Dissolved organic matter and terrestrial-lotic linkages in the Central Amazon Basin of Brazil

Abstract. Regions in the Amazon Basin have been associated with specific biogeochemical processes, but a detailed chemical classification of the abundant and ubiquitous dissolved organic matter (DOM), beyond specific indicator compounds and bulk measurements, has not yet been established. We sampled water from different locations in the Negro, Madeira/Jamari and Tapajós River areas to characterize the molecular DOM composition and distribution. Ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) combined with excitation emission matrix (EEM) fluorescence spectroscopy and Parallel Factor Analysis (PARAFAC) revealed a large proportion of ubiquitous DOM but also unique area-specific molecular signatures. Unique to the DOM of the Rio Negro area was the large abundance of high molecular weight, diverse hydrogen-deficient and highly oxidized molecular ions deviating from known lignin or tannin compositions, indicating substantial oxidative processing of these ultimately plant-derived polyphenols indicative of these black waters. In contrast, unique signatures in the Madeira/Jamari area were defined by presumably labile sulfur and nitrogen-containing molecules in this white water river system. Waters from the Tapajós confluence area did not show any substantial unique molecular signatures relative to those present in the Rio Madeira and Rio Negro, which implied a lower organic molecular complexity in this clear water tributary. Beside ubiquitous DOM at average H/C and O/C elemental ratios, a distinct and significant unique DOM pool prevailed in the black, white and clear water areas that were also highly correlated with EEM-PARAFAC components and define the frameworks for primary production and other aspects of aquatic life.

Download Full-text

Chemodiversity of dissolved organic matter in the Amazon Basin

Biogeosciences ◽

10.5194/bg-13-4279-2016 ◽

2016 ◽

Vol 13 (14) ◽

pp. 4279-4290 ◽

Cited By ~ 28

Author(s):

Michael Gonsior ◽

Juliana Valle ◽

Philippe Schmitt-Kopplin ◽

Norbert Hertkorn ◽

David Bastviken ◽

...

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Amazon Basin ◽

Molecular Ions ◽

Main Stem ◽

Ion Cyclotron Resonance ◽

Molecular Signatures ◽

Clear Water ◽

Aquatic Life ◽

Rio Negro

Abstract. Regions in the Amazon Basin have been associated with specific biogeochemical processes, but a detailed chemical classification of the abundant and ubiquitous dissolved organic matter (DOM), beyond specific indicator compounds and bulk measurements, has not yet been established. We sampled water from different locations in the Negro, Madeira/Jamari and Tapajós River areas to characterize the molecular DOM composition and distribution. Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) combined with excitation emission matrix (EEM) fluorescence spectroscopy and parallel factor analysis (PARAFAC) revealed a large proportion of ubiquitous DOM but also unique area-specific molecular signatures. Unique to the DOM of the Rio Negro area was the large abundance of high molecular weight, diverse hydrogen-deficient and highly oxidized molecular ions deviating from known lignin or tannin compositions, indicating substantial oxidative processing of these ultimately plant-derived polyphenols indicative of these black waters. In contrast, unique signatures in the Madeira/Jamari area were defined by presumably labile sulfur- and nitrogen-containing molecules in this white water river system. Waters from the Tapajós main stem did not show any substantial unique molecular signatures relative to those present in the Rio Madeira and Rio Negro, which implied a lower organic molecular complexity in this clear water tributary, even after mixing with the main stem of the Amazon River. Beside ubiquitous DOM at average H ∕ C and O ∕ C elemental ratios, a distinct and significant unique DOM pool prevailed in the black, white and clear water areas that were also highly correlated with EEM-PARAFAC components and define the frameworks for primary production and other aspects of aquatic life.

Download Full-text

Spatial and seasonal contrasts of sedimentary organic matter in floodplain lakes of the central Amazon basin

Biogeosciences ◽

10.5194/bg-13-467-2016 ◽

2016 ◽

Vol 13 (2) ◽

pp. 467-482 ◽

Cited By ~ 5

Author(s):

R. L. Sobrinho ◽

M. C. Bernardes ◽

G. Abril ◽

J.-H. Kim ◽

C. I Zell ◽

...

