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Variations in nitrogen isotopic composition (δ15N) and total chlorin accumulation rate (AR) are employed as proxies to reconstruct oceanic nitrate inventory, the balance between denitrification and N fixation, and paleoproductivity in a rapidly accumulating sediment drift deposit beneath the Western Pacific Warm Pool for the last 145 Kyr. Subsurface and deep waters of the northern South China Sea (SCS) are sourced from the shallow Kuroshio Current (KC) and Pacific Intermediate Water, respectively. Their relative importance in determining sedimentary δ15N and paleoproductivity have been altered by changes in equatorial circulation, summer- and winter-monsoon intensity and relative sea level. The location and basin configuration of the marginal SCS renders it especially sensitive to such changes. Assuming complete annual nitrate utilization, low δ15N values during glacial stages are interpreted as a reflection of reduced remote denitrification in the Eastern Tropical North Pacific (ETNP) source waters, while much of marine isotope stage (MIS) 3 and the last interglacial were characterized by high denitrification. However, intervals of anomalously low δ15N values are interpreted as reflecting the contribution from regional N fixation in West Pacific surface waters, transmitted to the site by the shallow KC. Unusually, the Holocene is characterized by declining δ15N values and an inverse correlation with organic matter content since ca. 8.2 Ka. Millennial-scale variations during MIS 3 indicate higher frequency variations in both ETNP denitrification and local N fixation, which may be coherent with a hemispheric response to Dansgaard–Oeschger events recorded at high latitudes. For much of the last 145 Kyr, paleoproductivity was decoupled from δ15N, and instead seems to reflect the extent of the global nitrate inventory stimulated by elevated dust fertilization, and regional mixed-layer deepening associated with the relative intensity of the SE Asian winter monsoon. Despite evaluation of possible conflicting influences on the record of each proxy, we interpret our data as clear evidence of glacial/interglacial changes in marine nutrient inventory across the whole of the North Pacific, with a corresponding biogeochemical response and important implications for global CO2 drawdown via an invigorated biological pump. The relative importance of local, regional and global contributions to our records appears to be strongly modulated by relative sea level, controlling trans- and extra-basinal circulation in the SCS.

Previous studies of maleimides (1-H-pyrrole-2,5-diones), oxidative degradation products of chlorophylls and bacteriochlorophylls, and aromatic compounds derived from certain carotenoids (i.e., isorenieratene) indicate that photic zone euxinia (PZE) occurred at least intermittently during deposition of the German Kupferschiefer (Late Permian). However, that work was restricted to a stratigraphic profile through the Kupferschiefer of the Lower Rhine Basin, a shallow lagoon setting, and it was not established if photic zone euxinia prevailed in the larger and deeper basins of the Permian Zechstein Sea. Here, we present maleimide and porphyrin distributions in sediments from the Northern and Southern Permian basins. In samples from both basins, methyl,iso-butyl (Me,i-Bu) maleimide was recovered from the free extractable fraction and upon oxidation of vanadyl and nickel alkyl porphyrins. On structural grounds, Me,i-Bu maleimide derives ultimately from bacteriochlorophyll (bchl) c, d, or e and is thus indicative of the presence of green sulfur bacteria in the ancient Zechstein Sea. Consistent with this, C34 and C35 porphyrins apparently derived from bacteriochlorophyll d were also identified in the Northern Basin samples. Because green sulfur bacteria require both light and free H2S, these results indicate that photic zone euxinia occurred at least periodically during the early history of the Zechstein Sea.

To investigate possible reasons for the discrepancy between the abundance of 4-methyl components in free sterols and steryl chlorin esters (SCEs) which is commonly observed in sediments, experiments in which the copepod Calanus helgolandicus grazed on the dinoflagellates Prorocentrum micans and Alexandrium tamarense were carried out. With P. micans all the algal sterols were esterified as SCEs in the faecal pellets, but there was clear discrimination against the uptake of 4-Me sterols. This discrimination was also evident with A. tamarense. To investigate changes in the faecal pellet SCE and the free sterol distributions during pellet ageing in the P. micans experiment, portions were allowed to stand for up to 29 days in seawater in the dark. Although degradation of SCEs occurred, their esterified sterol distribution remained unchanged. The free sterols were degraded more rapidly than the SCEs and changes in the distribution were observed. This provides further laboratory evidence that sedimentary SCE sterols are more robust markers of phytoplankton communities than the corresponding free sterol distributions. Comparison of the SCE abundance in sterilised and unsterilised pellets indicated that the degradation was a result of microbial activity.

The production of steryl chlorin esters (SCEs) of both pyrophaeophorbide a and pyrophaeophorbide b has been demonstrated in a laboratory experiment in which the copepod Calanus helgolandicus grazed on the prasinophyte Tetraselmis suecica. Both algal sterols were converted into SCEs a and b with equal efficiency, indicating that in this case the SCE sterols were directly representative of the substrate. The sterols of the animal were also converted to SCEs, although with some change in the distribution as a result of cholesterol demand by the copepod. The results show that during herbivory chlorophyll b undergoes the same biotransformation to SCEs as reported for chlorophyll a and predict that SCEs b should occur in sediments beneath a phytoplankton population containing a significant contribution of chlorophyll b.

