Marcelo C Bernardes | UFF - Universidade Federal Fluminense (original) (raw)
Papers by Marcelo C Bernardes
CONTRIBUCIONES A LAS CIENCIAS SOCIALES
O objetivo da pesquisa foi avaliar n-alcanos (C15 a C40) e esteróis, como indicadores da origem d... more O objetivo da pesquisa foi avaliar n-alcanos (C15 a C40) e esteróis, como indicadores da origem da matéria orgânica em sedimentos superficiais das lagoas costeiras do sistema lagunar de Jacarepaguá na cidade do Rio de Janeiro. As amostras de sedimentos foram coletas em 4 pontos de amostragem, extraídas em banho ultrassom para retirada da fase orgânica. O extrato foi fracionado de acordo com a polaridades dos grupos de compostos de interesse em cromatografia de coluna de sílica gel, adaptado em uma pipeta pasteur. Os alcanos e esteróis foram separados e quantificados por cromatografia a gás com detector de ionização de chama (CG-DIC) e suas identificações foram realizadas por comparação com tempo de retenção do padrão analítico. Os resultados mostraram que as concentrações individuais dos n-alcanos detectados variaram entre 0,65 a 71 µg g-1, e as concentrações totais de esteróis foram 0,55 a 13,42 µg g-1. O perfil de distribuição de alcanos teve destaque para Cmax de C28, C29, e C32 ...
Critical Reviews in Analytical Chemistry
Este estudo tem por objetivo caracterizar os sedimentos superficiais, quanto ao seu teor e qualid... more Este estudo tem por objetivo caracterizar os sedimentos superficiais, quanto ao seu teor e qualidade dos fenóis da lignina, em dois sistemas lacustres distintos: a Várzea do Lago Grande Curuái (PA) e o Lago do Caçó (MA). A Várzea do Lago Grande Curuái é localizada na margem direita do Rio Amazonas, aproximadamente 850 km da foz e é caracterizada pela presença de lagos de águas brancas e pretas. O Lago do Caçó está localizado no Maranhão, na borda do ecossistema amazônico. Foram realizadas análises da concentração de lignina (λ), carbono orgânico total (COT), nitrogênio e isótopos do carbono (δ 13 C). Os resultados indicam que os sedimentos superficias de lagos de águas brancas apresentam baixos valores de COT (1,5 a 3,6%), baixa concentração de λ (0,73 a 1,28 mg.100mg CO -1 ) e alto índice de degradação (0,29 a 2,01). Os sedimentos superficiais de lagos de águas pretas apresentam maiores valores de COT (6,0 a 12,1%) e de λ (1,44 a 1,93 mg.100mg CO -1 ) em relação aos sedimentos de lagos de águas brancas, porém baixos em comparação com os sedimentos do Lago do Caçó (7,2 ~ 15,3% e 1,83 ~ 4,64 mg .100mg CO -1 , respectivamente). Através das análises realizadas foi possível identificar diferentes contribuições de fontes assim como diferentes estados de preservação da matéria orgânica sedimentada nos dois sistemas apresentados. PalavRas-Chave: matéria orgânica, carbono, isótopos estáveis e lignina.
Nature Geoscience, 2012
Humans have used fire extensively as a tool to shape Earth's vegetation. The slash-and-burn destr... more Humans have used fire extensively as a tool to shape Earth's vegetation. The slash-and-burn destruction of Brazil's Atlantic forest, which once covered over 1.3 million km 2 of present-day Brazil and was one of the largest tropical forest biomes on Earth 1 , is a prime example. Here, we estimate the amount of black carbon generated by the burning of the Atlantic forest, using historical records of land cover, satellite data and black carbon conversion ratios. We estimate that before 1973, destruction of the Atlantic forest generated 200-500 million tons of black carbon. We then estimate the amount of black carbon exported from this relict forest between 1997 and 2008, using measurements of polycyclic aromatic black carbon collected from a large river draining the region, and a continuous record of river discharge. We show that dissolved black carbon (DBC) continues to be mobilized from the watershed each year in the rainy season, despite the fact that widespread forest burning ceased in 1973. We estimate that the river exports 2,700 tons of DBC to the ocean each year. Scaling our findings up, we estimate that 50,000-70,000 tons of DBC are exported from the former forest each year. We suggest that an increase in black carbon production on land could increase the size of the refractory pool of dissolved organic carbon in the deep ocean.