Keyword(s):

Organic Matter ◽

Amazon Basin ◽

Surface Sediments ◽

Vascular Plant ◽

High Water ◽

Floodplain Lakes ◽

Sedimentary Organic Matter ◽

C3 Plant ◽

Geochemical Tracers ◽

Central Amazon

Abstract. In this study, we investigated the seasonal and spatial pattern of sedimentary organic matter (SOM) in five floodplain lakes of the central Amazon basin (Cabaliana, Janauaca, Canaçari, Mirituba and Curuai) which have different morphologies, hydrodynamics and vegetation coverages. Surface sediments were collected in four hydrological seasons: low water (LW), rising water (RW), high water (HW) and falling water (FW) in 2009 and 2010. We investigated commonly used bulk geochemical tracers such as the C : N ratio and the stable isotopic composition of organic carbon (δ13Corg). These results were compared with lignin phenol parameters as an indicator of vascular plant detritus and branched glycerol dialkyl glycerol tetraethers (brGDGTs) to trace the input of soil organic matter (OM) from land to the aquatic settings. We also applied the crenarchaeol as an indicator of aquatic (rivers and lakes) OM. Our data showed that during the RW and FW seasons, the surface sediments were enriched in lignin and brGDGTs in comparison to other seasons. Our study also indicated that floodplain lake sediments primarily consisted of allochthonous, C3 plant-derived OM. However, a downstream increase in C4 macrophyte-derived OM contribution was observed along the gradient of increasing open waters – i.e., from upstream to downstream. Accordingly, we attribute the temporal and spatial difference in SOM composition to the hydrological dynamics between the floodplain lakes and the surrounding flooded forests.

Download Full-text

Review of manuscript bg-2016-72 “Chemodiversity of dissolved organic matter in the Amazon Basin” Anonymous Referee #2

10.5194/bg-2016-72-rc2 ◽

2016 ◽

Author(s):

Anonymous

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Amazon Basin

Download Full-text

Dissolved organic matter dynamic in the Amazon basin: Sorption by mineral surfaces

Chemical Geology ◽

10.1016/j.chemgeo.2011.05.004 ◽

2011 ◽

Cited By ~ 4

Author(s):

Marcela A.P. Pérez ◽

Patricia Moreira-Turcq ◽

Hervé Gallard ◽

Thierry Allard ◽

Marc F. Benedetti

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Amazon Basin ◽

Mineral Surfaces

Download Full-text

Spatial and seasonal contrasts of sedimentary organic matter in floodplain lakes of the central Amazon basin

Biogeosciences Discussions ◽

10.5194/bgd-12-8747-2015 ◽

2015 ◽

Vol 12 (11) ◽

pp. 8747-8787 ◽

Cited By ~ 3

Author(s):

R. L. Sobrinho ◽

M. C. Bernardes ◽

G. Abril ◽

J.-H. Kim ◽

C. I. Zell ◽

...

Keyword(s):

Organic Matter ◽

Amazon Basin ◽

Surface Sediments ◽

Vascular Plant ◽

High Water ◽

Floodplain Lakes ◽

Sedimentary Organic Matter ◽

C3 Plant ◽

Geochemical Tracers ◽

Central Amazon

Abstract. In this study, we investigated the seasonal and spatial pattern of sedimentary organic matter (SOM) in five floodplain lakes of the central Amazon basin (Cabaliana, Janauaca, Canaçari, Miratuba, and Curuai) which have different morphologies, hydrodynamics and vegetation coverages. Surface sediments were collected in four hydrological seasons: low water (LW), rising water (RW), high water (HW) and falling water (FW) in 2009 and 2010. We investigated commonly used bulk geochemical tracers such as the C : N ratio and the stable isotopic composition of organic carbon (δ13Corg). These results were compared with lignin-phenol parameters as an indicator of vascular plant detritus and branched glycerol dialkyl glycerol tetraethers (brGDGTs) to trace the input of soil organic matter (OM) from land to the aquatic settings. We also applied the isoprenoid GDGT (iGDGT) crenarchaeol as an indicator of riverine suspended particulate organic matter (SPOM). Our data showed that during the RW and FW seasons, the surface sediments were enriched in lignin and brGDGTs in comparison to other seasons. Our study also indicated that floodplain lake sediments primarily consisted of allochthonous, C3 plant-derived OM. However, a downstream increase in C4 macrophyte derived OM contribution was observed along the gradient of increasing open waters, i.e. from upstream to downstream. Accordingly, we attribute temporal and spatial difference in SOM composition to the hydrological dynamics between the floodplain lakes and the surrounding flooded forests.

Download Full-text