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Journal ArticleDOI

Delivery and deposition of organic matter in surface sediments of Lagoa do Caçó (Brazil)

TL;DR: The depth-related processes that affect the production and deposition of sedimentary organic matter in Lagoa do Caco (Brazil) were analyzed to identify the depthrelated processes as discussed by the authors.
Abstract: Elemental and isotopic compositions of organic matter in surficial sediments from five transects across Lagoa do Caco (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 δ13C values decreased between 0 and 4 m, whereas δ15N values increased. The variables remained stable in sediment from 4 m water depth to the center of the lake at 10 m. The depth-related patterns reflect differences in both the delivery and the deposition of organic matter in the lake. Organic matter is produced in abundance in the marginal area by emersed and submerged macrophyte vegetation that diminishes with depth and disappears at 4 meters. After the disappearance of macrophytes, organic matter is produced at low rates principally by open-lake phytoplankton. Drawdown of dissolved oxygen is high in the lake margins, but it is low in the oligotrophic open waters of the lake. Preservation of organic matter is consequently better in sediments of the lake margins than in deep waters. The depth-related pattern of organic matter delivery and deposition in the sediments of Lagoa do Caco, in which water levels are sensitive to groundwater fluctuations, shows that the elemental and isotopic compositions of sediment organic matter can provide a record of changes in the paleohydrology of this and other similar shallow lake systems.
Citations
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Journal ArticleDOI
TL;DR: In this paper, 67 surface sediment samples collected from Nam Co in central Tibet were analyzed for total carbon, total organic carbon and total nitrogen, and 51 of these samples were also analyzed for n-alkanes.
Abstract: In this study, 67 surface sediment samples collected from Nam Co in central Tibet were analyzed for total carbon, total organic carbon and total nitrogen, and 51 of these samples were also analyzed for n-alkanes. The origin and spatial distribution of organic matter were then investigated using these proxies, and the control factors responsible for the spatial distribution patterns and paleolimnological significance were discussed. The results indicated that the origin of organic matter in surface sediment of Nam Co is consistent with the sources of n-alkanes, which were primarily submerged plants, followed by terrestrial plants, and then aquatic algae and bacteria. The organic matter in surface sediments of the lake showed typical spatial variability. Because of the great influence of underwater topography, river inputs and water quality, the spatial distribution of organic matter is enriched from the source to the deposit center. This spatial variability of organic matter in the lake indicates that the sediments in different areas have different sensitivities to environmental changes, which is important to reconstruction of paleoenvironments and paleoclimate using lake sediment cores.

40 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the geochemical and isotopic compositions of surficial sediments from a plateau lake in Carajas, Southeastern Amazon region, to understand the spatial distribution of major and trace elements, δ13C, Δ15N, and C/N ratio, depositional processes, and the origin of inorganic and organic fractions.

37 citations

Journal ArticleDOI
TL;DR: In this paper, the authors collected 13 surface (0-2 cm) sediment samples in Bosten Lake and analyzed total organic carbon (TOC), total nitrogen (TN), stable carbon isotopic composition in TOC (δ13Corg), and grain size.
Abstract: . Lake sediment is an important carbon reservoir. However, little is known on the dynamics and sources of sediment organic carbon in Bosten Lake. We collected 13 surface (0–2 cm) sediment samples in Bosten Lake and analyzed total organic carbon (TOC), total nitrogen (TN), stable carbon isotopic composition in TOC (δ13Corg), and grain size. We found a large spatial variability in TOC content (1.8–4.4 %) and δ 13Corg value (−26.77 to −23.98 ‰). Using a three-end-member mixing model with measured TOC : TN ratio and δ13Corg, we estimated that 54–90 % of TOC was from autochthonous sources. Higher TOC content (> 3.7 %) was found in the east and central-north sections and near the mouth of the Kaidu River, which was attributable to allochthonous, autochthonous plus allochthonous, and autochthonous sources, respectively. The lowest TOC content was found in the mid-west section, which might be a result of high kinetic energy levels. Our study indicated that the spatial distribution of sediment TOC in the Bosten Lake was influenced by multiple and complex processes.

