Lipid geochemistry of sediments from Upton Broad,a small productive lake

Major lipid classes isolated from 3 sections of the sediment profile of Upton Broad, a shallow lake formed about 500 yr ago, were correlated with input and with changes attributable to early diagenesis. Surficial sediment contains lipids characteristics of the known recent algal and microbial input; preservation of chlorophyll pigments and absence of appropriate markers suggest that diagenesis is minimal. Older deposits from the eutrophic phase of the lake's history contain higher levels of bacterial lipids and diagenetic products. The earliest sediment contains lipids characteristic of terrigenous input subjected to more extensive diagenesis than the younger sediment. Recognition of early diagenesis in anoxic sediment suggests that distributions of the shorter-chain homologous free n-alkanes, alkanols and alkanoic acids result from microbial synthesis using material initially deposited at the sediment surface, rather than partial preservation of the lipids of primary source organisms.     

The stereochemistry of 2- and 3-hydroxy fatty acids in a Recent lacustrine sediment

Homologous series of 2- and 3-hydroxy fatty acids occur in both the free and the bound lipid fractions of an oligotrophic lacustrine sediment (Loch Clair, N.W. Scotland). The stereochemistry of each constituent was assigned by gas chromatographic separation of diastereoisomeric O-2(S)-phenylpropionyl methyl ester derivatives. Free and bound 2-hydroxyacids above C₂₀ showed the R configuration characteristic of by-products formed during fatty acid metabolism by α-oxidation. In the C₁₄–C₁₈ region, bound 2- and 3-hydroxyacids show the R configuration more dominantly than the corresponding free lipids. These bound 2(R)- and 3(R)-hydroxyacids are attributed to microbial cell wall lipids.     

Extractable and bound lipid components in a freshwater sediment

Lipids directly extracted by organic solvents from sediment of a small eutrophic lake (Crose Mere) comprise free hydrocarbons, alcohols, sterols and monocarboxylic acids together with an esterified component yielding additional amounts of alcohols, sterols and monocarboxylic acids on saponification. The carbon-number distributions of the free lipid compound classes indicate a major contribution from allochthonous sources whereas the distributions within compound classes released on saponification are attributable to autochthonous sources. The more advanced state of decomposition of terrestrial biota relative to aquatic biota and the composition of the source organisms are postulated to be factors leading to the differences in distribution of corresponding free and esterified lipid classes. Acid hydrolysis of solvent-extracted sediment liberates additional lipid constituents belonging to the above compound classes. Of these bound lipids, the n-alkanes and branched/cyclic alkanoic acids show a more significant bacterial contribution than do the corresponding components obtained by solvent extraction alone.     

Aliphatic components of Victorian brown coal lithotypes

Victorian brown coal occurs in five major lithotypes distinguishable by colour index, petrography and bulk chemical analyses. The distributions of solvent extractable (free) and base hydrolysable (bound) n-alkanes, n-monocar?ylic acids, n-?,ω-dicar?ylic acids, n-ω-hydroxycar?ylic acids and n-alcohols were determined for samples of each of the five lithotypes (lithotype profile) and for seven samples of identical lithotype classification spanning a 100 m interval (depth profile) taken from a continuous bore core. The distributions of free molecular components in all classes are indicative of the predominant higher plant origin of this immature coal and provide strong support for the view that different lithotypes have derived from different, yet fairly specific paleobotanical communities. Despite an overall similarity in the distributions of aliphatic components from samples of identical lithotype classification, changes in the absolute concentrations and carbon preference indices (CPIs) of specific functional classes are observed in response to catagenetic influences even across the very small rank interval of the depth profile samples. Molecular distributions of bound components are similar to those of their free counterparts except that CPIs are generally lower and the relative contributions of lower molecular weight homologues (i.e. <C₂₂) are higher. Thedistributions of bound dicar?ylic acids and hydroxycar?ylic acids appear to reflect variations in the oxic/anoxic nature of the depositional paleoenvironments.     

