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1.
The carbon and nitrogen isotope composition of organic matter has been widely used to trace biogeochemical processes in marine and lacustrine environments. In order to reconstruct past environmental changes from sedimentary organic matter, it is crucial to consider potential alteration of the primary isotopic signal by bacterial degradation in the water column and during early diagenesis in the sediments.In a series of oxic and anoxic incubation experiments, we examined the fate of organic matter and the alteration of its carbon and nitrogen isotopic composition during microbial degradation. The decomposition rates determined with a double-exponential decay model show that the more reactive fraction of organic matter degrades at similar rates under oxic and anoxic conditions. However, under oxic conditions the proportion of organic matter resistent to degradation is much lower than under anoxic conditions. Within three months of incubation the δ13C of bulk organic matter decreased by 1.6‰ with respect to the initial value. The depletion can be attributed to the selective preservation of 13C-depleted organic compounds. During anoxic decay, the δ15N values continuously decreased to about 3‰ below the initial value. The decrease probably results from bacterial growth adding 15N-depleted biomass to the residual material. In the oxic experiment, δ15N values increased by more then 3‰ before decreasing to a value indistinguishable from the initial isotopic composition. The dissimilarity between oxic and anoxic conditions may be attributed to differences in the type, timing and degree of microbial activity and preferential degradation. In agreement with the anoxic incubation experiments, sediments from eutrophic Lake Lugano are, on average, depleted in 13C (−1.5‰) and 15N (−1.2‰) with respect to sinking particulate organic matter collected during a long-term sediment trap study.  相似文献   

2.
δ13CPDB compositions for 39 samples of dissolved organic carbon (DOC) from the Gulf of Mexico-Caribbean Sea-Atlantic Ocean system, the South Pacific and Ross Sea are reported. Deep water values are similar with a mean of ?21.8%. attesting to the homogeneity of the oceanic DOC pool. In Antarctic waters, a 5%. difference between DOC and particulate organic carbon (POC), with POC having values similar to modern plankton (δ13CPDB approx ?27%.) supports the idea of the transient nature of POC as compared to DOC.Total, lipid, acid hydrolyzed, amino acid and residue fractions of POC are about 5, 3, 7, 5 and 3%. respectively, more negative in 2000 m water as compared to surface water samples from the Gulf of Mexico.  相似文献   

3.
Degradation patterns of sedimentary algal lipids were tracked with time under variable redox treatments designed to mimic conditions in organic-rich, bioturbated deposits. Uniformly 13C-labeled algae were mixed with Long Island Sound surface muddy sediments and exposed to different redox regimes, including continuously oxic and anoxic, and oscillated oxic: anoxic conditions. Concentrations of several 13C-labeled algal fatty acids (16:1, 16:0 and 18:1), phytol and an alkene were measured serially. Results showed a large difference (∼10×) in first-order degradation rate constants of cell-associated lipids between continuously oxic and anoxic conditions. Exposure to oxic conditions increased the degradation of cell-associated lipids, and degradation rate constants were positive functions (linear or nonlinear) of the fraction of time sediments were oxic. Production of two new 13C-labeled compounds (iso-15:0 fatty acid and hexadecanol) further indicated that redox conditions and oxic: anoxic oscillations strongly affect microbial degradation of algal lipids and net synthesis of bacterial biomass. Production of 13C-labeled iso-15:0 fatty acid (a bacterial biomarker) was inversely proportional to the fraction of time sediments were oxic, rapidly decreasing after 10 days of incubation under oxic and frequently oscillated conditions. Turnover of bacterial biomass was faster under continuously or occasionally oxic conditions than under continuously anoxic conditions. 13C-labeled hexadecanol, an intermediate degradation product, accumulated under anoxic conditions but not under oxic or periodically oxic conditions. The frequency of oxic: anoxic oscillation clearly alters both the rate and pathways of lipid degradation in surficial sediments. Terminal degradation efficiency and lipid products from degradation of algal material depend on specific patterns of redox fluctuations.  相似文献   

