Dissolved organic carbon and volatile fatty acids in marine sediment pore waters

(;eochvmro er Cormochumra Acta Vol. 44, pp. 1977 lo 1984 0 Pergamon Press Ltd 1980. Punted in Great Bnta~n

Dissolved organic carbon and volatile fatty acids in marine sediment pore waters MICHAEL J. BARCELONA Illinois State Water Survey. Box 232, Urbana, IL 61801, U.S.A. (Received

8 January

1980; accepted in reckedform

29 July 1980)

Abstract-The results of a study of the contribution of microbial metabolic products to total dissolved organic carbon (DOC) levels in coastal sediments are presented. The data indicate that acidic volatile compounds make up a substantial fraction of pore water DOC’s in both oxic and anoxic pore waters of coastal marine sediments. Formic, acetic and butyric acids are the principal volatile species identified at levels exceeding 10pM. Acid concentrations are up to five times higher in anoxic pore waters than in oxic waters. Volatile organic acids show promise as indicators of diagenetic processes in marine sediments and of the ecological succession of microorganisms, in particular.

INTRODUCTION

The importance of microorganisms to the composition of soils and aquatic sediments has been recognized for many years (LOHMANN, 1908). The involvement of microorganisms in the catabolism of both natural and synthetic substrates dictates that they impact critical fluxes within the global carbon cycle. Microorganisms play a pivotal role in the processes of early diagenesis of aquatic sediments. Since marine organic sedimentary input is particulate and mainly refractory, the soluble organic matter in pore waters must be generated in situ. Evidence for microbial transformations is clearly shown in comprehensive organic geochemical studies (BROWN et al., 1972; NIPSENBAUMet al., 1972; IKAN et al., 1975a,b,c; ANDER~QN et al., 1977). The bulk of the effort to date has been restricted to sparingly soluble fatty acids, alcohols, hydrocarbons, and pigments of long-term geochemical import (EGLINTON, 1973; HAJIBRAHIMet al., 1978; SALI~T et al., 1979). Direct biological evidence of microbial effects on sedment diagenesis is sparse (OPPENHEIMER, 1960; JORGENSEN,1978a). This may be attributed to the difficulties in sampling, isolation and culture of marine microorganisms. Counting techniques show little evidence of microbial activity below 30cm in marine sediments (ZOBELL and RITTENBERG, 1948; KAPLAN and RITTENBERG,1964). However, these measurements may not correlate well with activity (STARKEY, 1968). JORGENSEN (1978b) has demonstrated that activity correlates poorly with measured numbers of sulfate reducers in coastal sediments. Indirect evidence of microbial activity exists from studies of inorganic chemical species in marine sediments (SHOLKOVITZ, 1973; GOLDHABER et al., 1977; MURRAY et al., 1978). Direct chemical indications of microbial activity in the past have been restricted to studies dealing with the disappearance of easily assimilable substrates. notably: sugars and amino acids

(DEGENSet al., 1963; BROWN et al., 1972: HARE 1973). carbohydrates (LYONS et al., 1979). Recent pore water results reported by HENRICHS and FARRINCTON (1979) point out the unique character of the soluble amino acid distributions as opposed to those previously reported on dried acid-hydrolyzed sediments. Although the pore waters contain 2P100 x the dissolved organic carbon (DOC) of oceanic waters (WANGERSKY,1975; LYONS et uI., 1979) relatively little is known of the nature of the soluble organic compounds. Most pore water DOC measurements have been made by dry combustion of evaporated residues or by wet oxidation of acidified, nitrogen purged water samples followed by quantification of evolved C02. Since these procedures probably result in the loss of low molecular weight compounds, such DOC data represent a minimum level for the dissolved material. LYONS et al. (1979) have noted that nearly 30% of the dissolved compounds remain uncharacterized. Clearly the necessity exists for the study of pore water organic chemistry as a vital complement to the work on whole sediments. The need is particularly acute for volatile compounds which likely evade detection in DOC measurements. The volatile fatty acids are a natural starting point for the study w-hich serve as both metabolites and substrates for microbiological activity (DOELLE, 1975). HOERING (1967) reported the determination of C2&, volatile fatty acids in vacuum dried surface sediments from the California borderland. Acetic. propionic and butyric acids made up more than X0”< of the free, and oxidatively hydrolyzable compounds recovered. More recently, MILLER rt u/. (1979) reported the analysis of C,-C, fatty acids in acidic ethyl acetate extracts of carbon-rich sediments from Loch Eil. These workers noted the high concentration of acetic acid relative to longer chained homologs and its irregular distribution with depth in a reducing core.