Este estudo teve como objetivo avaliar a composição da matéria orgânica (MO) através de análises ... more Este estudo teve como objetivo avaliar a composição da matéria orgânica (MO) através de análises elementares, isotópicas e moleculares em dois testemunhos coletados na Lagoa do Caçó que registram os últimos 20.000 cal yrs BP e testar o potencial de ferramentas da geoquímica molecular no estudo paleoambiental. A Lagoa do Caçó é localizada no Maranhão numa área influenciada pelo deslocamento sazonal da zona de convergência intertropical (ZCIT). Os resultados e interpretações obtidos a partir da geoquímica orgânica durante o tardi-glacial evidenciaram a importância da abordagem multiparamétrica e corroboram os trabalhos prévios validando o uso dos fenóis da lignina e dos pigmentos sedimentares como ferramentas na interpretação paleoambiental em zona tropical. Foi possível identifcar três diferentes Fases holocênicas jamais mostradas em trabalhos precedentes destacando o potencial destes biomarcadores. Palavras-chave: Holoceno, biomarcadores orgânicos, Rock-Eval, mudanças paleoambientais.
Oceans, Rivers and Lakes: Energy and Substance Transfers at Interfaces, 1998
Pelagic and benthic carbon metabolism in the shallow tropical Barra Lagoon was studied weekly bet... more Pelagic and benthic carbon metabolism in the shallow tropical Barra Lagoon was studied weekly between 1990 and 1993, in periods characterized by temporary nitrogen limitation, fish kills and transitory colonization of the bottom by macro-algae. Diurnal and nocturnal metabolic rates were measured by monitoring changes in CO 2 content in entire water columns (free water and waters incubated in plexiglass tubes with and without inclusion of sediment). Total community carbon metabolism exhibited a marked autotrophism and high short term changes, dampening seasonal trends. Autotrophism and heterotrophism of the lagoon were controlled by phytoplankton biomass variations. In the presence of sediment, diurnal net benthic production was 11 to 64% of total diurnal net production, and nocturnal net benthic mineralization was 21 to 52% of total nocturnal net mineralization. The imbrication between the pelagic and benthic organic carbon cycles regulated carbon metabolism of the total community. A severe temporary nitrogen limitation, a fish kill and a temporary shift in primary producers did not substantially change metabolic rates because appropriate shifts occurred from the pelagic carbon cycle to the benthic carbon cycle, and vice-versa.
Frontiers in Microbiology, 2015
We evaluated in situ rates of bacterial carbon processing in Amazonian floodplain lakes and mains... more 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.
Acta Amazonica
This study aims to characterize the superficial sediments of lakes in black and white waters of a... more This study aims to characterize the superficial sediments of lakes in black and white waters of an Amazonian floodplain system in terms of carbon content and quality of lignin phenols. “Várzea do Lago Grande Curuái” floodplain is located on the right bank of the Amazon River about 850 km from the estuary. Superficial sediments samples were compared with superficial samples from Lake Caçó, located in Maranhão, the edge of the Amazon ecosystem. Concentration of lignin (λ), Total Organic Carbon (COT), nitrogen and isotope of carbon (δ13C) were undertaken. The results indicate that, in general, the superficial sediments of lakes of white water have low values of COT (1,5 to 3,6%), low concentrations of λ (0,73 to 1,28 mg.100mg CO-1) and high degradation index (0.29 to 2.01). Superficial sediments of lakes of black water had higher values of COT (6,0 to 12,1%) and λ (1,44 to 1,93 mg.100mg CO-1) than the sediments of lakes of white waters, but lower in comparison with the sediments of Caç...