4.
The study of the geochemical characteristics of the POC in the seamount area will be of great significance for further understanding the material cycle process in the seamount ecosystem. Based on a comprehensive survey of the Kocebu seamount in the Western Pacific Ocean in March, 2018, the distribution, source and composition of Particulate Organic Carbon (POC) in the seawater of the Kocebu seamount area were discussed. The results showed that the concentration of POC in the Kocebu seamount area gradually decreased with the increasing water depth, and slightly rose in the water layers near the bottom of the seamount. The average concentration of POC in each water mass was sorted from high to low in the order of North Pacific Tropic Water, North Pacific Intermediate Water and Deep Water (DW), and the concentration of POC at stations near the seamount summit was lower than that far from the seamount in the DW. There was upwelling at the water layers of 750~1 500 m above the seamount summit, causing the uplift of the 12.50 μg/L POC isoline in this region, however, no “seamount effect” was formed. The POC was mainly imported from the sea with an average POC/PON of 3.75. At the water layers of 0~300 m, only the POC/chlorophyll a (Chl a) at deep chlorophyll maximum layer was less than 200, indicating that the POC in this region was mainly in a form of life, while at the water layer of 300 m, the POC/Chl a increased sharply, indicating that the non-living POC contributed the most to the total POC.  相似文献   

5.
《Quaternary Science Reviews》2007,26(1-2):201-212
Temporal changes in oceanic denitrification, the bacterial reduction of nitrate under suboxic conditions, highlight the potential importance of N inventory changes and the production of N2O on the climate system. At the same time, the cause of the globally observed variation in denitrification remains unclear. High-resolution benthic foraminiferal oxygen isotope and bulk sediment nitrogen isotope records from ODP Site 1234 on the Chile Margin record integrated denitrification changes within the Peru–Chile Upwelling system over the last ∼70 ka. Denitrification changes in the southeast Pacific are coherent with Antarctic climate changes recorded by the Byrd ice core δ18O record, and lead northern hemisphere climate events. The southern-hemisphere character of the Chile margin δ15N record suggests that episodes of reduced denitrification in the SE Pacific represent times when more oxygen was supplied as the result of changes in the ventilation and preformed nutrient content of Subantarctic Mode Water (SAMW), which forms in the Subantarctic zone of the Southern Ocean and feeds into the low-latitude thermocline.  相似文献   

6.
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7.
To understand the effects of intracellular structural associations on degradation of algal chloropigments, we conducted a series of microcosm experiments by incubating Emiliania huxleyi cells (a marine haptophyte) in natural oxic and anoxic seawaters collected from a stratified water column in the Cariaco Basin. The incubated cell detritus were sequentially treated with two buffer solutions to separate pigment components into soluble and insoluble fractions. By using non-denaturing gel electrophoresis, several chlorophyll-complexes, free chlorophyll, and another unknown chlorophyll-containing component were further separated from the soluble fraction. The chlorophyll-complexes included those bound with high molecular weight core-proteins (CP-I and CP43+CP47) and low molecular weight polypeptides (LHC-I and LHC-II) in the cellular photosystems PS-I and PS-II. Overall pigment recovery from these fractions and gel bands was well equivalent to the total amount from direct acetone extraction of the cells. We followed the time-dependent concentration changes of chlorophyll-a (Chl-a), phaeophorbide-a (Ppb-a), and phaeophytin-a (Ppt-a) in all fractions and complexes to estimate the degradation rate constants of chloropigments in natural oxic and anoxic seawaters. Our experimental results demonstrated that the intracellular structural associations had important influences on degradation of chloropigments under different redox conditions. In general, total Chl-a degraded faster (∼4X) in oxic seawater than in anoxic seawater. However, the rate differences between oxic and anoxic conditions varied among the fractions and complexes. Degradation rate constants of Chl-a in soluble fraction were much higher (>10X) than those in insoluble fraction under both oxic and anoxic conditions. Chl-a bound with the complexes in PS-II appeared to be more reactive (∼2X) than that in PS-I under oxic conditions but the difference in degradation rate constants between two photosystems became indistinguishable under anoxic conditions. Variations of Ppb-a in different fractions and complexes during incubation showed different patterns, implying that cellular Chl-a could degrade through two different pathways: (1) internal degradation into Ppb-a within insoluble pool and polypeptide complexes; and (2) release first from protein complexes and followed by external degradation.  相似文献   

8.
Laboratory incubation experiments were conducted to determine the behavior of sterols at the sediment–water interface in oxic and anoxic sediments. Both plankton and 4- -cholesterol were used as tracers. Cholesterol was rapidly degraded at the sediment–water interface: 55% of -cholesterol was lost from sediments under anoxic conditions and 78% under oxic conditions over three and one-half months. About 3% of initially-added free radiolabel was incorporated into a bound pool that was released only by saponification of solvent-extracted sediment. Less than 1% of initially-added radiolabel remained in pore waters after three and one-half months. Rate constants for degradation of cholesterol in oxic and anoxic surficial sediments were estimated by tracking variations in radioactivity and sterol concentration as a function of time. We discuss our results in terms of factors affecting sterol degradation in coastal marine sediments, including molecular structure, sediment matrix effect, and redox conditions.  相似文献   