1977

M. J. BARCELONA

1978

The present work began with the development of a new analytical approach which permits the analysis of formic acid as well as Ct-CS volatile acids in aqueous samples (BARCELONA et ai., 1980). Results of analyses of marine sediment pore waters follows with a discussion of the significance, rections of the research.

limitations

and future di-

EXPERIMENTAL

Samples in the NE Pacific were collected to provide offshore sediments from both oxic and anoxic conditions. Gravity cores of oxic sediments (32.5 mm x 1 m) were taken at the head and mouth of the Newport Submarine Canyon at depths of 20 and 450m (33” 30.9’N, 117” !&SW). Sampling was conducted from the R/V Osprey (California Institute of T~hnology) in May 1979. Sub-cores of a 0.25 mz box core from (580m) were obtained on R/V Velcro IVCruise No. 1469 in the anoxic Santa Barbara Basin f34” 17.6’N. 119” 58.l’W). anorox. 4 km east of those taken by SHOL~OVITZ(1973).‘Ceil&se (acetate) butyrate core liners were used used after being alkaline leached (4 M NaOH) for 3 weeks, rinsed and then annealed at 65°C for at least 72 hr. This treatment was found to be most effective in avoiding volatile acid contamination. Core storage and squeezing was done at 4-6”C. Pore waters were obtained from 5 to 10 cm sections of the cores using an all Teflon@jViton* modification of the apparatus described by KALIL and GOLDHABER(1973). Precombusted (450°C) glass fiber filters were used in the pistons and pore waters were collected in precombusted 19/38 rd bottom flasks. Analytical psocrdures Dissolved sulfide was determined on 0.5 ml samples by Lauth’s Violet calorimetry (STRICKLAND and PARSONS, 1972). Sulfate was determined on 5 ml samples by BaSO+ gravimetry when sample volume permitted. Parallel aIiquots of 1ml were taken in precombusted vials for DOC analysis. One aliquot was acidified (100~1 85% H,PO,) and purged 5-f0min with dry, prepurjfied Nl while the second was left untreated. Both aliquots were then sealed in the vials and stored at 4°C until analysis. Analyses were performed with a Dohrman DC-50 Organic Carbon Analyzer equipped with flame ionization detection. The instrument’s organic carbon mode was used which provides for the stepwise determination of Volatile Organic Carbon (VOC) and Non-Volatile Organic Carbon (NVOC).

VOC is operationally defined as that volatile at 90-c (drying temp.) which is subsequently trapped on Porapak Q@ and thermally desorbed prior to admission into the combustion train to be converted into methane for quantification. Measurement of acidified~purged and untreated aliquots in parallel therefore provides a measure of acid volatiles lost in the purge step. It is assumed that trapping and desorption efficiencies are IO?;, for all volatile compounds. This assumption was found to be valid within experimental error (+6%) for acetate spiked samples. The remaining volume 5-25 mI was adjusted to pH 7.5-8.0 and stored at 4°C for stlbseqlient ~~ctermiilation of volatile acids. The method has been described in detail (BARCELONAet u/.. 1980). Briefly. the sampie is passed through a strong acid cation exchange resin in the K’ salt form (to insure removal of Ca* * + Mg” which would interfere with subsequent derivatization steps). qtnck frozen, lyophilized and then derivatized to form p-bromphenacyl esters following the procedure of DURSTC’Iuf. (1975). Separation was performed on a modular htgh pressure liquid chromatograph relative to authentic standards. Quantification of the esters was based on ultraviolet (254 nm) detection. All analyses were corrected for procedural blanks (co.1 l(g’l-‘) and standards made up in offshore surface seawater. The method provides a minimum detectable quantity of 50ng. Precision of the mean at the micromolar level range from 0.98 2 0.10 (formic to I.15 + 0.16 (pentanoic) at the 95%, confidence interval. Mean recoveries from three spiked samples were >90”, for formic through butyric acids, while pentanoic acid recoveries averaged 83%. RESULTS