PLoS ONE, 2012
One of the greatest challenges in understanding the Amazon basin functioning is to ascertain the ... more One of the greatest challenges in understanding the Amazon basin functioning is to ascertain the role played by floodplains in the organic matter (OM) cycle, crucial for a large spectrum of ecological mechanisms. Fatty acids (FAs) were combined with environmental descriptors and analyzed through multivariate and spatial tools (asymmetric eigenvector maps, AEM and principal coordinates of neighbor matrices, PCNM). This challenge allowed investigating the distribution of suspended particulate organic matter (SPOM), in order to trace its seasonal origin and quality, along a 800 km section of the Amazon river-floodplain system. Statistical analysis confirmed that large amounts of saturated FAs (15:0, 18:0, 24:0, 25:0 and 26:0), an indication of refractory OM, were concomitantly recorded with high pCO 2 in rivers, during the high water season (HW). Contrastingly, FAs marker which may be attributed in this ecosystem to aquatic plants (18:2v6 and 18:3v3) and cyanobacteria (16:1v7), were correlated with higher O 2 , chlorophyll a and pheopigments in floodplains, due to a high primary production during low waters (LW). Decreasing concentrations of unsaturated FAs, that characterize labile OM, were recorded during HW, from upstream to downstream. Furthermore, using PCNM and AEM spatial methods, FAs compositions of SPOM displayed an upstream-downstream gradient during HW, which was attributed to OM retention and the extent of flooded forest in floodplains. Discrimination of OM quality between the Amazon River and floodplains corroborate higher autotrophic production in the latter and transfer of OM to rivers at LW season. Together, these gradients demonstrate the validity of FAs as predictors of spatial and temporal changes in OM quality. These spatial and temporal trends are explained by 1) downstream change in landscape morphology as predicted by the River Continuum Concept; 2) enhanced primary production during LW when the water level decreased and its residence time increased as predicted by the Flood Pulse Concept.
Sediment cores from the Mundaú-Manguaba estuarine-lagoon system (MMELS),NE- Brazil, were analized... more Sediment cores from the Mundaú-Manguaba estuarine-lagoon system (MMELS),NE- Brazil, were analized for vertical distribution of organic carbon, organic nitrogen, stable carbon isotope ratio ( δ � 13 C) and lignin phenol concentration and composition. Results exhibited alterations in the deposition of organic matter from alochthonous and autochthonous sources, being different between the Mundaú and Manguaba lagoon compartments. At the mouth of Mundaú river the top to intermediate sediment layers harbored a mixture of terrestrial plant materials, mainly non-woody plants, and towards the base of the core a mixture of woody angiosperms and phytoplankton. In contrast, the top of the core from Manguaba lagoon largely harbored phytoplantonic organic matter and a gradual increase from the top to the bottom of a mixture of non-woody and woody terrestrial vegetation.
Water Research, 1999
AbstractÐConcentrations of biogenic gases (O 2 and CO 2 ) and respiration rates were measured at ... more AbstractÐConcentrations of biogenic gases (O 2 and CO 2 ) and respiration rates were measured at 7 sites along major tributaries of the Piracicaba River to address the eects of sewage loading on aquatic metabolism. Strictly aerobic conditions were observed at upstream sites (less polluted), with concentrations of O 2 at or above and CO 2 slightly above atmospheric equilibrium. Concentrations of biogenic gases were independent of variations in discharge and relatively constant during the sampling period. Respiration rates were signi®cantly higher at upstream sites and CO 2 concentrations were above atmospheric equilibrium. The concentrations of CO 2 at downstream sites were inversely correlated with discharge. At the downstream sites (more polluted), anthropogenic inputs of labile organic matter (sewage) altered the aquatic metabolism by creating a less aerobic environment. At these sites, O 2 concentrations were always below atmospheric equilibrium and directly related to discharge. #
Organic Geochemistry, 2013
A multi-proxy study has been performed on a sediment core from the Curuai floodplain, Central Ama... more A multi-proxy study has been performed on a sediment core from the Curuai floodplain, Central Amazonia. The combination of elemental, isotopic and molecular analysis of a 110 cm core (a record of ca. the last 100 yr) allowed reconstruction of the hydrological conditions of organic matter (OM) deposition. Two units could be delineated. The first (UI) was composed of three sub-units: UIa (0-15 cm), composed of highly degraded organic particles originating from the surrounding soil and indicative of restricted transport; UIb (15-48 cm), during which the region was permanently flooded and the material stored came from soil runoff, mainly from alluvial forest; and UIc (48-88 cm) composed of material from Amazon River suspended sediment, itself originating from OM degradation in forest soil. In UII (88-111 cm), the OM originated mainly from the forest soil and other plant remains in the floodplain. The data reveal that, during the four distinct depositional periods, the sedimentary OM alternated between land derived soil and alluvial vegetation due to changes in hydrodynamics.
