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Biomarkers in upper Holocene Eastern North Sea and

Wadden Sea sediments

Bart E. van Dongen

a,

*, W. Irene C. Rijpstra

a

, Catharina J. M. Philippart

b

,

Jan W. de Leeuw

a

, Jaap S. Sinninghe DamsteÂ

a

aDepartment of Marine Biogeochemistry and Toxicology, Netherlands Institute for Sea Research (NIOZ), PO Box 59, 1790 AB Den Burg, Texel, The Netherlands

bDepartment of Marine Ecology, Netherlands Institute for Sea Research (NIOZ), PO Box 59, 1790 AB Den Burg, Texel, The Netherlands

Abstract

Total extracts of sediment cores from ®ve di€erent stations in the North Sea and Wadden Sea were analysed for their biomarker composition. Only sediments of the Skagerrak contained signi®cant amounts of marine biomarkers (mainly alkenones), other sites contained predominantly terrestrial biomarkers. Bioturbation in the Skagerrak is, however, far too high to determine sea surface temperature (SST) changes within short time intervals. These results indicate that biomarkers contained in these sediments are not useful to reconstruct climate ¯uctuations during the upper Holocene. High amounts ofa-,b- ando-hydroxy fatty acids as well as small amounts ofa,b-dihydroxy fatty acids were released from the insoluble organic material of the sediments from the Wadden Sea station, indicating a signi®cant input of the eelgrassZostera marina.This was con®rmed by microscopic observations. This is the ®rst time thea,b-dihydroxy fatty acids have been found in a sediment core and they have proven to be potential biomarkers for these seagrass species.

#2000 Elsevier Science Ltd. All rights reserved.

Keywords:Biomarkers;Uk'37; SST;Zostera marina;Zostera noltii; Upper Holocene; North Sea; Sediments

1. Introduction

The North Sea is an epicontinental sea located on the northwest European passive continental margin and has been the focus of numerous studies. Besides biological and physical research a lot of e€ort has been put into the reconstruction of the origin of the sedimentary matter. The Norwegian Sea, the Atlantic Ocean and the Baltic Sea are the main sources of suspended sediments supplied to the North Sea. Furthermore, atmospheric input, primary production, rivers and coastal erosion add to the suspended and bed load of the North Sea (McManus and Prandle, 1997). Riverine input is extre-mely limited (Eisma et al., 1982). Of the organic carbon that is presently deposited in the North Sea about 20%

is estimated to be of terrigenous origin, the remainder is supplied by primary production (Beckmann and Liebe-zeit, 1988) and a small amount by import from the Norwegian Sea (de Haas and van Weering, 1997).

Biological data series collected from the North Sea and Wadden Sea have yielded a wealth of information on the decadal variability within these marine environ-ments during the last few decades (e.g. Kickel et al., 1989; Beukema, 1990; Witbaard and Klein, 1994). However, this timespan is too short to determine long-term variations of the North Sea and Wadden Sea eco-systems. Therefore, it is necessary to derive long-term information from other sources. One of these sources could be the sedimentary archives. Until now no attempt has been made to investigate the biomarker composition of sediment cores from the North Sea area. Changes in ecosystems may be recorded in the sedi-mentary biomarker record. For example, the sedimen-tary unsaturated long-chain ketones, biosynthesized by the coccolithophorid (Prymnesiophyta) Emiliania

hux-0146-6380/00/$ - see front matter#2000 Elsevier Science Ltd. All rights reserved. P I I : S 0 1 4 6 - 6 3 8 0 ( 0 0 ) 0 0 1 2 5 - X

Organic Geochemistry 31 (2000) 1533±1543

www.elsevier.nl/locate/orggeochem

* Corresponding author.Tel.: 222-319567; fax: +31-222-31967.

