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Generation of biogenic hydrocarbons during a spring bloom in Newfoundland coastal (NW Atlantic) waters
Org. Geochem. Vol. 26, No. 3/4, pp. 207 218, 1997 © 1997 ElsevierScienceLtd All rights reserved. Printed in Great Britain PII: S0146-6380(96)00159-3 0146-6380/97 $17.00 + 0.00
Pergamon
Generation of biogenic hydrocarbons during a spring bloom in Newfoundland coastal (NW Atlantic) waters* T. B I E G E R ~, T. A. A B R A J A N O L t and J. H E L L O U 2 'Department of Earth Sciences, Memorial University of Newfoundland, St. John's, Newfoundland, Canada AIB 3X5 and 2Science Branch, Department of Fisheries and Oceans, P.O. Box 5667, St. John's, Newfoundland, Canada A1C 5XI (Received 29 November 1995; returned to author for revision 22 January 1996; accepted 26 November 1996)
Abstract--The distribution and carbon isotopic composition of biogenic hydrocarbons in spring bloom plankton, bottom sediments, and benthic macrobiota in Conception Bay, Newfoundland (NW Atlantic) were determined by gas chromatography/mass spectrometry and gas chromatography/combustion/isotope ratio mass spectrometry. Although individual hydrocarbons were generally depleted by at least 3%0 relative to bulk organic matter, significant variations and temporal fluctuations in compoundspecific carbon isotopic compositions were documented in bloom samples and laboratory cultures. Marked 13C depletions in a suite of eight C25 highly branched isoprenoid alkenes, as well as a temporal shift in the 13C composition of spring bloom n-alkanes are suggested to be related to changes in the growth rates of bloom organisms. The input of multiple sources of organic matter into deep bay sediments could be recognized in the isotopic compositions of sedimentary n-alkanes. Overall, the carbon isotopic composition appeared to be primarily a reflection of the carbon fixing pathway of source organisms, with superimposed variations caused by fluctuations in growth rates and [CO2(aq)]. These findings highlight the need for more study of contemporary biogenic hydrocarbons; specifically of the influence of growth rate and timing of synthesis on the carbon isotopic composition of biomarkers over the course of phytoplankton blooms. © 1997 Elsevier Science Ltd Key words--Plankton blooms, compound-specific 13C, highly branched isoprenoid, laboratory culture of diatoms, Newfoundland
INTRODUCTION The carbon isotopic compositions of organic compounds (primarily of hydrocarbons) in sediments and oils have been used to speculate on sources of sedimentary organic matter, and on a wide range of paleoenvironmental conditions, including temperature, water column stratification, and [CO2(aq)] (e.g. Hayes et al., 1989; Kohnen et al., 1992; Schoell et al., 1992, 1994). The hydrocarbons that eventually become kerogen and crude oils, however, are originally synthesized by diverse organisms at different trophic levels via a number of distinct and complex biochemical pathways. These basic differences, as well as factors such as temperature, growth rate, and [CO2(aq)] contribute to the considerable variation in 13C composition observed among individual biomarkers. Given our limited understanding of the synthesis, distribution, cycling and degradation of compounds such as hydrocarbons, it would
appear important that more studies of the compound-specific isotopic composition of modern environments take place to ensure the correct interpretation of fossil isotopic signatures. This study examined the distributions and isotopic compositions of marine biogenic hydrocarbons in biota and modern sediments offshore of Newfoundland, Canada. The work was undertaken to measure the range of hydrocarbon isotopic compositions in a typical modern depositional environment, to test the use of isotopic compositions as tracers of biogenie hydrocarbons, and specifically to clarify the source of some enigmatic although ubiquitous highly branched isoprenoid hydrocarbons present in this particular environment.
METHODS Surface water plankton samples were collected periodically from Conception Bay between April and October of 1993 using a 20/zm hoop net towed behind a small boat at a depth of roughly 4 m . Bottom surface sediments were collected from this area by grab sampling. Surface sediment samples were also collected frorn several nearshore, estuar-
*Presented at the 17th International Meeting on Organic Geochemistry, Environmental Organic Geochemistry Session, Donostia-San Sebastian, Spain, 4-8 September, 1995. "['To whom correspondence should be addressed. 207
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(Thalassiosira nordenskioldii, Fragilaria striatula, Fragilariopsis cylindrus, and Nitzschia seriata) were obtained from the Provasoli-Guillard Centre for Culture of Marine Phytoplankton (West Boothbay Hr., Maine), and were filtered onto pre-cleaned glass fibre filters. Hydrocarbons were extracted from all samples (after drying) by standard Soxhlet extraction in dichloromethane for 24 h. Extracts were purified and separated into saturated and unsaturated compounds by silica and alumina gel (both 7.5% deacti-
vated) column chromatography (Llorente et al., 1987). Elemental sulfur was removed by passing sediment extracts over activated copper powder. Hydrocarbon extracts of the hepatopancreas of crabs (Chionectes opilio and Hyas coarctatus) and of the visceral mass of scallops (Placopecten magellanicus) from previous studies in Conception Bay and other locations around Newfoundland (Hellou et al., 1993, 1994) were also analyzed. Identification and quantification of hydrocarbons was performed using a Hewlett-Packard 5890 GC coupled with a 5970 mass spectrometer equipped with a 25 m CP-Sil 5 column and He carrier gas
Generation of biogenichydrocarbonsduring a spring bloom (Injector -275°C; Detector -300°C; 35°C for 1.5 min, increased to 280 °C at 2 °C/min where it remained for 10 min). The isotopic compositions of the individual hydrocarbons were determined using a VG Isochrom system consisting of a Hewlett Packard 589011 gas chromatograph coupled via a combustion interface and cold trap to a VG Optima isotope ratio mass spectrometer. The overall design, specifications, and performance of this machine are discussed by Freedman et al. (1988), and the facility used in this study is specifically described by O'Malley et al. (1994) and O'Malley (1994). Gas chromatographic conditions were identical to those used for GC-MS analyses. All carbon isotopic measurements are reported in conventional delta (6) notation relative to the Pee Dee Belemnite (PDB) standard [l~13Cs = 1 0 0 0 * {(13C/12C)s/(13C/ 1 2 C ) P D B - - 1}]. As reported by O'Malley et al. (1994) and O'Malley (1994), measurements generated by the equipment used generally have a precision of better than 0.3%o, and are accurate to within approximately 0.6%0, depending on the nature of the sample. Inaccuracies in GC/C/IRMS can arise due to the coelution of compounds and as a result of errors in the removal of the isotopic contribution of the background (Matthews and Hayes, 1978; Hayes et al., 1989). Samples with a significant background UCM (unresolved complex mixture) were spiked with pyrene and benzo(b)fluoranthene of known isotopic compositions as internal standards to monitor the effectiveness of the background correction. No significant problems due to background interference were encountered in the samples studied. RESULTS AND DISCUSSION
H y d r o c a r b o n distributions
Spring plankton samples (dominantly diatoms) contained primarily n-heneicosahexaene (HEH), a suite of eight C2s highly branched isoprenoid (HBI) alkenes, pristane, three isomers of phytadiene, and squalene (raw concentration data shown in Appendix A and selected molecular structures shown in Appendix B). Also present in lower concentrations were an unidentified branched C17 mono-olefin, two unidentified isomers of a branched C21 mono-olefin, and a series of n-alkanes from nC15 to n - C 3 3 with a CPI close to 1. The HBI alkenes (2 triene isomers, 4 tetraene isomers, and 2 pentaene isomers, all with a parent structure based on that of 2,6,10,14,18-pentamethyl-7-(3-methylpentyl)-pentadecane), appeared in almost identical ratios in all plankton samples (Fig. 2). Fall bloom plankton (dominantly dinoflagellates) contained primarily pristane, HEH, and squalene, but no HBI alkenes. Conception Bay bottom surface sediments contained the same suite of C25 HBI alkenes, squalene, OG 26/3~4--C
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HEH, and phytadienes as found in surface water plankton, as well as a series of strongly odd-dominant C21 33 n-alkanes. A complex mixture of tricyclic and pentacyclic terpenoids, dominated by diploptene (hop-22(29)-ene) was also present. Subsamples of the grab from anoxic layers ( > 10cm) in the sediment contained virtually the same hydrocarbon assemblage as surface sediments, except for lesser quantities of shorter chain ( < C25) n-alkanes, and no HEH. The nearshore and estuarine sediment samples contained primarily pristane, odd chain-length C23 33 n-alkanes, various terpenoids, and, in several locations, different isomers of C2o C25 HBI alkenes not detected in mid-bay samples. Riverine sediment samples contained primarily odd chain-length C23 33 n-alkanes and a series of terpenoids dominated by diploptene. The biogenic hydrocarbon assemblages of crabs and scallops were dominated by HB1 alkenes, again appearing in the same relative abundance as in Conception Bay surface water plankton and deep bay sediments (also compare Grand Banks sediments; Fig. 2). The crab samples also contained abundant squalene. The only hydrocarbon identified in the diatom cultures was HEH. The cultures of T. nordenskioldii, F. cylindrus, and N. seriata produced a single isomer identical to that extracted from Conception Bay plankton. The culture of F. striatula, however, produced two separate, isomers of HEH, one of which was not found in the natural samples. Isotopic compositions
The isotopic compositions of the hydrocarbons are summarized in Fig. 3a c (see Appendix A). Most of the known algal products found in plankton and sediments, such as HEH and pristane, had isotopic compositions between - 2 5 and -28%o. The HBI alkenes, however, were in all samples consistently depleted by at least 2%o (mean 613C = - 33%o) relative to most of the other known marine biogenic compounds. Among the four pairs of HBI alkene isomers, the later eluting isomer was in each pair consistently enriched in ~3C. The C20 25 alkenes found in the near-shore sediments were all significantly enriched in 13C (mean 613C = - 20.3%0) relative both to co-occuring hydrocarbons and to the C25 HBI alkenes in the mid-bay samples. The HBI alkenes in crab and scallop samples were isotopically similar to the same compounds in plankton tows and sediments. Squalene was relatively enriched (mean 613C = - 2 4 % 0 ) , whereas the C25 HBI alkenes were all strongly depleted (from -30.6 to -40.5%0). The average 613C of the n-alkanes in spring plankton fell over the course of the bloom from -23.7%0 to -29.6%o. The long-chain n-alkanes (>Czs) found in all sediment samples analysed were all consistently depleted in 13C (613C < -30%o) compared with shorter chain-length homologues.