Quantitative determinations of total DOC, VOC, and NVOC were performed on pore waters from the Santa Barbara Basin. The results are shown in Table 1. DOC levels were found to be relatively constant to a depth of 2.5cm. An abrupt increase occurs below this level and is largely due to an increase in NVOC. This general observation is in accord with the tendency towards humification noted by KR~M and SHOLKOVITZ (1977) in reducing pore waters. Variations in VOC are somewhat random in the upper 38cm of Santa Barbara Basin pore waters. At the very least, volatile compounds comprise I&‘,;, of the DOC and portions tanging from 1 to 30’!,, were lost

Table I. Dissolved organic carbon in Santa Barbara Basin sediment pore water dissolved organic carbon* (Subcore SB-1)

Depth in sediment (cm) o--5 6-10 11-15 16-20 21-25 26-30 31-35 36-38

Total organic carbon %t 3.1 2.7 2.2 2.1

Total DOC

Nonvolatile NVOC

Volatile VOC

Percent voc of DOC

96.7 85.9 77.8 82.2 94.3 140 159 150

51.5 47.9 53.4 56.9 56.X 110 136 122

45.2 38.0 24.4 25.3 37.5 30.2 22.9 28.2

47 44 31 31 40 22 14 19

? Percent of dry sediment weight after S~~OLKOVITZ (1973). * mg-I-’ DOC values are reproducible to + 13% at the 95% confidence interval. ** C,-Cs acids (as C-mg-1 _ ‘)/DOC.

Percent DOC lost on acidification 29 25 3.0 I.3 6.5 4.9 1.4 6.1

Percent DOC C,C,nzcids** ~15 22 7.2 I? 53 24 5.5 x.3

1979

Dissolved organic carbon and volatile fatty acids

marine sediments off the California Coast. Formic, acetic and butyric acids proved to be the most abundant compounds identified. Individual acid concentrations varied considerably with depth and exhibited subsurface maxima which parallel total acid maxima. This trend in volatile acid levels with the environment of sediment deposition mirrors that observed by previous workers. Figure 1 compares the present results with those of MILLER et al. (1979) from shallow marine sediments with relatively high terrestrial organic input. Acid concentrations are expressed in prnol. g- ’ dry sediment weight to facilitate comparison. From the figure, cores E-70 (oxidizing Co_ 223%) and LY-I (very reducing Corg 5-7x) (MILLER et al., (1979) had total acid concentrations in the near-surface 5-10 times those observed for offshore California coastal samples. The loch sediments probably reflect the heavy input of organic matter from a pulp and paper

on acidification and purging. Subsequent analytical determinations on these pore waters disclosed that the volatile acids (as mg-C. l- ‘) made up a significant portion of the DOC. In view of the amount of DOC represented in low molecular weight fatty acids, strong caution must be voiced on the use of DOC determinations by UV absorbance. Since these compounds exhibit minimal absorbance at wavelengths > 260 nm, methods utilizing 275 nm (AKIYAMA, 1971) or 280 nm (KROM and SHOLKOVITZ.1977) should be regarded as semi-quantitative. The fact that the DOC composition of individual samples is an environment dependent quality has been noted by WHEELER (1977) for coastal waters. V&tile

,futt_y ucids in murine sediments

Concentrations of pore water organic acids determined in this work are shown in Tables 2a,b,c for

Table 2.(a) Analyses of pore water in Santa Depth in sediment cm

Water content 0 0

Volatile acids mg.l-’