Organic Geochemistry, 2010
concentrations of a compound tentatively identified as arbor-8-en-3βol ME, a potential diagenetic... more concentrations of a compound tentatively identified as arbor-8-en-3βol ME, a potential diagenetic derivative of cylindrin. This increase in PTME corresponds to the beginning of intensive cultivation of Cynodon dactylon and Zoysia japonica (arundoin and cylindrin producers), for the production of turf to cover Brazilian football stadiums and golf practices. These results constitute a novel application of PTMEs to reconstruct land use changes from lake sediment archives.
Nature, 2013
River systems connect the terrestrial biosphere, the atmosphere and the ocean in the global carbo... more River systems connect the terrestrial biosphere, the atmosphere and the ocean in the global carbon cycle. A recent estimate suggests that up to 3 petagrams of carbon per year could be emitted as carbon dioxide (CO2) from global inland waters, offsetting the carbon uptake by terrestrial ecosystems. It is generally assumed that inland waters emit carbon that has been previously fixed upstream by land plant photosynthesis, then transferred to soils, and subsequently transported downstream in run-off. But at the scale of entire drainage basins, the lateral carbon fluxes carried by small rivers upstream do not account for all of the CO2 emitted from inundated areas downstream. Three-quarters of the world's flooded land consists of temporary wetlands, but the contribution of these productive ecosystems to the inland water carbon budget has been largely overlooked. Here we show that wetlands pump large amounts of atmospheric CO2 into river waters in the floodplains of the central Amazon. Flooded forests and floating vegetation export large amounts of carbon to river waters and the dissolved CO2 can be transported dozens to hundreds of kilometres downstream before being emitted. We estimate that Amazonian wetlands export half of their gross primary production to river waters as dissolved CO2 and organic carbon, compared with only a few per cent of gross primary production exported in upland (not flooded) ecosystems. Moreover, we suggest that wetland carbon export is potentially large enough to account for at least the 0.21 petagrams of carbon emitted per year as CO2 from the central Amazon River and its floodplains. Global carbon budgets should explicitly address temporary or vegetated flooded areas, because these ecosystems combine high aerial primary production with large, fast carbon export, potentially supporting a substantial fraction of CO2 evasion from inland waters.
Limnology and Oceanography, 1999
Abstract-Assuming the paradigm that catchment vegeta-tion is the main source of particulate organ... more Abstract-Assuming the paradigm that catchment vegeta-tion is the main source of particulate organic matter (POM) to rivers, the main objective of this study was to determine what the proportion of original C3 carbon from the forest had al-ready been replaced by C4 carbon from ...
Journal of Paleolimnology, 2011
Elemental and isotopic compositions of organic matter in surficial sediments from five transects ... more Elemental and isotopic compositions of organic matter in surficial sediments from five transects across Lagoa do Caçó (Brazil) were analyzed to identify the depth-related processes that affect the production and deposition of sedimentary organic matter in this shallow tropical lake. Each of four transverse transects began at a margin dominated by aquatic macrophytes (Eleocharis), crossed the central deep part of the lake, and terminated in the opposite, macrophyte-dominated margin. In each transect, TOC concentrations, C/N ratios, and d 13 C values decreased between 0 and 4 m, whereas d 15 N values increased.