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leyi(Volkman et al., 1980) andGeophryrocapsa oceanica

(Volkman et al., 1995) enable the determination of theUk370 (e.g. Brassell et al., 1986; Prahl and Wakeham,

1987; MuÈller et al., 1998) This ratio of C37 alkenones

with two and three double bounds can be used to reconstruct the sea surface temperatures SSTs. Bio-marker distributions may also re¯ect the biologic input into sediments, giving insight to the composition of the ecosystem(s) in the recent past. Thus, the biomarker information contained in sequences of undisturbed sediments may be used to explore the possible existence of long-term and short-term variations in the North Sea ecosystem over time spans of hundreds or thousands of years. In this paper we report the biomarker composi-tion in sediment cores from ®ve di€erent stacomposi-tions in the North Sea and Wadden Sea and discuss their potential to reconstruct climate ¯uctuations e€ecting the North Sea during the upper Holocene. In addition, we assess the contribution of seagrass to the biomarker ®nger-prints of Wadden Sea sediments.

2. Study area

The depth of the North Sea gradually decreases from approximately 200 m in the northern part to less than 30 m in the south. To the Northeast, in the Skagerrak region, the sea ¯oor steeply slopes down to more than 700 m. In the nutrient-rich waters of the shallow Southern Bight and along the eastern boundary most of the primary production occurs. Counterclockwise cur-rents transport ®ne-grained suspended material from the Southern Bight along the eastern boundaries of the North Sea towards the Skagerrak (Eisma and Kalf, 1987; Fig. 1). The deep Skagerrak is assumed to be the ultimate sink for organic matter (van Weering et al., 1993). A core was taken at a station (3) where the sedi-mentation rate is extremely high according to de Haas and van Weering (1997). Other sediment cores were taken at stations along the eastern boundaries of the North Sea; the Norwegian channel, Skagerrak, German Bight and the Wadden Sea. The sediment core from the Wadden Sea was taken in the `Vlieter'. The `Vlieter' is an abandoned channel in the Dutch Wadden Sea, which used to be the main drainage channel connecting the former `Zuiderzee' and the western Wadden Sea, before closure of the dike called ``Afsluitdijk'' in 1932.

3. Material and methods

3.1. Core material

Sediment cores were taken during the `Dynamo' cruise (28.05.96±5.06.96) using the RV `Pelagia'. Addi-tional sediment cores were taken in the `Vlieter' in June

1997 using the RV `Navicula' (see Fig. 1 and Table 1 for the exact locations of the sample sites). All the cores show somewhat lamination and were stored at 4C. At

least three subsamples were taken from every sediment core from di€erent depths and, if possible di€erent lay-ers, and analysed for their biomarker composition. Additional samples were taken from the core from sta-tion 3 from the Skagerrak, to increase the time resolu-tion.

3.2. Extraction and fractionation

The extraction, separation and identi®cation proce-dures followed are based on those described by Goos-sens et al. (1989a,b) and are schematically depicted in Fig. 2. Subsamples were taken from the cores at several depths (see Tables 1 and 3) and dried. The freeze-dried samples were Soxhlet extracted with dichloro-methane/methanol (DCM/MeOH, 7.5:1, v/v) for 32 h. In order to remove elemental sulfur, activated (2N HCl) copper curls were added. The fresh seagrass Zostera noltiiwas dried and ultrasonically extracted with DCM. The extracts obtained were concentrated using rotary evaporation and dried over magnesium sulfate. An ali-quot (1±5 mg) of the total extract was derivatized with diazomethane (CH2N2) in diethylether to convert fatty

acids into their corresponding methyl esters. Subse-quently, very polar compounds were removed by col-umn chromatography over silica gel with ethyl acetate as eluent. The eluate was dried under a stream of nitrogen.

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This fraction was dissolved in pyridine and bis(-trimethylsilyl)tri¯uroacetamide (BSTFA) was added. This mixture was heated (60C; 20 min) to convert

alcohols into their corresponding trimethylsilyl ethers. The compounds present were analysed by means of gas chromatography (GC) and gas chromatography-mass± spectrometry (GC±MS).

