Lipids in suspended matter and sediments from the East China Sea Shelf

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Lipids in suspended matter and sediments from the

East China Sea Shelf

Woei-Lih Jeng

a,

*

, Chih-An Huh

b

a_{Institute of Oceanography, National Taiwan University, Taipei, Taiwan, ROC} b_{Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan, ROC}

Received 28 June 2002; accepted 10 December 2003 (returned to author for revision 9 January 2003)

Abstract

Total suspended matter (TSM) and sediment samples from the East China Sea (ECS) Shelf were analyzed for

aliphatic hydrocarbons, alkanols and sterols. TSM samples showed a strong predominance of n-C

17

, pristane,

n-C

18

, n-C

19

, n-C

19:1

, n-C

21:6

and squalene, being attributed to plankton inputs. Stations with high percentages of these

hydrocarbons were generally situated near the Changjiang River mouth. Three stations with highest concentrations of

n-C

21:6

were located in the hot spot of chlorophyll reported in the literature (Gong et al., 1996, Continental Shelf

Research 16, 1561–1590). Phytol (the most abundant alcohol in TSM) and C

20:1

and C

22:1

n-alkenols were dominant in

the alcohol fraction, being representative of plankton contributions. The sterol composition of TSM was dominated by

24-methylcholesta-5,22E-dien-3b-ol, cholest-5-en-3b-ol, cholesta-5,22E-dien-3b-ol, and

27-nor-24-methylcholesta-5,22E-dien-3b-ol. Terrigenous lipids from the Changjiang River did not play a signiﬁcant role in TSM since they were transported

mainly southward. The sedimentary composition of these lipids showed a signiﬁcant depletion of planktonic compounds in

relation to other organic molecules. A comparison of these planktonic hydrocarbons in TSM and in sediments showed

that degradation is in the following order: n-C

21:6

> n-C

19:1

, n-C

19

, and n-C

17

> n-C

18

, pristane, and squalene. A

similar comparison for the alcohols showed the following degradation trend: C

20:1

and C

22:1

n-alkenols > phytol.

Carbon preference indices (CPIs) of suspended matter varied from 1.04 to 1.82(average 1.41), and those of sediment

ranged between 1.82and 3.74 (average 2

.81), reﬂecting higher contributions of the more refractory higher plant

n-alkanes in the sediments.

#

2004 Elsevier Ltd. All rights reserved.

1. Introduction

The main circulation patterns of the Changjiang

Estuary and adjacent East China Sea (ECS) can be

characterized by the northward ﬂow of warm (13

_{C) and}

saline (34 psu) waters of the Taiwan Warm Current

(TWC) and a southward ﬂow of the colder (5

_{C) and}

less saline (30 psu) waters of the Yellow Sea Coastal

Current (YSCC) (

Fig. 1

). During high river runoﬀ, one

part of the Changjiang plume with freshest water

extends to the south along the coast, and the other part

with low salinity extends oﬀshore toward the northeast

on average. However, during low river runoﬀ, the

sur-face plume only spreads toward the south (

Beardsley et

al., 1985

). The Changjiang River annually discharges

5 10

8

_{tons of sediment directly into the ECS}

(

Milliman and Meade, 1983

). This sediment is conﬁned

to the coastal zones of the ECS, being ultimately

trans-ported south and southwestward by the Changjiang

doi:10.1016/j.orggeochem.2003.12.002

www.elsevier.com/locate/orggeochem

* Corresponding author. Tel.: +886-2-23636040 301; fax: +886-2-23626092.

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Coastal Water (

Milliman et al., 1985

). Oﬀshore

transport is hindered by tidal currents and by the

northward movement of the Taiwan Warm Water

(

Milliman et al., 1989

).

Surface concentrations of suspended particles in the

ECS generally range from 1 to 100 mg/l in winter and

0.5 to 5 mg/l in summer. In winter near-bottom

con-centrations tend to be considerably higher than surface

values, largely due to resuspension of bottom sediments

during intense winter storms (

Millman et al., 1989

).

A detailed study of summer chlorophyll a distribution

indicates that there is a hot spot of chlorophyll a in

seawater on the mid-shelf of the ECS (

Gong et al.,

1996

). Previous studies on non-aromatic hydrocarbons

in suspended matter from the Changjiang Estuary (

Qiu

et al., 1991

) showed that anthropogenic and/or

petro-genic inputs were distributed around the river mouth,

being more widespread in winter than in summer. On

the other hand,

Sicre et al. (1993a)

studied n-alkanes

and polycyclic aromatic hydrocarbons in the suspended

particles from the Changjiang Estuary, and observed

that terrestrial and anthropogenic inputs prevailed.

Bouloubassi et al. (2001)

examined hydrocarbons in

surface sediments from the Changjiang Estuary and

concluded that the overall levels of anthropogenic

hydrocarbons were low in comparison to other areas

worldwide. Other studies in the Changjiang Estuary and

adjacent ECS were devoted to unraveling the

terrige-nous and marine sterols (

Tian et al., 1992; Sicre et al.,

1993b, 1994

).

Having this previous research in mind, the present

study clariﬁes what are the main sources contributing to

the lipid composition of suspended water particles and

sediments of the ECS. In addition, the inﬂuence of the

contributions from the Changjiang River to the ECS

will be assessed from the study of alkanes, alcohols and

sterols.

2. Experimental

2.1. Sampling

Eleven stations from the ECS mid-shelf were chosen

for sampling surface water (5 m), and nine stations for

surface sediments (

Fig. 1

). Sampling was performed

Fig. 1. Sampling sites on the East China Sea Shelf. Solid circles denote collection of both seawater and sediment samples; solid squares denote collection of water samples only. Contours are given in meters.

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between 29 May and 4 June 1999. Surface water (40–50

l) was collected with Niskin bottles on a rosette sampler.

Water was filtered in situ through glass fiber filters

(Whatman GF/F, 142mm diameter) right after

sam-pling. The ﬁlters were batch-washed with acetone,

methanol, and ethyl acetate several times prior to use.

The particulate-laden ﬁlters were stored at 20

_{C until}

analysis. Sediment samples were collected with a box

corer. The top (ca. 3 cm) sediment was sliced and kept

at 20

_{C until sample work-up.}

2.2. Sample preparation

Wet TSM-laden ﬁlters were freeze-dried. After adding

internal standards (n-C

24

D

50

and 1-heptadecanol), dried

TSM samples were extracted with a mixture of

di-chloromethane and methanol (1:1, v/v) for 24 h in a

Soxhlet apparatus. The lipid extract was then saponiﬁed

by reﬂux for 3 h with 0.5 N KOH solution in methanol.

The non-saponiﬁable lipids were separated by n-hexane

extraction four times and concentrated using N

2

gas.