CONTRIBUCIONES A LAS CIENCIAS SOCIALES
O objetivo da pesquisa foi avaliar n-alcanos (C15 a C40) e esteróis, como indicadores da origem d... more O objetivo da pesquisa foi avaliar n-alcanos (C15 a C40) e esteróis, como indicadores da origem da matéria orgânica em sedimentos superficiais das lagoas costeiras do sistema lagunar de Jacarepaguá na cidade do Rio de Janeiro. As amostras de sedimentos foram coletas em 4 pontos de amostragem, extraídas em banho ultrassom para retirada da fase orgânica. O extrato foi fracionado de acordo com a polaridades dos grupos de compostos de interesse em cromatografia de coluna de sílica gel, adaptado em uma pipeta pasteur. Os alcanos e esteróis foram separados e quantificados por cromatografia a gás com detector de ionização de chama (CG-DIC) e suas identificações foram realizadas por comparação com tempo de retenção do padrão analítico. Os resultados mostraram que as concentrações individuais dos n-alcanos detectados variaram entre 0,65 a 71 µg g-1, e as concentrações totais de esteróis foram 0,55 a 13,42 µg g-1. O perfil de distribuição de alcanos teve destaque para Cmax de C28, C29, e C32 ...
Critical Reviews in Analytical Chemistry
Este estudo tem por objetivo caracterizar os sedimentos superficiais, quanto ao seu teor e qualid... more Este estudo tem por objetivo caracterizar os sedimentos superficiais, quanto ao seu teor e qualidade dos fenóis da lignina, em dois sistemas lacustres distintos: a Várzea do Lago Grande Curuái (PA) e o Lago do Caçó (MA). A Várzea do Lago Grande Curuái é localizada na margem direita do Rio Amazonas, aproximadamente 850 km da foz e é caracterizada pela presença de lagos de águas brancas e pretas. O Lago do Caçó está localizado no Maranhão, na borda do ecossistema amazônico. Foram realizadas análises da concentração de lignina (λ), carbono orgânico total (COT), nitrogênio e isótopos do carbono (δ 13 C). Os resultados indicam que os sedimentos superficias de lagos de águas brancas apresentam baixos valores de COT (1,5 a 3,6%), baixa concentração de λ (0,73 a 1,28 mg.100mg CO -1 ) e alto índice de degradação (0,29 a 2,01). Os sedimentos superficiais de lagos de águas pretas apresentam maiores valores de COT (6,0 a 12,1%) e de λ (1,44 a 1,93 mg.100mg CO -1 ) em relação aos sedimentos de lagos de águas brancas, porém baixos em comparação com os sedimentos do Lago do Caçó (7,2 ~ 15,3% e 1,83 ~ 4,64 mg .100mg CO -1 , respectivamente). Através das análises realizadas foi possível identificar diferentes contribuições de fontes assim como diferentes estados de preservação da matéria orgânica sedimentada nos dois sistemas apresentados. PalavRas-Chave: matéria orgânica, carbono, isótopos estáveis e lignina.
Nature Geoscience, 2012
Humans have used fire extensively as a tool to shape Earth's vegetation. The slash-and-burn destr... more Humans have used fire extensively as a tool to shape Earth's vegetation. The slash-and-burn destruction of Brazil's Atlantic forest, which once covered over 1.3 million km 2 of present-day Brazil and was one of the largest tropical forest biomes on Earth 1 , is a prime example. Here, we estimate the amount of black carbon generated by the burning of the Atlantic forest, using historical records of land cover, satellite data and black carbon conversion ratios. We estimate that before 1973, destruction of the Atlantic forest generated 200-500 million tons of black carbon. We then estimate the amount of black carbon exported from this relict forest between 1997 and 2008, using measurements of polycyclic aromatic black carbon collected from a large river draining the region, and a continuous record of river discharge. We show that dissolved black carbon (DBC) continues to be mobilized from the watershed each year in the rainy season, despite the fact that widespread forest burning ceased in 1973. We estimate that the river exports 2,700 tons of DBC to the ocean each year. Scaling our findings up, we estimate that 50,000-70,000 tons of DBC are exported from the former forest each year. We suggest that an increase in black carbon production on land could increase the size of the refractory pool of dissolved organic carbon in the deep ocean.