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,5'~C (Oloo) Fig. 3, Isotopic compositions of aliphatic hydrocarbons in (a) plankton, (b) mid-bay sediments, and (c) nearshore sediments (bars denote 1 S.D.). The HEH produced by the cultures of T. nordenskioldii, F. cylindrus, and N, seriata, was isotopically identical to that extracted from natural plankton. The two separate isomers produced by F. striatula, however, were depleted by almost 4%o relative to the HEH in the other cultures. Bulk spring bloom particulate organic matter (POM) in Conception Bay has a 613C value between approximately -21%o and -23%o (Ostrom, 1992). Since lipids are normally expected to be depleted relative to total biomass by roughly 3 to 4%o as a result of fractionation during early synthetic stages (Monson and Hayes, 1980), the isotopic compositions of most of the marine biogenic hydrocarbons in this study fall within the expected range for local bloom phytoplankton. Notable exceptions to this pattern are the C25 HBI alkenes, discussed below. The durability of the isotopic signatures of hydrocarbons in the water column of Conception
Generation of biogenic hydrocarbons during a spring bloom Bay is demonstrated by the consistency of the isotopic compositions of HBI alkenes in plankton, sediments and benthic macrobiota. Similarly, extensive degradation of HEH in the water column does not appear to affect the isotopic composition of this highly labile compound, as surface water and bottom sediment ~513C values for HEH are identical within instrumental precision. H B I alkenes
The consistent distribution and isotopic signature of the HBI alkenes over a wide geographic area would tend to suggest that they are synthesized by one organism during the spring bloom. Based on the recent work of Volkman et al. (1994) documenting C25 HBI production in the diatom Haslea ostrearia, a diatom species other than one of those cultured in this study would appear to be the most likely source. As described by Freeman et al. (1994), however, such an origin would be expected to result in a relative enrichment in 13C, due both to the more exhaustive use of dissolved CO2 during the blooms in which diatoms commonly grow, and to the capability of some diatoms of assimilating 13C-enriched bicarbonate. C25 HBI aikenes were, in fact, among the most isotopically enriched hydrocarbons found by these authors in Black Sea and the Cariaco Trench particulate organic carbon. The marked depletion observed in this study among HBI alkenes relative to co-occurring known diatom products (both isoprenoid and non-isoprenoid, and especially HEH) could indicate that these compounds have some alternate source in Conception Bay. This alternate origin is further supported by the observation that while Rhizosolenia setigra, a diatom species reported to synthesize C30 homologues of the C25 HBI alkenes (Volkman et al., 1994), was present in abundance in Conception Bay, no C30 HBI aikenes were found in any samples from the area. As shown by Laws et al. (1995), however, the isotopic composition of primary producers, such as marine diatoms is also a function of growth rate, in that the isotopic discrimination factor involved in the assimilation and fixing of dissolved inorganic carbon (DIC) is reduced during periods of intense growth. Thus, compounds synthesized before or after a bloom, when growth rates are lower, would be expected to have lower 613C values. It has been suggested by some that production of C25 HBI alkenes in the diatom H. ostrearia is associated with the rise of these pennate diatoms in the water column and the onset of growth (S. Rowland, oral communication). It is thus possible that the low ~513C values of the HBI alkenes in Conception Bay are due to their synthesis, still by diatoms, but only before the main growth phase of individual organisms, before the onset of extensive photosynthesis and carbon assimilation during the spring diatom
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increase. It is possible that the other slightly depleted branched alkenes in the plankton tows (brC21:l and brClT:l) are of similar origins, produced perhaps slightly later than the more strongly depleted C25 HBI alkenes. Based on this model, the other hydrocarbons detected will have been synthesized during or just after the main growth phase of the spring diatom increase. The particularly intense isotopic depletion seen in the C25 HBI aikenes in Conception Bay could also be partially due to early synthesis of these compounds in deeper water. Ostrom (1992) reported DIC 613C values in the deeper waters of Conception Bay (below approximately 50 m) to be consistently lower (by approximately 2-4%o) than in surface waters. Thus, while the isotopic compositions of the C25 HBI alkenes initially suggest a non-diatom origin, the low 613C values these compounds exhibit may merely be a reflection of the timing of the synthesis of these compounds. The molecular distribution and enriched 13C signatures of the HBI alkenes in nearshore and estuarine samples suggest that these compounds have a source that is distinct from that of the mid-bay HBI alkenes. The enrichment seen in these compounds conforms more closely with a standard mid-bloom algal (diatom) origin, and may also be partially a result of slightly higher water temperatures and greater productivity/growth rates in these waters. It is also possible that the nearshore compounds are derived from sedentary benthic biota, which, due to transport limitations in their diffusive boundary layers, may assimilate heavier isotopes more readily than mobile organisms (France, 1995). H E H and squalene
HEH (n-C21:6) is synthesized by a wide variety of marine algae (especially diatoms) primarily during periods of rapid growth and active cell division (Schultz and Quinn, 1977; Blumer and Thomas, 1965; Blumer et al., 1970). Squalene, a C30 isoprenoid, is commonly found in diatom blooms (e.g. Osterroht and Petrick, 1982; Matsueda et al., 1986). The exact functions of these compounds in marine algae are un:' :ar, although it has been suggested that squalene could be used to control buoyancy. Given the large number of possible source organisms for these compounds, the isotopic compositions of HEH and squalene in Conception Bay are surprisingly constant. The isotopic similarity of HEH and squalene exemplifies the lack of isotopic contrast observed in this study between straightchain and isoprenoid hydrocarbons in general. However, as shown by the variations in the 613C of different isomers of HEH synthesized by the culture of F. striatula, differences in the biosynthetic pathways of related hydrocarbons can in some cases be associated with marked isotopic differences. Although previous authors have found fatty acid
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desaturation to be associated with a preferential loss of Z3C (Fang et al., 1993), the lack of a significant isotopic depletion among these highly unsaturated hydrocarbons suggests that relatively little isotopic discrimination occurs during desaturation. In fact, the fatty acid 22:6~o3, from which HEH is believed to be derived, has been reported in Conception Bay mussels (present presumably from algal dietary intake) to have a lower 613C (approximately -29%o; Murphy and Abrajano, 1994), than the HEH in the present study.
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In the absence of phytane, pristane in the marine environment is generally accepted to be derived from degradation of the phytol side chain of chlorophyll (Avigan and Blumer, 1968). Phytadienes are also believed to have a similar origin (Blumer and Thomas, 1965). Although these compounds are isotopically identical in mid-bay sediments, they follow distinct trends during the spring bloom. In general, especially in the mid-bloom samples, pristane is enriched in n3C, as would be expected for a compound produced largely during periods of high productivity, high growth rates, and high CO2 demand. The 6~3C of pristane decreases later in the bloom, possibly as a result of the general decrease in growth rates and the greater expression of isotope effects associated with hydrocarbon synthesis. The 6~3C of the phytadienes, however, rises from an average of-27.4%0 at mid-bloom to -25.4%0 at the end of the bloom. Because many different photosynthetic organisms produce chlorophyll during a plankton bloom, these isotopic fluctuations may be the result of the production and mixing of chlorophyll of differing isotopic composition from a succession of bloom organisms. n-Alkanes
The smooth distribution ( C P I ~ 1) among the series of C15_33 n-alkanes observed in the spring bloom plankton samples is often taken to indicate a petroleum origin. Although residual traces of lubricating oil contamination from urban runoff and outboard motor exhausts were detected in some plankton and sediment samples (discussed in Bieger et al., 1996), the change in 613C among the Cls-2s n-alkanes over the course of the spring bloom suggests that these compounds are of recent biogenic origin. Similar n-alkane distributions have in fact been documented in many unpolluted regions (e.g. Matsueda and Handa, 1986; Serrazanetti et al., 1991; Nichols et al., 1988). The shift in 613C during the bloom could be caused by the mixing of alkanes from different sources, perhaps from a succession of different species. Alternatively, the 13C depletion in late bloom samples could again be a reflection of the less rapid growth and resultant more intense fractionation of carbon isotopes during the tail of
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Fig. 4. (a) Mean isotopic composition of n-alkanes from all sediments and (b) carbon chain lengths and isotopic compositions of three proposed sources of n-alkanes in sediments. the bloom. If this latter explanation is the case, then the appearance of this shift only among nalkanes (and not in known algal products such as HEH) suggests that these hydrocarbons are of a non-algal, possibly microbial, origin. The consistent depletion among the long chain (> C25) odd-dominant n-alkanes found in all riverine, nearshore, and mid-bay sediments clearly reflects the origin of these compounds in terrestrial plant leaf waxes (e.g. Rieley et al., 1991, 1993). A summary of average n-alkane isotopic compositions for all sediment samples combined is presented in Fig. 4(a). Two patterns are evident in this figure. First, there is a general decrease in 613C with increasing alkane chain length. This trend could be the result of fractionation of carbon isotopes during progressive elongation of the fatty acids that are the precursors of linear hydrocarbons, as suggested by Fang et al. (1993). More likely, though, it is a reflection of the predominantly terrestrial source of long-chain n-alkanes. Secondly, this decrease in 613C is more pronounced among odd chain-length n-alkanes than among even chain-length homologues, resulting in a sawtooth pattern featuring relatively ~3C-enriched odd-chain length n-alkanes in the Ct5-20 range and relatively 13C-depleted oddchain length homologues in the C28-33 range. This pattern can be explained by the dominance of odd n-alkanes in most organic matter sources. Since odd
Generation of biogenic hydrocarbons during a spring bloom chain-length homologues are more abundant, the isotopic compositions of these compounds should be less altered by mixing with alkanes from isotopically distinct sources than the compositions of the less abundant even chain-length homologues. Odd chain-length n-alkanes should thus isotopically more closely resemble the sources from which they are derived. This pattern suggests the mixing of an odd-dominant, isotopically relatively heavy (i.e. marine) Cl5 2o n-alkane assemblage with an odddominant, isotopically more depleted (i.e. terrestrial) C2s-33 n-alkane assemblage. These two sources also contribute some of the even chain-length nalkanes in Conception Bay. However, the consistent deflection of the even homologue isotopic compositions to the center of Fig. 4(a) suggests a third major source of n-alkanes of intermediate isotopic composition which may be bacterial or petroleum. Although it is possible that more than three sources contributed to the overall isotopic signature shown in Fig. 4(a), at least three primary sources of nalkanes appear to be required as shown in Fig. 4(b).