Dried residues after extraction and aliquots of the underivatized extracts were saponi®ed by re¯uxing with 1N KOH/MeOH (1 h). After cooling the reaction mix-tures were neutralised with 2N HCl/MeOH (1:1; v/v) to pH 3.5, centrifuged and transferred to a separation funnel. The residues were washed subsequently with

MeOH/H2O, MeOH and DCM. Each time the

super-natants were transferred to the separation funnel. Water was added and the DCM-layers were separated. The MeOH/H2O layers were washed with DCM (2). The

combined DCM layers were concentrated using rotary evaporation, dried over magnesium sulfate and deriva-tized as described above.

The dried residues after saponi®cation were also treated with 4N HCl (6 h; 100C). After cooling the

reaction mixture was neutralised with 16N KOH to pH 8.5, freeze-dried and saponi®ed as above. The extracts were washed, separated and derivatized as described above.

Table 1

Location, water depth, type of core, estimated average sedimentation rate and core length analysed of the sediment cores from the North Sea and Wadden Sea

Area Station Position Water depth (m) Core typea Estimated average

sedimentation rate (mm yearÿ1)

Core length analysed (cm)

Skagerrak 3 5846.290N±1008.580E 235 p 8±10b 200

5 5736.590N±0734.790E 316 p 1±2b 100

The ``Vlieter'' (Wadden Sea)

7-1c 5301.570N±0504.190E 6.5 b 9±11c 30

Norwegian Channel 14 6040.720N±0435.150E 358 p 2-4b 100

German Bight 17 5406.350N±0806.080E 22 p ± 100

a p, piston core; b, box core. b de Haas and van Weering (1997). c Unpublished results.

Fig. 2. Extraction and isolation scheme.

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3.3. Gas chromatography

GC was performed using a Hewlett Packard 6890 or a Hewlett Packard 5890 instrument, both equipped with on-column injectors. A fused silica capillary column (25 m0.32 mm) coated with CP-Sil-5 (®lm thickness 0.12

mm) using helium as carrier gas. Compounds separated

by the HP 6890 were detected by a ¯ame ionisation detector (FID). Compounds separated by the HP 5890 were detected simultaneously by FID and a sulfur-selective ¯ame photometric detector (FPD), using a stream splitter at the end of the column (split ratio FID: FPD=1:1). The samples were dissolved in ethyl acetate and injected at 70C. Subsequently, the oven was

pro-grammed to 130C at 20C/min and then at 4C/min to

310C at which it was held for 15 min.

3.4. Gas chromatography±mass spectrometry (GC±MS)

GC±MS was performed using a Hewlett-Packard 5890 gas chromatograph interfaced to a VG Autospec Ultima mass spectrometer operated at 70 eV with a mass range of m/z 50±800 and a cycle time of 1.7 s (resolution 1000). The gas chromatograph was equipped with a fused silica capillary column (25 m0.32 mm)

coated with CP Sil-5 (®lm thickness=0.12 mm) The carrier gas was helium. The samples were on column injected at 70C and subsequently the oven was

pro-grammed to 130C at 20C/min and then at 4C/min to

310C at which it was held for 10 min. Compounds were

identi®ed by comparison of mass spectra and retention times with those reported in literature.

3.5. Microscopy

The microscopic determination of the seagrass parts was performed on a Zeiss Axiophot microscope with 40

magni®cation.

4. Results

4.1. General

Cores from the North Sea and Wadden Sea were analysed for their biomarker composition. Because the core of the Wadden Sea revealed a signi®cant input of seagrass the leaf fragments found in the core were ana-lysed microscopically. In order to compare the two spe-cies of seagrass present in the Wadden Sea and to verify which one is present in the core, freshZ. noltiiwas also analysed chemically. The biomarker composition of

Zostera marina was already known (de Leeuw et al., 1995).