Este estudo teve como objetivo avaliar a composição da matéria orgânica (MO) através de análises ... more Este estudo teve como objetivo avaliar a composição da matéria orgânica (MO) através de análises elementares, isotópicas e moleculares em dois testemunhos coletados na Lagoa do Caçó que registram os últimos 20.000 cal yrs BP e testar o potencial de ferramentas da geoquímica molecular no estudo paleoambiental. A Lagoa do Caçó é localizada no Maranhão numa área influenciada pelo deslocamento sazonal da zona de convergência intertropical (ZCIT). Os resultados e interpretações obtidos a partir da geoquímica orgânica durante o tardi-glacial evidenciaram a importância da abordagem multiparamétrica e corroboram os trabalhos prévios validando o uso dos fenóis da lignina e dos pigmentos sedimentares como ferramentas na interpretação paleoambiental em zona tropical. Foi possível identifcar três diferentes Fases holocênicas jamais mostradas em trabalhos precedentes destacando o potencial destes biomarcadores. Palavras-chave: Holoceno, biomarcadores orgânicos, Rock-Eval, mudanças paleoambientais.
Oceans, Rivers and Lakes: Energy and Substance Transfers at Interfaces, 1998
Pelagic and benthic carbon metabolism in the shallow tropical Barra Lagoon was studied weekly bet... more Pelagic and benthic carbon metabolism in the shallow tropical Barra Lagoon was studied weekly between 1990 and 1993, in periods characterized by temporary nitrogen limitation, fish kills and transitory colonization of the bottom by macro-algae. Diurnal and nocturnal metabolic rates were measured by monitoring changes in CO 2 content in entire water columns (free water and waters incubated in plexiglass tubes with and without inclusion of sediment). Total community carbon metabolism exhibited a marked autotrophism and high short term changes, dampening seasonal trends. Autotrophism and heterotrophism of the lagoon were controlled by phytoplankton biomass variations. In the presence of sediment, diurnal net benthic production was 11 to 64% of total diurnal net production, and nocturnal net benthic mineralization was 21 to 52% of total nocturnal net mineralization. The imbrication between the pelagic and benthic organic carbon cycles regulated carbon metabolism of the total community. A severe temporary nitrogen limitation, a fish kill and a temporary shift in primary producers did not substantially change metabolic rates because appropriate shifts occurred from the pelagic carbon cycle to the benthic carbon cycle, and vice-versa.
Frontiers in Microbiology, 2015
We evaluated in situ rates of bacterial carbon processing in Amazonian floodplain lakes and mains... more 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.
Acta Amazonica
This study aims to characterize the superficial sediments of lakes in black and white waters of a... more This study aims to characterize the superficial sediments of lakes in black and white waters of an Amazonian floodplain system in terms of carbon content and quality of lignin phenols. “Várzea do Lago Grande Curuái” floodplain is located on the right bank of the Amazon River about 850 km from the estuary. Superficial sediments samples were compared with superficial samples from Lake Caçó, located in Maranhão, the edge of the Amazon ecosystem. Concentration of lignin (λ), Total Organic Carbon (COT), nitrogen and isotope of carbon (δ13C) were undertaken. The results indicate that, in general, the superficial sediments of lakes of white water have low values of COT (1,5 to 3,6%), low concentrations of λ (0,73 to 1,28 mg.100mg CO-1) and high degradation index (0.29 to 2.01). Superficial sediments of lakes of black water had higher values of COT (6,0 to 12,1%) and λ (1,44 to 1,93 mg.100mg CO-1) than the sediments of lakes of white waters, but lower in comparison with the sediments of Caç...