9.
Suboxic trace metal geochemistry in the Eastern Tropical North Pacific   总被引：3，自引：0，他引：3  
We analyzed Al, Ti, Fe, Mn, Cu, Ba, Cd, U, Mo, V, and Re in water column, settling particulate, and sediment (0 to 22 cm) samples from the intense oxygen minimum zone (OMZ) of the eastern tropical North Pacific near Mazatlán, Mexico. The goal was to determine how the geochemistry of these elements was influenced by suboxic water column conditions and whether the sediments have a unique “suboxic” geochemical signature.The water column was characterized by a Mn maximum, reaching ∼8 nmol kg−1 at 400 m. Concentrations of Cu, Ba, Cd, Mo, Re, U, and V were unaffected by the low O2 conditions and were comparable to those of the open ocean. Sinking particles were composed of lithogenic particles of detrital origin and nonlithogenic particles of biogenic origin. Al, Ti, and Fe were mostly (at least 79%) lithogenic. About 75% of the Mn was nonlithogenic. Significant amounts (at least 58%) of Cu, Ba, Cd, and Mo were nonlithogenic.Sediment geochemistry varied across the continental shelf and slope. Cadmium, U, and Re have prominent maxima centered at 310 m, with 12.3 ppm, 10.9 ppm, and 68.3 ppb, respectively, at the core top. High values of Mo (averaging 6.8 ppm) and V (averaging 90 ppm) are seen in OMZ surface sediment. Additional down-core enrichment occurs for all redox-sensitive elements in the top 10 cm. For U, Mo, V, and Re, surface sediments are a poor indicator of metal enrichment. Comparison of the nonlithogenic composition of sediments with sinking particles suggests that direct input of plankton material enriched in metals makes a significant contribution to the total composition, especially for Cd, U, and Mo.We evaluated Re/Mo and Cd/U ratios as tracers for redox environments. Rhenium and Mo concentrations and Re/Mo ratios do not lead to consistent conclusions. Concurrent enrichments of Re and Mo are an indicator of an anoxic depositional environment. In contrast, high Re/Mo ratios are an indicator of suboxic conditions. Cadmium is enriched in surface sediments, while U has considerable down-core enrichment. The concentrations of Cd and U and the Cd/U ratio do not follow patterns predicted from thermodynamics. Though the water column is suboxic, these four redox-sensitive elements indicate that the sediments are anoxic. The implication for paleostudies is that a trace metal sediment signature that indicates anoxic conditions is not necessarily attributable to an anoxic water column.  相似文献   

10.
Amino acid biogeo- and stereochemistry in coastal Chilean sediments   总被引：1，自引：0，他引：1  
The spatial distribution of total hydrolysable amino acids (THAA) and amino acid enantiomers (d- and l-forms) was investigated in sediments underlying two contrasting Chilean upwelling regions: at ∼23 °S off Antofagasta and at ∼36 °S off Concepción. The contribution of amino acids to total organic carbon (%TAAC: 7-14%) and total nitrogen (%TAAN: 23-38%) in surface sediments decreased with increasing water depth (from 126 to 1350 m) indicating that organic matter becomes increasingly decomposed in surface sediments at greater water depth. Changes in the ratio between the protein amino acid aspartate and its non-protein degradation product β-alanine confirmed this observation. Furthermore, estimates of THAA mineralization showed that sedimentary amino acid reactivity decreased with both increasing water depth as well as progressive degradation status of the organic matter that was incorporated into the sediment. Reactivity of organic matter in the sediment was also assessed using the Degradation Index (DI) developed by [Dauwe, B., Middelburg, J.J., 1998. Amino acids and hexosamines as indicators of organic matter degradation state in North Sea sediments. Limnol. Oceanogr.43, pp. 782-798.]. Off Concepción, DI was successfully applied to examine the degradation status of sedimentary organic matter at different water depths. However, unexpected results were obtained at the Antofagasta stations as DI increased with sediment depth, suggesting more degraded organic matter at the surface than deeper in the cores. The contribution of peptidoglycan amino acids to THAA was estimated from the concentrations of d-aspartate, d-glutamic acid, d-serine, and d-alanine. Peptidoglycan amino acids accounted for >18% of THAA in all investigated samples. In surface sediments peptidoglycan amino acids accounted for a progressively larger fraction of THAA at increasing water depths (up to >26%). Further, the contribution of peptidoglycan amino acids to THAA increased with increased sediment depth and age (up to 288-year-old) reaching up to 59%. Independent estimates based on d-amino acid concentrations in selected laboratory strains, bacterial counts and the sedimentary concentrations of d-amino acids indicate that a large fraction of the measured d-amino acids (>47 to >97%) originated from cell wall residues rather than from enumerated cells.  相似文献   