33 citations


Cites background from "Delivery and deposition of organic ..."

  • ...A number of studies have demonstrated that TOC in small and shallow lakes are attributable to allochthonous sources, but TOC in larger25 and deeper lakes to autochthonous sources that are derived from planktonic organisms (Shanahan et al., 2013; Sifeddine et al., 2011; Barnes and Barnes, 1978)....

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  • ...There is evidence of littoral sources of TOC in small and shallow lakes, but autochthonous sources, derived from planktonic organisms, in larger and deeper lakes, especially fjord lakes (Shanahan et al., 2013; Sifeddine et al., 2011; Barnes and Barnes, 1978)....

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  • ...…Discussion D iscussion P aper | D iscussion P aper | D iscussion P aper | D iscussion P aper | The magnitudes and spatial distribution of TOC in lake sediment may reflect multiple, complex processes (Sifeddine et al., 2011; Woszczyk et al., 2011; Dunn et al., 2008; Wang et al., 2012)....

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  • ...For example, aqueous organic matters have low C : N ratios (4–10) (Meyers, 2003) whereas vascular land plants have much higher C : N ratios (> 20) (Rumolo et al., 2011; Lamb et al., 2004; Sifeddine et al., 2011)....

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Journal ArticleDOI
TL;DR: In this article, the authors calibrate the δ 18 O record of speleothems against historical precipitation and river discharge data in central Brazil, a region directly influenced by the Southern Atlantic Convergence Zone (SACZ), a major feature of the South American Monsoon System (SAMS).

31 citations


Cites background from "Delivery and deposition of organic ..."

  • ...…been analyzed to document paleoclimate variability, including ice cores (e.g. Thompson et al., 2013), lake sediments (e.g. Cordeiro et al., 2011; Sifeddine et al., 2011), tree rings (e.g. Brienen et al., 2012; Ferrero et al., 2015) and marine cores (e.g. Haug et al., 2003; Chiessi et al., 2009)....

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  • ..., 2013), lake sediments (e.g. Cordeiro et al., 2011; Sifeddine et al., 2011), tree rings (e....

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Journal ArticleDOI
TL;DR: In this paper, the results of organic petrographic and rock-Eval pyrolysis assessments of the biological origin and preservation state of the organic matter (OM) in modern sediments from two deep transects of the lake were presented.

30 citations


Cites background from "Delivery and deposition of organic ..."

  • ...The differences in surface sediment OM elemental and isotopic composition among the depth related zones in this lake (Sifeddine et al., 2011) suggest that changes in lake level can leave an imprint on the sediment record....

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References
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Book
01 May 1986
TL;DR: In this article, the authors present a graphical representation of data using Principal Component Analysis (PCA) for time series and other non-independent data, as well as a generalization and adaptation of principal component analysis.
Abstract: Introduction * Properties of Population Principal Components * Properties of Sample Principal Components * Interpreting Principal Components: Examples * Graphical Representation of Data Using Principal Components * Choosing a Subset of Principal Components or Variables * Principal Component Analysis and Factor Analysis * Principal Components in Regression Analysis * Principal Components Used with Other Multivariate Techniques * Outlier Detection, Influential Observations and Robust Estimation * Rotation and Interpretation of Principal Components * Principal Component Analysis for Time Series and Other Non-Independent Data * Principal Component Analysis for Special Types of Data * Generalizations and Adaptations of Principal Component Analysis