4.2. North Sea stations

Analyses of the total extracts (fraction E1; Fig. 2) of samples from sediment cores of the North Sea stations revealed mainly biomarkers of terrestrial origin (Fig. 3 and Table 2). Especially C22±C30alcohols, C24±C32fatty

acids (both with an even-over-odd carbon number pre-dominance) and C25±C31n-alkanes (odd-over-even car-Table 2

Relative abundancea of biomarker classes found in the total

extracts (fraction E1) of samples from the di€erent sampling stations

desmethyldinosterol ÿ ÿ + +/ÿ +

dinosterol + + ÿ + +

5b-sitostanol + + + + +

b-sitosterol + + + + +

Wax esters ÿ ÿ + ÿ ÿ

a ++ Abundant, + present, +/ÿtrace and

ÿabsent.

Table 3

Core depth andUk0

37values of samples from sediment station 3

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Fig. 3. Gas chromatograms of the total extracts (fraction E1; Fig. 2) from (a) Skagerrak (station 3), (b) Skagerrak (station 5), (c) Norwegian Channel (station 14) and (d) German Bight (station 17). Numbers indicate carbon chain length and IS= internal standard.

B.E.

van

Dongen

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31

(2000)

1533±15

43

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bon number predominance) were found. Also present, but in a signi®cant lower amount, was a complex mix-ture of sterols (predominantly: b-sitosterol, 5b -sitosta-nol, dinosterol, desmethyldinosterol and 5a -cholestan-3b-ol) and hopanols [mainly 17b,21b (H)-bishomoho-pan-32-ol].

Analyses of samples from the sediment core from station 3 of the Skagerrak revealed also high amounts of di- and tri-unsaturated C37±C39 long-chain alkenones.

The analyses of di€erent sections of the sediment core 3 showed no signi®cant change inUk370 as shown in Table

3.

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4.3. Wadden Sea station

Like all sediments investigated from the North Sea stations, the total extract (fraction E1) of samples from sediments core of the Wadden Sea station revealed predominantly terrestrial biomarkers (Fig. 4a). In con-trast, signi®cant amounts of o-hydroxy fatty acids were also found (Table 2). High amounts of C16±C28

o-hydroxy fatty acids were released from the residues by base hydrolysis (fraction E3; Fig. 4b). High amounts of C22-C27 a- and C12-C20 b-hydroxy fatty

acids as well as trace amounts of C22±C24 a,b

-dihy-droxy fatty acids were released from the residues by acid hydrolysis (fraction E4; Fig. 4c). Since the mass spectra of theb-hydroxy fatty acids do not contain suf-®cient information to distinguish iso (i)-, anteiso (ai )-branched or normal (n)-hydroxy fatty acids, these assignments are based upon relative retention times in analogy to the identi®cation of hydroxy fatty acids by Boon et al. (1977).

Further investigation of the sediments from the Wadden Sea station revealed a signi®cant amount of 2-methylmercaptobenzthiazole (MTBT) and N -methyl-mercaptobenzthiazole (NMTBT) as shown in Fig. 5.

4.4. Seagrass

Microscopic observations of leaf fragments found in the sediments of the Wadden Sea station revealed a sig-ni®cant amount of the eelgrassZ. marina(Fig. 6), which chemical composition is reported by de Leeuw et al. (1995). The chemical analysis of the other potential species,Z. noltii, revealed a similar fatty acid distribu-tion patterns in all fracdistribu-tions. Besides the C16 saturated

fatty acid a signi®cant contribution comes from the unsaturated C18 fatty acid. The a-hydroxy fatty acids

are released after acid treatment (fraction E4; Fig. 7). Theb-hydroxy fatty acids are absent or virtually absent in all fractions of the living seagrass. The o-hydroxy fatty acids are only encountered in fraction E2. Only traces of C22±C24a,b-dihydroxy fatty acids were found

in fraction E4.