Steryl esters of the chlorophyll a transformation product pyrophaeophorbide a (SCEs), were formed when the copepod Calanus helgolandicus was allowed to graze on the marine diatom Thalassiosira weissflogii , confirming an earlier preliminary experiment. All of the animal and algal sterol components were found in the SCEs although there were distributional changes attributed to alteration prior to esterification to pyrophaeophorbide a , which resulted from utilisation by the copepod to produce cholesterol. This indicates that where there is insufficient cholesterol in the zooplankton diet in the natural environment, sedimentary SCE sterol distributions may not accurately reflect the original phytoplanktonic free sterol distribution. Although the concentration of SCEs dropped markedly as a result of pellet ageing, their abundance relative to the other major chlorins increased. This relative stability provides an explanation for a previous observation that SCEs in surface sediments are present in higher abundance than in the corresponding water column particulates and accounts for their significant abundance in the solvent extractable chlorins in sediments. Two novel products, tentatively proposed as the phytyl ester and the 24-methylcholesta-5,24(28)-dien-3β-yl ester of 13 2 -oxopyrophaeophorbide a were also observed in the pellets, although the widely occurring rearranged sedimentary chlorin 13 2 -hydroxychlorophyllone a (chlorophyllone) was only detected in aged pellets.

A multi-user integrated suite of instruments designed to optimize the search for evidence of life on Mars is described. The package includes: • ∗ Surface inspection and surface environment analysis to identify the potential Mars landing sites, to inspect the surface geology and mineralogy, to search for visible surficial microbial macrofossils, to study the surface radiation budget and surface oxidation processes, to search for niches for extant life. • ∗ Analysis of surface and subsurface minerals and organics to characterize the surface mineralogy, to analyse the surface and subsurface oxidants, to analyze the mineralogy of subsurface aliquots, to analyze the organics present in the subsurface aliquots (elemental and molecular composition, isotopes, chirality). • ∗ Macroscopic and microscopic inspection of subsurface aliquots to search for life's indicators (paleontological, biological, mineralogical) and to characterize the mineralogy of the subsurface aliquots. The study is led by ESA Manned Spaceflight and Microgravity Directorate.

Stepwise chemical degradation involving cleavage of ester bonds (KOH/MeOH), sulfide and remaining ester bonds (Li/EtNH2), ether bonds (HI/LiAlH4) and sub-units linked to aromatic moieties (RuO4) has been carried out on the kerogens of two immature sulfur-rich marls (IV-1.4 and 1.8, TOC ca. 1.5%) from evaporitic cycle IV of the Gesosso-solfifera Formation (Messinian, Vena del Gesso, Italy). Up to 80% of the organic matter was converted to solvent-soluble material, with the greatest proportion released by Li/EtNH2. The majority by far of the extracts comprises polar macromolecular material which is thought to correspond to high molecular weight sub-units of the kerogen. Quantification of the small amounts (

Messinian marls from evaporitic cycle IV of the Gessoso-solfifera formation (Italy) are known to contain in high abundance the diaromatic carotenoid isorenieratene of green sulfur bacterial (Chlorobiaceae) origin along with a second diaromatic carotenoid. The previous tentative assignment of the latter as a cis diastereomer of isorenieratene has now been confirmed; this indicates that double bond isomerization occurs during early diagenesis and provides further evidence for the pathway proposed previously to link isorenieratene to a number of aromatic isoprenoid hydrocarbon biomarkers. Stable carbon isotopic data confirm the Chlorobiaceae origin of the intact all-trans isorenieratene isomer and indicate that the isomerization is accompanied by little or no kinetic isotope effect. Comparison of the δ13C values of each of the isolated carotenoids (measured as isorenieratane after hydrogenation) with those of their sulfide-bound counterpart in the polar fraction of the extracts (also measured as isorenieratane) indicates that sulfurization resulted in little depletion in 13C.

3 β -Hydroxy-5 α -androstan-17-one (epiandrosterone), 5 α -androstan-3,17-dione, 3 α -hydroxy-5 α -androstan-17-one (androsterone), 5 α -androstan-3 β ,17 β -diol and 5 α -androstan-3 α ,17 β -diol have been identified in the solvent soluble fraction of peat from Bolton Fell Moss (Cumbria, U.K.). The structures and δ 13 C values of these androstane derivatives indicate a diagenetic origin in sterols also present in the peat and provide the first evidence that cleavage of the C-17 side-chain can occur during early diagenesis, microbial oxidation being the most likely mechanism.

To investigate the effect of bacterial diagenesis on the distributions of algal lipids, the marine haptophyte Emiliania huxleyi was incubated with estuarine sediment slurries under defined conditions (oxic, sulfate reducing and methanogenic). Rapid initial degradation of lipids corresponded to increased bacterial populations, both of which subsequently declined. Under oxic conditions the algal C31 dienes were rapidly and completely degraded within 178 days. Extensive degradation of the characteristic C37 methyl alkenones occurred under all conditions (up to 85% under oxic conditions); however, the U37K′ index remained essentially constant, except for a slight increase at the longest oxic incubation time. Under anoxic conditions the alkyl alkenoates were preferentially degraded relative to the alkenones and changes in the AA36 index occurred. These results demonstrate that lipids are part of the “labile” organic matter; however, they were generally degraded at multiple rates which slowed during incubation, resulting in their partial preservation. Hence, laboratory experiments conducted over only short periods cannot predict the preservation potential of lipid components. Furthermore, preservation differed between sulfate reducing and methanogenic conditions, so the roles of anaerobic processes need to be considered individually with regard to oxic vs. anoxic preservation.