Seasonal variation of fatty acids from drip water in Heshang Cave, central China

In order to investigate how lipids in cave water respond to seasonal climate change, drip water samples were collected from 2006 to 2008 in Heshang Cave, central China for fatty acid analysis. These lipids are abundant in the drip water. Their compositions are dominated by lower-molecular-weight nC16:0, nC18:0 and nC14:0 acids, together with mono-unsaturated nC18:1, nC16:1 and nC14:1. Analysis of one water sample revealed marked differences between the dissolved and particulate fractions. The dissolved fraction contains total fatty acids one order of magnitude higher than that of the particulate fraction. The distributional patterns of the fatty acids suggest that microbes living in the overlying soils and/or groundwater system contribute most fatty acids to the drip water. This 2-a monitoring experiment reveals that the abundance of mono-unsaturated fatty acids relative to the saturated homologues (nC16:1/nC16:0 and nC18:1/nC18:0) relate inversely to the changes of synchronous external air temperature. Higher values occur under cold conditions (winter/spring), while lower values appear in warm intervals (summer). Further studies are needed to elucidate the dynamic processes by which the external temperature affects fatty acids in drip water and to confirm the potential application of fatty acid ratios such as nC16:1/nC16:0 and nC18:1/nC18:0 in paleotemperature reconstructions.     

Mathematical modeling of the aquatic macrophyte inputs of mid-chain n-alkyl lipids to lake sediments: Implications for interpreting compound specific hydrogen isotopic records

We present a systematic study of chain-length distributions and D/H ratios of n-alkyl lipids (both n-alkanes and n-alkanoic acids) in a wide range of terrestrial and aquatic plants around and in Blood Pond, Massachusetts, USA. The primary goal is to establish a model to quantitatively assess the aquatic plant inputs of the mid-chain length n-alkyl lipids to lake sediments and to determine the average hydrogen isotopic ratios of these lipids in different plants. Our results show that middle-chain n-alkyl lipids (C₂₁-C₂₃n-alkanes and C₂₀-C₂₄n-alkanoic acids) are exceptionally abundant in floating and submerged aquatic plants, in contrast to the dominance of long-chain n-alkyl lipids (C₂₇-C₃₁n-alkanes and C₂₆-C₃₂n-alkanoic acids) in other plant types, which are consistent with previously published data from Mountain Kenya and the Tibetan Plateau. Combining available data in different environmental settings allows us to establish statistically robust model distributions of n-alkyl lipids in floating/submerged macrophytes relative to other plant types. Based on the model distributions, we established a multi-source mixing model using a linear algebra approach, in order to quantify the aquatic inputs of mid-chain n-alkyl lipids in lake sediments. The results show that ∼97% of the mid-chain n-alkyl lipids (C₂₃n-alkane and C₂₂n-acid (behenic acid)) in Blood Pond sediments are derived from floating and submerged macrophytes. In addition, D/H ratios of C₂₂n-acid and C₂₃n-alkane in the floating and submerged plants from Blood Pond display relatively narrow ranges of variation (−161 ± 16‰ and −183 ± 18‰, respectively). Our study demonstrates that mid-chain n-alkyl lipids such as C₂₃n-alkane and C₂₂n-acid could be excellent recorders of past lake water isotopic ratios in lakes with abundant floating and submerged macrophyte inputs.     

Variations in the content and distribution of n-alkanes in a series of carboniferous vitrinites and sporinites of bituminous rank

n-Alkanes in the soluble organic matter extracted from a series of vitrinite and sporinite concentrates have been analysed by gas chromatography. The macerals were isolated from coals ranging in rank from 77.1% to 86.6% carbon (vitrinite: dry, ash-free), and yields of n-alkanes ranged from 10 to 580 ppm for vitrinites and from 20 to 970 ppm for sporinites. The maximum yields were found at a rank of 85.4% C from vitrinites and 86.6% C from sporinites.Distribution maxima of the n-alkanes, as shown by gas chromatography, range from C₂₇ and C₂₉ at lower ranks to as low as C₁₆ at higher ranks. The distributions also show a progressive decrease in the preference of odd-carbon-number homologues with increasing rank. Virtually smooth distributions were attained in high-volatile bituminous A coals. Quantitative data show that the loss of the odd-carbon-number preference occurred, for the most part, while individual long-chain homologues increased in concentration.There is a progressive increase in the amounts of shorter-chain n-alkanes with increasing rank. It is suggested that sequential processes may have occurred whereby the rate of formation of long-chain n-alkanes in high-volatile bituminous A rank macerals becomes slower than their rate of subsequent fragmentation to shorter chain lengths. Consequently, assuming derivation from the insoluble maceral matrices, the chain-length distributions of parent n-alkyl structures within the insoluble material may retain characteristics pertaining more to the nature of the source organic matter at the time of deposition than do the extractable n-alkane patterns, especially at higher ranks.     