The aliphatic hydrocarbon fraction and the fraction

containing fatty alcohols and sterols were isolated from

the neutral lipids by silica gel (5 g, deactivated with 5%

H

2

O) column chromatography using n-hexane (20 ml)

and a mixture of dichloromethane/methanol (4/1, v/v,

40 ml), respectively. The lipids between the two

frac-tions were eluted with n-hexane/dichloromethane (2/3,

v/v, 30 ml) and discarded. The isolated alcohols and

sterols were taken to dryness, redissolved in benzene,

and derivatized with N,O-bis(trimethylsilyl)acetamide.

2.3. Analysis by gas chromatography

An HP 5890A gas chromatograph equipped with a

split/splitless injector and a ﬂame ionization detector

(FID) was used for gas chromatographic analysis. An

SGE (Australia) OCI-5 cool on-column injector was

also ﬁtted in the gas chromatograph. Aliphatic

hydro-carbons were separated with an SPB-1 capillary column

(30 m 0.25 mm i.d.), and alkanols/sterols (as TMS

ethers) with an SPB-1 column (25 m 0.25 mm i.d.).

Oven temperature programming was 45–90

_{C at 15}

_C/

min and 90–270

_{C at 3}

_{C/min for aliphatic}

hydro-carbons, and 45–90

_{C at 15}

_{C/min and 90–250}

_{C at}

3 _{C/min, 30 min at 250}

_{C for alkanols/sterols.}

Identiﬁ-cation was made with co-injection of authentic

stan-dards and gas chromatography-mass spectrometry

(GC-MS). Compound quantitation was performed using

internal standards. Based on replicate analyses, the

analytical precision of lipids was calculated to be 2–8%.

The GC-MS analyses were performed with an HP 6890

GC (HP-1MS crosslinked methyl siloxane column, 30 m

0.25 mm i.d.) interfaced directly to an HP 5973

quadruple mass selective detector (electron impact,

electron energy 70 eV, scanned from 50 to 550 Daltons).

3. Results and discussion

3.1. Total suspended matter

3.1.1. Aliphatic hydrocarbons

A representative GC trace of aliphatic hydrocarbons

from suspended matter is shown in

Fig. 2

. Seven

pre-dominant components were n-C

17

, pristane, n-C

18

,

n-C

19:1

, n-C

19

, n-C

21:6

and squalene; other n-alkanes up

to C

35

were minor. This pattern was similar to the one

found at station 1 in DH2reported by

Qiu et al. (1991)

although in this latter case squalene was not found. The

7 hydrocarbons are produced chieﬂy from plankton

(

Winters et al., 1969; Blumer et al., 1971

) and for

sim-plicity are termed planktonically-derived hydrocarbons

(PDHCs) in the present study. High relative percentages

(80–94%) of the seven PDHCs were observed in the

hydrocarbon distributions of stations 10, 12, 14, 16, 22,

24, 32 and 36, and relatively low percentages (45–61%)

were found at stations 18, 20 and 34 (

Table 1

). Thus the

stations with high percentages of PDHCs were located

close to the Changjiang River. In contrast, a very

dif-ferent aliphatic hydrocarbon distribution pattern was

obtained in a previous study performed during high ﬂow

in September 1988 (

Sicre et al., 1993a

). In this case,

there was no predominance of the 7 PDHCs, and

n-C

19:1

, n-C

21:6

and squalene were absent in the

Chang-jiang Estuary. Relatively lower percentages (range 6–

27%, average 13%, calculated from their data) of

PDHCs were obtained in this previous case. Another

study reported the occurrence of ﬁve types of aliphatic

hydrocarbon distributions in the Changjiang Estuary by

Qiu et al. (1991)

. The results of the present study, based

on samples located farther oﬀ shore, only show two

distributions of n-alkanes that can be diﬀerentiated by

the proportion of PDHC’s, one with high amounts of

these alkanes and alkenes, and the other by near equal

concentrations of n-alkanes. In any case, the present

result suggests a weaker inﬂuence of the anthropogenic

and riverine inputs than in the previous studies.

In general both photosynthetic algae and bacteria

contain n-C

17

or pristane as the most abundant

hydro-carbon component (

Oro et al., 1967; Han et al., 1968;

Winters et al., 1969

). Non-photosynthetic bacteria may

have hydrocarbon distributions dominated by other

n-alkanes such as n-C

18

in E. coli, n-C

19

in Micrococcus

lysodeikticus, and n-C

20

in yeast (

Han et al., 1968

).

Seven samples (stations 12, 16, 18, 20, 22, 32 and 34)

showed higher abundance of n-C

18

or n-C

19

over n-C

17

(

Table 1

), which suggests a higher bacterial contribution

in these samples. n-C

19:1

accounts for 85–98% of

hydrocarbons in three species of marine blue-green

algae (

Winters et al., 1969

) and occurs in some

zoo-plankton species (Eucalanus sp.) (

Saliot, 1981

). Higher

concentrations of n-C

19:1

than n-C

17

were observed in 6

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and contribution from blue-green algae and copepods is

suggested.

The compound cis-heneicosahexa-3,6,9,12,15,18-ene

(n-C

21:6

) is known to predominate in ﬁve classes of

marine phytoplankton, notably (but not exclusively)

diatoms (

Blumer et al., 1971; Nichols et al., 1988

) and

has been generally related to primary productivity

(

Schultz and Quinn, 1977; Osterroht and Petrick, 1982

).

The highest concentrations in n-C

21:6

(56.7, 48.5 and 104

mg/g at stations 22, 24 and 32, respectively) were located

within the ‘‘hot spot of chlorophyll a’’, deﬁned from the

observation of chlorophyll a concentrations of 0.2mg

m

3

₍

_{Gong et al., 1996}

_{). These two concurrent ﬁndings}

suggest the occurrence of phytoplankton bloom every

summer at this site.

The

abundances

of

PDHCs

were

statistically

compared to test common sources. Because the data

are not normally distributed and include outliers, the

Spearman rank coeﬃcient of correlation is the more

appropriate statistical test. With this type of correlation,

data are measured on a ranking scale rather than the

equidistant scale used in the Pearson’s product-moment

correlation. The Spearman rank coeﬃcients of

corre-lation for the 7 PDHCs are given in

Table 2

, in which

tied ranks were assigned to the less-thans. As seen in

Table 2

, the 7 PDHCs were not well correlated,

sug-gesting diverse plankton sources. However, n-C

17

, n-C

18

,

n-C

19:1

and n-C

19

were signiﬁcantly correlated, possibly

indicating that they may derive mainly from

nano-plankton and piconano-plankton. As noted by

Wakeham and

Lee (1989)