Pyrophaeoporphyrins c 1 and c 2 ( I a, b ), transformation products of chlorophylls c 1 and c 2 ( II a, b ) occur as minor pigments in the surface sediment (0–5 cm) of Priest Pot, a small eutrophic lake (Cumbria, U.K.) and in the products from feeding the diatom Thalassiosira weissflogii to the copepod Calanus helgolandicus . These findings, based on comparisons with standards prepared from the chlorophylls c 1 and c 2 , indicate that enzymatic removal of the C-13 2 carbomethoxy substituent, a prerequisite for the diagenetic transformation pathway of the chlorophylls c to a number of sedimentary alkyl porphyrins, occurs mainly in the water column as a result of zooplankton herbivory.

The sterol distributions in the steryl chlorin esters (SCEs) from three marine and two lacustrine sediments have been compared with the free sterols and known water column sterol distributions. The comparison provides further evidence that the SCE sterol distributions are more representative of the original phytoplanktonic sterol distribution than are the free sterol distributions. This is most clearly seen in the relative abundance of C 26 sterols and 4-methyl sterols, and in the stanol/stenol ratios. It appears that in general the SCE sterols are less susceptible to selective biodegradation than the free sterols.

Speciation of iron and sulfur species was determined for two recent sediments (La Trinitat and Lake Cisó) which were deposited in environments with a high biological productivity and sulfate-reducing activity. In sediments from calcite ponds of La Trinitat an excess of reactive iron species (iron monosulfides, iron hydroxides) results in a depletion of reactive sulfur which is accompanied by a virtual absence of organo-sulfur compounds, both in low (LMW) and high molecular-weight (HMW) fractions. Small amounts of phytanyl and highly branched isoprenoid (HBI) thiophenes in the extract demonstrate that these molecules exhibit a higher reactivity towards reduced sulfur species as compared to detrital iron. Euxinic sediments from Lake Cisó are characterised by an excess of reduced sulfur species which can rapidly trap reactive iron. High concentrations of H2S results in the formation of organo-sulfur compounds which were encountered in both LMW and HMW fractions. The major part of the organic sulfur is bound to the carbohydrate portion of woody tissues, whose presence was revealed by a specific alkylthiophene distribution in the flash pyrolysate and by Li/EtNH2 desulfurisation of the kerogen which resulted in the solubilisation of the sulfur-enriched hemicellulose fraction. Relatively high amounts of sulfurised C25 HBI compounds in the sediment extract of Lake Cisó reflect the incorporation of sulfur into algal derived organic matter upon early diagenesis. The combined approach of the speciation of iron and sulfur species and the molecular analysis of sedimentary fractions demonstrates that abiotic sulfur binding to organic matter occurs at the earliest stages of diagenesis under specific depositional conditions (anoxic, stratified water column) in which an excess of reduced sulfur species relative to the amount of reactive iron is a controlling factor.

Biomarker distributions based on GC and GC-MS data supplemented by stable carbon isotopic compositions based on irm (isotope ratio monitoring) GC-MS data have been used to investigate changes in depositional conditions in a number of samples from a 2 m core (Rheinberger Heide) covering the entire deposition of the Permian Kupferschiefer (Lower Rhine Basin, northwest Germany). Compound classes investigated are aliphatic and aromatic hydrocarbons and maleimides (1H-pyrrole-2,5-diones). The core has been previously divided into four sections: TI, TIIA, TIIB and TIII based on lithology. The biomarker distributions and the δ13C values of components indicate contributions from cyanobacteria, algae, green sulphur bacteria and higher plants (minor) throughout Kupferschiefer deposition. All of the phytoplanktonic components show 13C enrichment in the lowest section, suggesting a greater productivity. The occurrence of components derived from green sulphur bacteria (Chlorobiaceae) indicates that the entire deposition was characterised by periods of photic zone anoxia. Such conditions were rapidly established after the initial transgression of the Zechstein Sea and may have been productivity-driven, but were less prevalent during deposition of the upper core sections.

The so-called Heinrich layers, found in North Atlantic sediments, have been attributed to quasi-periodic discharges of armadas of icebergs originating from the Laurentide ice sheet. Using the distribution of biomarkers in a sediment core (BOFS 5K) we have attempted to provide more information about their origin and the effect of the Heinrich events on oceanic circulation and the climatic system. Estimates of sea surface temperature changes, via U3K7 measurements, show that the surface ocean underwent significant cooling during the events, probably as a result of incoming iceberg meltwater. The low sea temperatures and the rapid variation in the accumulation of chlorophyll-derived pigments suggest that the events provoked a major change in oceanographic conditions, which may have affected the thermohaline circulation in the Atlantic Ocean. Within the most recent layers we have also found vanadyl alkyl porphyrins and aryl isoprenoid hydrocarbons, diagenetic products of photosynthetic pig- ments (chlorophylls and carotenoids, respectively). These components are not expected to occur in late Quaternary sediments, so their presence demonstrates a contribution to the layers of ancient, organic rich sedimentary material of continental origin. The presence of vanadyl porphyrins and absence of their nickel counterparts, and the distributional features of the aryl isoprenoids (e.g., presence of the C40 reduced carotenoid isorenieratane of green sulphur bacterial origin) indicate the existence of anoxic conditions in the photic zone of a marine water column in the original depositional setting of the contributed ancient sediment. These results suggest that it should be possible, using a biomarker correla- tion approach, to determine the source area of the ancient sediment eroded by the icebergs. Copyright © 1997 Elsevier Science Ltd

A study of the distributions of free and S-bound biomarkers and their δ13C values in the extract of a bulk sample of the Permian Kupferschiefer from the Lower Rhine Basin has been carried out to provide a more detailed characterization of the biological inputs. The distributions and isotopic compositions of selected components released from nickel boride desulphurization have been compared with those of components in the free fraction. The free biomarkers occur in greater abundance than their S-bound counterparts. The distribution and carbon isotopic composition of both free and bound components in the extract indicate a major cyanobacterial and algal input. Likewise, the free and bound aromatic hydrocarbons contain components which reveal an origin from the carotenoids of Chlorobiaceae (green sulphur bacteria), providing molecular evidence for the occurrence of photic zone anoxia in the water column. Most of the components in the complex mixture of mono-, di-, tri- and tetra-aromatics in the free aromatic hydrocarbon fraction result from cyclization and aromatization reactions.