Effect of different wetness conditions on Sphagnum lipid composition in the Erxianyan peatland,central China

Samples of Sphagnum palustre and peat from the Erxianyan peatland, central China, were analyzed for lipids and their carbon isotopes to investigate how lipid distributions respond to hydrological change and to evaluate the importance of the contribution of microbial lipids to the peat moss. The lipids in samples collected from different hydrological settings in and around a pond and in the central part of the bog show clear variation along the hydrological gradient, with higher n-C₂₃/n-C₂₅ alkane ratio values and lower ACL (average chain length) values of long chain n-alkanes, n-fatty alcohols and n-fatty acids at the wetter sites. Although the relationship between the S. palustre lipids and the hydrological conditions can be partially overprinted in peat by an input from vascular plants, lipid ratios such as P_aq and ACL can provide useful qualitative information about Sphagnum contributions. In addition, lipid composition and carbon isotope values provide information about microbial activity associated with S. palustre. The occurrence of a high abundance of 7-methylheptadecane in submerged S. palustre is an indication of cyanobacteria in the living peat moss. The relatively ¹³C-depleted carbon isotope values of the n-C₂₃ alkane could result from the influence of symbiotic methanotrophs on the carbon available for assimilation by S. palustre.     

δC and δD identification of sources of lipid biomarkers in sediments of Lake Haruna (Japan)

Organic materials in lacustrine sediments are from multiple terrestrial and aquatic sources. In this study, carbon (δ¹³C) and hydrogen isotopic compositions (δD) of phytol, various sterols, and major n-fatty acids in sediments at Lake Haruna, Japan, were determined in their solvent-extractable (free) and saponification-released forms (bound). The δ¹³C-δD distributions of these lipid molecules in sediments are compared with those of terrestrial C3 and C4 plants, aquatic C3 plants, and plankton to evaluate their relative contributions. δ¹³C-δD of free phytol in sediments is very close to that of phytol in plankton samples, whereas δ¹³C-δD of bound phytol in sediments is on a mixing line between terrestrial C3 plant and plankton material. Unlike phytol, no significant δ¹³C-δD difference between free and bound forms was found in sterols and n-fatty acids. δ¹³C-δD values of algal sterols such as 24-methylcholesta-5,22-dien-3β-ol in sediments are close to those of plankton, whereas δ¹³C-δD of multiple-source sterols such as 24-ethylcholest-5-en-3β-ol and of major n-fatty acids such as n-hexadecanoic acid in sediments are between those of terrestrial C3 plants and plankton samples. Thus, δ¹³C-δD distributions clearly indicate the specific source contributions of biomarkers preserved in a lacustrine environment. Free phytol and algal sterols can be attributed to phytoplankton, and bound phytol, multiple source sterols, and major n-fatty acids are contributed by both terrestrial C3 plants and phytoplankton.     

Taraxerol and Rhizophora pollen as proxies for tracking past mangrove ecosystems

Angola Basin and Cape Basin (southeast Atlantic) surface sediments and sediment cores show that maxima in the abundance of taraxerol (relative to other land-derived lipids) covary with maxima in the relative abundance of pollen from the mangrove tree genus Rhizophora and that in the surface sediments offshore maxima in the relative abundance of taraxerol occur at latitudes with abundant coastal mangrove forests. Together with the observation that Rhizophora mangle and Rhizophora racemosa leaves are extraordinarily rich in taraxerol, this strongly indicates that taraxerol can be used as a lipid biomarker for mangrove input to the SE Atlantic. The proxy-environment relations for taraxerol and Rhizophora pollen down-core show that increased taraxerol and Rhizophora pollen abundances occur during transgressions and periods with a humid climate. These environmental changes modify the coastal erosion and sedimentation patterns, enhancing the extent of the mangrove ecosystem and/or the transport of mangrove organic matter offshore. Analyses of mid-Pleistocene sediments show that interruption of the pattern of taraxerol maxima during precession minima occurs almost only during periods of low obliquity. This demonstrates the complex environmental response of the interaction between precession-related humidity cycles and obliquity-related sea-level changes on mangrove input.     