11.
反硝化条件下河岸渗滤过程中苯胺的降解   总被引：2，自引：0，他引：2  
吴耀国  曾睿  惠林  尹德忠 《地球科学》2006,31(2):273-278
通过河岸渗滤作用(riverbankfiltration, RBF) 诱发河水的补给, 增大地下水的允许开采量可以满足更多居民生活饮用水需求.受人类活动的影响, 河流等地表水体遭受苯胺污染, 可能通过RBF进入地下水, 以致饮用该地下水存在健康风险.为研究反硝化条件下, 苯胺在RBF中的转化, 采集渭河河床沉积物及沿岸地下水含水层的含水介质, 装置土柱, 进行土柱动态模拟实验.经过153 d的实验研究发现, 利用苯胺对RBF中土著反硝化微生物进行驯化, 大约经过37d菌种完全适应.具有该菌种的RBF系统, 对苯胺具有巨大降解能力, 在NO3——N约为23.0 mg/L的条件下, RBF系统可使40、80甚至400 mg/L浓度的苯胺100%降解, 矿化率分别达97.99%、91.39%与75.30%.反硝化条件下, 苯胺在RBF中的降解仅有少部分经过脱氨作用, 绝大部分与腐殖质以共价键形式形成耦合物, 该耦合物更易为微生物降解, 且降解过程中不产生对研究环境微生物有毒的中间产物, 可实现反硝化条件下RBF中苯胺的连续降解.   相似文献   

12.
Particulate organic carbon (POC) of 161 water samples collected from 8 depths (surface to 1000 m) at 21 stations was measured. The POC concentrations ranged from 154 to 554 ¼g per litre at the surface and decreased in the upper 300 m water column. At greater depths (> 300 m), POC concentrations increased and were similar (145 to 542 ¼g1?1) to those observed at surface. Deep water POC maximum was embedded within the oxygen minimum layer and was also associated with high phosphate-phosphorus. The POC contents increased, whereas oxygen decreased as the distance away from the shore increased. Phytoplankton biomass was a major source of POC. The observed pattern of POC is discussed with respect to some physicochemical and biological factors.  相似文献   

13.
The solubility controls on vanadium (V) in groundwater were studied due to concerns over possible harmful health effects of ingesting V in drinking water. Vanadium concentrations in the northeastern San Joaquin Valley ranged from <3 μg/L to 70 μg/L with a median of 21 μg/L. Concentrations of V were highest in samples collected from oxic groundwater (49% > 25 μg/L) and lowest in samples collected from anoxic groundwater (70% < 0.8 μg/L). In oxic groundwater, speciation modeling (SM) using PHREEQC predicted that V exists primarily as the oxyanion H2VO4−. Adsorption/desorption reactions with mineral surfaces and associated oxide coatings were indicated as the primary solubility control of V5+ oxyanions in groundwater. Environmental data showed that V concentrations in oxic groundwater generally increased with increasing groundwater pH. However, data from adsorption isotherm experiments indicated that small variations in pH (7.4–8.2) were not likely as an important a factor as the inherent adsorption capacity of oxide assemblages coating the surface of mineral grains. In suboxic groundwater, accurate SM modeling was difficult since Eh measurements of source water were not measured in this study. Vanadium concentrations in suboxic groundwater decreased with increasing pH indicating that V may exist as an oxycationic species [e.g. V(OH)3+]. Vanadium may complex with dissolved inorganic and organic ligands under suboxic conditions, which could alter the adsorption behavior of V in groundwater. Speciation modeling did not predict the existence of V-inorganic ligand complexes and organic ligands were not collected as part of this study. More work is needed to determine processes governing V solubility under suboxic groundwater conditions. Under anoxic groundwater conditions, SM predicts that aqueous V exists as the uncharged V(OH)3 molecule. However, exceedingly low V concentrations show that V is sparingly soluble in anoxic conditions. Results indicated that V may be precipitating as V3+- or mixed V3+/Fe3+-oxides in anoxic groundwater, which is consistent with results of a previous study. The fact that V appears insoluble in anoxic (Fe reducing) redox conditions indicates that the behavior of V is different than arsenic (As) in aquifer systems where the reductive dissolution of Fe-oxides with As adsorbed to the surface is a well-documented mechanism for increasing As concentrations in groundwater. This hypothesis is supported by the relation of V to As concentrations in oxic versus anoxic redox conditions.Sequential extraction procedures (SEP) applied to aquifer material showed that the greatest amount of V was recovered by the nitric acid (HNO3) extract (37–71%), followed by the oxalate-ascorbic acid extract (19–60%) and the oxalate extract (3–14%). These results indicate that V was not associated with the solid phase as an easily exchangeable fraction. Although the total amount of V recovered was greatest for the HNO3 extract that targets V adsorbed to sorption sites of crystalline Al, Fe and Mn oxides, the greatest V saturation of sorption sites appeared to occur on the amorphous and poorly crystalline oxide solid phases targeted by the oxalate and oxalate-ascorbic acid extracts respectively. Adsorption isotherm experiments showed no correlation between V sorption and any of the fractions identified by the SEP. This lack of correlation indicates the application of an SEP alone is not adequate to estimate the sorption characteristics of V in an aquifer system.  相似文献   

