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Hydrological pulse regulating the bacterial heterotrophic metabolism between Amazonian mainstems and floodplain lakes.

Vidal LO, Abril G, Artigas LF, Melo ML, Bernardes MC, Lobão LM, Reis MC, Moreira-Turcq P, Benedetti M, Tornisielo VL, Roland F - Front Microbiol (2015)

Bottom Line: Our results showed that bacterial production (BP) was lower and more variable than bacterial respiration, determined as total respiration.In addition, the hydrological pulse effects on mainstems and floodplains lakes connectivity were found for BP and BGE in LW.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.

View Article: PubMed Central - PubMed

Affiliation: Laboratório de Ciências Ambientais, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense Rio de Janeiro, Brazil.

ABSTRACT
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.

No MeSH data available.


Location of study areas across the Amazonian River ecosystems in a large (A–C) and small scale (D–F). Dashed black lines delineate the Cabaliana, Janauaca, Miratuba, Canaçari, and Curuai floodplains (Abril et al., 2014).
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Figure 1: Location of study areas across the Amazonian River ecosystems in a large (A–C) and small scale (D–F). Dashed black lines delineate the Cabaliana, Janauaca, Miratuba, Canaçari, and Curuai floodplains (Abril et al., 2014).

Mentions: The Amazon River is the world’s largest river with a drainage basin area of 6.1 × 106 km2 covering about 40% of South America (Goulding et al., 2003). The mean annual discharge is 200 × 103 m3 s-1 at Óbidos, the most downstream gauging station in the Amazon River (Callede et al., 2000). Due to the equatorial position (Figures 1A–C), temperature in the central Amazon basin is relatively constant around the year with a mean annual air temperature (MAAT) of ca. 27°C (New et al., 2002). Rivers within the Amazon drainage basin are traditionally classified according to water color, as well as physical and chemical parameters (Sioli, 1956): white water (e.g., Solimões and Madeira), black water (e.g., Negro), and clear water (e.g., Tapajós). Large parts of the central Amazon basin are subjected to periodical floods due mainly to spatial and temporal distribution of rainfall in the headwaters. This creates large temporary wetlands, i.e., seasonally flooded forests which cover a total area of ca. 350 × 103 km2 (Junk, 1997; Melack and Hess, 2011). There is water exchange between flooded forests and the Amazon River which is highly influenced by the rising and falling of water during the rainy or dry seasons, respectively (Lesack and Melack, 1995). Five floodplain lakes were investigated in this study (Figure 1C): Cabaliana, Janauaca, Miritituba, Canaçari, and Curuai (Figures 1D–F), located in a gradient of decreasing flooded forests and increasing open waters (Bourgoin et al., 2007). Cabaliana has a large area surrounded by flooded forests and two sub-regions. In the northern region, Piranha stream discharges black water while in the southern region white water, brought by the Solimões River, mixes with black water. Janauaca has a peculiar morphology with a ravine shape surrounded by flooded forests. Solimões water comes through the channel in the north and black water comes through the stream system in the south. Miritituba receives white water from the Madeira River and the Amazon River. It can be considered as a white water lake surrounded by flooded forests, with no significant contribution of black water streams. Canaçari has two well-defined sub-regions. In the northern region, the Urubu River discharges black water and in the southern region, the Amazon River discharges white water. Canaçari is surrounded by grass plains but is disconnected from flooded forests most of the year. Curuai is the largest lake in the central Amazon basin, mainly surrounded by grass plains and open waters. It receives white water from the Amazon River through small channels, apart from the main channel in the eastern side. There are no significant contributions of black water streams for Curuai Lake.


Hydrological pulse regulating the bacterial heterotrophic metabolism between Amazonian mainstems and floodplain lakes.

Vidal LO, Abril G, Artigas LF, Melo ML, Bernardes MC, Lobão LM, Reis MC, Moreira-Turcq P, Benedetti M, Tornisielo VL, Roland F - Front Microbiol (2015)

Location of study areas across the Amazonian River ecosystems in a large (A–C) and small scale (D–F). Dashed black lines delineate the Cabaliana, Janauaca, Miratuba, Canaçari, and Curuai floodplains (Abril et al., 2014).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4588699&req=5

Figure 1: Location of study areas across the Amazonian River ecosystems in a large (A–C) and small scale (D–F). Dashed black lines delineate the Cabaliana, Janauaca, Miratuba, Canaçari, and Curuai floodplains (Abril et al., 2014).
Mentions: The Amazon River is the world’s largest river with a drainage basin area of 6.1 × 106 km2 covering about 40% of South America (Goulding et al., 2003). The mean annual discharge is 200 × 103 m3 s-1 at Óbidos, the most downstream gauging station in the Amazon River (Callede et al., 2000). Due to the equatorial position (Figures 1A–C), temperature in the central Amazon basin is relatively constant around the year with a mean annual air temperature (MAAT) of ca. 27°C (New et al., 2002). Rivers within the Amazon drainage basin are traditionally classified according to water color, as well as physical and chemical parameters (Sioli, 1956): white water (e.g., Solimões and Madeira), black water (e.g., Negro), and clear water (e.g., Tapajós). Large parts of the central Amazon basin are subjected to periodical floods due mainly to spatial and temporal distribution of rainfall in the headwaters. This creates large temporary wetlands, i.e., seasonally flooded forests which cover a total area of ca. 350 × 103 km2 (Junk, 1997; Melack and Hess, 2011). There is water exchange between flooded forests and the Amazon River which is highly influenced by the rising and falling of water during the rainy or dry seasons, respectively (Lesack and Melack, 1995). Five floodplain lakes were investigated in this study (Figure 1C): Cabaliana, Janauaca, Miritituba, Canaçari, and Curuai (Figures 1D–F), located in a gradient of decreasing flooded forests and increasing open waters (Bourgoin et al., 2007). Cabaliana has a large area surrounded by flooded forests and two sub-regions. In the northern region, Piranha stream discharges black water while in the southern region white water, brought by the Solimões River, mixes with black water. Janauaca has a peculiar morphology with a ravine shape surrounded by flooded forests. Solimões water comes through the channel in the north and black water comes through the stream system in the south. Miritituba receives white water from the Madeira River and the Amazon River. It can be considered as a white water lake surrounded by flooded forests, with no significant contribution of black water streams. Canaçari has two well-defined sub-regions. In the northern region, the Urubu River discharges black water and in the southern region, the Amazon River discharges white water. Canaçari is surrounded by grass plains but is disconnected from flooded forests most of the year. Curuai is the largest lake in the central Amazon basin, mainly surrounded by grass plains and open waters. It receives white water from the Amazon River through small channels, apart from the main channel in the eastern side. There are no significant contributions of black water streams for Curuai Lake.

Bottom Line: Our results showed that bacterial production (BP) was lower and more variable than bacterial respiration, determined as total respiration.In addition, the hydrological pulse effects on mainstems and floodplains lakes connectivity were found for BP and BGE in LW.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.

View Article: PubMed Central - PubMed

Affiliation: Laboratório de Ciências Ambientais, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense Rio de Janeiro, Brazil.

ABSTRACT
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.

No MeSH data available.