Organic geochemical studies of a recent Inner Great Barrier Reef sediment—I. Assessment of input sources

The concentration of solvent-extractable (SE) and bound hydrocarbons, ketones, alcohols, sterols, monocarboxylic acids, hydroxyacids and α,ω-dicarboxylic acids of a surface sample (0–2.5 cm) from a recent carbonate tropical sediment taken at 60ft (18m) depth north-west of the Low Isles, North Queensland, are reported in detail. n-Alkanes are a minor constituent in the SE and bound hydrocarbon fractions with the major component being unresolved complex hydrocarbon material which is not an anthropogenic input. 6,10,14-Trimethylpentadecan-2-one derived from chlorophyll, as well as phytol, were identified as major components of the ketone and alcohol constituents. No chlorophyll pigments or pigmented degradation products were present, implying degradation before incorporation into the sediment. This conclusion is consistent with evidence for higher-plant input in which all sensitive lipids have been degraded before incorporation. SE and bound fractions have been studied in detail and show considerable differences probably arising from the importance of viable biomass in the SE fraction. Inputs to the sediment are determined as higher plants, algae, bacteria, fungi and meiofauna in descending order of importance.     

A quantitative study of the degradation of whale bone lipids: Implications for the preservation of fatty acids in marine sediments

The degradation and preservation affecting the biomarker record of ancient metazoa are not fully understood. We report on a five month experiment on the fate of fatty acids (FAs) during the degradation of recent whale vertebrae (Phocoena phocoena). Whale bones were analysed for extractable FAs and macromolecularly bound n-acyl compounds. Fresh bone showed extractable FAs dominated by 16:1ω7c, 16:0, 18:1ω9c and 18:0. Calculated degradation rate constant (k) values showed a rapid decrease in FA concentration, with k values higher for unsaturated than for saturated compounds (0.08/day for 18:1ω9c, 0.05/day for 16:0). The appearance or increased abundance of distinctive methyl branched (e.g. i/ai-15:0 and -17:0, 10Me-16:0) and hydroxy FAs (e.g. 10OH-16:0 and 10OH-18:0) were observed, providing clear evidence for the microbial degradation of bone organic matter and an input of lipids from specialised bacteria. Catalytic hydropyrolysis (HyPy) of demineralised extraction residues released up to 0.13% of the total n-C₁₆ and n-C₁₈ moieties in the degraded bones. This revealed that only a small, yet sizeable, portion of bone-derived fatty acyl units was sequestered into (proto)kerogen during the earliest stages of degradation.     

两种纯化方法获得脂肪酸的链长及碳同位素分布特征对比

饱和脂肪酸及其同位素组成是重建古环境和古气候的重要代用指标,目前存在多种提取及纯化流程。在全球变化研究中,基于不同原理的纯化流程得到的脂肪酸含量及其同位素组成是否一致,直接影响着该指标应用于不同区域重建结果的对比。本文用两种常见的脂肪酸纯化流程提取脂肪酸标准、现生植物和泥炭样品类脂物,通过对比发现:对脂肪酸标准两种流程都可以得到纯净的单体脂肪酸,而且回收率均较高(85%以上),都是较为可靠的脂肪酸纯化流程;然而对于天然样品,虽然高碳数脂肪酸(碳数>C₂₄)的回收率相近,流程1却能够获得相对较多的低碳数饱和脂肪酸,如泥炭样品中该流程获得的n-C₂₂脂肪酸是流程2的3倍;两种流程纯化狗尾草(Setaira viridis)和三叶草(Trifolium repens)得到n-C₁₆脂肪酸的δ¹³C不同,流程1分别为-21.1‰和-36.2‰;流程2分别为-23.3‰和-34.9‰,表明两个实验流程得到的低碳数脂肪酸的含量、脂肪酸链长分布模式以及碳同位素组成均存在明显的差异。实验结果显示,流程2分离纯化样品可得到几乎全部的游离态脂肪酸,而流程1可提纯样品中游离态和酯态存在的总脂肪酸。由于在沉积物中游离态脂肪酸和酯态脂肪酸可以相互转化,因此使用流程1分析样品中的总脂肪酸更为合适,也可以将类脂物皂化使酯态脂肪酸释放为游离态,然后使用流程2。     