14.
Particulate organic carbon (POC) was measured for 77 water samples collected over a 3000 m water column along 88° E in the central Bay of Bengal. The POC values varied from 80 to 895 μg per litre at the surface and 171 to 261 μg per litre at 2000 m. The POC decreased with increasing water depth at all the stations. Deep water concentrations of POC were higher than those reported from other oceanic waters. Distribution of POC was not influenced by water masses. The POC was not significantly correlated with chlorophylla.  相似文献   

15.
We studied the distribution of glycerol dialkyl glycerol tetraethers (GDGTs) in suspended particulate matter from the water column of Lake Tanganyika (East Africa), where sediment studies had shown the applicability of the TEX86 proxy for reconstructing surface lake water temperature. GDGTs, in particular crenarchaeol, showed maximum abundance within the suboxic zone (100–180 m), suggesting that this is the preferred niche of ammonia-oxidizing Thaumarchaeota. Despite evidence for anaerobic methane oxidation in deep anoxic water (300–1200 m) no unambiguous evidence for an imprint of methanotrophic archaea on GDGT distribution was found. Comparison of TEX86 and BIT indices with those of surface sediments suggests that the sedimentary GDGTs are derived predominantly from the oxic zone and suboxic zone of the lake.  相似文献   

16.
INTRODUCTION Riverbankfiltration(RBF)isaprocessbywhich surfacewaterissubjectedtogroundpassagebeforebe ingcollectedandusedasadrinkingwatersource(His cockandGrischek,2002;Rayetal.,2002;Doussanet al.,1997).Duringinfiltrationandtravelthroughthe riverbedandaquifersediments,surfacewaterissubjec tedtoacombinationofphysical,chemical,andbiologi calprocessesthatcansignificantlyimprovetherawwa terquality(HiscockandGrischek,2002).Thus,RBF hasbeenusedasapretreatedmethodtoimprovedrink ingwate…  相似文献   

17.
The biodegradation of various wastewater-derived organic trace pollutants occurring in different aquatic compartments of the environment was previously reported to be influenced by the prevailing redox conditions. However, comparative studies on the redox-dependent degradation behavior of organic trace pollutants are scarce. The objective of the study presented herein, was to compile and evaluate data from several comparable previous tank experiments, thus, providing an overview on the redox-dependent removal of a total of 27 wastewater-derived trace compounds, including phenazone type compounds, antimicrobials, ß-blockers, psychoactive drugs and sulfonamides. Removal rate constants were fitted assuming first-order degradation kinetics. Six compounds were identified to be removed solely under oxic, three compounds solely under anoxic conditions. Others persisted under all experimental conditions, while some were removed under both oxic and anoxic conditions.  相似文献   