Individual Cz

C1

c&5 6610 II 15 16-20 21-25 26 ~30 31-35

88 84 75 71 68 66 61

29.8 47.1 14.8 6.5 121 70.3 25.0

204 424 60 44 1,270 332 308

91 159 201 33 471 147 103

36~ 38

59

21.4

154

68

Barbara

acid concentration C3 C‘Q”* ,.,,/ nM tr (cO.1) * tr * tr * * *

SB-1)

Basin (Subcore

C5

Dissolved sulfide

Dissolved sulfate

mM

mM

15 205 tr 28 548 549 53

130 tr * * tr tr *

tr (0.05) 0.06 0.08 tr 0.48 0.19 0.44

-21.1 25.5 22.0 __ __ __

I85

*

0.24

19.8

*Undetectable. -- Not determined. Table 2.(b) Analyses Water content “/0

Depth in sediment cm (r5 610 1 l-15 I6620 21-25 26~30 31-35 36 40

15 69 63 62 59 61 60 62

of pore water in Newport

Submarine

Volatile acids mg,l-’

Cl

Individual

15.2 8.3 17.3 25.1 29.6 7.1

94 54 66 395 269 51

111 51 51 116 280 74

tr * * * * *

9.9

52

72

11.2

90

19

C2

Canyon

(Gravity

acid concentration C3

C4,.+,...~

C5

PM

Core NP-2) Dissolved sulfide mM

Dissolved sulfate mM

48 15 110 tr tr tr

tr 38 * * * *

* * * * __ *

+

31

*

*

27.4 __ __ __ __ __ __

*

23

*

*

21.2

* Undetectable. - - Not determined.

Table 2.(c) Analyses Depth in sediment cm

Water content 0 0

of pore water in Newport Volatile acids mg.l-i

Cl

Submarine

Individual C2

(Gravity

Core NP-1)

c5

Dissolved sulfide mM

Dissolved sulfate mM

0.05 0.06 0.05 0.14 0.11

28.3 28.8 27.8 24.0 22.1

acid concentration c3

cd,“+

/
PM

I ll20

Cl0

75 73

48.3 17.4

555 111

304 204

* *

21-30 3140 4149

68 65 64

59.9 39.2 115

166 235 331

823 181 1,150

* tr tr

* Undetectable.

Canyon

51 tr 33 199 347

tr * * tr tr

1980

M. J.

BARCELONA

0 l A

5 -%

E-70 Miller, et aZ. (1979) LY-I Miller, et aZ. (1979) Hoering (1967) cl - c5

0

8 A

NP-I NP-2 ~6-1

i -

3’

5'

ACID CDNC~~TRATION (miCrOmOle5.g-I, dry weight)

Fig. I. Volatile fatty acids in marine sediments and pore waters. Profiles of total volatile fatty acids (~~rnol~g-’ dry wt) with depth (cm) in the sediment are shown from the work of HOERING (1967);* --Miller et al. (1979): 0, tand this work; q, m, A- for offshore California surface sediments. Scottish Loch sediments and California Borderland sediments, respectively.

mill effluent. The areas of dominant marine input (NP-I, NP-2 and SB-1) show total acid concentrations below 5 pmot -g- ‘. This fact is supported by whole sediment volatile acid levels reported by HOERING (1967), for an offshore basinal location, shown on the figure. Specific acid concentrations (Tables 2a, b, and c) show significant differences from oxic to reducing conditions. Although formic and acetic acids dominate both distributions, oxic (NP-2) pore waters contained traces of n-butyric. The reducing samples (NP-1. SB- 1) showed considerably more total C4 acid, of which more than half was the branched isomer. Among the additional amount of C4 in these samples

were several poorly resolved C, species which have not been identified. Profiles of individual acid species with depth in the sediment are shown in Fig. 2(a), and (b) for two of the sites. Cores NP-2 (2a) and SB-1 (2b) are from areas of similar depth which differ principally in the oxygen content of overlying waters and the sediment accumulation rate. The oxic Newport Canyon sediment underlies bottom waters with dissolved oxygen levels >0.4 ml. L- ’ (NORTH, 1979). There was no trace of dissolved sulfide nor sulfate depletion observed in this work. The pore water acid levels are below 400pmol.L-’ and the variation in acid profiles is tempered by: (I) the slow accumulation of sediment