Lipids of aquatic organisms as potential contributors to lacustrine sediments—II

The relationship between the lipid composition of organisms in the water column of an eutrophic lake and the lipid composition of underlying sediments, previously examined for n-alkanols and steroids, is now reported for hydrocarbons, ketones and carboxylic acids.The n-C₇ alkane and alkenoic acids from two primary sources are rapidly metabolized in the water column and surficial sediment. Bacterial biomarkers, including hopenes and fatty acids, were detected in the photosynthetic bacterial layer occurring just above the sediment-water interface.Within the sediment the apparent conversion of free n-alkanes, alkan-2-ones and ω-hydroxy acids to the corresponding bound form is noted; microbiological oxidation of n-alkanes to alkan-2-ones is supported by the detection of the intermediate alkan-2-ols with a distribution similar to that of the ketones. The geochemistry of sediment deposited c. 1900, prior to biological study of the site, was interpreted from stable biomarkers and the diagenetic changes recognised in the study of contemporary deposition. A qualitative difference in algal input to the older sediment is inferred from the low Δ⁷-sterol content and presence of 2,6,10-trimethyl-7-(3-methylbutyl)-dodecane. However, there was still significant dinoflagellate input, as indicated by the presence of 4α-methylsterols. A difference in higher-plant input to the older sediment, indicated from the n-alkane, alkene and triterpenoid ketone distributions, is consistent with the recent development of tree cover.     

Identifying “free” and “bound” lipid fractions in stalagmite samples: An example from Heshang Cave,Southern China

Stalagmites are good archives for paleoecological change, as they are easy to date, and contain multiple environmental proxy records, including climatic records from oxygen isotopes. Lipid biomarkers preserved within stalagmites have recently been used to investigate changes in the overlying soil and vegetation. However, the understanding of lipid records from stalagmites is still at an early stage, and is hindered by the low abundances of lipids preserved and the complexity of the organic matter signal. Here the first results of a sequential extraction procedure are presented, that enables examination of the distribution patterns of “free” (solvent extraction) and “bound” (including physically bound within the calcite matrix and chemically bound to macromolecules) lipids in a stalagmite from southern China. In both groups the dominant compounds are saturated fatty acids, which are an order of magnitude more abundant in the “bound” phase. n-alkanes and n-alcohols chiefly appear in the “free” lipids. In contrast, 3-hydroxy acids are predominantly released under strong acid reflux conditions, suggesting a principal input from bacterial membrane compounds. A direct comparison between the present results and the published data from an Ethiopian stalagmite shows significant differences in the lipid signals from separate sites, with a stronger microbial signal in the Chinese sample. This preliminary investigation of lipid distributions in different modes highlights the importance of microbial geochemical processes in karst systems and supports the use of stalagmites in paleoecological reconstruction.     

Holocene climatic variations and postglacial sea-level rise geochemically recorded in the sediments of the brackish karst lake An Loch Mor, western Ireland

Palaeohydrology of the brackish karst lake An Loch Mór (Inis Oirr) was reconstructed based on its 11 600 year sedimentation record. Low calcareous early Holocene sediments, characterized by high TOC contents and deposited at generally low accumulation rates, show a gradual decrease upwards in the concentration of the siliciclastic sediment until c . 7000 cal. yr BP. From c . 9000 cal. yr BP, sediment accumulation became increasingly dominated by the deposition of autochthonous calcite and organic matter. The deposition of autochthonous calcite and its chemical composition (Ca/Sr, Ca/Mg) are determined by the subsurface inflow of freshwater from the catchment of the lake and by the balance between freshwater and seawater influx. During the early Holocene, the lake mainly received input of sea salt by sea-spray. The sediments document the further development from seasonal towards the onset of diurnal infiltration of seawater at c . 5100 cal. yr BP. At that time, the relative sea level must have risen nearly to its present level in Galway Bay. Diurnal seawater infiltration during high tides was controlled by freshwater input. Freshwater inflow from the catchment gradually increased with human impact on local vegetation (EVPT decrease). Permanent diurnal seawater infiltration in concert with this general freshwater increase made the geochemical sedimentation record highly sensitive to changes in annual precipitation. We use information from the palynological record to interpret geochemically inferred freshwater inflow variations in terms of dry and wet climatic periods and document distinct century-scale successions between wet and dry climatic episodes for western Ireland.     