, small particles collected by in situ ﬁltration

in the epipelagic zone are similar in composition to

phytoplankton. On the other hand, the correlation of

n-C

21:6

, pristane and squalene suggests a common source,

Fig. 2. (upper) Chromatogram of aliphatic hydrocarbons from the total suspended matter of station 14. (lower) Chromatogram of the alkanol/sterol fraction from the total suspended matter of station 22. Sterol identiﬁcations: (A) 24-nor-5a-cholest-22E-en-3b-ol, (B) 27-nor-24-methylcholesta-5,22E-dien-3b-ol, (C) 27-nor-24-methyl-cholest-22E-dien-3b-ol, (D) cholesta-5,22E-dien-3b-ol, (E) 5a-cholest-22E-en-3b-ol, (F) cholest-5-en-3b-ol, (G) 5a-cholestan-3b-ol, (H) 24-methylcholesta-5,22E-dien-3b-ol, (I) 24-methyl-5a-chol-est-22E-en-3b-ol, (J) 24-methylcholesta-5,24(28)-dien-3b-ol, (K) methylcholest-5-en-3b-ol+methyl-5a-cholest-24(28)-en-3b-ol(?), (L) methyl-5a-cholestan-3b-ol, (M) 23,dimethylcholesta-5,22E-dien-3b-ol, (N) ethylcholesta-5,22E-dien-3b-ol, (O) 24-ethyl-5a-cholest-22E-en-3b-ol, (P) 24-ethylcholest-5-en-3b-ol, (Q) 24-ethyl-5a-cholestan-3b-ol+unknown, and (R) 4a,23,24-trimethyl-5a-cholest-22E-en-3b-ol.

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Table 1

Concentrations (mg/g) of aliphatic hydrocarbons for total suspended matter

Compound Sample 10 12 14 16 18 20 22 24 32 34 36 n-C15 – – 0.094 1.92– – – – – – 3.00 n-C16 – – 0.171 1.74 0.540 – – 0.635 – – 1.93 n-C17 29.6 12.9 19.4 103. 3.59 – 27.6 13.5 36.1 0.214 13.2 Pr 3.25 2.63 0.692 4.01 0.519 – 1.35 4.17 5.36 – 4.06 n-C18 5.65 3.89 2.79 17.6 4.02 0.126 14.8 2.58 12.7 0.636 5.37 Ph 0.503 – 0.176 – 0.757 – – 0.461 – – 1.20 n-C19:1 38.9 11.27.5254.0 4.48 0.318 45.212.7 50.6 4.527.49 n-C19 15.1 18.5 14.9 122. 10.1 2.12 87.7 4.22 56.6 3.53 12.7 n-C20 0.996 0.639 0.506 1.94 3.35 0.315 2.54 0.539 1.66 0.448 1.64 n-C21:6 7.91 23.3 16.6 30.9 17.0 1.58 56.7 48.5 104. 8.49 43.3 n-C21 1.13 0.561 0.559 2.27 4.13 0.381 2.88 0.505 2.07 0.549 1.75 n-C22 1.08 0.498 0.776 1.46 4.09 0.412 2.20 0.653 1.96 0.583 1.98 n-C23 1.28 0.903 1.05 3.00 4.71 0.578 3.21 1.48 5.14 0.955 3.27 n-C24 0.577 0.654 0.559 1.56 3.13 0.426 2.20 1.37 3.43 0.651 2.32 n-C25 0.535 0.654 0.321 1.26 2.55 0.429 2.09 1.31 3.70 0.530 1.85 n-C26 0.461 0.420 0.142 0.709 2.92 0.358 2.14 0.940 2.61 0.579 1.24 n-C27 0.608 0.888 0.263 0.993 2.96 0.406 2.93 0.861 3.92 0.639 1.22 n-C28 0.598 0.748 0.198 0.709 2.79 0.398 1.92 0.609 3.27 1.01 0.693 Sq 7.01 13.1 6.93 26.0 16.6 1.36 49.1 11.9 57.4 1.16 27.1 n-C29 1.05 1.62 0.757 1.84 4.28 0.942 7.61 0.766 7.48 1.79 2.91 n-C30 0.587 0.934 0.359 1.80 2.10 0.318 2.99 1.14 4.60 0.831 2.12 n-C31 0.818 0.966 0.345 1.28 3.13 0.693 4.85 0.557 4.46 1.09 2.12 n-C32 0.440 0.592 0.215 0.871 1.34 0.246 2.37 0.305 2.69 0.677 1.39 n-C33 0.493 0.452 0.166 0.669 1.25 0.366 2.59 0.287 2.56 0.613 0.774 n-C34 0.336 – 0.130 0.790 0.627 0.215 1.13 0.165 1.74 0.369 1.24 n-C35 0.419 – 0.137 – 1.320.200 – 0.315 1.520.560 0.342 %PDHC 90 89 91 94 55 45 87 88 86 61 80 CPI 1.39 1.54 1.521.16 1.30 1.74 1.821.04 1.41 1.30 1.24 TSM 4.81 4.06 13.1 1.66 1.39 12.1 1.49 8.00 0.128 5.68 2.40

Pr=pristane; Ph=phytane; Sq=squalene

% PDHC=% planktonically-derived hydrocarbons

=% (n-C17+Pr+n-C18+n-C19:1+n-C19+n-C21:6+Sq) =PDHC/HC

CPI=carbon preference index ¼1 2 nC25þnC27þnC29þnC31þnC33 nC24þnC26þnC28þnC30þnC32 þnC25þnC27þnC29þnC31þnC33 nC26þnC28þnC30þnC32þnC34 =1.41(average)

TSM=total suspended matter (mg/l) –=less than 0.05 mg/g

Table 2

Spearman correlation coeﬃcients for 7 planktonically-derived hydrocarbons of suspended matter. The coeﬃcients were calculated using the rank values converted from lipid concentrations

C17 Pristane C18 C19:1 C19 C21:6 Squalene C17 1 Pristane 0.688 1 C18 0.827 0.533 1 C19:1 0.936 0.702 0.791 1 C19 0.836 0.487 0.900 0.864 1 C21:6 0.518 0.729 0.564 0.618 0.545 l Squalene 0.573 0.651 0.809 0.591 0.700 0.855 1

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either diatoms or zooplankton. In the ECS, the

phyto-plankton was composed of 140 species, 104 of which

belong to Bacillariophyceae (

Wu et al., 2000

). In

sum-mer and winter, copepods dominate the zooplankton

community (

Liu and He, 1990

). Diatoms and copepods

are both likely sources of n-C

21:6

, pristane and squalene.

On the other hand, a calculation of the carbon

preference index (CPI) in the range of C

25

–C

33

does not

show any consistent geographic distribution for these

minor n-alkanes which suggests that the terrigenous

input from the Changjiang River does not imprint the

TSM distribution.