The (22 R )-30a,30b-dihomohopan-30b-yl and tetrahymanyl esters of pyrophaeophorbide a , chlorophyll a transformation products resulting from zooplankton herbivory, occur in an extract of surface sediment from Lake Valencia (Venezuela). The former was identified by HPLC-PDA-MS comparison with a standard and the latter after reduction of the extract and GC-MS analysis of the released alcohols.

Maleimides (1 H -pyrrole-2,5-diones), degradation products of photosynthetic tetrapyrrole pigments, have been found for the first time in the polar fraction of the solvent extracts of two marine sediments deposited in restricted basins: Kupferschiefer (Permian) and Serpiano shale (Mid-Triassic). GC and GC—MS analyses of the TBDMS ( tertiary -butyldimethylsilyl) derivatives show a simple component distribution, dominated by Me Et maleimide, mainly of planktonic origin; Me n -Pr and Me i -Bu maleimides, present in low abundance, are thought on structural grounds to be derived from the bacteriochlorophylls c, d , or e of Chlorobiaceae (anoxygenic green sulfur bacteria). This is confirmed for Kupferschiefer by isotope ratio monitoring (irm) GCMS which shows them to be enriched in 13 C as a result of their photosynthetic carbon assimilation, which takes place by the reversed tricarboxylic acid (TCA) cycle. The structurally more specific Me i -Bu maleimide is, however, slightly more enriched in 13 C than Me n -Pr maleimide, suggesting that the latter is derived in part from reduction of the C 3 -acid substituent at C-17 of phytoplanktonic chlorophyll. These results provide evidence for the existence in both depositional settings of microbial communities containing Chlorobiaceae. In turn, this indicates that there must have been periods when the water column was highly stratified and anoxia extended into the zone of light penetration.

Steryl chlorin esters (SCEs) were formed in laboratory feeding experiments when starved females of the copepod Calanus helgolandicus were allowed to graze on a culture of the diatom Thalassiosira weissflogii. They were found when the zooplankton had grazed for 48 hours and were also identified in fecal pellets subsequently left in seawater in the dark. The distribution contained the diatom sterols in approximately the same relative abundance as the free sterols in the substrate, as well as the most abundant copepod sterol, all esterified to the chlorophyll a degradation product, pyropheophorbide a. Hence, in studies aimed at using sedimentary SCE sterol distributions as indicators of phytoplankton community structure, cholesterol should not be considered since the cholesteryl ester of pyropheophorbide a was a significant component in the fecal pellet SCEs. The findings represent a step forward in unravelling the transformations undergone by chlorophyll a in aquatic environments, since the abundance and wide occurrence of sedimentary SCEs indicate that they are a significant preservational sink for the chlorophyll a biosynthesised in the photic zone.

Kerogens isolated from nine samples from a single marl bed of the Gessoso-solfifera formation in the Vena del Gesso basin (Upper Miocene, Italy) were treated with CrCl 2 and Li/EtNH 2 to remove inorganic and organic sulphur, respectively. The untreated and “desulphurized” (CrCl 2 and Li/EtNH 2 ) kerogens were qualitatively and quantitatively analyzed by flash pyrolysis-gas chromatography-mass spectrometry. Typically, significant variations in the relative contributions and abundances of n -alk-1-enes/ n -alkanes, alkylated pyrroles, thiophenes and supposedly S-bound moieties released as phytenes and sterenes were observed. The first series of products ( n -hydrocarbons) contributed relatively more to the pyrolyzates of the desulphurized kerogens, suggesting an enrichment of microalgal-derived aliphatic macromolecules. These marine micro-organisms are thought to belong in part to the class of Eustigmatophyceae. Alkylated pyrroles were barely detectable in the untreated kerogen pyrolyzates, whereas they contributed significantly to those from the treated kerogens. Similar treatment of a porphyrin, octaethylporphyrin, revealed that alkyl porphyrins are thermally too stable to be cleaved upon pyrolysis. However, Li/EtNH 2 treatment reduced the porphyrin standard, such that it could generate mainly monopyrroles upon pyrolysis. It is concluded that Li/EtNH 2 treatment reduced tetrapyrrole moieties bound to the desulphurized kerogen network.