18.
We report solid phase sulfur speciation of six cores from sediments underlying oxic, suboxic and anoxic-sulfidic waters of the Black Sea. Our dataset includes the five sulfur species [pyrite-sulfur, acid volatile sulfides (AVS), zerovalent sulfur (S(0)), organic polysulfides (RSx), humic sulfur] together with reactive iron and manganese, as quantified by dithionite extraction, and total organic carbon. Pyrite – sulfur was the major phase in all cores [200-400 µmol (g dry wt)- 1] except for the suboxic core. However, zerovalent sulfur and humic sulfur also reached very significant levels: up to about 109 and 80 µmol (g dry wt)- 1, respectively. Humic sulfur enrichment was observed in the surface fluff layers of the eastern central basin sediments where Unit-1 type depositional conditions prevail. Elemental sulfur accumulated as a result of porewater sulfide oxidation by reactive iron oxides in turbidities from the anoxic basin margin and western central basin sediments. The accumulation of elemental sulfur to a level close to that of pyrite-S in any part of central Black Sea sediments has never been reported before and our finding indicates deep basin turbidites prevent the build-up of dissolved sulfide in the sediment. This process also contributes to diagenetic pyrite formation whereas in the non-turbiditic parts of the deep basin water column formed (syngenetic) pyrite dominates the sulfur inventory. In slope sediments under suboxic waters, organic sulfur (humic sulfur + organic polysulfides) account for 33-42% of total solid phase S, indicating that the suboxic conditions favor organosulfur formation. Our study shows that the interactions between depositional patterns (Unit 1 vs. turbidite), redox state of overlying waters (oxic-suboxic-sulfidic) and organic matter content determine sulfur speciation and enable the accumulation of elemental sulfur and organic sulfur species close to a level of pyrite-S.  相似文献   

19.
Mn(II) oxidation in the suboxic zone of the water column was studied at four stations in the western Black Sea. We measured Mn(II) oxidation rates using 54Mn tracer and tested the hypothesis of alternative oxidants for Mn(II) other than dissolved oxygen. In anoxic incubation experiments with water from different depths of the chemocline, Mn(II) was not oxidized by nitrite, nitrate, or iodate. In the presence of light, Mn(II) also was not oxidized under anoxic conditions as well. Anaerobic Mn(II) oxidizing microorganisms could not be enriched. In oxic incubation experiments, the addition of alternative oxidants did not significantly increase the Mn(II) oxidation rate. The lack of an anaerobic Mn(II) oxidation in our experiments does not unambiguously prove the absence of anaerobic Mn(II) oxidation in the Black Sea but suggests that dissolved oxygen is the only oxidant for biologically catalyzed Mn(II) oxidation. Lateral intrusions of modified Bosphorus water were shown to be the main mechanism providing dissolved oxygen in the suboxic and the upper anoxic zones and explaining observed Mn(II) oxidation rates. Maximum in situ Mn(II) oxidation rates in the suboxic zone were 1.1 nM Mn(II) per h in the central Black Sea, 25 nM Mn(II) per h on the Romanian continental slope and 60 nM Mn(II) per h on the Anatolian continental slope. These rates correlate with the amount of particulate Mn and the number of Mn-oxide particles and are in agreement with rates measured 13 yr before. Our study highlights the importance of lateral intrusions of oxygen for the ventilation of the suboxic zone and the anoxic interior and for the regulation of different oxidation-reduction processes in the chemocline, including Mn(II) oxidation, which may be significant for other anoxic basins as well.  相似文献   

20.
Microbial decomposition experiments were used to characterize changes in the amino acid and amino sugar yields and compositions of natural marine substrates during early diagenesis in seawater. On average, 63% of added carbon and 68% of added nitrogen were removed within the first 30 days of decomposition. In all cases, amino acid utilization accounted for a substantial fraction of the removed C and N. Carbon-normalized amino acid yields decreased to less than 50% of their starting values and most of this change occurred within the first 10 days of decomposition. Increases in the concentrations of amino sugars and decreases in the GlcN:GalN ratio in particulate organic matter (POM) illustrated the significance of microbial production during the decomposition of added substrates. Changes in the mol % composition of amino acids during early diagenesis were substantial but highly variable with substrate. Previous survey data collected from the same region were used in conjunction with the experimental data to investigate the utility of several established amino acid-based indices of organic matter diagenesis. This comparison showed that a combination of these degradation indexes is most effective for describing the diagenetic state of dissolved organic matter (DOM). Carbon-normalized amino acid yields were found to be the most effective indicator for early diagenesis. Relative abundances of amino acids were effective indicators of intermediate stages of diagenesis and the mol % composition of the non-protein amino acid γ-Aba (γ-aminobutyric acid) was an effective indicator of advanced DOM diagenesis.  相似文献   

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