Higher Plant Detritus Research Articles

The formation of ferromanganese nodules in the southwest Indian Ocean; an abiotic process

AbstractFerromanganese nodules have been recognized widely as potentially important resources for strategic metals. However it remains unclear if the formation of these nodules is purely an abiotic process or if microorganisms are involved in their formation. To determine the microbial contributions, detailed organic geochemical analyses were performed on ferromanganese nodules collected from across the southwest Indian Ocean. These analyses reveal the presence of specific terrestrial, marine and petroleum derived biomarkers, consistent with formation in a marine setting with a substantial influx of terrestrially derived (higher plant detritus) and naturally occurring petroleum-related organic matter. In contrast, only trace amounts of general bacterial biomarkers, commonly present in these types of depositional environments, were present. This indicates that the formation of these ferromanganese nodules is predominantly an abiotic process although a minor contribution from microbial mediated processes to the growth of these nodules cannot be completely ruled out.

Long-term observations of saccharides in remote marine aerosols from the western North Pacific: A comparison between 1990–1993 and 2006–2009 periods

Anhydrosugars (galactosan, mannosan and levoglucosan), sugars (xylose, fructose, glucose, sucrose and trehalose) and sugar alcohols (erythritol, arabitol, mannitol and inositol) were measured in the aerosol samples collected in a remote island (Chichi-Jima, Japan) in the western North Pacific from 1990 to 1993 and from 2006 to 2009. Total concentrations of anhydrosugars, the biomass burning tracers, were 0.01–5.57 ng m−3 (average 0.76 ng m−3) during 1990–1993 versus 0.01–7.19 ng m−3 (0.64 ng m−3) during 2006–2009. Their seasonal variations were characterized by winter/spring maxima and summer/fall minima. Such a seasonal pattern should be caused by the enhanced long-range atmospheric transport of biomass burning products and terrestrial organic matter (such as higher plant detritus and soil dust) from the Asian continent in winter/spring seasons, when the westerly or winter monsoon system prevails over the western North Pacific. Sugars and sugar alcohols showed different seasonal patterns. The monthly mean concentrations of erythritol, arabitol, mannitol, inositol, fructose, glucose and trehalose were found to be higher in spring/summer and lower in fall/winter during both 1990–1993 and 2006–2009 periods, indicating an enhanced biogenic emission of aerosols in warm seasons. Interestingly, saccharides showed a gradual decrease in their concentrations from 1991 to 1993 and an increase from 2006 to 2009. In addition, the monthly averaged concentrations of sugars and sugar alcohols showed maxima in early summer during 1990–1993, which occurred about 1–2 months earlier than those during 2006–2009. Such a clear seasonal shift may be attributable to the changes in the strength of westerly and trade wind systems during two periods.

Natural product biomarkers as indicators of sources and transport of sedimentary organic matter in a subtropical river

The sources and transformations of sedimentary organic matter along the Harney River, a representative subtropical river of the Florida Everglades, were assessed using a natural product biomarker approach. Sediment samples were collected from the headwaters to the Continental Shelf, with characteristic vegetation dominated by freshwater marsh species, mangrove (middle to lower estuary), and seagrass as the marine end-member. A peat sample was collected inland. All sample extracts were analyzed by GC–MS as underivatized and as silylated compounds. With these total extract analyses, major compound classes can be defined: n-alkanols, n-alkanoic acids, methyl alkanoates, methyl α- and ω-hydroxyalkanoates, triterpenoids, phytosterols and saccharides, with traces of hydrocarbons. In general, the peat sample extract has a different overall composition compared to the sediment extracts. The major differences include distinct carbon number maxima for the lipid series (e.g., C max = 28 for n-alkanols) probably from sawgrass and periphyton biomass, and predominance of phytosterols (sitosterol and stigmasterol) from higher plant detritus. In contrast, river sediment extracts contain biomarkers predominantly from mangrove-derived organic matter, such as the triterpenoids taraxerol and myricadiol. Significant amounts of saccharides and ω-hydroxyalkanoates are also found. Generally, compound concentrations decrease downstream due to dilution, and alteration of organic compounds from plant waxes and coastal vegetation is obvious in both peat and sediment samples. This is confirmed by the significant low abundance of n-alkanes and n-alkenoic acids due to biodegradation, oxidation of α-tocopherol to homophytanic acid γ-lactone, and presence of traces of dihydrolacunosic acid, a photochemical alteration product of taraxerol.

Sedimentation of chlorophylls in an Arctic fjord under freshwater discharge

Sedimentation of chlorophylls was studied during summer 1997 in Adventfjorden (Spitsbergen, Arctic). During the period of study, the water column was found to be well stratified by a freshened surface layer (salinity <31 PSS). A high load of suspended particulate matter from riverine discharge reduced the euphotic zone to an interval of 0.4–1.1 m. Total particulate matter sedimentation rates were about twice as high in June as in July. The following chlorophylls were distinguished in the sedimented particles: chl a and its degradation products (allomer chl a, phaeophytin a, phaeophorbide a, chlorophyllide a), chl b and chl c 1 + c 2. The quantitatively most important derivative of chl a was phaeophorbide a (31--41% of porphyrin a). Generally, the sedimentation rate of chlorophylls increased with depth. Linear relationships between concentrations of chl a and phaeophorbide a (r 2=0.92), as well as between concentrations of chl a and phaeophytin a (r 2=0.90) indicated a strong connection between phytoplankton abundance and zooplankton grazing. The significant correlation between chl a and chlorophyllide a concentrations (r 2=0.82) showed that most of the sinking chl a belonged primarily to diatoms, and low chlorophyllide a:chl a ratio (∼0.03) indicated that cellular senescence was not an important reason for the sinking of chl a. Moreover, very low chl b:chl a ratios (about 0.05 calculated for samples where chl b was detectable) suggest that contributions of green algae and/or higher plant detritus were negligible in sinking particles. The ratio of chl c 1 + c 2:chl a was 0.85 indicating that chl c-containing algae were dominating.