Bacterial populations and activity were quantified at three sites in the Cascadia Margin accretionary wedge, off the West Canadian/American coast (ODP Leg 146). At two sites sediments contained gas hydrates, Site 889/890 had a discrete zone of hydrate approximately 10 m above a bottom simulating reflector (BSR) at 225 m below sea floor (mbsf) and Site 892 had disseminated hydrate in the upper 20 mbsf and a BSR at 74 mbsf. Site 888 was a control site without gas hydrates. The control site (888) and top approximately 90 mbsf of Site 889/890 had bacterial distributions similar to previous Pacific Ocean sites. In the upper approximately 30 m of Site 892, however, bacterial populations were much lower, suggesting inhibition by the high concentrations of H 2 S within the hydrate zone. Below this depth bacterial populations rose to concentrations consistent with other sites. The control site was dominated by SO 4 reduction and rates of CH 4 oxidation in the top 90 m were low (0.002–0.033 nmol cm −3 d −1 ). At Site 889/890 bacterial populations and activity were stimulated in the discrete hydrate zone. CH 4 oxidation rates increased in the middle of this zone to 134.5 nmol cm −3 d −1 (ca. 9 times the average rate at other depths), resulting in a significant (× 10) increase in the total bacterial population. The anaerobic process(es) responsible for this oxidation remain unclear, despite SO 4 -reducing bacteria, previously associated with CH 4 oxidation, also being stimulated in this zone. Fluid flux into accretionary wedge sediments may be an important process in providing electron acceptors to maintain these relatively high rates of CH 4 oxidation. This first microbiological study of gas hydrates indicates that bacterial processes are influenced by gas and fluid venting, and they play a major role in geochemical changes within these deep (> 200 mbsf) sediments.

The iron porphyrin fraction of Kupferschiefer, an organic-rich sedimentary rock deposited in the Zechstein Sea during the Permian (ca. 235Myr before present) contains three minor components characterised by 1 H NMR spectroscopy. The carbon skeletons correlate specifically with members of one series of the bacteriochlorophylls d of the Chlorobiaceae, which are obligate anaerobes. Their structures therefore reveal the occurrence of anoxic conditions extending up into the zone of light penetration in the water column of the original depositional setting in the Lower Rhine Basin.

A sensitive, semi-automated method has been developed for the rapid estimation of the total concentration of chlorophyll a transformation products (chlorins) in solvent extracts of aquatic sediments. The methodology utilizes a laboratory robot for sample extraction and work up and a high pressure liquid chromatography (HPLC) system operated under off-column conditions. Use of an on-line tuneable fluorescence detector allows measurement of total chlorin concentration at greater sensitivity than conventional u.v./vis spectrophotometric detection, and allows reproducible results to be obtained from smaller sediment samples. This is relevant to palaeoceanographic studies at high stratigraphic resolution or where sample demand is high for other stratigraphic studies.

Kerogens of nine samples from a single marl bed of the Gessoso-solfifera Formation in the Vena del Gesso basin (Messinian, Italy) were qualitatively and quantitatively studied by analytical pyrolysis. Relationships between the nature of the pyrolysis products and the source organisms were determined. The high abundance of (i) algal-derived components (n-alkanes and n-alk-1-enes) and (ii) sulphur-containing and sulphur-bound products signifying a high degree of early diagenetic sulphurization were observed. Presence of photic zone anoxia during the deposition of these sediments was discussed via the presence of 1,2,3,4-tetramethylbenzene in the pyrolysates. Unusual distributions were found for three series of pyrolysis products (i.e. C13 and C14n-alkylated thiophenes and thiolanes and C12 and C13n-1,3-alkadienes were by far the major products of these series) in the pyrolysates of two samples corresponding to the middle of the cycle (samples 3 and 5) which also have the highest δ13CTOC values and the highest pyrolysis yields. Therefore, the contribution of organisms biosynthesizing resistant algal biopolymer was considered as much more important during the deposition of the sediments associated with samples 3 and 5. We finally proposed partial structural elements from which the specific low molecular weight compounds of samples 3 and 5 can be derived upon pyrolysis.

The porphyrins and carotenoids of marl horizons within the Messinian evaporitic cycles of the Vena del Gesso basin show variations in abundance and composition throughout a sequence of ten cycles. Significant variations are also apparent within individual marl horizons. The differences in pigment distribution reflect significant changes in the environmental conditions during sediment deposition. The presence of significant amounts of isorenieratene and co-occurrence of an alkyl porphyrin with a C 34 skeleton provide evidence for anoxic conditions extending into the photic zone of the palaeo-water column. Variations in the free pigment contents of the marls reflect a regressive trend both during deposition of an individual marl, and over the entire sequence.

Lithium in ethylamine ( Li EtNH 2 ) treatment has been carried out on sulphur-rich kerogens from 10 sub-samples of the cycle IV marl from the Vena del Gesso evaporitic sediments (Upper Miocene, Italy). The treatment releases, after chromatography of the resulting solvent extracts, up to 30% of the kerogen total organic carbon. The biomarkers released are dominated by components of algal origin. The concentrations of the aliphatic hydrocarbons obtained are of the same order of magnitude as the bound alkanes released upon desulphurization of polar fractions from organic extracts and show similar distributions. The presence of diaromatic isoprenoids derived from Chlorobiaceae indicates that photic zone anoxia occurred during the deposition of the cycle IV marl, such conditions being more prevalent at the middle of the section. Polar material makes up by far most of the organic material released and contains in particular alcohols and amides which may result from the cleavage of ester bonds present in these immature kerogens, the amides being secondary products formed by reaction with the EtNH2. In the case of the alcohols, however, these components could also arise from cleavage of sulphide-bound moieties.

An abundant chlorophyll a transformation product, found previously in a lake sediment (chlorophyllone a ) has been identified by LC-MS in sediments from five aquatic environents, both marine and lacustrine. Its previously unrecognized wide sedimentary occurrence and apparent post burial stability suggest it is an important preservational sink for the chlorophyll produced in the euphotic zone. It contains a seven-membered ring fused to a five-membered ring, and therefore provides further evidence for a transformation pathway linking chlorophyll a to a recently reported sedimentary bicycloalkanochlorin and a suite of sedimentary porphyrins of the bicycloalkanoporphyrin (bi-CAP) type.