CONCLUSIONS (1) Overall, no clear or consistent isotopic distinction or trend was apparent between hydrocarbons of distinct or differing biochemical origins, e.g. between isoprenoids and linear hydrocarbons, or between saturated and unsaturated compounds. In general, the isotopic compositions of biogenic compounds in this study appeared to be primarily a reflection of the carbon fixing mechanism of the organisms producing the compounds, with variations related to changes in growth rate and CO2(aq) demand superimposed on these basic patterns. (2) Several fluctuations or apparent discrepancies in isotopic composition observed in this study (e.g. among C25 HBI alkenes and in spring bloom n-alkanes) may be related to changes in growth rates. It is suggested that the timing of synthesis of a biomolecule during a plankton bloom, or during the growth cycle of a bloom organism, may be a more important factor in determining isotopic composition than previously recognized. Future studies involving more detailed sampling over the course of plankton blooms and throughout the growth cycles of isolated organisms should be undertaken to investigate the isotopic 'imprint' left by the timing of synthesis. (3) Significant isotopic differences were observed between some compounds produced via slightly different pathways in different organisms (e.g. HEH in different cultures). The possibility of inter-species biosynthetic differ-
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ences thus must always be considered when making inferences from sedimentary isotopic patterns. (4) The isotopic compositions of the hydrocarbons analyzed are fairly durable markers, as they were not altered by degradation (HEH) or cycling through sediments and benthic macrobiota (C25 HBI alkenes). (5) The mixing of organic matter from different sources, containing hydrocarbons of differing distributions and isotopic compositions (e.g. terrestrial, marine, and bacterial) can be recognized and modeled using the isotopic compositions of n-alkanes. (6) Clearly, more extensive study of the 13C composition of contemporary hydrocarbons is necessary before ancient sedimentary patterns can be fully understood and interpreted with authority. Associate E d i t o r - - B . R. T. Simoneit Acknowledgements--This work was supported by the
Natural Science and Engineering Research Council (TAA) and the Canadian Green Plan Toxic Chemicals Program (JH). T. Bieger received support from the A.G. Hatcher Scholarship Fund, the School of Graduate Studies at Memorial University and the Government of the Province of Newfoundland and Labrador. REFERENCES
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and polycyclic aromatic hydrocarbons in molluscs collected from waters around Newfoundland. Arch. Environ. Contain. Toxicol. 24, 249-257. Hellou J., Upshall C., Taylor D., O'Keefe P., O'Malley V. and Abrajano T. (1994) Unsaturated hydrocarbons in muscle and hemolymph of two crab species, Chionectes opilio and Hyas coarctatus. Mar. Poll. Bull. 28, 482-488. Laws E. A., Popp B. N., Bidigare R. R., Kennicutt M. C. and Macko S. A. (1995) Dependence of phytoplankton carbon isotopic composition on growth rate and [CO2~q)]: Theoretical considerations and experimental results. Geochim. Cosmochim. Acta 59, 1131 1138. Llorente G. A., Farran A., Ruiz X. and Albaiges J. (1987) Accumulation and distribution of hydrocarbons, polychlorobiphenyls, and DDT in tissues of three species of Anatidae from the Ebro Delta, (Spain). Arch. Environ. Contam. ToxicoL 16, 563-572. Matthews D. E. and Hayes J. M. (1978) Isotopic-ratiomonitoring mass-spectrometry. Anal. Chem. 50, 1465 1473. Matsueda H. and Handa N. (1986) Vertical flux of hydrocarbons as measured in sediment traps in the eastern North Pacific ocean. Mar. Chem. 20, 179-195. Matsueda H., Handa N., Inoue I. and Takano H. (1986) Ecological significance of salp fecal pellets collected by sediment trap experiments in the eastern North Pacific. Mar. Biol. 91,421-431. Monson K. D. and Hayes J. M. (1980) Biosynthetic control of the natural abundance of carbon 13 at specific positions within fatty acids in Escherichia coil J. Biol. Chem. 255, 11435 11441. Murphy D. E. and Abrajano T. A. Jr (1994) Carbon isotope compositions of fatty acids from mussels from Newfoundland estuaries. Est. Coast. Shell" Sci. 39, 261 272. Nichols P. D., Volkman J. K., Palmisano A. C., Smith G. A. and White D. C. (1988) Occurrence of an isoprenoid C25 diunsaturated alkene and high neutral lipid content in Antarctic sea-ice diatom communities. J. Phycol. 24, 90 96. O'Malley V. P. (1994) Compound-specific carbon isotope geochemistry of polycyclic aromatic hydrocarbons in eastern Newfoundland estuaries. Ph.D. Thesis,
Memorial University of Newfoundland, St. John's, Newfoundland. O'Malley V. P., Abrajano T. A. Jr and Hellou J. (1994) Determination of the 13C/12C ratios of individual PAH from environmental samples: Can PAH sources be apportioned? Org. Geochem. 21, 809-822. Osterroht C. and Petrick G. (1982) Aliphatic hydrocarbons in particulate matter from the Baltic Sea. Mar. Chem. 11, 55-70. Ostrom N. E. (1992) Stable isotope variation in particulate organic matter and dissolved inorganic compounds in a northern t]ord: implications for present and past environments. Ph.D. Thesis, Memorial University, St. John's, Newfoundland. Rieley G., Collier R. J., Jones D. M., Eglinton G., Eakin P. A. and Fallick A. E. (1991) Sources of sedimentary lipids deduced from stable isotope analyses of individual compounds. Nature 352, 425-427. Rieley G., Collister J. W., Stern B. and Eglinton G. (1993) Gas chromatography/isotope ratio mass spectrometry of leaf wax n-alkanes from plants of differing carbon dioxide metabolisms. Rapid Commun. Mass Spectrom. 7, 488~491. Schoell M., McCafferty M. A., Fago F, J. and Moldowan J. M. (1992) Carbon isotopic composition of 28,30-bisnorhopanes and other biological markers in a Monterey crude oil. Geochim. Cosmochim. Acta 56, 1391 1399. Schoell M., Schouten S., Sinninghe-Damst6 J. S., de Leeuw J. W. and Summons R. E. (1994) A molecular organic carbon isotope record of Miocene climate changes. Science 263, 1122 -1130. Schultz D. M. and Quinn J. G. (1977) Suspended material in Narragansett Bay: fatty acid and hydrocarbon composition. Org. Geochem. 1, 27-36. Serrazanetti G. P., Conte L. S., Carpen4 E., Bergami C. and Fonda-Umani S. (1991) Distribution of aliphatic hydrocarbons in plankton of Adriatic sea open waters. Chemosphere 23(7), 925 938. Volkman J. K., Barrett S. M. and Dunstan G. A, (1994) C25 and C30 highly branched isoprenoid alkenes in laboratory cultures of two marine diatoms. Org. Geochem. 21,407-413.
Generation of biogenic hydrocarbons during a spring bloom
215
APPENDIX
Tables o f (1) Raw Concentration Data and (2) Chromatographic Conditions with Retention Indices. a: Plankton tows and scallops (all concentrations in/~g/g dry weight, all J3C values in per mil vs. PDB (tr. - - trace, n.d. - - not detected, n.m. - - not measured P L A N K T O N TOWS April 15 Plankton conc del 13C
May 18 Plankton conc. del ~3C
May 20 Plankton conc. del JaC
N ov 8 Plankton conc, del 13C
Scallop (visc. mass) conc. del 13C
0.31 0.68 0.71 0.62 0.40 0.37 0.34 0.37 0.37 0.43 0.46 0.43 0.40 0.34 0.15 0.12 0.09 0.06 0.03
n.m. -25.5 -23.2 -24.3 -24.1 -23.4 n.m. -23.7 -23.4 -23.3 -23.3 -23.2 -21.4 -22.8 -24.0 -23.5 -23.5 -22.9 -21.4
0.17 0.50 0.84 1.14 1.38 1.35 1.31 1.38 1.65 1.98 2.49 2.05 1.78 1.36 1.11 0.45 0.34 0.25 0.17
n.m. -28.0 -26.4 -27.3 -27.2 -27.2 -29.1 -27.6 -27.4 -27.3 -27.2 -27.2 -27.3 -27.2 -27.7 -27.2 -27.5 -27.4 -27.4
0.18 0.27 0.46 0.46 0.55 0.62 0.71 0.79 1.01 1.37 1.65 1.48 1.68 1.12 0.92 0.37 0.18 0.15 0.11
n,m. n,m. -29.7 -30.7 -29.8 -30.0 -30.6 -30.0 -29.0 -29.7 -29.2 -29.1 -29.3 -28.8 -29.1 -28.6 -29.3 -30.1 -30.9
1.13 0.28 0.56 0.39 2.54 1.07 1.35 1.13 1.69 2.25 3.49 3.38 5.02 2.54 6.48 3.21 3.38 0.62 1.24
n.m. n.m. n.m. n.m. -25.4 n.m. n.m. n.m. n.m. n.m. -26.4 -26.3 -26.6 n.m. -27.5 n.m. -27.1 n.m. n.m.
n.m. n.m. n.m. n.m. n.m, n.m, n.m, n.m, n.m, n.m, n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m.
n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m.
5.85 0.31 n.m. n.m. n.m. n.d. n.d. 15.39 5.85 9.23 8.00 0.77 0.62 2.92 0.46 12.31
-23.5 -25.4 -26.8 -27.9 -27.4 n.d. n.d. -34.2 -34.8 -35.2 n.m. n.m. n.m. n.m. n.m. -26.3
7.74 0.45 n.m. n.m. n.m. n.d. n.d. 9.92 2.35 5.21 2.35 1.18 1.18 2.19 1.01 10.26
-25.0 -27.6 -26.7 -27.5 -27.3 n.d. n.d. -38.7 -35.7 -37.2 -37.4 -34.3 -35.4 -36.6 -34.5 -25.1
1.87 0.22 n.m. n.m. n.m. n.d. n.d. 9.89 3.11 4.94 2.38 0.92 0.92 2.56 1.28 8.24
-27.5 -30.8 -24.9 -25.5 -25.8 n.d. n.d. -38.5 -35.6 -36.0 -39.7 -30.7 -31.3 -34.4 -28.8 -25.5
21.98 0.39 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. 5.07
-26.3 n.m. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.m.
n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m.
n.m. n.m. n.m. n.m. n.m. n.m. n.m. -33.6 -30.8 -34.4 n.m. n.m. n.m. -32.9 n.m. n.m.
24.62 0.92 2.00 1.23 n.d. n.d. n.d. n.d.
-26.9 -27.9 -29.3 -28.3 n.d. n.d. n.d, n.d.
14.97 2.01 3.03 2.02 n.d. n.d. n.d. n.d.
-26.6 -31.9 -32.3 -30.1 n.d. n.d. n.d. n.d.
15.56 0.18 1.70 0.77 n.d. n.d. n.d. n.d.
-26.4 n.m. -35.0 -32.1 n.d. n.d. n.d. n.d.