If the quantities of fatty acids and hydroxy fatty acids in fresh Z. noltii are compared with those in freshZ. marina, analysed by de Leeuw et al. (1995), only fraction E4 reveals any signi®cant di€erences (Fig. 7). The Z. marina E4 fraction contains a signi®cant amount of

Fig. 5. Partial gas chromatogram from total extract E1 of sediment from the Wadden Sea station with (a) a ¯ame ionisa-tion detector and (b) a sulfur-selective ¯ame photometric detector. *2-methylmercaptobenzthiazole (MTBT); **N -methylmercaptobenzthiazole (NMTBT).

Fig. 6. Photomicrographs of leaves from (a)Z. marinafound in sediment core of the Wadden Sea station (b) freshZ. marina

and (c) freshZ. noltii.

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b-hydroxy fatty acids anda,b-dihydroxy fatty acids but only traces were found in Z. noltii. Furthermore, the contribution of unsaturated fatty acids, especially the unsaturated C18fatty acid, is relatively higher in theZ. noltiithan in theZ. marina.

5. Discussion

5.1. All stations

In total extracts (fraction E1) of all the sediments terrestrial biomarkers dominate. This is most likely due to the oxic conditions experienced by the organic mate-rial during frequently occurring transport through resuspension and sedimentation in the North Sea. This process likely leads to an enrichment of the more refractory terrestrial biomarkers relative to the more labile marine biomarkers (Haddad et al., 1992; Harvey, 1994; Santos et al., 1994; Canuel and Martens, 1996; Colombo et al., 1997; Budge and Parrish, 1998). Our samples contain signi®cant though lower amounts of marine sterols (i.e. dinosterol and desmethyldinosterol) and hopanols. This indicates a contribution of dino-¯agellate algae (Shimizu et al., 1976; Boon et al., 1979; Withers, 1983) and bacteria (Rohmer et al, 1992; Yun-ker et al., 1995), respectively. These biomarYun-kers may provide some palaeo-environmental information. How-ever, the bioturbation, the long residence time in the basin, the transport through the North Sea, sedimenta-tion and erosion must have caused considerable dis-turbance of the record. This and the relative small amounts of the biomarkers found, makes them less use-ful for palaeo-environmental reconstruction.

5.2. Skagerrak (station 3)

Only the sediments from the Skagerrak (station 3) revealed a signi®cant amount of unsaturated C37±C39

long-chain alkenones, probably derived from blooms of

Emiliania huxleyiin the area (Buitenhuis et al., 1996). The long-chain alkenones are only found in this area probably due to the extremely high sedimentation rates in combination with the depth. Analyses of di€erent sections in the sediment core showed an average SST of 11±12C without any change in temperature variation,

indicating no apparent short-and long-term variation in SST. Dauwe et al. (1998) recently reported the presence of fauna up to 20 cm depth in the sediment causing a lot of disturbance and mixing in the Skagerrak. This will make it impossible to determineUk0

37 and SST changes

within a short period of time (yearly to decennial). The absence of long-term variations (decennial to cen-tennial) in SST can be caused by the fact that there are no SST changes over a longer period of time or they are too small to be noticed.

5.3. Wadden Sea station

The high amounts ofo-hydroxy fatty acids, in frac-tions E1 and E3, anda- and b-hydroxy fatty acids, in fraction E4, indicates a high input of seagrass in the sediment of the `Vlieter'. The composition of the hydroxy fatty acids is similar to that reported by de Leeuw et al. (1995) in decomposing eelgrassZ. marina. The relative small amounts ofa,b-dihydroxy fatty acids, found in fraction E4, is worthy of note sincea,b -dihy-droxy fatty acids have only been encountered inZ. mar-inaandZ. muelleri. Hence they may be highly speci®c