The transformations undergone by chlorophyll a under anoxic conditions have been simulated by using the widespread marine prymnesiophyte Emiliania huxleyi as a substrate for a mixed bacterial community by incubation in a sediment slurry under sulphate reducing conditions. This resulted in the formation of pyrophaeophytin a after 77 days, along with smaller amounts of phaeophorbide a, pyrophaeophorbide a and mesopyrophaeophorbide a, from an original pigment distribution comprising mainly phaeophytin a, with a lower abundance of chlorophyll a. Mesopyrophaeophorbide a has not been reported previously as a product of any chlorophyll a defunctionalization study. Its formation under the conditions used suggests that the reduction of the C-3 vinyl substituent, required for transformation of chlorophyll a to a number of sedimentary porphyrins and chlorins, is a process which involves anaerobic bacterial communities.

A study of the pigment composition in the water column particulates and bottom sediment column of an anoxic lake, Lake Ciso (Catalonia, Spain), has been carried out. The depth-dependencies of the carotenoid and chlorophyll distributions in the water column during stratification and holomixis, as well as during the diurnal cycles, have been determined. In the sediment, the composition of the pigments has been studied over the top 25 cm. The analyses were carried out by high performance liquid chromatography (HPLC) and HPLC coupled to mass spectrometry. The distributions of carotenoids, bacteriochlorophylls and chlorophylls in the water particulates closely follow the population dynamics of the photosynthetic organisms during stratification and holomixis. Among these, only chlorophyll a transformation products are found in the water column, namely phaeophytin a , pyrophaeophytin a and pyrophaeophorbide a . These derivatives also occur in the sediment, where they are found together with bacteriophaeophytin a and pyrobacteriophaeophytin a . This compartment-dependent occurrence corresponds to a higher degree of preservation of the bacterial vs algal pigments. The former occur in the anoxic hypolimnion or mixed water column during holomixis, and the latter in the oxic epilimnion. The presence of these compounds and the very low abundance of phaeophorbide a and absence of bacteriophaeophorbide a point to a transformation pathway where, in the absence of zooplankton grazing or high abundances of the enzyme chlorophyllase, the loss of the phytyl chain occurs predominantly after loss of the C-13 2 carbomethoxyl group. Okenone, alloxanthin, α-carotene and zeaxanthin/lutein are the major water column carotenoids. Their relative abundances contrast with their distribution in the sediments where okenone is the predominant compound and zeaxanthin/lutein are below detection limit. This effect may be in part a consequence of a more uniform okenone concentration in the water particulates over the year, leading to a higher annual sedimentation flux. Again, it may also be influenced by the higher degree of preservation of the bacterial vs algal carotenoids. A similar situation is observed for the relative abundances of chlorophyll a and bacteriochlorophyll a in water particulates and sediments.

The distributions of carotenoids, chlorophylls, and their degradation products have been studied in two microbial mat systems developed in the calcite and calcite/gypsum evaporite domains of a solar saltern system. Phormidium valderianum and Microcoleus chthonoplastes are the dominant cyanobacterial species, respectively, and large amounts of Chloroflexus-like bacteria occur in the carbonate/gypsum mat. In both systems, the major pigments are chlorophyll a, zeaxanthin, β-carotene and myxoxanthophyll, which originate from these mat-building cyanobacteria. This common feature contrasts with differences in other pigments that are specific for each mat community. Thus, chlorophyll c and fucoxanthin, reflecting diatom inputs, are only found in the calcite mat, whereas the calcite/gypsum mat contains high concentrations of bacteriochlorophylls c produced by the multicellular green filamentous bacteria. In both cases, the depth concentration profiles (0–30 and 0–40 mm) show a relatively good preservation of the cyanobacterial carotenoids, zeaxanthin, β-carotene, myxoxanthophyll, and echinenone. This contrasts with the extensive biodegradation of cyanobacterial remains observed microscopically. Fucoxanthin in the calcite mat is also transformed at a faster rate than the cyanobacterial carotenoids. Chlorophyll a, the major pigment in both mats, exhibits different transformation pathways. In the calcite/gypsum mat, it is transformed via C-132 carbomethoxy defunctionalization prior to loss of the phytyl chain, leading to the formation of pyrophaeophytin a and, subsequently, pyrophaeophorbide a. On the other hand, the occurrence of the enzyme chlorophyllase, attributed to diatoms in the calcite mat, gives rise to extensive phytyl hydrolysis, with the formation of chlorophyllide a, pyrophaeophorbide a and, in minor proportion, phaeophorbide a. Studies of the sources of the photosynthetic pigments and of their transformation pathways in such simplified ecosystems provide a basis for the understanding of the distribution patterns of these compounds in more complex aquatic environments.

The tetrapyrroles in a highly immature Late Pliocene lacustrine sediment (Willershausen, Germany) show a simple distribution of both chlorin and porphyrin components as the free bases. The major components are C[sub 32] desoxophylloerythroaetioporphyrin (DPEP), a C[sub 33] bicycloalkano porphyrin, the chlorine analogue of the latter, and desoxophylloerythrin and its chlorin counterpart. The structure of the novel bicycloalkano chlorin was determined using a combination of two-dimensional phase-sensitive COSY NMR and nOe studies. Measurements of [delta][sup 13]C and other data indicate that DPEP and the bicycloalkano porphyrin were derived from the chlorophyll(s) of photosynthetic organisms utilizing a common source of CO[sub 2], probably diatoms. The occurrence of DPEP and other minor alkyl porphyrins indicates that the chlorophyll defunctionalization pathway leading to these components can occur at low temperature and was probably biologically mediated, as was the condensation reaction leading to the fused ring components.

