro de Energia Nuclear e Agricultura, São Paulo Universidade Federal de São Paulo São Paulo, Brazil.
Valdemar L
VL
Tornisielo
Departamento de Biologia, Instituto de Ciências Biológicas, Universidade Federal de Juiz de Fora Juiz de Fora, Brazil.
Fabio
F
Roland
Amazonian freshwater ecosystems; bacterial carbon demand; bacterial growth efficiency; bacterial production; bacterial respiration; hydrological pulse