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biomarkers for these seagrasses as proposed by de Leeuw et al. (1995). Fresh Z. noltii, the other seagrass present in the Wadden Sea (Phillippart, 1994), also contains traces of a,b-dihydroxy fatty acids in fraction E4. This makes it chemically impossible to distinguishZ. marina fromZ. noltii. The leaf fragments found in the sediment core of the Wadden Sea station were micro-scopically analysed (Fig. 6) and when compared with leaves from freshZ. marinaandZ. noltii, the presence of

Z. marina was con®rmed. This makes the presence of remnants ofZ. noltiiin the sediment core less likely.

De Leeuw et al. (1995) also analysed decomposingZ. marina, about 12.5 years old. These fractions were compared with the same fractions from the sediment core of the Wadden Sea station. Especially fraction E4 gave a completely di€erent picture. In this fraction of the sediment from the Wadden Sea station the a -hydroxy fatty acids are relatively low and thea,b -dihy-droxy fatty acids are only present in trace amounts. The presense of a signi®cant input ofb-hydroxy fatty acids indicates the presence of bacterial biomass, because iso-and anteiso-b-hydroxy fatty acids occur as amide-bound moieties of lipopolysaccharides in gram-negative bac-teria (Goossens et al., 1986). This could explain that not only theZ. marinacontributed to this fraction but there was also a signi®cant contribution of fatty acids andb -hydroxy fatty acids coming from bacteria. It must also be considered that the sediments of the Wadden Sea station analysed covered the last 25 years but theZ. marina pre-sent is probably much older material (as will be explained below) and therefore thea,b-dihydroxy fatty acids and thea-fatty acids can be more biodegraded.

Until the early 1930s, the Z. marina was present in large quantities in the Wadden Sea (Oudemans et al., 1870; van Goor, 1919; van Eerde, 1942; de Jonge and Ruiter, 1996). After the epidemic that struck the North Atlantic population of seagrass in the early thirties, known as the `wasting disease' (Reigersman et al., 1939; den Hartog, 1987) and the closure of the `Zuiderzee' in 1932 theZ. marinawas almost wiped out and failed to return in the Wadden Sea (Michaelis et al., 1971; Short et al., 1988). Nowadays there are only a few small beds left near the island `Terschelling' (Dijkema et al., 1989; Philippart, 1994). This means that theZ. marinapresent in the `Vlieter' can originate from these beds transported by the ¯ow from the Vlie basin towards the Marsdiep basin and passing the `Vlieter' (Ridderinkhof et al., 1990), if it is fresh, new, seagrass. However, the amounts of eelgrass found in the sediments of the Wadden Sea station are relatively high and it is unlikely that it origi-nates from the few small beds near `Terschelling'. An alternative explanation is that it is old material, which was deposited somewhere else, washed away and rede-posited in the `Vlieter' much later. After the closure of the `Zuiderzee', increased the ¯ow in some channels in the Wadden Sea resulted in a lot of erosion. Glim et al.

(1987) for instance reported an increased ¯ow in the `Doove Balg', a channel near the `Vlieter' causing a lot of erosion near the `Meerwaard', a large oldZ. marinabed. The high amounts of terrestrial biomarkers and the high input of eelgrass in the sediments suggest that the `Vlieter' is one of the major depositional sites of the Wadden Sea ecosystem. This is further supported by the input of 2-methylmercaptobenzthiazole and N -methyl-mercaptobenzthiazole (Fig. 5). Benzothiazoles have gained widespread application in industrial processes. They are well-known vulcanisation accelerators (Fiehn et al., 1994) in the rubber industry, manufacture of rubber tyres, and can be found in street runo€ (Spies et al., 1987). MBTB is an impurity that appears to be environmentally stable. NMBTB is not a well-known impurity but may be formed by a methyl shift of MBTB during the vulcanisation process. Where these com-pounds originate from is not clear. It is possible they come from the ``Afsluitdijk'' on which a highway is present. Another possibility is that they are originating from somewhere else and through transport (rainwater, rivers, etc.) end up in the `Vlieter'. The appearance of these compounds in the sediment in combination with the high sedimentation rates makes it more likely that the `Vlieter' is a major depositional site of the Wadden Sea ecosystem.