17,446 citations

Reference EntryDOI
15 Oct 2005
TL;DR: Principal component analysis (PCA) as discussed by the authors replaces the p original variables by a smaller number, q, of derived variables, the principal components, which are linear combinations of the original variables.
Abstract: When large multivariate datasets are analyzed, it is often desirable to reduce their dimensionality. Principal component analysis is one technique for doing this. It replaces the p original variables by a smaller number, q, of derived variables, the principal components, which are linear combinations of the original variables. Often, it is possible to retain most of the variability in the original variables with q very much smaller than p. Despite its apparent simplicity, principal component analysis has a number of subtleties, and it has many uses and extensions. A number of choices associated with the technique are briefly discussed, namely, covariance or correlation, how many components, and different normalization constraints, as well as confusion with factor analysis. Various uses and extensions are outlined. Keywords: dimension reduction; factor analysis; multivariate analysis; variance maximization

14,773 citations

Journal ArticleDOI
TL;DR: The amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records as discussed by the authors, but only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation.

2,421 citations


"Delivery and deposition of organic ..." refers background in this paper

  • ...Protein-rich algal organic matter has molar C/N values that are usually between 4 and 8, whereas vascular land plants, which are cellulose-rich and protein-poor, commonly create organic matter that has C/N ratios of 20 and more (Meyers 1994; Meyers and Teranes 2001)....

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Book ChapterDOI
01 Jan 2002
TL;DR: The organic matter content of lake sediments provides a variety of indicators, or proxies, that can be used to reconstruct paleoenvironments of lakes and their watersheds and to infer histories of regional climate changes as mentioned in this paper.
Abstract: The organic matter content of lake sediments provides a variety of indicators, or proxies, that can be used to reconstruct paleoenvironments of lakes and their watersheds and to infer histories of regional climate changes. Organic matter constitutes a minor but important fraction of lake sediments. It originates from the complex mixture of lipids, carbohydrates, proteins, and other organic matter components produced by organisms that have lived in and around the lake (e.g., Meyers, 1997; Rullkotter, 2000). As an accumulation of “geochemical fossils”, the organic matter content of lake sediments provides information that is important to interpretations of both natural and human-induced changes in local and regional ecosystems.

807 citations

Journal ArticleDOI
TL;DR: This paper explored the use of carbon and nitrogen isotopes (δ13C and δ15N) in sedimented organic matter (OM) as proxy indicators of trophic state change in Florida lakes.
Abstract: We explored the use of carbon and nitrogen isotopes (δ13C and δ15N) in sedimented organic matter (OM) as proxy indicators of trophic state change in Florida lakes. Stable isotope data from four 210Pb-dated sediment cores were compared stratigraphically with established proxies for historical trophic state (diatom-inferred limnetic total phosphorus, sediment C/N ratio) and indicators of cultural disturbance (sediment total P and 226Ra activity). Diatom-based limnetic total P inferences indicate a transition from oligo-mesotrophy to meso-eutrophy in Clear Lake, and from eutrophy to hypereutrophy in Lakes Parker, Hollingsworth and Griffin. In cores from all four lakes, the carbon isotopic signature of accumulated OM generally tracks trophic state inferences and cultural impact assessments based on other variables. Oldest sediments in the records yield lower diatom-inferred total limnetic P concentrations and display relatively low δ13C values. In the Clear, Hollingsworth and Parker records, diatom-inferred nutrient concentrations increase after ca. AD 1900, and are associated stratigraphically with higher δ13C values in sediment OM. In the Lake Griffin core, both proxies display slight increases before ~1900, but highest values occur over the last ~100 years. As Lakes Clear, Hollingsworth and Parker became increasingly nutrient-enriched over the past century, the δ15N of sedimented organic matter decreased. This reflects, in part, the increasing relative contribution of nitrogen-fixing cyanobacteria to sedimented organic matter as primary productivity increased in these waterbodies. The Lake Griffin core displays a narrow range of both δ13C and δ15N values. Despite the complexity of carbon and nitrogen cycles in lakes, stratigraphic agreement between diatom-inferred changes in limnetic total P and the stable isotope signatures of sedimented OM suggests that δ13C and δ15N reflect shifts in historic lake trophic state.

303 citations