PLoS ONE, 2012
One of the greatest challenges in understanding the Amazon basin functioning is to ascertain the ... more One of the greatest challenges in understanding the Amazon basin functioning is to ascertain the role played by floodplains in the organic matter (OM) cycle, crucial for a large spectrum of ecological mechanisms. Fatty acids (FAs) were combined with environmental descriptors and analyzed through multivariate and spatial tools (asymmetric eigenvector maps, AEM and principal coordinates of neighbor matrices, PCNM). This challenge allowed investigating the distribution of suspended particulate organic matter (SPOM), in order to trace its seasonal origin and quality, along a 800 km section of the Amazon river-floodplain system. Statistical analysis confirmed that large amounts of saturated FAs (15:0, 18:0, 24:0, 25:0 and 26:0), an indication of refractory OM, were concomitantly recorded with high pCO 2 in rivers, during the high water season (HW). Contrastingly, FAs marker which may be attributed in this ecosystem to aquatic plants (18:2v6 and 18:3v3) and cyanobacteria (16:1v7), were correlated with higher O 2 , chlorophyll a and pheopigments in floodplains, due to a high primary production during low waters (LW). Decreasing concentrations of unsaturated FAs, that characterize labile OM, were recorded during HW, from upstream to downstream. Furthermore, using PCNM and AEM spatial methods, FAs compositions of SPOM displayed an upstream-downstream gradient during HW, which was attributed to OM retention and the extent of flooded forest in floodplains. Discrimination of OM quality between the Amazon River and floodplains corroborate higher autotrophic production in the latter and transfer of OM to rivers at LW season. Together, these gradients demonstrate the validity of FAs as predictors of spatial and temporal changes in OM quality. These spatial and temporal trends are explained by 1) downstream change in landscape morphology as predicted by the River Continuum Concept; 2) enhanced primary production during LW when the water level decreased and its residence time increased as predicted by the Flood Pulse Concept.
Sediment cores from the Mundaú-Manguaba estuarine-lagoon system (MMELS),NE- Brazil, were analized... more Sediment cores from the Mundaú-Manguaba estuarine-lagoon system (MMELS),NE- Brazil, were analized for vertical distribution of organic carbon, organic nitrogen, stable carbon isotope ratio ( δ � 13 C) and lignin phenol concentration and composition. Results exhibited alterations in the deposition of organic matter from alochthonous and autochthonous sources, being different between the Mundaú and Manguaba lagoon compartments. At the mouth of Mundaú river the top to intermediate sediment layers harbored a mixture of terrestrial plant materials, mainly non-woody plants, and towards the base of the core a mixture of woody angiosperms and phytoplankton. In contrast, the top of the core from Manguaba lagoon largely harbored phytoplantonic organic matter and a gradual increase from the top to the bottom of a mixture of non-woody and woody terrestrial vegetation.
Water Research, 1999
AbstractÐConcentrations of biogenic gases (O 2 and CO 2 ) and respiration rates were measured at ... more AbstractÐConcentrations of biogenic gases (O 2 and CO 2 ) and respiration rates were measured at 7 sites along major tributaries of the Piracicaba River to address the eects of sewage loading on aquatic metabolism. Strictly aerobic conditions were observed at upstream sites (less polluted), with concentrations of O 2 at or above and CO 2 slightly above atmospheric equilibrium. Concentrations of biogenic gases were independent of variations in discharge and relatively constant during the sampling period. Respiration rates were signi®cantly higher at upstream sites and CO 2 concentrations were above atmospheric equilibrium. The concentrations of CO 2 at downstream sites were inversely correlated with discharge. At the downstream sites (more polluted), anthropogenic inputs of labile organic matter (sewage) altered the aquatic metabolism by creating a less aerobic environment. At these sites, O 2 concentrations were always below atmospheric equilibrium and directly related to discharge. #
Organic Geochemistry, 2013
A multi-proxy study has been performed on a sediment core from the Curuai floodplain, Central Ama... more A multi-proxy study has been performed on a sediment core from the Curuai floodplain, Central Amazonia. The combination of elemental, isotopic and molecular analysis of a 110 cm core (a record of ca. the last 100 yr) allowed reconstruction of the hydrological conditions of organic matter (OM) deposition. Two units could be delineated. The first (UI) was composed of three sub-units: UIa (0-15 cm), composed of highly degraded organic particles originating from the surrounding soil and indicative of restricted transport; UIb (15-48 cm), during which the region was permanently flooded and the material stored came from soil runoff, mainly from alluvial forest; and UIc (48-88 cm) composed of material from Amazon River suspended sediment, itself originating from OM degradation in forest soil. In UII (88-111 cm), the OM originated mainly from the forest soil and other plant remains in the floodplain. The data reveal that, during the four distinct depositional periods, the sedimentary OM alternated between land derived soil and alluvial vegetation due to changes in hydrodynamics.