6. Conclusions

1. Except for the Skagerrak, where alkenones are present, the North Sea sediments contain pre-dominantly terrestrial biomarkers.

2. Bioturbation in the Skagerrak is far too high to determine SST within a short period of time (yearly to decennial) and the changes in averaged SST (over approximately the last 200 years) seem to be too small to be noticed.

3. The sediments from these stations are thus not useful to reconstruct climate ¯uctuations during the upper Holocene.

4. High amounts ofa-,b- ando-hydroxy fatty acids and traces ofa,b-dihydroxy fatty acids indicate a signi®cant input of the eelgrass Z. marinain the Wadden Sea site. This is the ®rst time that these

a,b-dihydroxy fatty acids are found in a sediment core and that they have proven to be potential biomarkers for these classes of eelgrass.

5. The `Vlieter' is a major depositional site of the Wadden Sea system.

Acknowledgements

C.J.N. Winter is gratefully acknowledged for his assistance with collecting of the core samples and G.

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Nieuwland for his help with taking of the microscopic photos. We wish to thank Dr. H.J. Lindeboom, Dr. S. Schouten and Dr. G.J.M. Versteegh for helpful discus-sions. The research was ®nancially supported by the Netherland-Bremen Oceanography Program (NEB-ROC). Sampling of the sediment cores was performed within the Frame-work of an EU-project (DYNAMO; Fair-ct95-0710). This is NIOZ contribution 3414.

References

Beckmann, M., Liebezeit, G., 1986. Organic carbon in the North Sea in May/June : Distribution and controlling fac-tors. Mitteilungen aus dem Geol.-palaÈontologischer Institut der UniversitaÈt Hamburg 65, 1988, 99-116.

Beukema, J.J., 1990. Expected e€ects of changes in winter temperatures on benthic animals living in soft sediments in coastal North Sea areas. In: Beukema, J.J., Wol€, W.J. (Eds.), Expected E€ects of Climate Change on Marine Coastal Ecosystems. Kluwer Academic Publishers, Dor-drecht, pp. 83±92.

Boon, J.J., de Lange, F., Schuyl, P.J.W., de Leeuw, J.W., Schenck, P.A., 1975. Organic geochemistry of Walvis Bay diatomaceous ooze. II. Occurrence and signi®cance of the hydroxy fatty acids. In: Campos, R., Goni, J. (Eds.), Advances in Organic Geochemistry 1977. Enadimsa, Madrid, pp. 255±273.

Boon, J.J., Rijpstra, W.I.C., de Lange, F., de Leeuw, J.W., Yoshioka, M., Shimizu, Y., 1979. Black Sea sterol-a mole-cular fossil for dino¯afellate blooms. Nature 277, 125±126. Brassell, S.C., Eglinton, G., Marlowe, I.T., P¯aumann, U.,

Sarnthein, M., 1986. Molecular stratigraphy: a new tool for climate assessment. Nature 320, 129±133.

Budge, S.M., Parrish, C.C., 1998. Lipid biogeochemistry of plankton, settling matter and sediments in Trinity Bay, Newfoundland II. Fatty acids.. Organic Geochemistry 29, 1547±1559.

Buitenhuis, E., van Bleijswijk, J., Bakker, D., Veldhuis, M., 1996. Trends in inorganic and organic carbon in a bloom of

Emiliania huxleyiin the North Sea. Marine Ecology Progress Series 143, 271±282.

Canuel, E.A., Martens, C.S., 1996. Reactivity of recently deposited organic matter: Degradation of lipid compounds near the sediment-water interface. Geochimica et Cosmochi-mica Acta 60, 1793±1806.