Table 3

Concentrations (mg/g) of alkanols and sterols for total suspended matter

Compound Sample 10 12 14 16 18 20 22 24 32 34 36 Alkanols n-C14OH 1.17 2.29 0.339 2.51 4.82 0.497 7.00 3.17 6.08 1.30 4.59 n-C15OH 0.317 0.512 0.142 1.43 2.13 0.263 2.11 0.662 2.33 0.424 1.17 n-C16OH 5.68 13.7 1.37 19.2 16.2 6.97 70.2 21.6 36.7 12.2 34.4 n-C18OH 8.92 19.2 2.97 39.1 28.0 5.53 34.1 9.42 32.3 13.0 17.8 phytol 112 81.5 67.6 166 137 20.9 364 184 566 48.9 126 n-C19OH 1.07 2.08 0.442 2.29 7.11 0.289 2.73 1.22 5.63 1.15 1.66 n-C20:1OH 0.947 – – – – 11.5 93.8 31.3 11.5 9.86 48.6 n-C20OH 2.53 3.44 0.881 8.92 12.9 1.92 13.8 3.57 10.3 3.17 7.30 n-C21OH 1.08 1.85 0.407 3.06 4.01 0.740 7.722.69 3.18 0.730 3.47 n-C22:1OH 2.86 – – – 5.18 25.1 217 73.2 28.5 19.8 105 n-C22OH 30.2 42.6 9.16 79.6 166 10.6 108 26.4 46.3 15.4 52.3 n-C23OH 1.22 1.60 0.413 3.43 6.60 0.493 4.32 1.14 2.27 0.701 1.92 n-C24OH 3.58 4.32 1.18 9.41 19.4 1.42 12.4 2.97 7.27 2.04 5.30 n-C25OH 0.420 – 0.161 – 2.26 0.179 – 0.225 1.70 0.226 – n-C26OH 15.1 10.1 3.54 25.1 12.5 0.390 41.3 10.7 31.5 0.549 10.3 n-C27OH 0.488 – 0.558 – 8.15 – 3.76 0.9124.20 – 0.481 n-C28OH 3.47 7.77 1.20 5.49 52.5 0.594 16.2 1.29 21.0 1.98 7.16 Sterols A 0.760 0.900 0.300 1.77 1.09 1.16 3.76 0.687 2.46 0.571 1.07 B 28.2 43.1 9.20 39.8 21.8 5.34 151 43.9 91.1 31.0 44.4 C 1.50 – 0.436 – 2.20 0.445 10.2 1.80 – 1.62 3.63 D 36.4 60.7 21.3 106 45.7 9.28 202 22.2 138 27.1 51.2 E 3.923.14 0.8528.85 18.9 1.77 8.03 1.86 23.4 7.64 3.61 F 40.3 97.6 44.7 101 101 20.5 295 50.8 281 50.3 78.3 G 4.77 10.2 4.15 24.5 28.4 4.49 40.4 4.68 46.7 8.87 11.2 H 256 226 102 552 135 35.1 863 121 808 122 176 I 4.08 8.54 2.8215.4 19.23.36 30.3 3.55 28.9 5.00 8.92 J 18.0 47.2 21.2 68.0 54.2 9.17 101 36.8 127 18.0 26.4 K 8.53 21.4 9.85 55.0 40.3 7.61 62.7 6.03 41.8 10.9 5.86 L 1.51 2.78 0.933 7.15 9.27 1.22 7.72 0.954 3.76 2.16 – M 6.03 17.6 3.16 22.6 13.7 2.59 38.4 4.60 29.8 8.81 7.74 N 14.1 23.6 11.2 76.6 63.4 5.19 87.0 11.1 109 30.9 21.5 O 15.3 13.6 4.0241.3 30.8 6.21 55.9 11.1 56.210.7 10.6 P 27.9 76.0 32.9 102 65.5 11.0 260 46.8 221 65.3 83.7 Q 37.0 44.5 49.291.3 68.0 15.8 183 36.4 188 30.0 59.7 R 19.3 16.5 7.44 47.3 67.2 11.4 72.0 44.2 92.3 25.8 20.4 B+D+F+H 360.9 427.4 177.2 798.8 303.5 70.2 1511 237.9 1318 230.4 349.9 A R 523.6 713.4 325.7 1360 785.6 151.6 2471 448.5 2288 448.7 632.3 %major sterols 69 60 54 59 39 46 61 53 58 51 55 TSM 4.81 4.06 13.1 1.66 1.39 12.1 1.49 8.00 0.128 5.68 2.40

Sterol identiﬁcations: (A) 24-nor-5a-cholest-22E-en-3b-ol, (B) 27-nor-24-methylcholesta-5,22E-dien-3b-ol, (C) 27-nor-24-methyl-5a-cholest-22E-dien-3b-ol, (D) cholesta-5,22E-dien-3b-ol, (E) 5a-cholest-22E-en-3b-ol, (F) cholest-5-en-3b-ol, (G) 5a-cholestan-3b-ol, (H) 24-methylcholesta-5,22E-dien-3b-ol, (I) 5a-cholest-22E-en-3b-ol, (J) 24-methylcholesta-5,24(28)-dien-3b-ol, (K) 24-methyl-cholest-5-en-3b-ol+24-methyl-5a-cholest-24(28)-en-3b-ol(?), (L) 24-methyl-5a-cholestan-3b-ol, (M) 23,24-dimethylcholesta-5,22E-dien-3b-ol, (N) 24-ethylcholesta-5,22E-23,24-dimethylcholesta-5,22E-dien-3b-ol, (O) 5a-cholest-22E-en-3b-ol, (P) 24-ethylcholest-5-en-3b-ol, (Q) 24-ethyl-5a-cholestan-3b-ol+unknown, and (R) 4a,23,24-trimethyl-5a-cholest-22E-en-3b-ol. % major sterols=(B+D+F+H)/A R; TSM=total suspended matter (mg/l); –=less than 0.1 mg/g.

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3.1.2. Fatty alcohols

The distribution of n-alkanols observed in suspended

matter was similar among all stations, and was

domi-nated by shorter chain ( < C

22

) alcohols with phytol

being the most signiﬁcant constituent (

Fig. 2

,

Table 3

).

This distribution reﬂects a major contribution from

marine sources. In contrast, saturated alcohols from higher

plant waxes ( > C

22

) were present in a minor proportion,

indicating that terrigenous alcohols played a minor

role.

Among

the

shorter

chain

alcohols,

mono-unsaturated n-alkenols C

20:1

and C

22:1

can originate

from marine zooplankton especially calanoid copepods

(

Sargent and Lee, 1975; Saito and Kotani, 2000

). Both

C

20:1

and C

22:1

n-alkenols were not detected at the

sta-tions close to land (stasta-tions 12, 14, and 16) and were

present at much higher concentrations at the stations

farther oﬀshore (stations 20, 22, 24, 42, 34 and 36). This

spatial distribution suggests a cross-shelf gradient of

zooplankton, with higher abundances oﬀshore.

Spearman

correlation

coeﬃcients

showed

that

hexadecan-1-ol and C

20:1

and C

22:1

n-alkenols were

correlated (

Table 4

), their most likely source being

copepods (

Sargent and Lee, 1975

). Copepods are the

most dominant zooplankton in the Changjiang River

and its adjacent waters (

Liu and He, 1990

).