22.54 n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.m. n.d. n.d. n,d. n,d. n,d. n,d. n.d.
n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m.
n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m.
n-alkanes
nC15 nC16 nC17 nCl8 nCl9
nC20 nC21 nC22
nC23 nC24 nC25 nC26 nC27 nC28 nC29 nC30
nC31 nC32
nC33 Isoprenoids pritane phytane neo-phytadiene 1,3-phytadiene 2,4-phytadiene brC20:l brC20:1' brC25:3 brC253' brC25:4a brC25:4b brC25:4a' brC25:4b' brC25:5 brC25:5' Squalene
Other HEH brC17:l brC21:l brC2 1:l' brC23:2a brC23:2b brC25:4c brC25:3b
2,4-phytadiene brC20:1 brC20:1' brC25:3 brC25Y brC25:4a brC25:4b brC25:4a' brC25:4b' brC25:5 brC25:5' Squalene Other HEH brC 17:1 brC21:l brC21:1' brC23:2a brC23:2b brC25:4c brC25:3b
1,3-phytadiene
n-alkanes nCl5 nCl6 nC17 nC18 nCl9 nC20 nC 21 nC22 nC23 nC24 nC25 nC26 nC27 nC28 nC29 nC30 nC31 nC32 nC33 lsoprenoids pritane phytane neo-phytadiene
-27.8 n.m. n.d. n.d. n.d. -11.5 n.m. -34.8 -30.2 -34.4 -31.7 -35.8 -30.2 -33.2 -26.3 n.m.
-26.1 -26.8 n.d. n.d. n.d, n.d. n.d, n.d.
0.36 0.03 n.d. n,d, n.d. 0.05 0.05 1.05 0.57 0.67 0.57 0.20 0.18 0.38 0.05 0.38
0.46 0.04 n.d. n.d. n.d. n.d. n.d. n.d.
0.16 0.30 0.20 0.27 0.19 0.56 0.20 0.63 0.16 0.54 0.09 0.25
0.15
0.05
0.11
-29.3 -29.3 -27.0 -29.0 -28.4 -29.4 -29.3 -28.9 -29.4 -30.2 -29.7 -30.2 -30.5 -28.9 -30.6 -30.1 30.5 30.5 n.n.
0.09 0.12 0.11 0.11
n.d. 0.02 n.d. n.d. n.d. n.d. n.d. n.d.
0.22 n.d. n.d. tr. tr. 0.04 0.04 1.16 0.64 0.40 0.30 0.20 0.15 0.30 0.20 0.47
n.m. 0.04 0.08 0.10 n.m. 0.10 0,29 0.24 0.56 0.32 0.66 0.38 1.01 0.41 1.16 0.29 0.99 0.11 0.42
n.d. n.m. n.d. n.d. n.d. n.d. n.d. n.d.
n.m. n.d. n.d. n.m. n.m. n.m. n.m. -32.3 -27,7 32.9 -26.9 -29.7 -31.6 -28.3 -27.7 n.m.
n.m. n.m. n.m. n.m. n.m. n.m. -28.8 -28.3 -29.5 -30.8 -30.4 -31.2 -30.6 -31.4 -31.1 -31.0 -31.5 -29.8 -32.6
Conc. Bay (30 cm) conc, del 13C
MID BAY SEDIMENTS
Conc. Bay (surf.) conc. del 13C
n.d. tr n.d. n.d. 0.12 0.09 0,09 n,d,
0.03 0.03 n.d. n.d. n.d. 0.03 0.09 n.d. n.d. 0.46 tr. 0.21 n.d. 0.52 0.18 n.d.
0.33 0.14 0.51 0.15 0.30 0.05 0.12
0.11
0.02 0.03 0.07 0.03 0.13 0.02 0.09 0.05 0.29 0.09 0.25
n.d. n,m. n.d. n,d. -19.5 -21.7 -24.2 n.d.
n.m. n.m. n.d. n.d. n.d. -22.4 n.m. n.d. n.d. -20.1 n.m. -21.1 n.d. -17.56 -23.6 n.d.
-23.8 -23.8 n.m. -27.7 -22.6 -28.1 -21.5 -27.9 -26.2 -28.5 -27.9 -28,9 -28.6 -28.9 -30.1 -28.8 -30.4 n.m. -32.4
Spaniards Bay conc, del 13C
n.d. n.d. n,d. n.d. n.d. n.d, n.d. n,d.
0.09 0.06 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d, n.d. n.d.
0.05 0.06 0.09 0.10 0.16 0.15 0.28 0.23 0.35 0.27 0.38 0.30 0.50 0.26 0.54 0.18 0.46 0.09 0.28
n.d. n,d, n.d, n.d, n.d, n.d. n.d. n,d.
-27.5 -27.0 n.d. n.d. n.d. n,d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d, n.d. n.d.
-26.8 -26.1 -26.6 -27.3 -27.1 -27.4 -27.6 -27.9 -28.5 -28.1 -29.0 -28.4 -29.7 -29.4 -30.7 -28.5 -31.2 n.m. -31.9
Avondale conc. del 13C
NEARSHORE SEDIMENTS
n.d. n.d. n.d, n.d, n,d. n.d. n.d. n.d,
0.13 0.09 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
tr. 0.01 0.04 0.01 0.04 0.04 0.11 0.04 0.20 0.07 1.19 0.06 0.58 0.07 0.56 0.07 0.49 0.03 0.19
n.d. n.d. n.d. n.d. n.d. n,d. n,d. n,d.
-29.8 -29.1 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.m. n.m. -29.0 n.m. -27.7 -25.5 -28.0 -28.9 -29.5 -28.9 -29.8 -28.4 -29.7 -29.0 -30.8 -29.0 -30,4 n.m. -31.7
St. Phillip's conc. del 13C
n.d. 0,02 n.d. n,d. 0.13 0.33 0.31 0.28
0.04 0.04 n.d. n.d. n.d. 0.03 0.02 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
0.03 0.03 0.10 0.05 0.35 0.07 0.36 0.13 0.53 0.16 0.52 0.15 0.54 0.14 0.55 0.09 0.39 0.02 0.11
n.d. n.d. n.d. n.d. -18.8 n.m. -18.0 -20.6
-29.5 -26.5 n.d. n.d. n.d. -16.4 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
-28.9 -29.8 -24.8 -28.6 -20.3 -28.6 -19.9 -28.7 -23.6 -29.5 -26.7 -30.0 -27.6 -29.2 -30.5 -29.8 -31.7 -30.2 -31.8
South River conc. del 13C
ESTURINE SEDIMENTS
b: Sediments (all concentrations in #g/g dry weight, all 13C values in per mil vs. PDB (tr. - - trace, n.d. - - not detected, n.m. - - not measured
n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
0.07 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.d. n.d. n.d. tr. 0.02 0.02 0.09 0.03 0.16 0.04 0.16 0.04 0.34 0.06 0.32 0.02 0.22 n.d. 0.05
n.d. n.d. n.d. n.d. n.d. n.d. n,d, n.d.
-30.5 n,d, n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.d. n.d. n.d. n.m. -28.4 -29.0 -29.8 -31.5 -28.9 -31.1 -30.3 -32.9 -30.6 -31.2 -32.2 -31.5 -33.5 n.d. -34.5
Topsail conc. del t3C
n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.d. n,d, n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.d. n.d. n.d. n.d. n.d, n.d. n.d. 0.85 16.98 4.24 36.08 16.13 123.09 2.12 72.16 tr. 16.55 tr. 2.12
n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.m. -31.5 n.m. -31.5 -30.0 -31.1 n.m. -31.9 n.m. -32.0 n.m. -31.6
Holyrood conc. del 13C
n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.d. n.d. n.d. n.d. n.d. n.d. n,d, n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.d. n.d. 0.64 0.49 0.90 0.90 2.54 1.19 3.43 1.04 3.73 1.19 4.48 1.34 6.27 0.67 3.73 0.30 1.49
n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.d. n.d. -31.8 -26.7 -31.1 -26.7 -31.6 -32.5 -30.4 -32.1 -32.9 -33.7 -33.0 -33.1 -32.1 -31.3 -31.8 -31.4 -31.5
Job's Cove conc. del J3C
RIVERINE SEDIMENTS
W
Compound C-20 highly-branched isoprenoid compounds br-C20:1 br-C20:1 C-25 highly-branched isoprenoid compound suite (Plankton tows/mid-bay samples, macrobiota): br-C25:3 br-C25:3' br-C25:4a br-C25:4b br'C25:da' br-C25:4b' br-C25:5 br-C25:5' C20-25 branched compounds (nearshore/esturine samples): br-C23:2a br-C23:2b br-C23:3a br-C25:4¢
Retention index (R.I.) and characteristic major ion fragments of selected compounds. Gas chromatograph: HP 5890GC + 5970MSD, 70 eV electron impact. Column: CP-Sil 5 column, 25 m × 0.25 mm i.d., film thickness 0.12 ~m. Conditions: He carrier gas @ 1 "L/min, 1 mL splitless injection, inj. @275 °C, det. @300 °C. Temperature Program: 1.5 min @ 35 °C; 2°C/min to 280°C. Characteristic major fragment ions (base ion first) 69, 83, 111, 181, 196, 210, 280 69, 83, 126, 140, 196, 210, 280 83, 165, 233, 261,291,346 83, 165, 233, 261,291,346 69, 109, 180, 231,233, 259, 275, 344 69, 163, 233, 259, 289, 344 69,109, 149, 180, 205, 259, 275, 344 69, 123, 163, 231,259, 289, 344 69, 177, 218 260, 273, 342 69, 217, 273, 342 55, 95, 179, 207, 266, 277, 320 55, 95, 179, 207, 266, 277, 320 55, 149, 233, 261,289, 346 69, 163, 218, 259, 273, 275, 344