1981

Dissolved organic carbon and volatile fatty acids ACID CONCENTRATION (micromoies~L-l) 200

400

I

I

600

0

200

400

600

800

I

I

I

I

1000

1200

,

I

I

I

0.2

I 0.3

I

0.1

0.4

0.5

0.6

SUBCORE SB-

CORE NP-

a

I

I

lb 0

1400

I

I

1

0. 7

DISSOLVED SULFIDE (millimoles.Lel)

Fig. 2. Volatile fatty acids in both oxic and anoxic marine pore waters. Profiles of pore water volatile acids (/tM) wth depth (cm) in recent oxic sediments from: (a) The Newport Canyon (NP-2). and from (b) The reducing sediments of the Santa Barbara Basin (SB-I). Figure 2(b) includes the observed profile of dissolved sulfide (mM) for the core.

under oxidizing

conditions

rt cd.. 1963), (2) bioturbation

(- 15cm./ 1000 yr,

DEGENS

by macroinfauna and (3) the utilization of organic matter by aerobic bacteria. The presence of some butyric acid and local maxima in the acetic and formic acid profiles are suggestive of ongoing fermentation and perhaps denitrification. The Santa Barbara basinal sample SB-I (Fig. 2b) showed more complex volatile acid distributions. The span of this core lies within the active sulfate reduction zone identified by G~LDHABER and KAPLAN (1974). Maxima in the acid profiles roughly correspond with the local maximum in dissolved sulfide observed between 20 and 25 cm. The similarity of concentration range between the organic microbial metabolites and inorganic products indicates that the volatile acids are important products of sediment diagenesis. The ‘preservation’ of their concentration profiles is probably the result of rapid sediment accumulation (- 400 cm~lOO0 yr, K~IDE er ul., 1972) and the lack of bioturbation in these unoxic sediments.

DISCUSSlOW

The present work is preliminary. Therefore. detailed conclusions on volatile organic acid geochemistry and particularly those concerning acid distributions indicative of microbial mediation of diagenesis must await further study. Thr most simple hypothesis that cm he @&x~d irl erplanution thut

these acids ure

the products

of the data is

qf irxornplete

utili-_utiorl

of‘ orqnic

matter.

.4s such,

mi-

their concentration profiles in sediment pore waters result from various factors including: type and source of organic matter, type and extent of microbial activity, availability of electron acceptors (0, NO;, SO:, etc.) or inhibitors, and finally decomposition of the volatile acids themselves. The two deep water sediment cores investigated in this study (NP-2 and SB-I ) receive predominantly marine inputs of organic matter. However, the Newport Canyon sediment accumulates slowly under oxic conditions which permits the utilization of the bulk of cro&l