Diagenesis of organic matter in georgia salt marshes

Organic matter preserved in sediments of Georgia salt marshes derives from Spartina alterniflora and planktonic and bacterial substances. Sources and diagenesis of sedimentary organic material were studied by means of stable C and N isotopes and gas chromatography of pyrolysates from plants, suspended sediments, and a series of muds (modern to 1400 years old) from St Catherines Island, Georgia. Suspended particulate matter ( > 20 μm) has isotopic compositions (δ 13C = −18 to −22), which are composed of an average 34–42% plankton carbon and 58–65% higher plant detritus, as determined by isotopic mass balance of the system. The δ 13C of bulk sediments and humic acids (δ 13C = −18 to −19) extracted from them remain relatively constant over time. The δ 13C of acid hydrolysates, however, changed from − 15‰ in surface marsh sediment to a δ 13C of −19 from sediment sampled at a depth of 125 cm. Higher-plant normal-hydrocarbons are present in muds and in particulate matter from the water column, and δ 13C in lipids and gas chromatography of pyrolysates of samples reflect this addition. With increasing age, δ 15N of total sediments and acid hydrolysates increases, and the ratio of odd-to-even hydrocarbons in the pyrolysates decreases. Initially, low density material in sediments consists primarily of plant fragments. With time, this material is decayed and diluted by microbial material, changes that are reflected by more negative δ 13C of −15 to −17·5, as compared to δ 13C of −12 for moden Spartina, and the addition of n-alkanes in the range of C 13–19. The isotopic heterogeneity in surface sediments with carbon as an example, ranged from a δ 13C of −15 (plant fragments) to −22 (sediment following lipid, humic acid, and plant fragment extraction). Nowhere was the C isotopic composition of total Spartina expressed even though microscopic plant pieces, lignocellulose pyrolysis fragments, and n-alkanes from C 22–27 were detected in suspended particulate matter, total sediments, and humic acids.

Organic geochemical studies of a recent Inner Great Barrier Reef sediment—II. Factor analysis of sedimentary organic materials in input source determinations

The abundance of bound monocarboxylic acids at seven sites in a tropical carbonate Inner Great Barrier Reef sediment depth profile has been analysed to determine input source variations. Bound components were chosen as after deposition they are degraded less than the free ones. Factor analysis of acid components reduces the large initial data matrix of acid abundances at each depth into a smaller number of hypothetical factors which can be interpreted in terms of input sources. The factors are consistent with six inputs; one of higher plant derived material, three which are related to previously defined bacterial chemotypes and two microbial or invertebrate inputs. Three of these inputs, higher plant detritus, bacteria defined by a high concentration of 18:1ω7 and bacteria identified by the presence of branched acids as major components are consistent with inputs previously identified in the surface sediment using biological markers.

Monoterpinenes as terrigenous markers in Okinawa Trough sediments

Monoterpinenes were isolated from Okinawa Trough sediments at the 1000-m water depth by thin-layer chromatography (TLC) and identified by gas chromatography (GC) and gas chromatography-mass spectrometry-data system (GC-MS-DS). Identification has revealed cyclohexene, 1-methyl-5-(1-methylethenyl), cyclohexene, 1-methyl-3-(1-methylethenyl), and cyclohexane, 1-methyl-4-(1-methylethylidene). These monoterpinenes are believed to have been derived from terrigenous higher plant detritus, which may serve as new terrigenous markers.

A preliminary organic geochemical investigation of the Kimmeridgian oil shales

The Kimmeridge oil shales have assumed renewed significance because of their role as the prime source-rock for North Sea oil, and because of the need to assess their potential as a possible future supply of shale oil. This paper presents the results of a preliminary investigation of selected Kimmeridge oil shales. The immature shales are rich in organic matter with a dominantly marine type II kerogen showing evidence of algal contributions and a general sparsity of land-derived, higher plant detritus. Column chromatographic and capillary column gas chromatographic examinations of bitumens, pyrolysates and pyrolysis gas chromatograms of kerogen isolates show a predominance of aromatics in the hydrocarbon fractions, with bitumen n -alkane gas chromatograms showing evidence of algal-derived organic matter with n -alkane maxima in the n -C 17 region. Possible contributions from lower land plants are indicated by a second n -alkane maximum at n -C 23 , whilst higher land plant detritus makes only a limited contribution. Reflected light microscopic examination of the shales also shows a general sparsity of recognizable land-derived woody or herbaceous material. Shale oil compositions reflect their pyrolytic origin, with unsaturates forming a large part of the aliphatic hydrocarbon fraction, together with significant amounts of isoprenoid alkanes; organic sulphur compounds are also prominent in the hydrocarbon fractions. Finally, considerable amounts of sterane and pentacyclic triterpane hydrocarbons have been found in the bitumen aliphatic hydrocarbon fractions, their distributions allowing Blackstone samples to be differentiated from those of lower stratigraphic levels.