R.I 1690 1705 2046 2089 2077 2080 2118 2123 2110 2156 2084 2091 2105 2138
t~
0 0
Z
e~
0
0
0
g~
£
T. Bieger et al.
218
APPENDIX Selected Molecular Structures
a. 2,6,10-trimethyl-7-(3-methyl)-dodecane (C2o HBI alkene parent structure)
b. 2,6,10,14-tetramethyl-7-(3-methylpentyl)pentadecane (C25 HBI alkene parent structure)
c.n-heneicosahexaene
d. squalene
e. neo-phytadiene
f. 1,3-phytadiene
g. 2,4-phytadiene
Pergamon
Generation of biogenic hydrocarbons during a spring bloom in Newfoundland coastal (NW Atlantic) waters* T. B I E G E R ~, T. A. A B R A J A N O L t and J. H E L L O U 2 'Department of Earth Sciences, Memorial University of Newfoundland, St. John's, Newfoundland, Canada AIB 3X5 and 2Science Branch, Department of Fisheries and Oceans, P.O. Box 5667, St. John's, Newfoundland, Canada A1C 5XI (Received 29 November 1995; returned to author for revision 22 January 1996; accepted 26 November 1996)
Abstract--The distribution and carbon isotopic composition of biogenic hydrocarbons in spring bloom plankton, bottom sediments, and benthic macrobiota in Conception Bay, Newfoundland (NW Atlantic) were determined by gas chromatography/mass spectrometry and gas chromatography/combustion/isotope ratio mass spectrometry. Although individual hydrocarbons were generally depleted by at least 3%0 relative to bulk organic matter, significant variations and temporal fluctuations in compoundspecific carbon isotopic compositions were documented in bloom samples and laboratory cultures. Marked 13C depletions in a suite of eight C25 highly branched isoprenoid alkenes, as well as a temporal shift in the 13C composition of spring bloom n-alkanes are suggested to be related to changes in the growth rates of bloom organisms. The input of multiple sources of organic matter into deep bay sediments could be recognized in the isotopic compositions of sedimentary n-alkanes. Overall, the carbon isotopic composition appeared to be primarily a reflection of the carbon fixing pathway of source organisms, with superimposed variations caused by fluctuations in growth rates and [CO2(aq)]. These findings highlight the need for more study of contemporary biogenic hydrocarbons; specifically of the influence of growth rate and timing of synthesis on the carbon isotopic composition of biomarkers over the course of phytoplankton blooms. © 1997 Elsevier Science Ltd Key words--Plankton blooms, compound-specific 13C, highly branched isoprenoid, laboratory culture of diatoms, Newfoundland
INTRODUCTION The carbon isotopic compositions of organic compounds (primarily of hydrocarbons) in sediments and oils have been used to speculate on sources of sedimentary organic matter, and on a wide range of paleoenvironmental conditions, including temperature, water column stratification, and [CO2(aq)] (e.g. Hayes et al., 1989; Kohnen et al., 1992; Schoell et al., 1992, 1994). The hydrocarbons that eventually become kerogen and crude oils, however, are originally synthesized by diverse organisms at different trophic levels via a number of distinct and complex biochemical pathways. These basic differences, as well as factors such as temperature, growth rate, and [CO2(aq)] contribute to the considerable variation in 13C composition observed among individual biomarkers. Given our limited understanding of the synthesis, distribution, cycling and degradation of compounds such as hydrocarbons, it would
appear important that more studies of the compound-specific isotopic composition of modern environments take place to ensure the correct interpretation of fossil isotopic signatures. This study examined the distributions and isotopic compositions of marine biogenic hydrocarbons in biota and modern sediments offshore of Newfoundland, Canada. The work was undertaken to measure the range of hydrocarbon isotopic compositions in a typical modern depositional environment, to test the use of isotopic compositions as tracers of biogenie hydrocarbons, and specifically to clarify the source of some enigmatic although ubiquitous highly branched isoprenoid hydrocarbons present in this particular environment.
METHODS Surface water plankton samples were collected periodically from Conception Bay between April and October of 1993 using a 20/zm hoop net towed behind a small boat at a depth of roughly 4 m . Bottom surface sediments were collected from this area by grab sampling. Surface sediment samples were also collected frorn several nearshore, estuar-
*Presented at the 17th International Meeting on Organic Geochemistry, Environmental Organic Geochemistry Session, Donostia-San Sebastian, Spain, 4-8 September, 1995. "['To whom correspondence should be addressed. 207
T. Bieger et al.
208
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(Thalassiosira nordenskioldii, Fragilaria striatula, Fragilariopsis cylindrus, and Nitzschia seriata) were obtained from the Provasoli-Guillard Centre for Culture of Marine Phytoplankton (West Boothbay Hr., Maine), and were filtered onto pre-cleaned glass fibre filters. Hydrocarbons were extracted from all samples (after drying) by standard Soxhlet extraction in dichloromethane for 24 h. Extracts were purified and separated into saturated and unsaturated compounds by silica and alumina gel (both 7.5% deacti-
vated) column chromatography (Llorente et al., 1987). Elemental sulfur was removed by passing sediment extracts over activated copper powder. Hydrocarbon extracts of the hepatopancreas of crabs (Chionectes opilio and Hyas coarctatus) and of the visceral mass of scallops (Placopecten magellanicus) from previous studies in Conception Bay and other locations around Newfoundland (Hellou et al., 1993, 1994) were also analyzed. Identification and quantification of hydrocarbons was performed using a Hewlett-Packard 5890 GC coupled with a 5970 mass spectrometer equipped with a 25 m CP-Sil 5 column and He carrier gas
Generation of biogenichydrocarbonsduring a spring bloom (Injector -275°C; Detector -300°C; 35°C for 1.5 min, increased to 280 °C at 2 °C/min where it remained for 10 min). The isotopic compositions of the individual hydrocarbons were determined using a VG Isochrom system consisting of a Hewlett Packard 589011 gas chromatograph coupled via a combustion interface and cold trap to a VG Optima isotope ratio mass spectrometer. The overall design, specifications, and performance of this machine are discussed by Freedman et al. (1988), and the facility used in this study is specifically described by O'Malley et al. (1994) and O'Malley (1994). Gas chromatographic conditions were identical to those used for GC-MS analyses. All carbon isotopic measurements are reported in conventional delta (6) notation relative to the Pee Dee Belemnite (PDB) standard [l~13Cs = 1 0 0 0 * {(13C/12C)s/(13C/ 1 2 C ) P D B - - 1}]. As reported by O'Malley et al. (1994) and O'Malley (1994), measurements generated by the equipment used generally have a precision of better than 0.3%o, and are accurate to within approximately 0.6%0, depending on the nature of the sample. Inaccuracies in GC/C/IRMS can arise due to the coelution of compounds and as a result of errors in the removal of the isotopic contribution of the background (Matthews and Hayes, 1978; Hayes et al., 1989). Samples with a significant background UCM (unresolved complex mixture) were spiked with pyrene and benzo(b)fluoranthene of known isotopic compositions as internal standards to monitor the effectiveness of the background correction. No significant problems due to background interference were encountered in the samples studied. RESULTS AND DISCUSSION
H y d r o c a r b o n distributions
Spring plankton samples (dominantly diatoms) contained primarily n-heneicosahexaene (HEH), a suite of eight C2s highly branched isoprenoid (HBI) alkenes, pristane, three isomers of phytadiene, and squalene (raw concentration data shown in Appendix A and selected molecular structures shown in Appendix B). Also present in lower concentrations were an unidentified branched C17 mono-olefin, two unidentified isomers of a branched C21 mono-olefin, and a series of n-alkanes from nC15 to n - C 3 3 with a CPI close to 1. The HBI alkenes (2 triene isomers, 4 tetraene isomers, and 2 pentaene isomers, all with a parent structure based on that of 2,6,10,14,18-pentamethyl-7-(3-methylpentyl)-pentadecane), appeared in almost identical ratios in all plankton samples (Fig. 2). Fall bloom plankton (dominantly dinoflagellates) contained primarily pristane, HEH, and squalene, but no HBI alkenes. Conception Bay bottom surface sediments contained the same suite of C25 HBI alkenes, squalene, OG 26/3~4--C
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210
T. Bieger et al.
HEH, and phytadienes as found in surface water plankton, as well as a series of strongly odd-dominant C21 33 n-alkanes. A complex mixture of tricyclic and pentacyclic terpenoids, dominated by diploptene (hop-22(29)-ene) was also present. Subsamples of the grab from anoxic layers ( > 10cm) in the sediment contained virtually the same hydrocarbon assemblage as surface sediments, except for lesser quantities of shorter chain ( < C25) n-alkanes, and no HEH. The nearshore and estuarine sediment samples contained primarily pristane, odd chain-length C23 33 n-alkanes, various terpenoids, and, in several locations, different isomers of C2o C25 HBI alkenes not detected in mid-bay samples. Riverine sediment samples contained primarily odd chain-length C23 33 n-alkanes and a series of terpenoids dominated by diploptene. The biogenic hydrocarbon assemblages of crabs and scallops were dominated by HB1 alkenes, again appearing in the same relative abundance as in Conception Bay surface water plankton and deep bay sediments (also compare Grand Banks sediments; Fig. 2). The crab samples also contained abundant squalene. The only hydrocarbon identified in the diatom cultures was HEH. The cultures of T. nordenskioldii, F. cylindrus, and N. seriata produced a single isomer identical to that extracted from Conception Bay plankton. The culture of F. striatula, however, produced two separate, isomers of HEH, one of which was not found in the natural samples. Isotopic compositions
The isotopic compositions of the hydrocarbons are summarized in Fig. 3a c (see Appendix A). Most of the known algal products found in plankton and sediments, such as HEH and pristane, had isotopic compositions between - 2 5 and -28%o. The HBI alkenes, however, were in all samples consistently depleted by at least 2%o (mean 613C = - 33%o) relative to most of the other known marine biogenic compounds. Among the four pairs of HBI alkene isomers, the later eluting isomer was in each pair consistently enriched in ~3C. The C20 25 alkenes found in the near-shore sediments were all significantly enriched in 13C (mean 613C = - 20.3%0) relative both to co-occuring hydrocarbons and to the C25 HBI alkenes in the mid-bay samples. The HBI alkenes in crab and scallop samples were isotopically similar to the same compounds in plankton tows and sediments. Squalene was relatively enriched (mean 613C = - 2 4 % 0 ) , whereas the C25 HBI alkenes were all strongly depleted (from -30.6 to -40.5%0). The average 613C of the n-alkanes in spring plankton fell over the course of the bloom from -23.7%0 to -29.6%o. The long-chain n-alkanes (>Czs) found in all sediment samples analysed were all consistently depleted in 13C (613C < -30%o) compared with shorter chain-length homologues.
a.