3.1.3. Sterols

All GC traces of sterols (

Fig. 2

) in the suspended

matter were very similar. The major feature was the

dominance of 24-methylcholesta-5,22E-dien-3b-ol

(bras-sicasterol-diatomsterol), cholest-5-en-3b-ol (cholesterol),

cholesta-5,22E-dien-3b-ol (22-dehydrocholesterol), and

27-nor-24-methylcholesta-5,22E-dien-3b-ol. They

accoun-ted for an average of 55% of total sterols (

Table 3

),

which ranks in the upper proportion of marine sterol

distributions when compared to particles sampled closer

to the shore (36, 44 and 57% as calculated from

Tian

et al., 1992; Sicre et al., 1993b, 1994

, respectively). In

the suspended matter, sterols common to diatoms,

dinoﬂagellates and zooplankton made up the major

proportion of the sterol fraction (

Goad and Withers,

1982; Volkman, 1986

) (

Table 3

). The biomarkers for a

given species of plankton are not always speciﬁc

enough to identify a single source (

Volkman, 1986;

Wakeham, 1995

). Stations 22 and 32 were distinguished

from other stations by their high concentrations of

24-methyl-cholesta-5,24(28)-dien-3b-ol

and

4a,23,24-trimethyl-5a-cholest-22E-en-3b-ol (dinosterol), but a

major contribution from dinoﬂagellates (

Volkman,

1986

) could not be conclusive.

Table 5

shows the Spearman correlations of the 18

sterols quantiﬁed. Almost all sterols were signiﬁcantly

correlated except

27-nor-24-methyl-5a-cholest-22E-dien-3b-ol. This sterol was the fourth most abundant and was

only correlated with 9 sterols of the 17 sterols. This

compound was found in suspended particles of the

Ta

ble 4 Spea rma n correlation coeffi cients for alka nols of suspe nded matte r. Th e coeffi cients were calculated usin g the rank values converte d fr o m lipid concen trations C14 OH C15 OH C16 OH C18 OH ph ytol C19 OH C20:1 OH C20 OH C21 OH C22:1 OH C22 OH C23 OH C24 OH C25 OH C26 OH C27 OH C28 OH C14 OH 1 C15 OH 0.945 1 C16 OH 0.936 0.855 1 C18 OH 0.791 0.873 0.755 1 phyt ol 0.855 0.845 0.836 0.7 1 C19 OH 0.882 0.955 0.736 0.891 0.764 1 C20:1 OH 0.4620.2 19 0.616 0.047 0.345 0.005 1 C20 OH 0.964 0.964 0.873 0.891 0.827 0.936 0.284 1 C21 OH 0.936 0.891 0.855 0.773 0.782 0.845 0.382 0.945 1 C22:1 OH 0.615 0.395 0.697 0.147 0.431 0.183 0.96 0.45 0.5321 C22 OH 0.827 0.864 0.691 0.864 0.673 0.891 0.075 0.918 0.927 0.229 1 C23 OH 0.845 0.9 0.7 0.891 0.718 0.927 0.051 0.936 0.918 0.211 0.991 1 C24 OH 0.845 0.9 0.7 0.891 0.718 0.927 0.051 0.936 0.918 0.211 0.991 11 C25 OH 0.028 0.135 0.195 0.195 0.056 0.093 0.143 0.005 0.084 0.005 0.079 0.009 0.009 1 C26 OH 0.736 0.755 0.664 0.727 0.9 0.718 0.196 0.773 0.736 0.248 0.736 0.782 0.782 0.0421 C27 OH 0.609 0.563 0.414 0.2 0.665 0.54 0.203 0.544 0.554 0.38 0.409 0.456 0.456 0.5 0.577 1 C28 OH 0.818 0.864 0.627 0.791 0.636 0.936 0.009 0.845 0.809 0.165 0.873 0.9 0.9 0.13 0.673 0.526 1 Numb ers in boldfa ce indica te valu es (exc ept diag onal) at the sign ifican ce level of a =0.0 5 (two-t ailed test).

(8)

Changjiang Estuary by

Sicre et al. (1994)

, but not by

Tian et al. (1992)

nor

Sicre et al. (1993b)

. This might

suggest the sterol from a group of marine plankton only

blooming in certain time and at some locations. The

three common sterols of higher plant origin,

24-methyl-cholest-5-en-3b-ol (campesterol),

24-ethylcholesta-5,22E-dien-3b-ol (stigmasterol) and 24-ethylcholest-5-en-3b-ol

(sitosterol), were correlated with most sterols of marine

origin,

possibly

implying

predominantly

similar

marine sources. As examples, some dinoﬂagellates and

diatoms contain 24-methylcholest-5-en-3b-ol (campesterol)

(

Volkman, 1986

). Among the 14 species of marine diatoms

from the CSIRO Culture Collection of Microalgae

(sources mainly from Australian waters), most of the

centric species have

24-methylcholesta-5,24(28)-dien-3b-ol (24-methylenech24-methylcholesta-5,24(28)-dien-3b-olester24-methylcholesta-5,24(28)-dien-3b-ol) and 24-methylch24-methylcholesta-5,24(28)-dien-3b-olest-5-en-

24-methylcholest-5-en-3b-ol (campesterol) as two of their major sterols (

Barrett

et al., 1995

). Four species of marine coccolithophorids

(from Plymouth Culture Collection, UK) have been

reported to contain 24-ethylcholesta-5,22E-dien-3b-ol

(stigmasterol) as the major component (

Volkman et al.,

1981

). 24-Ethylcholest-5-en-3b-ol (sitosterol) has been

found in diatoms, prymnesiophyceae, chlorophyceae,

and cyanobacteria (

Volkman, 1986

).

24-Ethylcholesta-5,22E-dien-3b-ol (stigmasterol) is the principal sterol in

diatom Amphora coﬀaeformis, while

24-ethylcholest-5-en-3b-ol (sitosterol) is the major sterol in diatom

Navi-cula pelliculosa

(

Gladu et al., 1991

). The present results

suggest that most sterols are derived from marine

sour-ces. However, in a previous study by

Sicre et al. (1994)

on sterols from the suspended particles of the

Chang-jiang Estuary, it was concluded from factor analysis that

24-ethylcholesta-5,22-dien-3b-ol was probably b-sitosterol,

a tracer of terrigenous inputs.