Isotope ratio monitoring GC-MS (irm-GCMS) analyses of individual hydrocarbons isolated from the surface sediment of a small eutrophic lake (Priest Pot, U.K.) and a phytoplankton tow sample from the upper water column have been undertaken in order to assign sources of sedimentary lipids. The δ 13C values for the sedimentary n-alkanes showed no clear distinction between lower molecular weight components (C17–C19) of presumed algal origin and higher members (C23–C33) of presumed higher plant origin, thus indicating a limitation to the use of compound specific isotope analysis in the freshwater system studied. In contrast, the δ 13C values of sedimentary hopenes were markedly depleted (by over 20%) compared with those in the phytoplankton sample from the upper water column. Hop-22(29)-ene in the surficial sediment had a δ 13C value of −55.2%, which contrasts witht he value of the phytoplankton component (−32.7%), attributed to cyanobacteria. These values indicate that a highly 13C-depleted source provides a major contribution to the sedimentary component. It is proposed that the sedimentary hopenes originate in part from methanotrophic bacteria, demonstrating the presence of a bacterial methane cycle in this environment.

To obtain further information about the origin of sedimentary tetrapyrroles such as the alkyl porphyrin desoxophylloerythroaetioporphyrin, the defunctionalization of chlorophyll a has been studied in batch cultures of the marine diatom Phaeodactylum tricornutum, which were induced to undergo senescence by the exclusion of light. Identification of pigments by combined reversed phase high-performance liquid chromatography-mass spectrometry (LC-MS), with on-line photo-diode array detection, revealed conversion of chlorophyll a to phaeophytin a and pyrophaeophorbide a. The results demonstrate that certain chlorophyll a transformation products which occur commonly in aquatic sediments can be formed in part by the action of algal enzymes in the water column. The study provides the first unambiguous identification of pyrophaeophorbide a during senescence of a non-mutant alga.

The abundances and distribution patterns of mono-, di- and trimethylated 2-methyl-2-(4,8,12-trimethyltridecyl) chromans (MTTCs) and long-chain alkylbenzenes in extracts of marl (66 samples), anhydrite (15) and halite (1) strata of the Salt IV Formation of the Oligocene Mulhouse Basin are reported. The distributions of the methylated MTTCs indicate salinity changes of the upper part of a density stratified water column of the basin. These variations are explained by a tectonically or climatically induced change in the supply of water of relative lower salinity to form a layer overlying the deeper water brine. Hence, it is suggested that mesohaline (3.5–15%) conditions in the surface waters were established as a result of periodic incursions of marine water and subsequent evaporation. Conversely, during periods when the surface water was derived mainly from fresh water from the hinterland, lower average salinity in the surface layer resulted. The distributions of long-chain alkylbenzenes also appear to record these changes.

The lower Oligocene evaporite sequence of the Mulhouse Basin (France) contains organic matter-rich marl deposits. These marls display an overall cyclic variation of sedimentation rate, organic carbon content, hydrogen index and selected molecular parameters over a 30 m thick stratigraphic interval. The integration of all sedimentological and geochemical parameters has allowed the reconstruction and characterization of the paleoenvironment of deposition. The marls were deposited in a perennial lake that was at times connected to the sea. Two organic facies end members could be assigned to a lake stage with a marine connection and a lake stage that received dominantly continental water input. The overall stratigraphic variation in the organic matter content is interpreted to reflect the adaptation of the Oligocene flora to the changing paleoclimate and environmental conditions.

Principal components analysis (PCA) has been used to investigate changes in concentrations of the components of the hydrocarbon fractions extracted from 71 marl samples, selected to cover two total organic carbon (TOC) maxima in the lower part of the Salt IV formation, a Lower Oligocene evaporitic sequence from the Mulhouse Basin, France. The analysis indicates that the fractions can be ascribed as lying between two end member distributions. The changes in these distributions are gradual, suggesting that they resulted from fairly gradual changes in the depositional palaeoenvironment. These changes are related to increased algal productivity associated with the evolution of a restricted lacustrine environment through to one with a greater marine influence. Systematic variations in the concentrations of selected components relative to the TOC profile point to a repeated sequential evolution in the biological assemblage during deposition of the sequence.

A suite of steryl esters of pyrophaeophorbide a ( 1a ), a water column degradation product of phytoplankton chlorophyll a, has been prepared in good yield using dicyclohexylcarbodiimide as dehydrating agent. Comparison and co-injection of these standards with the complex mixtures of steryl chlorin esters in various recent sediments, using negative ion HPLC-MS, has confirmed the structures of a number of the natural components.

Reduction of a sulphur-rich asphaltene from a crude oil (Rozel Point) with lithium in ethylamine (Li/EtNH2) affords an alkane fraction similar to that obtained from desulphurisation with Raney nickel, but in higher yield. Using Li/EtND2, deuterium-labelled alkanes were obtained, thereby confirming the presence of sulphide linkages in the asphaltene fraction. Reduction of two sulphur-rich kerogens with similar sulphur contents, Serpiano shale (M. Triassic) and Jurf Ed Darawish (JED, U. Cretaceous) afforded significant quantities of polar solvent-extractable material. Both kerogens also yielded low amounts of hydrocarbons although the amount released from JED kerogen was significantly higher. The results indicate that, whereas the kerogens contain hydrocarbon moieties intermolecularly linked by sulphide bridges, the distributions of the precursors lipids which were incorporated were different. For example, GC-MS analysis of the labelled products from JED kerogen revealed them to be dominated by steranes of algal origin, with the position(s) of deuterium labelling providing evidence of sulphide linking and cross-linking. On the other hand, the labelled products from Serpiano kerogen were dominated by hopanes of bacterial origin which were linked terminally via the side chain.