Organic Geochemistry, 2010
concentrations of a compound tentatively identified as arbor-8-en-3βol ME, a potential diagenetic... more concentrations of a compound tentatively identified as arbor-8-en-3βol ME, a potential diagenetic derivative of cylindrin. This increase in PTME corresponds to the beginning of intensive cultivation of Cynodon dactylon and Zoysia japonica (arundoin and cylindrin producers), for the production of turf to cover Brazilian football stadiums and golf practices. These results constitute a novel application of PTMEs to reconstruct land use changes from lake sediment archives.
Nature, 2013
River systems connect the terrestrial biosphere, the atmosphere and the ocean in the global carbo... more River systems connect the terrestrial biosphere, the atmosphere and the ocean in the global carbon cycle. A recent estimate suggests that up to 3 petagrams of carbon per year could be emitted as carbon dioxide (CO2) from global inland waters, offsetting the carbon uptake by terrestrial ecosystems. It is generally assumed that inland waters emit carbon that has been previously fixed upstream by land plant photosynthesis, then transferred to soils, and subsequently transported downstream in run-off. But at the scale of entire drainage basins, the lateral carbon fluxes carried by small rivers upstream do not account for all of the CO2 emitted from inundated areas downstream. Three-quarters of the world's flooded land consists of temporary wetlands, but the contribution of these productive ecosystems to the inland water carbon budget has been largely overlooked. Here we show that wetlands pump large amounts of atmospheric CO2 into river waters in the floodplains of the central Amazon. Flooded forests and floating vegetation export large amounts of carbon to river waters and the dissolved CO2 can be transported dozens to hundreds of kilometres downstream before being emitted. We estimate that Amazonian wetlands export half of their gross primary production to river waters as dissolved CO2 and organic carbon, compared with only a few per cent of gross primary production exported in upland (not flooded) ecosystems. Moreover, we suggest that wetland carbon export is potentially large enough to account for at least the 0.21 petagrams of carbon emitted per year as CO2 from the central Amazon River and its floodplains. Global carbon budgets should explicitly address temporary or vegetated flooded areas, because these ecosystems combine high aerial primary production with large, fast carbon export, potentially supporting a substantial fraction of CO2 evasion from inland waters.
Limnology and Oceanography, 1999
Abstract-Assuming the paradigm that catchment vegeta-tion is the main source of particulate organ... more Abstract-Assuming the paradigm that catchment vegeta-tion is the main source of particulate organic matter (POM) to rivers, the main objective of this study was to determine what the proportion of original C3 carbon from the forest had al-ready been replaced by C4 carbon from ...
Journal of Paleolimnology, 2011
Elemental and isotopic compositions of organic matter in surficial sediments from five transects ... more Elemental and isotopic compositions of organic matter in surficial sediments from five transects across Lagoa do Caçó (Brazil) were analyzed to identify the depth-related processes that affect the production and deposition of sedimentary organic matter in this shallow tropical lake. Each of four transverse transects began at a margin dominated by aquatic macrophytes (Eleocharis), crossed the central deep part of the lake, and terminated in the opposite, macrophyte-dominated margin. In each transect, TOC concentrations, C/N ratios, and d 13 C values decreased between 0 and 4 m, whereas d 15 N values increased.