M. J. BARCELONA

1982

A HYPOTHETICAL

SULFATE

REDUCTION

ECOSYSTEM

SULFATE REDUCERS (Desulfwibrio sp.1

3,&4 CARBON

ACIDS (9.g. Lactafe, Succmtel

FERMENTATIVE BACTERIA

SUGARS MONOMERS b

(Eaneroides sp. Clostridium

ANAEROBIC HETEAOTROPHS

SP.b t

i

CH4 t

f-l METHANOGENIC BACTERIA

Fig. 3. A hypothetical sulfate reduction ecosystem

the easily assimilable materials by aerobic bacteria before burial. The Santa Barbara Basin sediment rapidly accumulates under oxygen-poor conditions which preserves a portion of the labile organic substrate to be broken down by anaerobic organisms prior to the fermentative breakdown of more reduced refractory polymers. Thus in oxic pore waters one would expect low levels of volatile acid metabolites with rather featureless profiles until the onset of denitrification or fermentation when the oxygen has been depleted. This is essentially the case for core NP-2 (see Fig. 2a) though supportive data, i.e. NO; or NH; levels, is lacking. On the other hand, the reducing sediments of the Santa Barbara Basin present a more complex picture. Sulfate reduction is the principal diagenetic process observed in these sediments. Within the present hypothesis, one would expect low levels of the volatile acids to accumulate in the upper 1S-20 cm of the sediment as a result of the decomposition of easily assimilable organic matter. Deeper in the core, sulfate depletion occurs, inhibitory levels of sulfide accumulate and suitable organic substrate becomes less available, The sulfate reducers then find it increasingly more difficult to satisfy their metabolic needs. Judging from basinal sedimentation rates, this condition would be reached in about 40yr. Under such limitations, the sulfate reducers must rely on heterotrophic and fermentative microorganisms for their nutrition. SOKOKIN (1962) and BERNER (1972) have discussed this concept of a sulfate reduction ecology. More recently JP~RGENSEN(1977) extended the idea in his study of bacterial dynamics within the sulfur cycle of a coastal

sediment. In Fig. 3, I have outlined a possible structure for this ecological assemblage in order to better interpret the consequent distribution of volatile acid metabolites observed in the present work (Fig. 3). Briefly, sulfate reducers are supplied with 3 and Ccarbon acids from fermentative and anaerobic heterotrophic bacteria. Formic, acetic and butyric acids are produced as waste products with the possible utilization of acetic acid by a unique sulfate Desulfotomtlculum clcetoriduns reducing species, reported by WIDDELL and PFENNIC (1977). The methanogens present deeper in the core may supplement the energy needs of the ecosystem and, to some extent, utilize its waste products (JBERGENSEN,1978). The potential significance of methane as a carbon source for sulfate reduction has been recognized by MURRAY et al. (1978) in anoxic Saanich Inlet sediments. The formic acid maximum at 2@-25 cm is more pronounced than those of acetic and butyric acids since few anaerobic microorganisms (except for methanogens) reportedly utilize formate and it accumulates as a waste product. Both acetic and butyric acids may serve as substrates for fermentative or heterotrophic activity and are not allowed to build up as is formic acid. Much deeper in the core, methane production becomes the dominant process and since the volatile acids are all suitable substrates, their concentrations fall to very low levels. The work of PELTZER (1979) with acid-hydrolyzed sediments in the Santa Barbara Basin provides support for the preceding idealized scheme. He showed a definite maximum (- 0.5 prnol’ g _ ‘) in lactic acid content at 20 cm depth. Lactate is: a common metabolite

Dissolved organic carbon and volatile fatty acids of fermentative organisms, a preferred substrate of sulfate reducers and is present in reasonable proportion to acid metabolites which are not good substrates, e.g. formate, acetate, and butyrate; 1.73, 0.64 and 0.75 prnol. g- * dry weight, respectively. PELTZER further suggested from the variation in lactate enantiomer percentages that the sediment column may support mixed bacterial populations. This explanation of profiles of volatile acids within a reducing sediment is far from complete. The relative ubiquity of the acids is clear. If discrete redox zones of oxygen utilization followed by that of NP$-/NO:-, Fe (III) and Mn (IV), SOi- and finally CO2 are to be the chemically characterized, the volatile acids will prove marginally useful. Complete description of the microbial impact on sediment diagenesis will depend on the parallel use of indicator compounds specific to individual species of organisms. The work of JOHNS and ONDER (1975), ANDERWNet al. (1977), BROOKS et al. (1976, 1977), and PERRY et al. (1979) shows how faithfully certain compounds reflect in situ syntheses in unique environments. Soluble compounds in sediment pore waters pose a significant analytical challenge, but promise to be a valuable link between chemical and biological views of sediment diagenesis. CONCLUSIONS

1983

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ANDERSONR., KATES M., BAEUECKERM. J., KAPLAN I. R. and ACKWANR. G. (1977) The stereoisometic compo-