3.2. Comparison of TSM with sediment

3.2.1. Degradation of lipids

The sedimentary aliphatic hydrocarbon composition

in the nine samples studied was quite similar. The

unsaturated hydrocarbons n-C

19:1

and n-C

21:6

were in

trace to minor quantities, but squalene was a major

constituent (

Table 6

). The diﬀerence between suspended

particles and sediments could be attributed to the easy

degradation of labile hydrocarbons of algal (n-C

19:1

and

n-C

21:6

) origin relative to terrigenous components

(

Meyers et al. 1984; Gagosian and Peltzer; 1986

). In this

respect, a comparison of aliphatic hydrocarbons in

plankton, sediment trap particulates and sediments

from Dabob Bay indicates that most pronounced

decreases have been found for pristane and two

unsat-urated compounds (

Prahl et al., 1980

). Furthermore, in

Table 5

Spearman correlation coeﬃcients for sterols of suspended matter. The coeﬃcients were calculated using the rank values converted from lipid concentrations

A B C D E F G H I J K L M N O P Q R A 1 B 0.445 1 C 0.018 0.220 1 D 0.700 0.773 0.018 1 E 0.609 0.418 0.028 0.736 1 F 0.674 0.724 0.087 0.897 0.743 1 G 0.755 0.664 0.110 0.909 0.900 0.916 1 H 0.645 0.709 0.046 0.945 0.727 0.756 0.818 1 I 0.764 0.673 0.193 0.918 0.873 0.925 0.991 0.827 1 J 0.647 0.688 0.078 0.852 0.688 0.963 0.843 0.738 0.834 1 K 0.591 0.291 0.220 0.718 0.700 0.756 0.700 0.682 0.718 0.738 1 L 0.618 0.191 0.046 0.636 0.791 0.711 0.736 0.600 0.755 0.661 0.891 1 M 0.655 0.691 0.046 0.955 0.809 0.920 0.918 0.882 0.927 0.856 0.845 0.782 1 N 0.618 0.573 0.055 0.882 0.900 0.879 0.927 0.818 0.918 0.815 0.855 0.782 0.955 1 O 0.700 0.573 0.073 0.836 0.864 0.806 0.855 0.873 0.845 0.825 0.773 0.818 0.864 0.836 1 P 0.655 0.818 0.064 0.936 0.682 0.943 0.891 0.800 0.900 0.879 0.673 0.545 0.918 0.873 0.709 1 Q 0.645 0.573 0.028 0.836 0.691 0.870 0.827 0.764 0.818 0.893 0.691 0.545 0.782 0.818 0.727 0.845 1 R 0.636 0.645 0.229 0.709 0.873 0.834 0.864 0.664 0.855 0.802 0.618 0.691 0.773 0.809 0.855 0.745 0.691 1 Numbers in boldface indicate values (except diagonal) at the signiﬁcance level of a=0.05 (two-tailed test). Sterol identiﬁcations: (A) 24-nor-5a-cholest-22E-en-3b-ol, (B) 27-nor-24-methyl5,22E-dien-3b-ol, (C) 27-nor-24-methyl-5a-cholest-22E-dien-3b-ol, (D) cholesta-5,22E-dien-3b-ol, (E) 5a-cholest-22E-en-3b-ol, (F) cholest-5-en-3b-ol, (G) 5a-cholestan-3b-ol, (H) 24-methylcholesta-cholesta-5,22E-dien-3b-ol, (I) 24-methyl-5a-cholest-22E-en-3b-ol, (J) 24-methylcholesta-5,24(28)-dien-3b-ol, (K) 24-methylcholest-5-en-3b-ol+24-methyl-5a-cholest-24(28)-en-3b-ol(?), (L) 24-methyl-5a-cholestan-3b-ol, (M) 23,24-dimethylcholesta-5,22E-dien-3b-ol, (N) 24-ethylcholesta-5,22E-dien-3b-ol, (O) 24-ethyl-5a-cholest-22E-en-3b-24-ethylcholesta-5,22E-dien-3b-ol, (P) 24-ethylcholest-5-en-3b-24-ethylcholesta-5,22E-dien-3b-ol, (Q) 24-ethyl-5a-cholestan-3b-ol+unknown, and (R) 4a,23,24-trimethyl-5a-cholest-22E-en-3b-ol.

(9)

a deltaic environment, labile hydrocarbons of both algal

(C

15:1

, C

17:1

and C

21:6

etc.) origin have not been found in

the underlying sediments (water depths < 20 m) due to

prevailing oxic conditions (

Albaiges et al., 1984

).

Assuming that the PDHCs in sediments were deposited

from the overlying suspended matter. Their degradation

was assessed by the ratio between normalized

concen-tration in TSM and sediments. In both types of samples

PDHC concentrations were normalized to n-C

23

. The

ratio values vary over 2orders of magnitude, the highest

corresponding to the most labile compounds (

Table 7

).

By order of decreasing degradation, PDHCs were

ranked as follows: n-C

21:6

> n-C

19:1

, n-C

19

and n-C

17

>

n-C

18

, pristane and squalene. This result is similar to

that in

Albaiges et al. (1984)

. In the case of squalene, the

hypothesis that this compound was mainly from the

water column is not valid, as halophilic bacteria are

an important source of sedimentary squalene under

non-aerated

conditions

(

Tornabene,

1978

),

which

distorts the calculated ratio (

Table 7

).

Similar ratios may be calculated for the linear

alco-hols. In this case, n-eicosan-1-ol was used as a reference

compound since it is not substantially enhanced by

inputs of land or marine plants. Both C

20:1

and C

22:1

n-alkenols degrade faster than phytol i.e., by factors of 3–

4 (

Table 7

). Compared to n-alkanols, phytol is relatively

labile in sediment. Extractable phytol in sediments has

been shown to be highly reactive in studies from other

locations, partly as a result of its conversion to bound

phytol (

Jeng et al., 1997; Sun et al., 1998

).

Application of the same approach to the sterols

showed lower degradation values than PDHCs. These

low values indicate that sterols are relatively resistant to

degradation, which is in agreement with the results

Table 6

Concentrations (ng/g) of aliphatic hydrocarbons for bottom sediments

Compound Sample 10 14 18 20 22 24 32 34 36 n-C15 – – – – – – – 5 6 n-C16 2 – 5 4 6 3 3 15 18 n-C17 4 7 15 18 18 24 14 25 37 Pristane 6 3 10 11 9 329 1221 n-C18 4 1215 18 19 13 17 20 30 Phytane 1 4 5 6 7 5 6 6 11 n-C19:1 1 5 2 4 5 18 14 3 5 n-C19 3 13 11 18 13 16 13 16 2 4 n-C20 213 9 14 10 8 10 1219 n-C21:6 1 3 3 3 2 - 4 3 4 n-C21 8 20 11 24 18 12 16 18 26 n-C22 3 18 8 17 128 13 14 21 n-C23 5 31 17 33 2 2 14 2 6 32 39 n-C24 3 2 1 11 2 1 14 10 19 2 0 2 1 n-C25 5 40 18 43 2 7 15 33 42 40 n-C26 3 2 9 11 2 7 18 10 2 1 2 4 2 2 n-C27 7 65 29 69 43 22 51 74 56 n-C28 7 33 16 33 18 14 2 5 33 2 7 Squalene – – 115 154 105 150 144 105 198 n-C29 15 136 65 140 94 48 106 167 118 n-C30 13 60 44 81 45 45 50 6268 n-C31 14 167 77 171 112 51 127 217 136 n-C32 2 21 9 24 15 9 17 22 23 Diploptene 13 58 3270 47 28 53 81 57 n-C33 6 80 39 75 46 19 52 89 65 n-C34 1 9 7 13 7 5 8 13 13 n-C35 6 48 325236 27 33 4270 CPI 2.74 3.10 2.57 2.74 3.03 1.82 2.93 3.74 2.65

CPI=carbon preference index ¼1 2 nC25þnC27þnC29þnC31þnC33 nC24þnC26þnC28þnC30þnC32 þnC25þnC27þnC29þnC31þnC33 nC26þnC28þnC30þnC32þnC34 =2.81 (average) –=less than 1 ng/g

(10)

reported by

Saliot et al. (1991) and Quemeneur and

Marty (1992)

. It is noted that the three most readily

degraded sterols were

24-methylcholesta-5,22E-dien-3b-ol,

27-nor-24-methylcholest-5,22-dien-3b-ol

and

24-methylcholesta-5,24(28)-dien-3b-ol. These diatom and

dinoﬂagellate derived sterols appear to be relatively

more labile.