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,5'~C (Oloo) Fig. 3, Isotopic compositions of aliphatic hydrocarbons in (a) plankton, (b) mid-bay sediments, and (c) nearshore sediments (bars denote 1 S.D.). The HEH produced by the cultures of T. nordenskioldii, F. cylindrus, and N, seriata, was isotopically identical to that extracted from natural plankton. The two separate isomers produced by F. striatula, however, were depleted by almost 4%o relative to the HEH in the other cultures. Bulk spring bloom particulate organic matter (POM) in Conception Bay has a 613C value between approximately -21%o and -23%o (Ostrom, 1992). Since lipids are normally expected to be depleted relative to total biomass by roughly 3 to 4%o as a result of fractionation during early synthetic stages (Monson and Hayes, 1980), the isotopic compositions of most of the marine biogenic hydrocarbons in this study fall within the expected range for local bloom phytoplankton. Notable exceptions to this pattern are the C25 HBI alkenes, discussed below. The durability of the isotopic signatures of hydrocarbons in the water column of Conception
Generation of biogenic hydrocarbons during a spring bloom Bay is demonstrated by the consistency of the isotopic compositions of HBI alkenes in plankton, sediments and benthic macrobiota. Similarly, extensive degradation of HEH in the water column does not appear to affect the isotopic composition of this highly labile compound, as surface water and bottom sediment ~513C values for HEH are identical within instrumental precision. H B I alkenes
The consistent distribution and isotopic signature of the HBI alkenes over a wide geographic area would tend to suggest that they are synthesized by one organism during the spring bloom. Based on the recent work of Volkman et al. (1994) documenting C25 HBI production in the diatom Haslea ostrearia, a diatom species other than one of those cultured in this study would appear to be the most likely source. As described by Freeman et al. (1994), however, such an origin would be expected to result in a relative enrichment in 13C, due both to the more exhaustive use of dissolved CO2 during the blooms in which diatoms commonly grow, and to the capability of some diatoms of assimilating 13C-enriched bicarbonate. C25 HBI aikenes were, in fact, among the most isotopically enriched hydrocarbons found by these authors in Black Sea and the Cariaco Trench particulate organic carbon. The marked depletion observed in this study among HBI alkenes relative to co-occurring known diatom products (both isoprenoid and non-isoprenoid, and especially HEH) could indicate that these compounds have some alternate source in Conception Bay. This alternate origin is further supported by the observation that while Rhizosolenia setigra, a diatom species reported to synthesize C30 homologues of the C25 HBI alkenes (Volkman et al., 1994), was present in abundance in Conception Bay, no C30 HBI aikenes were found in any samples from the area. As shown by Laws et al. (1995), however, the isotopic composition of primary producers, such as marine diatoms is also a function of growth rate, in that the isotopic discrimination factor involved in the assimilation and fixing of dissolved inorganic carbon (DIC) is reduced during periods of intense growth. Thus, compounds synthesized before or after a bloom, when growth rates are lower, would be expected to have lower 613C values. It has been suggested by some that production of C25 HBI alkenes in the diatom H. ostrearia is associated with the rise of these pennate diatoms in the water column and the onset of growth (S. Rowland, oral communication). It is thus possible that the low ~513C values of the HBI alkenes in Conception Bay are due to their synthesis, still by diatoms, but only before the main growth phase of individual organisms, before the onset of extensive photosynthesis and carbon assimilation during the spring diatom
211
increase. It is possible that the other slightly depleted branched alkenes in the plankton tows (brC21:l and brClT:l) are of similar origins, produced perhaps slightly later than the more strongly depleted C25 HBI alkenes. Based on this model, the other hydrocarbons detected will have been synthesized during or just after the main growth phase of the spring diatom increase. The particularly intense isotopic depletion seen in the C25 HBI aikenes in Conception Bay could also be partially due to early synthesis of these compounds in deeper water. Ostrom (1992) reported DIC 613C values in the deeper waters of Conception Bay (below approximately 50 m) to be consistently lower (by approximately 2-4%o) than in surface waters. Thus, while the isotopic compositions of the C25 HBI alkenes initially suggest a non-diatom origin, the low 613C values these compounds exhibit may merely be a reflection of the timing of the synthesis of these compounds. The molecular distribution and enriched 13C signatures of the HBI alkenes in nearshore and estuarine samples suggest that these compounds have a source that is distinct from that of the mid-bay HBI alkenes. The enrichment seen in these compounds conforms more closely with a standard mid-bloom algal (diatom) origin, and may also be partially a result of slightly higher water temperatures and greater productivity/growth rates in these waters. It is also possible that the nearshore compounds are derived from sedentary benthic biota, which, due to transport limitations in their diffusive boundary layers, may assimilate heavier isotopes more readily than mobile organisms (France, 1995). H E H and squalene
HEH (n-C21:6) is synthesized by a wide variety of marine algae (especially diatoms) primarily during periods of rapid growth and active cell division (Schultz and Quinn, 1977; Blumer and Thomas, 1965; Blumer et al., 1970). Squalene, a C30 isoprenoid, is commonly found in diatom blooms (e.g. Osterroht and Petrick, 1982; Matsueda et al., 1986). The exact functions of these compounds in marine algae are un:' :ar, although it has been suggested that squalene could be used to control buoyancy. Given the large number of possible source organisms for these compounds, the isotopic compositions of HEH and squalene in Conception Bay are surprisingly constant. The isotopic similarity of HEH and squalene exemplifies the lack of isotopic contrast observed in this study between straightchain and isoprenoid hydrocarbons in general. However, as shown by the variations in the 613C of different isomers of HEH synthesized by the culture of F. striatula, differences in the biosynthetic pathways of related hydrocarbons can in some cases be associated with marked isotopic differences. Although previous authors have found fatty acid
212
T. Bieger et al.
desaturation to be associated with a preferential loss of Z3C (Fang et al., 1993), the lack of a significant isotopic depletion among these highly unsaturated hydrocarbons suggests that relatively little isotopic discrimination occurs during desaturation. In fact, the fatty acid 22:6~o3, from which HEH is believed to be derived, has been reported in Conception Bay mussels (present presumably from algal dietary intake) to have a lower 613C (approximately -29%o; Murphy and Abrajano, 1994), than the HEH in the present study.
"26 -27 _~ -211
-~ ~ -29 ~ .~ ro -31 -32 -33
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15 t 8 17 18 19 20 21 22 23 24 28 2q, 27 28 29 30 31 32 33
Alkane Carbon Number
Pristane a n d phytadienes
In the absence of phytane, pristane in the marine environment is generally accepted to be derived from degradation of the phytol side chain of chlorophyll (Avigan and Blumer, 1968). Phytadienes are also believed to have a similar origin (Blumer and Thomas, 1965). Although these compounds are isotopically identical in mid-bay sediments, they follow distinct trends during the spring bloom. In general, especially in the mid-bloom samples, pristane is enriched in n3C, as would be expected for a compound produced largely during periods of high productivity, high growth rates, and high CO2 demand. The 6~3C of pristane decreases later in the bloom, possibly as a result of the general decrease in growth rates and the greater expression of isotope effects associated with hydrocarbon synthesis. The 6~3C of the phytadienes, however, rises from an average of-27.4%0 at mid-bloom to -25.4%0 at the end of the bloom. Because many different photosynthetic organisms produce chlorophyll during a plankton bloom, these isotopic fluctuations may be the result of the production and mixing of chlorophyll of differing isotopic composition from a succession of bloom organisms. n-Alkanes
The smooth distribution ( C P I ~ 1) among the series of C15_33 n-alkanes observed in the spring bloom plankton samples is often taken to indicate a petroleum origin. Although residual traces of lubricating oil contamination from urban runoff and outboard motor exhausts were detected in some plankton and sediment samples (discussed in Bieger et al., 1996), the change in 613C among the Cls-2s n-alkanes over the course of the spring bloom suggests that these compounds are of recent biogenic origin. Similar n-alkane distributions have in fact been documented in many unpolluted regions (e.g. Matsueda and Handa, 1986; Serrazanetti et al., 1991; Nichols et al., 1988). The shift in 613C during the bloom could be caused by the mixing of alkanes from different sources, perhaps from a succession of different species. Alternatively, the 13C depletion in late bloom samples could again be a reflection of the less rapid growth and resultant more intense fractionation of carbon isotopes during the tail of
-26
b, M o d e l sources
-27 -28
~
.2s
~
-3o
m,oom(cPt-
11
-31 -32 -33
32 33 Alkane Carbon Number
Fig. 4. (a) Mean isotopic composition of n-alkanes from all sediments and (b) carbon chain lengths and isotopic compositions of three proposed sources of n-alkanes in sediments. the bloom. If this latter explanation is the case, then the appearance of this shift only among nalkanes (and not in known algal products such as HEH) suggests that these hydrocarbons are of a non-algal, possibly microbial, origin. The consistent depletion among the long chain (> C25) odd-dominant n-alkanes found in all riverine, nearshore, and mid-bay sediments clearly reflects the origin of these compounds in terrestrial plant leaf waxes (e.g. Rieley et al., 1991, 1993). A summary of average n-alkane isotopic compositions for all sediment samples combined is presented in Fig. 4(a). Two patterns are evident in this figure. First, there is a general decrease in 613C with increasing alkane chain length. This trend could be the result of fractionation of carbon isotopes during progressive elongation of the fatty acids that are the precursors of linear hydrocarbons, as suggested by Fang et al. (1993). More likely, though, it is a reflection of the predominantly terrestrial source of long-chain n-alkanes. Secondly, this decrease in 613C is more pronounced among odd chain-length n-alkanes than among even chain-length homologues, resulting in a sawtooth pattern featuring relatively ~3C-enriched odd-chain length n-alkanes in the Ct5-20 range and relatively 13C-depleted oddchain length homologues in the C28-33 range. This pattern can be explained by the dominance of odd n-alkanes in most organic matter sources. Since odd
Generation of biogenic hydrocarbons during a spring bloom chain-length homologues are more abundant, the isotopic compositions of these compounds should be less altered by mixing with alkanes from isotopically distinct sources than the compositions of the less abundant even chain-length homologues. Odd chain-length n-alkanes should thus isotopically more closely resemble the sources from which they are derived. This pattern suggests the mixing of an odd-dominant, isotopically relatively heavy (i.e. marine) Cl5 2o n-alkane assemblage with an odddominant, isotopically more depleted (i.e. terrestrial) C2s-33 n-alkane assemblage. These two sources also contribute some of the even chain-length nalkanes in Conception Bay. However, the consistent deflection of the even homologue isotopic compositions to the center of Fig. 4(a) suggests a third major source of n-alkanes of intermediate isotopic composition which may be bacterial or petroleum. Although it is possible that more than three sources contributed to the overall isotopic signature shown in Fig. 4(a), at least three primary sources of nalkanes appear to be required as shown in Fig. 4(b).