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1. Volatile organic compounds make up a substantial fraction of the dissolved organic matter (DOC) in marine pore waters. This fact and the acid composition of the volatiles suggests that methods of DOC determination based on COz quantification or U.V. DURST H. D.. M~LAXOM.. KIKTA E. J.. CONNELLY S. A. absorbance must be very carefully applied to marine and GRUSHKAE. (1975) Phenacyl esters of fatty acids via samples. crown ether catalysts for enhanced ultraviolet detection 2. Formic, acetic, n and iso-butyric acids are the in liquid chromatography. Anul. Chetn. 47. 1797-i X01 dominant volatile acids in marine pore waters reachEGLINTONG. (I 973)Chemical fossils: A combined organic ing levels exceeding 2OOpM in reducing environgeochemical and environmental approach. &>I,. Pure Appl. Chem. 34, 6 1I 632. ments. GOLDHARERM. B. and KAPLAN I. R. (1974) The sulfur 3. Profiles of acid metabolic products in anoxic cycle. In The Sea (Edited by E. D. Goldberg), Vol. 5. sediments correspond to marked gradients in levels of Chapt. 7. pp. 569-656. Wiley Interscience. dissolved sulfide. In the case of sulfate reduction, the GOLUHABERM. G., ALLEN R. C.. COCFIRAKJ. K.. RostYFELD J. K.. MARENS C. S. and BEHNERR. 4. (1977) acid assemblages support the idea of energy transfer Sulfate reduction. diffusion and bioturbation in Long within a sulfate reduction ecology. Island Sound sediments: Report of the FOAM group, 4. The volatile fatty acids alone provide only a genAm. J. Sci. 277, 193-237. eral indication of the succession of microorganisms HAJIBRAF~IM S. K., TIBBETTSP. J. C., WATTSC. D.. MAXwithin a marine sediment. Additional information on WELL J. R., EGLINTONG.. COLIN H. and G[ ICHONG. (1978) Analysis of carotenoid and porphyrin pigments of specific indicator compounds is expected to enhance geo~hemical interest by high-~rformance liquid the chemical study of microbial mediated diagenetic chromatography. Anal. Chem. 50. 549.-553. processes. HAREP. E. (1973) Amino acids, amino sugars and ammonia in sediments Ackno~ledgenietrts--The author is indebted to Dr WHEELER NORTH, California institute of Technology, for support during the early experimental stages of this work. Thanks are due to the support personnel of the R/V Osprr): (CIT) and the R/V Velcro iV(USC) for aid in the sampling. The author further thanks Drs FRAN HEIN, JAMESJ. MORGAN, HEINZ LOWENSTAMand RALPH WOI.FE, as well as Mr TOM STEPHANand PAMELA C. BEAVERS for help during varying stages of the work. The thoughtful review of Drs FARRINGTON,KAPLAN, MEYERS, PELTZER and SHOLKOVITZ is well appreciated.

from the Cariaco

Trench.

Z,liriai

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M. J. BARCELONA

1984

organic matter in recent marine sediment. II. Isoprenoids. Grochim. Cosmochim. Acta 39, 187-194. IKAN R. rt al. (1975~) Thermal experiments on alteration of organic matter in recent marine sediment. III. Aliphatic and steroidal alcohols. Grochim. Cosmochim. Acta 39, 195-203. JBERGENSEN M. H. (1978) Anaerobic formation of volatile acids in a chemostat. Eur. J. Appl. Micro&o/ BiotechnoL 6. 181-187. JOHNS R. B. and ONDER 0. M. (1975) Biological diagenesis: dicarboxylic acids in recent sediments. Geochim. Cosmochim. Acts 39, 129--l 36. J@RG~.NSENB. B. (1977) The sulfur cycle of a cosatal marine sediment (Limfjorden, Denmark) Limnol. Oceunoyr. 22, 814-832. JQRGENSEN B. B. (1978a) A comparison of methods for the quantification of bacterial sulfate reduction in coastal marine sediments. I. Measurements with radiotracer techniques. Geomicrobiol. J. 1, 1 l-27. JORGENSEN B. B. (1978b) A comparison of methods for the quantification of bacterial sulfate reduction in coastal marine sediments. III. Estimation from chemical and bacteriological field data GromicrohioL J. 1, 49-64. KALIL E. K. and GOLDHABER M. (1973) A sediment squeezer for removal of pore waters without air contact. J. Sedimenr.

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