The

above

reported

comparisons

involve

the

assumption that the predominant lipid sources for the

sediments are only from the TSM, and that the

con-centrations sampled at 5 meter depth are representative

of the water column composition. Otherwise, the

ratios cannot be interpreted in terms of degradation

processes.

3.2.2. Carbon preference index of n-alkanes

Carbon preference indices (CPIs) of suspended matter

varied between 1.04 and 1.82with an average of 1.41

(

Table 1

), and those of sediment ranged between 1.82

and 3.74 with a mean of 2.81 (

Table 6

). The lower CPIs

in suspended matter than in sediment are similar to the

observations reported in Dabob Bay (Washington) in

which n-alkane CPI

20-34

averaged 2.52 in sediment traps

and 3.99 in surface sediments (

Prahl et al., 1980

).

3.2.3. Sterol concentration diﬀerence between TSM and

sediments

Despite the general similarity in the sterol distribution

of suspended matter (

Fig. 2

) and sediments (

Fig. 3

),

there are signiﬁcant diﬀerences in the relative

propor-tions of sterols. In TSM

24-methylcholesta-5,22E-dien-3b-ol was the most abundant constituent followed by

cholest-5-en-3b-ol (

Table 3

), but this order is reversed in

the sediments (

Table 8

), as currently observed in other

coastal marine sediments (

Harvey, 1994; Mudge and

Norris, 1997

). The predominance of cholest-5-en-3b-ol

in the sediments of the ECS suggests the

super-imposition of meiofaunal lipids (

Goad, 1978

). In this

respect, the studied sediments contained shell fragments

and cholesterol is usually the dominant sterol of

mol-lusks (

Ballantine et al., 1983

and references therein). At

station 18, the sterol proﬁles in TSM and sediment were

remarkably similar, which may reﬂect a major

con-tribution from resuspended sediment (

Tables 3 and 8

).

Table 7

Ratios of planktonically-derived hydrocarbons normalized to n-C23for TSM to those for sediments as well as ratios of alkenols, phytol and sterols normalized to n-C20OH for TSM to those for sediments

Compound Ratio

Hydrocarbons

Average (n-C17/n-C23)TSM/average (n-C17/n-C23)sediment 10

Average (pristane/n-C23)TSM/average (pristane/n-C23)sediment 1.6

Average (n-C18/n-C23)TSM/average (n-C18/n-C23)sediment 3.7

Average (n-C19:1/n-C23)TSM/average (n-C19:1/n-C23)sediment 28

Average (n-C19/n-C23)TSM/average (n-C19/n-C23)sediment 21

Average (n-C21:6/n-C23)TSM/average (n-C21:6/n-C23)sediment 130

Average (squalene/n-C23)TSM/average (squalene/n-C23)sediment 1.7

Alcohols

Average (C20:1OH/n-C20OH)TSM/average (C20:1OH /n-C20OH)sediment 15.4

Average (C22:1OH/n-C20OH)TSM/average (C22:1OH /n-C20OH)sediment 12.7

Average (phytol/n-C20OH)TSM/average (phytol/n-C20OH)sediment 4.0

Sterols

Average (27-nor-24-methylcholest-5,22-dien-3b-ol/n-C20OH)TSM/average (27-nor-24-methylcholest-5,22-dien-3b-ol/n-C20OH)sediment

4.7 Average (cholesta-5,22E-dien-3b-ol/n-C20OH)TSM/average (cholesta-5,22E-dien-3b-ol/n-C20OH)sediment 2.8

Average (cholest-5-en-3b-ol/n-C20OH)TSM/average (cholest-5-en-3b-ol/n-C20OH)sediment 1.4

Average (24-methylcholesta-5,22E-dien-3b-ol/n-C20OH)TSM/average (24-methylcholesta-5,22E-dien-3b-ol/ n-C20OH)sediment

5.3 Average (24-methylcholesta-5,24(28)-dien-3b-ol/n-C20OH)TSM/average (24-methylcholesta-5,24(28)-dien-3b-ol/

n-C20OH)sediment

3.6 Average (24-methylcholest-5-en-3b-ol/n-C20OH)TSM/average (24-methylcholest-5-en-3b-ol/n-C20OH)sediment 1.3 Average (24-ethylcholesta-5,22E-dien-3b-ol/n-C20OH)TSM/average (24-ethylcholesta-5,22E-dien-3b-ol/

n-C20OH)sediment

1.3 Average (24-ethylcholest-5-en-3b-ol/n-C20OH)TSM/average (24-ethylcholest-5-en-3b-ol/n-C20OH)sediment 1.8 Average (4a,23,24-trimethyl-5a-cholest-22E-en-3b-ol/n-C20OH)TSM/average

(4a,23,24-trimethyl-5a-cholest-22E-en-3b-ol/n-C20OH)sediment

(11)