固城湖沉积物中羟基酸和α,ω—二元酸的组成分布及其地球化学意义

对固城湖沉积物中呈不同赋存状态的羟基酸和α,ω－二元酸进行了分析,结果表明,在相对含量上,游离类脂组分中的羟基酸和二元酸低于呈结合态和强结合态存在的对应羟基酸和二元酸,指示了类脂质。尤其是基极性组分在早期成岩作用过程中的稳定性较差。由游离类脂→结合态类脂→强结合太类脂,其中β－羟基酸的业源渐趋于单一化,其生源指示意义更加明确。在固城湖沉积剖面１２．２８ｍ之上和之下,沉积物中的强结合态β－羟在酸的分     

The fractionation of a Recent sediment for organic geochemical analysis

A Recent unconsolidated lacustrine sediment was separated into five size fractions which were characterized by microscopy and XRD. Higher plant detritus predominated in the coarsest fractions, but decreased in proportion in the intermediate ones in which algal debris was predominant. The overall proportion of organic debris decreased from coarse to fine fractions. Quartz and feldspar were most abundant in the intermediate size fractions, while the coarsest fraction contained chlorite with some kaolinite and quartz, and the finest fraction was composed mainly of illite.Concentrations (per fraction dry weight) of solvent extract, total long chain hydrocarbons and total fatty acids decreased from coarse to fine fractions, with the exception of the finest fraction, in which they showed an increase. The change in relative abundance of higher plant to algal debris in the coarse and intermediate size fractions was paralleled by a decrease in the relative abundance of n-C₂₉ and n-C₃₁ alkanes and an increase in the relative abundance of -C₁₇ alkane. There was a progressive decrease in n-alkane carbon preference index, and a progressive increase in the unresolved envelope of hydrocarbons with decreasing grain size. The unresolved hydrocarbons, which probably originate from biodegraded lubricating oil, appear to be associated with the clay fraction. Fractionation in this way and lipid analysis of the separate fractions may give more definitive information about input sources than analysis of unfractionated sediments.     

n-Alkane evidence for the onset of wetter conditions in the Sierra Nevada,California (USA) at the mid-late Holocene transition, ~ 3.0 ka

n-Alkane biomarker distributions in sediments from Swamp Lake (SL), in the central Sierra Nevada of California (USA), provide evidence for an increase in mean lake level ~ 3000 yr ago, in conjunction with widespread climatic change inferred from marine and continental records in the eastern North Pacific region. Length distributions of n-alkane chains in modern plants growing at SL were determined and compared to sedimentary distributions in a core spanning the last 13 ka. As a group, submerged and floating aquatic plants contained high proportions of short chain lengths (< nC₂₅) compared to emergent, riparian and upland terrestrial species, for which chain lengths > nC₂₇ were dominant. Changes in the sedimentary n-alkane distribution over time were driven by variable inputs from plant sources in response to changing lake level, sedimentation and plant community composition. A shift toward shorter chain lengths (nC_21, nC₂₃) occurred between 3.1 and 2.9 ka and is best explained by an increase in the abundance of aquatic plants and the availability of shallow-water habitat in response to rising lake level. The late Holocene expansion of SL following a dry mid-Holocene is consistent with previous evidence for increased effective moisture and the onset of wetter conditions in the Sierra Nevada between 4.0 and 3.0 ka.     

Distribution of n-alkanes in lacustrine sediments from subtropical lake in Brazil

The geochemical composition of lake bed sediments of a tropical reservoir in Brazil have been investigated. The C, N, P composition showed almost no variation between the different sampling points. All samples contained inorganic phosphorus (IP) ranging from 52 to 70%. The Redfield ratios show that the lake is without significant anthropogenic inputs. Most of the organic matter is composed by higher plants decomposition revealed in the total organic carbon (TOC):nitrogen (N) ratio ranging from 15.4 to 57.2. Also, TOC:organic phosphorus (OP) ranged from 265.3 to 933.6, suggesting that most of the organic matter has terrestrial origin from wood plants. The ratios suggest that most organic matter is influenced by the terrestrial characteristics of the watershed. Furthermore, the relative abundance of n-alkane homologues in the sediments was investigated. All samples have been analyzed for the n-alkanes C₈ to C₄₀. The sediments were dominated by n-alkanes C₂₅–C₃₈. It is concluded that n-alkane in sediments mainly come from terrestrial plants, however there is a contribution of submerged aquatic plants, especially in those sites in deeper areas of the lake. On the basis of P_aq index the n-alkanes in sediments comes from terrestrial plants, however there is a contribution from emerged/floating plants.The investigated lake seems to be considered as meso to eutrophic. Because of the relatively high primary productivity in the lakes, there is a substantial organic-matter flux to the sediments, which rapidly becomes anoxic. According to the pristine/phytane ratio the sediments represent an anoxic environment with values found between 0.38 and 1.72.