Combined liquid chromatography-mass spectrometry studies of the pigment distributions of a variety of lake and marine sediments from different depositional settings reveal the presence of steryl chlorin esters as significant components of the chlorin assemblages. The components are water column transformation products of phytoplankton chlorophyll a, and it is suggested that they form through an enzymatic esterification or transesterification process during senescence or decay. Remarkably, the steroidal alcohols are esterified mainly to a common nucleus, pyrophaeophorbide a. The transformation pathway involved appears to be a ubiquitous one in marine and lacustrine environments, and the components represent a significant sedimentary “sink” for the chlorophyll biosynthesised in the euphotic zone. Future water column studies of the changes in photosynthetic pigments in phytoplankton blooms and of pigment fluxes should take into account the likely presence of steryl chlorin esters.

The distribution patterns of sedimentary A-ring methylated steranes have changed markedly over geological time. Although dinosterane and its isomer 24-ethyl-4α-methylcholestane have been tentatively identified in three Proterozoic rock units, they are either not detectable or occur in low abundance relative to 3-methyl steranes throughout most of the Palaeozoic. Between Permian and middle Triassic times (260-220 Ma ago), 4-methyl sterane abundances in marine sediments increased markedly. The presence of dinosterane in some middle Triassic marine sediments is contemporaneous with the appearance of fossil cysts of uncontested dinoflagellate affinity. 4-Methyl steranes, including dinosterane or their precursor sterenes and sterols, then show a continuous presence, often in high abundance, in marine sediments from the late Triassic through to the present day. Assemblages of 4-methyl steranes and their precursors, but with dinosterane absent or in low relative abundance, are often the predominant steroids in lacustrine sediments in the Cainozoic. Dinosterane appears to arise predominantly from marine dinoflagellates and, as a consequence, is a useful biological marker for Mesozoic and Cainozoic marine organic matter. The isomer 24-ethyl-4α-methylcholestane is likely to have multiple origins although its very high abundance in Tertiary lacustrine sediments and oils, compared to older materials, suggests that dinoflagellates could also be the source in these cases.

Negative-ion liquid chromatographic-mass spectrometric analysis of the pigment composition of the bottom sediment (15–20 cm) of a eutrophic lake revealed the presence of a novel series of chlorophyll transformation products, in which a series of C 27 C 30 sterols and stanols are esterified to a pyrophaeophorbide a nucleus of algal origin. The major components are algal-derived chlorophyll a and b degradation products, and the presence of a bacteriochlorophyll-related phaeophytin indicates the presence of anoxic conditions extending into the photic zone when the sediment was laid down.

The major esterified tetrapyrrole in a Miocene oil shale (Marau, Brazil) is a free base chlorin, most likely pyrophaeophorbide a, esterified to 24-ethyl-4α-methyl-5α(H)-cholestan-3β-ol, the structure being assigned by FAB-MS and 1H NMR, and by GC-MS analysis of the sterol liberated by hydrolysis. FAB-MS and electronic absorption spectrophotometric data for the second most abundant component are consistent with the mesopyrophaeophorbide counterpart. Only one other minor esterified chlorin was detected, implying a highly specific and, hence, biologically-mediated esterification. It is not clear whether the reaction took place during biosynthesis of an unknown precursor chlorophyll or resulted from esterification of a hydrolysis product(s) from a known chlorophyll (most likely chlorophyll a) after cellular disruption, although the second possibility is considered more likely.

An unusual series of quinone pigments in a pink Eocene (c. 45x106 yr) sepiolite (quincyte, France) has been characterised by spectroscopy. The structure of the major pigment (c. 75% of total), 2,8-di-isopropyl-peri-xanthenoxanthene-4,10-quinone, was confirmed by synthesis. Spectroscopy revealed six minor related components with various oxygenated C-2 substituents (C1–C3) and, generally, a C-8 isopropyl group. Although the origin of the pigments is unknown, they (or their precursors) appear to have been biosynthesised by the acyl-malonate pathway.

The identities of the two major tetrapyrroles in the bottom sediment of a eutrophic lake, assigned previously by spectral comparison with standards, have been confirmed as phaeophytin a and pyrophaeophytin a through the use of 2D COSY and nOe difference NMR techniques. This provides the first unambiguous characterization of sedimentary chlorins, the components being early products in the degradative pathway of chlorophyll a in the aquatic environment.

The major chlorin in Messel oil shale (Eocene, lacustrine, F.R.G.) has been isolated and assigned as the nickel complex of mesopyrophaephorbide a by spectral comparison with a synthesised standard. The component, whose structure clearly indicates a chlorophyll origin and which co-occurs with its free-base counterpart, has the same carbon skeleton as the major nickel porphyrin acid assigned previously, but is present in much lower abundance and still retains the C-131 carbonyl group found in all chlorophylls. It appears that mesopyrophaeophorbide a represents the major part of the residual chlorin fraction which has survived aromatisation and carbonyl reduction and, like the alkyl porphyrins and carboxylic acids, has become metallated with nickel.