3.2.4. Stanol/stenol ratio

Signiﬁcant diﬀerences exist between the stanol/stenol

ratios in suspended matter and sediments, involving

lower stanol content in the former (

Table 9

). Similar

diﬀerences between surface sediments and suspended

particles have been observed elsewhere, e.g., the shelf oﬀ

north Taiwan (

Jeng and Huh, 2001

). Suspended matter,

which probably represents the lower stanol content of

suspended particles, is consistent with their marine

plankton origin (

Volkman, 1986

). The conversion of

stenol to stanol by bacteria is expected to be slow in oxic

surface waters. In contrast, the high stanol/stenol ratios

of the shelf sediments may be caused by selective

degradation of stenols relative to stanols at the

Table 8

Concentrations (ng/g) of alkanols and sterols for sediments

Compound Sample 10 14 18 20 22 24 32 34 36 Alkanols n-C14OH 5 11 10 14 17 2 4 14 19 19 n-C15OH 3 9 6 9 13 15 9 14 12 n-C16OH 20 56 42 58 75 97 70 84 67 n-C18OH 10 55 39 59 63 48 53 60 68 phytol 79 469 345 469 473 839 365 306 457 n-C19OH 211 6 1211 8 8 11 15 n-C20:1OH 2– – – – 41 21 15 – n-C20OH 9 83 4289 74 40 68 83 82 n-C21OH 2 22 10 24 18 12 19 22 25 n-C22:1OH 4 8 9 10 3 98 55 34 17 n-C22OH 64 392207 391 361 183 366 396 476 n-C23OH 4 37 15 40 2 9 13 31 36 39 n-C24OH 33 218 83 217 158 95 159 203 183 n-C25OH 2 35 10 30 19 8 20 26 22 n-C26OH 14 218 114 255 182 144 233 154 215 n-C27OH 3 43 20 61 55 25 52 51 58 n-C28OH 23 344 97 264 180 88 200 295 203 n-C29OH – – – – – – – – – n-C30OH – – 48 123 105 – 163 231 74 Sterols A – – 19 41 2 7 2 4 37 35 41 B 23 85 63 83 55 152 197 78 101 C – – 2 0 41 31 36 42 30 46 D 43 349 203 245 185 238 365 195 348 E 14 222 54 93 74 78 120 70 149 F 165 1350 758 912496 544 1300 727 1040 G 34 382 179 358 229 145 241 228 333 H 111 896 471 626 383 831 830 431 716 I 29 309 118 225 155 147 153 153 217 J 31 236 99 156 126 207 167 82 175 K 41 360 152 230 189 224 230 179 227 L 15 14249 10278 54 67 72 83 M 22 272 71 108 105 129 101 98 139 N 51 522 210 396 306 214 351 352 430 O 26 250 86 189 146 162 187 149 207 P 107 809 419 627 432 485 740 468 734 Q 57 502 211 479 315 265 378 320 447 R 60 730 311 605 523 502 881 939 567

Sterol identiﬁcations: (A) 24-nor-5a-cholest-22E-en-3b-ol, (B) 27-nor-24-methylcholesta-5,22E-dien-3b-ol, (C) 27-nor-24-methyl-5a-cholest-22E-dien-3b-ol, (D) cholesta-5,22E-dien-3b-ol, (E) 5a-cholest-22E-en-3b-ol, (F) cholest-5-en-3b-ol, (G) 5a-cholestan-3b-ol, (H) 24-methylcholesta-5,22E-dien-3b-ol, (I) 5a-cholest-22E-en-3b-ol, (J) 24-methylcholesta-5,24(28)-dien-3b-ol, (K) 24-methyl-cholest-5-en-3b-ol+24-methyl-5a-cholest-24(28)-en-3b-ol(?), (L) 24-methyl-5a-cholestan-3b-ol, (M) 23,24-dimethylcholesta-5,22E-dien-3b-ol, (N) 24-ethylcholesta-5,22E-23,24-dimethylcholesta-5,22E-dien-3b-ol, (O) 5a-cholest-22E-en-3b-ol, (P) 24-ethylcholest-5-en-3b-ol, (Q) 24-ethyl-5a-cholestan-3b-ol+unknown, and (R) 4a,23,24-trimethyl-5a-cholest-22E-en-3b-ol. –=less than 2ng/g

(12)

Table 9

Stanol/stenol ratios for total suspended matter and sediments from the East China Sea. Note that numbers in parentheses are water depths Stanol/stenol Sta.10 (37 m) Sta.14 (60 m) Sta.18 (80 m) Sta.20 (65 m) Sta.22 (45 m) Sta.24 (32m) Sta.32 (45 m) Sta.34 (40 m) Sta.36 (80 m) Avg. TSM E/D 0.108 0.040 0.414 0.191 0.040 0.084 0.169 0.282 0.071 0.155 G/F 0.118 0.093 0.281 0.219 0.137 0.092 0.166 0.176 0.143 0.158 I/H 0.016 0.028 0.142 0.096 0.035 0.029 0.036 0.041 0.051 0.053 Sediment E/D 0.326 0.636 0.266 0.380 0.400 0.328 0.329 0.359 0.428 0.384 G/F 0.206 0.283 0.236 0.393 0.462 0.267 0.185 0.314 0.320 0.296 I/H 0.261 0.345 0.251 0.359 0.415 0.177 0.184 0.355 0.303 0.294

Sterol assignment: (D) cholesta-5,22E-dien-3b-ol, (E) 5a-cholest-22E-en-3b-ol, (F) cholest-5-en-3b-ol, (G) 5a-cholestan-3b-ol, (H) 24-methylcholesta-5,22E-dien-3b-ol, (I) 24-methyl-5a-cholest-22E-en-3b-ol

Fig. 3. (upper) Chromatogram of aliphatic hydrocarbons from the sediment of station 14. (lower) Chromatogram of the alkanol/ sterol fraction from the sediment of station 22. Sterol identiﬁcations as inFig. 2.

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sediment/water interface (

Nishimura and Koyama,

1977

) or microbiological hydrogenation of stenols

(

Edmunds et al., 1980; Taylor et al., 1981

).

4. Conclusions

The hydrocarbon, n-alkan-1-ol and sterol

composi-tions of TSM from the ECS is dominated by marine

planktonic

inputs.

High

proportions

of

PDHCs

appeared to be located at stations near the Changjiang

River. Terrigenous lipids are not important

con-tributors. The prevailing oxic conditions in the shelf

water of the ECS contributed to the easy degradation of

labile hydrocarbons and n-alkenols of planktonic origin.

The concentrations of lipids in TSM are correlated in

diﬀerent groups. The correlation of n-C

17

, n-C

18

, n-C

19:1

and n-C

19

indicates a common source, namely

phyto-plankton species other than diatoms and copepods.

Another group of correlated hydrocarbons is composed

of n-C

21:6

, pristane and squalene, suggesting a common

source such as diatoms (microplankton). The close

correlation between C

16

, C

20:1

and C

22:1

alcohols

sug-gests a contribution from copepods. Most sterols are also

correlated, being therefore attributed to marine sources.

Labile lipid biomarkers like PDHCs and

mono-unsaturated alcohols dominated in TSM, but were only

found in trace or minor amounts in the surface

sedi-ments. The prevailing oxic condition in the water

col-umn likely led to their degradation. Rough estimates of

the relative degradation of these biomarkers in the ECS

could be made using lipid data of TSM and of

sedi-ments. The sterol composition reﬂects predominant

inputs from phytoplankton and zooplankton in TSM,

and marine and terrigenous detritus, meiofauna and

bivalves in sediments.

Acknowledgements

We are grateful to captain, crew and technicians of the

R/V Ocean Researcher I for assistance with sample

col-lection. Our special thanks go to two anonymous referees

for constructive comments and suggestions, and to

Professor J. O. Grimalt for editorial editing. This study

was ﬁnancially supported by a grant from the National

Science Council, ROC (grant no. NSC90-2611-M-002-007).

Associate Editor—J. Grimalt

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