CONCLUSIONS (1) Overall, no clear or consistent isotopic distinction or trend was apparent between hydrocarbons of distinct or differing biochemical origins, e.g. between isoprenoids and linear hydrocarbons, or between saturated and unsaturated compounds. In general, the isotopic compositions of biogenic compounds in this study appeared to be primarily a reflection of the carbon fixing mechanism of the organisms producing the compounds, with variations related to changes in growth rate and CO2(aq) demand superimposed on these basic patterns. (2) Several fluctuations or apparent discrepancies in isotopic composition observed in this study (e.g. among C25 HBI alkenes and in spring bloom n-alkanes) may be related to changes in growth rates. It is suggested that the timing of synthesis of a biomolecule during a plankton bloom, or during the growth cycle of a bloom organism, may be a more important factor in determining isotopic composition than previously recognized. Future studies involving more detailed sampling over the course of plankton blooms and throughout the growth cycles of isolated organisms should be undertaken to investigate the isotopic 'imprint' left by the timing of synthesis. (3) Significant isotopic differences were observed between some compounds produced via slightly different pathways in different organisms (e.g. HEH in different cultures). The possibility of inter-species biosynthetic differ-
213
ences thus must always be considered when making inferences from sedimentary isotopic patterns. (4) The isotopic compositions of the hydrocarbons analyzed are fairly durable markers, as they were not altered by degradation (HEH) or cycling through sediments and benthic macrobiota (C25 HBI alkenes). (5) The mixing of organic matter from different sources, containing hydrocarbons of differing distributions and isotopic compositions (e.g. terrestrial, marine, and bacterial) can be recognized and modeled using the isotopic compositions of n-alkanes. (6) Clearly, more extensive study of the 13C composition of contemporary hydrocarbons is necessary before ancient sedimentary patterns can be fully understood and interpreted with authority. Associate E d i t o r - - B . R. T. Simoneit Acknowledgements--This work was supported by the
Natural Science and Engineering Research Council (TAA) and the Canadian Green Plan Toxic Chemicals Program (JH). T. Bieger received support from the A.G. Hatcher Scholarship Fund, the School of Graduate Studies at Memorial University and the Government of the Province of Newfoundland and Labrador. REFERENCES
Avigan J. and Blumer M. (1968) On the origin of pristane in marine organisms. J. Lipid Res. 9, 350-352. Bieger T., Abrajano T. A. and Hellou J. H. (1996) Petroleum biomarkers as tracers of lubricating oil contamination. Mar. Poll. Bull. 32, 270-274. Blumer M., Mullin M. M. and Guillard R. R. L. (1970) A polyunsaturated hydrocarbon (3-6-9-12-15-8-heneicosahexaene) in the marine food web. Mar. Biol. 6, 226-235. Blumer M. and Thomas D. W. (1965) Phytadienes in zooplankton. Science 147, 1148-1149. Fang J., Abrajano T. A., Comet P. A., Brooks J. M., Sassen R. and MacDonald I. A. (1993) Gulf of Mexico hydrocarbon seep communities. XI. Carbon isotopic fractionation during fatty acid biosynthesis of seep organisms and its implication for chemosynthetic processes. Chem. Geol. 109, 271-279. France R. L. (1995) Littoral-pelagic differences in algal carbon isotopes. Mar. Ecol. Prog. Ser, (in press). Freeman K. H., Wakeham S. G. and Hayes J. M. (1994) Predictive isotopic biogeochemistry: hydrocarbons from anoxic marine basins. Org. Geochem. 21,629-644. Freedman P. A., Gillyon E. C. P. and Jumeau E. J. (1988) Design and application of a new instrument for GC-isotope ratio MS. Am. Lab. 8, 114-119. Kohnen M. E. L., Schouten S., Sinninghe Damste J. S., de Leeuw J. W., Merritt D. A. and Hayes J. M. (1992) Recognition of paleobiochemicals by a combined molecular sulfur and isotope geochemical approach. Science 256, 358-362. Hayes J. M., Freeman K. H., Popp B. N. and Hoham C. H. (1989) Compound-specific isotopic analyses: a novel tool for reconstruction of ancient biogeochemical processes. Org. Geoehem. 16, 1115-1128. Hellou J., Upshall C., Payne J. F., Naidu S. and Paranjape M. A. (1993) Total unsaturated hydrocarbons
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and polycyclic aromatic hydrocarbons in molluscs collected from waters around Newfoundland. Arch. Environ. Contain. Toxicol. 24, 249-257. Hellou J., Upshall C., Taylor D., O'Keefe P., O'Malley V. and Abrajano T. (1994) Unsaturated hydrocarbons in muscle and hemolymph of two crab species, Chionectes opilio and Hyas coarctatus. Mar. Poll. Bull. 28, 482-488. Laws E. A., Popp B. N., Bidigare R. R., Kennicutt M. C. and Macko S. A. (1995) Dependence of phytoplankton carbon isotopic composition on growth rate and [CO2~q)]: Theoretical considerations and experimental results. Geochim. Cosmochim. Acta 59, 1131 1138. Llorente G. A., Farran A., Ruiz X. and Albaiges J. (1987) Accumulation and distribution of hydrocarbons, polychlorobiphenyls, and DDT in tissues of three species of Anatidae from the Ebro Delta, (Spain). Arch. Environ. Contam. ToxicoL 16, 563-572. Matthews D. E. and Hayes J. M. (1978) Isotopic-ratiomonitoring mass-spectrometry. Anal. Chem. 50, 1465 1473. Matsueda H. and Handa N. (1986) Vertical flux of hydrocarbons as measured in sediment traps in the eastern North Pacific ocean. Mar. Chem. 20, 179-195. Matsueda H., Handa N., Inoue I. and Takano H. (1986) Ecological significance of salp fecal pellets collected by sediment trap experiments in the eastern North Pacific. Mar. Biol. 91,421-431. Monson K. D. and Hayes J. M. (1980) Biosynthetic control of the natural abundance of carbon 13 at specific positions within fatty acids in Escherichia coil J. Biol. Chem. 255, 11435 11441. Murphy D. E. and Abrajano T. A. Jr (1994) Carbon isotope compositions of fatty acids from mussels from Newfoundland estuaries. Est. Coast. Shell" Sci. 39, 261 272. Nichols P. D., Volkman J. K., Palmisano A. C., Smith G. A. and White D. C. (1988) Occurrence of an isoprenoid C25 diunsaturated alkene and high neutral lipid content in Antarctic sea-ice diatom communities. J. Phycol. 24, 90 96. O'Malley V. P. (1994) Compound-specific carbon isotope geochemistry of polycyclic aromatic hydrocarbons in eastern Newfoundland estuaries. Ph.D. Thesis,
Memorial University of Newfoundland, St. John's, Newfoundland. O'Malley V. P., Abrajano T. A. Jr and Hellou J. (1994) Determination of the 13C/12C ratios of individual PAH from environmental samples: Can PAH sources be apportioned? Org. Geochem. 21, 809-822. Osterroht C. and Petrick G. (1982) Aliphatic hydrocarbons in particulate matter from the Baltic Sea. Mar. Chem. 11, 55-70. Ostrom N. E. (1992) Stable isotope variation in particulate organic matter and dissolved inorganic compounds in a northern t]ord: implications for present and past environments. Ph.D. Thesis, Memorial University, St. John's, Newfoundland. Rieley G., Collier R. J., Jones D. M., Eglinton G., Eakin P. A. and Fallick A. E. (1991) Sources of sedimentary lipids deduced from stable isotope analyses of individual compounds. Nature 352, 425-427. Rieley G., Collister J. W., Stern B. and Eglinton G. (1993) Gas chromatography/isotope ratio mass spectrometry of leaf wax n-alkanes from plants of differing carbon dioxide metabolisms. Rapid Commun. Mass Spectrom. 7, 488~491. Schoell M., McCafferty M. A., Fago F, J. and Moldowan J. M. (1992) Carbon isotopic composition of 28,30-bisnorhopanes and other biological markers in a Monterey crude oil. Geochim. Cosmochim. Acta 56, 1391 1399. Schoell M., Schouten S., Sinninghe-Damst6 J. S., de Leeuw J. W. and Summons R. E. (1994) A molecular organic carbon isotope record of Miocene climate changes. Science 263, 1122 -1130. Schultz D. M. and Quinn J. G. (1977) Suspended material in Narragansett Bay: fatty acid and hydrocarbon composition. Org. Geochem. 1, 27-36. Serrazanetti G. P., Conte L. S., Carpen4 E., Bergami C. and Fonda-Umani S. (1991) Distribution of aliphatic hydrocarbons in plankton of Adriatic sea open waters. Chemosphere 23(7), 925 938. Volkman J. K., Barrett S. M. and Dunstan G. A, (1994) C25 and C30 highly branched isoprenoid alkenes in laboratory cultures of two marine diatoms. Org. Geochem. 21,407-413.
Generation of biogenic hydrocarbons during a spring bloom
215
APPENDIX
Tables o f (1) Raw Concentration Data and (2) Chromatographic Conditions with Retention Indices. a: Plankton tows and scallops (all concentrations in/~g/g dry weight, all J3C values in per mil vs. PDB (tr. - - trace, n.d. - - not detected, n.m. - - not measured P L A N K T O N TOWS April 15 Plankton conc del 13C
May 18 Plankton conc. del ~3C
May 20 Plankton conc. del JaC
N ov 8 Plankton conc, del 13C
Scallop (visc. mass) conc. del 13C
0.31 0.68 0.71 0.62 0.40 0.37 0.34 0.37 0.37 0.43 0.46 0.43 0.40 0.34 0.15 0.12 0.09 0.06 0.03
n.m. -25.5 -23.2 -24.3 -24.1 -23.4 n.m. -23.7 -23.4 -23.3 -23.3 -23.2 -21.4 -22.8 -24.0 -23.5 -23.5 -22.9 -21.4
0.17 0.50 0.84 1.14 1.38 1.35 1.31 1.38 1.65 1.98 2.49 2.05 1.78 1.36 1.11 0.45 0.34 0.25 0.17
n.m. -28.0 -26.4 -27.3 -27.2 -27.2 -29.1 -27.6 -27.4 -27.3 -27.2 -27.2 -27.3 -27.2 -27.7 -27.2 -27.5 -27.4 -27.4
0.18 0.27 0.46 0.46 0.55 0.62 0.71 0.79 1.01 1.37 1.65 1.48 1.68 1.12 0.92 0.37 0.18 0.15 0.11
n,m. n,m. -29.7 -30.7 -29.8 -30.0 -30.6 -30.0 -29.0 -29.7 -29.2 -29.1 -29.3 -28.8 -29.1 -28.6 -29.3 -30.1 -30.9
1.13 0.28 0.56 0.39 2.54 1.07 1.35 1.13 1.69 2.25 3.49 3.38 5.02 2.54 6.48 3.21 3.38 0.62 1.24
n.m. n.m. n.m. n.m. -25.4 n.m. n.m. n.m. n.m. n.m. -26.4 -26.3 -26.6 n.m. -27.5 n.m. -27.1 n.m. n.m.
n.m. n.m. n.m. n.m. n.m, n.m, n.m, n.m, n.m, n.m, n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m.
n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m.
5.85 0.31 n.m. n.m. n.m. n.d. n.d. 15.39 5.85 9.23 8.00 0.77 0.62 2.92 0.46 12.31
-23.5 -25.4 -26.8 -27.9 -27.4 n.d. n.d. -34.2 -34.8 -35.2 n.m. n.m. n.m. n.m. n.m. -26.3
7.74 0.45 n.m. n.m. n.m. n.d. n.d. 9.92 2.35 5.21 2.35 1.18 1.18 2.19 1.01 10.26
-25.0 -27.6 -26.7 -27.5 -27.3 n.d. n.d. -38.7 -35.7 -37.2 -37.4 -34.3 -35.4 -36.6 -34.5 -25.1
1.87 0.22 n.m. n.m. n.m. n.d. n.d. 9.89 3.11 4.94 2.38 0.92 0.92 2.56 1.28 8.24
-27.5 -30.8 -24.9 -25.5 -25.8 n.d. n.d. -38.5 -35.6 -36.0 -39.7 -30.7 -31.3 -34.4 -28.8 -25.5
21.98 0.39 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. 5.07
-26.3 n.m. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.m.
n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m.
n.m. n.m. n.m. n.m. n.m. n.m. n.m. -33.6 -30.8 -34.4 n.m. n.m. n.m. -32.9 n.m. n.m.
24.62 0.92 2.00 1.23 n.d. n.d. n.d. n.d.
-26.9 -27.9 -29.3 -28.3 n.d. n.d. n.d, n.d.
14.97 2.01 3.03 2.02 n.d. n.d. n.d. n.d.
-26.6 -31.9 -32.3 -30.1 n.d. n.d. n.d. n.d.
15.56 0.18 1.70 0.77 n.d. n.d. n.d. n.d.
-26.4 n.m. -35.0 -32.1 n.d. n.d. n.d. n.d.
22.54 n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.m. n.d. n.d. n,d. n,d. n,d. n,d. n.d.
n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m.
n.m. n.m. n.m. n.m. n.m. n.m. n.m. n.m.
n-alkanes
nC15 nC16 nC17 nCl8 nCl9
nC20 nC21 nC22
nC23 nC24 nC25 nC26 nC27 nC28 nC29 nC30
nC31 nC32
nC33 Isoprenoids pritane phytane neo-phytadiene 1,3-phytadiene 2,4-phytadiene brC20:l brC20:1' brC25:3 brC253' brC25:4a brC25:4b brC25:4a' brC25:4b' brC25:5 brC25:5' Squalene
Other HEH brC17:l brC21:l brC2 1:l' brC23:2a brC23:2b brC25:4c brC25:3b
2,4-phytadiene brC20:1 brC20:1' brC25:3 brC25Y brC25:4a brC25:4b brC25:4a' brC25:4b' brC25:5 brC25:5' Squalene Other HEH brC 17:1 brC21:l brC21:1' brC23:2a brC23:2b brC25:4c brC25:3b
1,3-phytadiene
n-alkanes nCl5 nCl6 nC17 nC18 nCl9 nC20 nC 21 nC22 nC23 nC24 nC25 nC26 nC27 nC28 nC29 nC30 nC31 nC32 nC33 lsoprenoids pritane phytane neo-phytadiene
-27.8 n.m. n.d. n.d. n.d. -11.5 n.m. -34.8 -30.2 -34.4 -31.7 -35.8 -30.2 -33.2 -26.3 n.m.
-26.1 -26.8 n.d. n.d. n.d, n.d. n.d, n.d.
0.36 0.03 n.d. n,d, n.d. 0.05 0.05 1.05 0.57 0.67 0.57 0.20 0.18 0.38 0.05 0.38
0.46 0.04 n.d. n.d. n.d. n.d. n.d. n.d.
0.16 0.30 0.20 0.27 0.19 0.56 0.20 0.63 0.16 0.54 0.09 0.25
0.15
0.05
0.11
-29.3 -29.3 -27.0 -29.0 -28.4 -29.4 -29.3 -28.9 -29.4 -30.2 -29.7 -30.2 -30.5 -28.9 -30.6 -30.1 30.5 30.5 n.n.
0.09 0.12 0.11 0.11
n.d. 0.02 n.d. n.d. n.d. n.d. n.d. n.d.
0.22 n.d. n.d. tr. tr. 0.04 0.04 1.16 0.64 0.40 0.30 0.20 0.15 0.30 0.20 0.47
n.m. 0.04 0.08 0.10 n.m. 0.10 0,29 0.24 0.56 0.32 0.66 0.38 1.01 0.41 1.16 0.29 0.99 0.11 0.42
n.d. n.m. n.d. n.d. n.d. n.d. n.d. n.d.
n.m. n.d. n.d. n.m. n.m. n.m. n.m. -32.3 -27,7 32.9 -26.9 -29.7 -31.6 -28.3 -27.7 n.m.
n.m. n.m. n.m. n.m. n.m. n.m. -28.8 -28.3 -29.5 -30.8 -30.4 -31.2 -30.6 -31.4 -31.1 -31.0 -31.5 -29.8 -32.6
Conc. Bay (30 cm) conc, del 13C
MID BAY SEDIMENTS
Conc. Bay (surf.) conc. del 13C
n.d. tr n.d. n.d. 0.12 0.09 0,09 n,d,
0.03 0.03 n.d. n.d. n.d. 0.03 0.09 n.d. n.d. 0.46 tr. 0.21 n.d. 0.52 0.18 n.d.
0.33 0.14 0.51 0.15 0.30 0.05 0.12
0.11
0.02 0.03 0.07 0.03 0.13 0.02 0.09 0.05 0.29 0.09 0.25
n.d. n,m. n.d. n,d. -19.5 -21.7 -24.2 n.d.
n.m. n.m. n.d. n.d. n.d. -22.4 n.m. n.d. n.d. -20.1 n.m. -21.1 n.d. -17.56 -23.6 n.d.
-23.8 -23.8 n.m. -27.7 -22.6 -28.1 -21.5 -27.9 -26.2 -28.5 -27.9 -28,9 -28.6 -28.9 -30.1 -28.8 -30.4 n.m. -32.4
Spaniards Bay conc, del 13C
n.d. n.d. n,d. n.d. n.d. n.d, n.d. n,d.
0.09 0.06 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d, n.d. n.d.
0.05 0.06 0.09 0.10 0.16 0.15 0.28 0.23 0.35 0.27 0.38 0.30 0.50 0.26 0.54 0.18 0.46 0.09 0.28
n.d. n,d, n.d, n.d, n.d, n.d. n.d. n,d.
-27.5 -27.0 n.d. n.d. n.d. n,d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d, n.d. n.d.
-26.8 -26.1 -26.6 -27.3 -27.1 -27.4 -27.6 -27.9 -28.5 -28.1 -29.0 -28.4 -29.7 -29.4 -30.7 -28.5 -31.2 n.m. -31.9
Avondale conc. del 13C
NEARSHORE SEDIMENTS
n.d. n.d. n.d, n.d, n,d. n.d. n.d. n.d,
0.13 0.09 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
tr. 0.01 0.04 0.01 0.04 0.04 0.11 0.04 0.20 0.07 1.19 0.06 0.58 0.07 0.56 0.07 0.49 0.03 0.19
n.d. n.d. n.d. n.d. n.d. n,d. n,d. n,d.
-29.8 -29.1 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.m. n.m. -29.0 n.m. -27.7 -25.5 -28.0 -28.9 -29.5 -28.9 -29.8 -28.4 -29.7 -29.0 -30.8 -29.0 -30,4 n.m. -31.7
St. Phillip's conc. del 13C
n.d. 0,02 n.d. n,d. 0.13 0.33 0.31 0.28
0.04 0.04 n.d. n.d. n.d. 0.03 0.02 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
0.03 0.03 0.10 0.05 0.35 0.07 0.36 0.13 0.53 0.16 0.52 0.15 0.54 0.14 0.55 0.09 0.39 0.02 0.11
n.d. n.d. n.d. n.d. -18.8 n.m. -18.0 -20.6
-29.5 -26.5 n.d. n.d. n.d. -16.4 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
-28.9 -29.8 -24.8 -28.6 -20.3 -28.6 -19.9 -28.7 -23.6 -29.5 -26.7 -30.0 -27.6 -29.2 -30.5 -29.8 -31.7 -30.2 -31.8
South River conc. del 13C
ESTURINE SEDIMENTS
b: Sediments (all concentrations in #g/g dry weight, all 13C values in per mil vs. PDB (tr. - - trace, n.d. - - not detected, n.m. - - not measured
n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
0.07 n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.d. n.d. n.d. tr. 0.02 0.02 0.09 0.03 0.16 0.04 0.16 0.04 0.34 0.06 0.32 0.02 0.22 n.d. 0.05
n.d. n.d. n.d. n.d. n.d. n.d. n,d, n.d.
-30.5 n,d, n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.d. n.d. n.d. n.m. -28.4 -29.0 -29.8 -31.5 -28.9 -31.1 -30.3 -32.9 -30.6 -31.2 -32.2 -31.5 -33.5 n.d. -34.5
Topsail conc. del t3C
n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.d. n,d, n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.d. n.d. n.d. n.d. n.d, n.d. n.d. 0.85 16.98 4.24 36.08 16.13 123.09 2.12 72.16 tr. 16.55 tr. 2.12
n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.m. -31.5 n.m. -31.5 -30.0 -31.1 n.m. -31.9 n.m. -32.0 n.m. -31.6
Holyrood conc. del 13C
n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.d. n.d. n.d. n.d. n.d. n.d. n,d, n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.d. n.d. 0.64 0.49 0.90 0.90 2.54 1.19 3.43 1.04 3.73 1.19 4.48 1.34 6.27 0.67 3.73 0.30 1.49
n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
n.d. n.d. -31.8 -26.7 -31.1 -26.7 -31.6 -32.5 -30.4 -32.1 -32.9 -33.7 -33.0 -33.1 -32.1 -31.3 -31.8 -31.4 -31.5
Job's Cove conc. del J3C
RIVERINE SEDIMENTS
W
Compound C-20 highly-branched isoprenoid compounds br-C20:1 br-C20:1 C-25 highly-branched isoprenoid compound suite (Plankton tows/mid-bay samples, macrobiota): br-C25:3 br-C25:3' br-C25:4a br-C25:4b br'C25:da' br-C25:4b' br-C25:5 br-C25:5' C20-25 branched compounds (nearshore/esturine samples): br-C23:2a br-C23:2b br-C23:3a br-C25:4¢
Retention index (R.I.) and characteristic major ion fragments of selected compounds. Gas chromatograph: HP 5890GC + 5970MSD, 70 eV electron impact. Column: CP-Sil 5 column, 25 m × 0.25 mm i.d., film thickness 0.12 ~m. Conditions: He carrier gas @ 1 "L/min, 1 mL splitless injection, inj. @275 °C, det. @300 °C. Temperature Program: 1.5 min @ 35 °C; 2°C/min to 280°C. Characteristic major fragment ions (base ion first) 69, 83, 111, 181, 196, 210, 280 69, 83, 126, 140, 196, 210, 280 83, 165, 233, 261,291,346 83, 165, 233, 261,291,346 69, 109, 180, 231,233, 259, 275, 344 69, 163, 233, 259, 289, 344 69,109, 149, 180, 205, 259, 275, 344 69, 123, 163, 231,259, 289, 344 69, 177, 218 260, 273, 342 69, 217, 273, 342 55, 95, 179, 207, 266, 277, 320 55, 95, 179, 207, 266, 277, 320 55, 149, 233, 261,289, 346 69, 163, 218, 259, 273, 275, 344
R.I 1690 1705 2046 2089 2077 2080 2118 2123 2110 2156 2084 2091 2105 2138
t~
0 0
Z
e~
0
0
0
g~
£
T. Bieger et al.
218
APPENDIX Selected Molecular Structures
a. 2,6,10-trimethyl-7-(3-methyl)-dodecane (C2o HBI alkene parent structure)
b. 2,6,10,14-tetramethyl-7-(3-methylpentyl)pentadecane (C25 HBI alkene parent structure)
c.n-heneicosahexaene
d. squalene
e. neo-phytadiene
f. 1,3-phytadiene
g. 2,4-phytadiene