Colombo, J.C., Silverberg, N., Gearing, J.N., 1997. Lipid bio-geochemistry in the Laurentian Trough Ð II Changes in composition of fatty acids, sterols and aliphatic hydrocarbons during early diagenesis.. Organic Geochemistry 26, 257±274. Dauwe, B., Herman, P.M.J., Heip, C.H.R., 1998. Community

structure and bioturbation potential of macrofauna at four North Sea stations with contrasting food supply. Marine Ecology Progress Series 173, 67±83.

Dijkema, K.S., van Tienen, G., van Beek, J.G., 1989. Habitats of the Netherlands, German and Danish Wadden Sea. Research Institute for Nature Management and Veth foun-dation Leiden, Texel.

van Eerde, L.A., 1942. De landaanwinning van het Noorder-leergse Buitenveld.. Tijdschrift van het Nederlands Aar-drijkskundig Genootschap 59, 1±23.

Eisma, D., CadeÂe, G.C., Laane, R., 1982. Supply of suspended matter and particulate and dissolved organic carbon from the Rhine to the coastal North Sea. Mitteilungen aus dem Geol.-palaÈontologischer Institut der UniversitaÈt Hamburg 58, 483±505.

Eisma, D., Kalf, J., 1987. Dispersal, concentration and deposi-tion of suspended matter in the North Sea. Journal of Geo-logical Society (Lond) 144, 161±178.

Fiehn, O., Remtsma, T., Jekel, M., 1994. Extraction and ana-lysis of various benzothiazoles from industrial wastewater. Analytica Chimica Acta 295, 297±305.

Glim, G.W., Kool, G., Lieshout, M.F., de Boer, M., 1987. Erosie en sedimentatie in de binnendelta van het Zeegat van

Texel 1932±1982. Rapportage ANWX-87.H201

Dee-londerzoek no. 1.

van Goor, A.C.J., 1919. Het zeegras (Zostera marina L) en zijn betekenis voor het leven der vischen. Rapp. verh. Rijksinst. Viss. Onderz 1, 22±25.

Goossens, H., Rijpstra, W.I.C., Duren, R.R., de Leeuw, J.W., Schenck, P.A., 1986. Bacterial contribution to sedimentary organic matter; a comparartive study of lipid moieties in bacteria and recent sediments. Organic Geochemistry 10, 683±696.

Goossens, H., DuÈren, R.R., de Leeuw, J.W., Schenck, P.A., 1989a. Lipids and ther mode of occurrence in bacteria and sediments Ð II Lipids in the sediment of a strati®ed, fresh-water lake. Organic Geochemistry 14, 27±41.

Goossens, H., de Leeuw, J.W., Rijpstra, W.I.C., Meyburg, G.J., Schenck, P.A., 1989b. Lipids and their mode of occur-rence in bacteria and sediments Ð I A methodological study of the lipid composition ofAcinetobacter calcoaceticusLMD 79-41. Organic Geochemistry 15-25, 14.

de Haas, H., van Weering, T.C.E., 1997. Recent sediment accumulation, organic carbon burial and transport in the northeastern North Sea. Marine Geology 136, 173±187. Haddad, R.I., Martens, C.S., Farrington, J.W., 1992.

Quanti-fying early diagenesis of fatty acids in a rapidly accumulating coastal marine sediment. Organic Geochemistry 19, 205±216. den Hartog, C., 1987. ``Wasting disease'' and other dynamic

phenomena inZosterabeds. Aquatic Botany 27, 3±14. Harvey, H.R., 1994. Fatty acids and sterols as source markers

of organic matter in sediments of the North Carolina con-tinantel slope. Deep-Sea Research 41, 783±796.

Hickel, W., Bauer®eld, E., Niermann, U., von Westernhagen, H., 1989. Oxygen de®ciency in the south eastern North Sea: sources and biological e€ects. Berichte der Biologishcen Anstalt Helgoland NO 4, 1±148.

de Jonge, V.N., Ruiter, J.F., 1996. How subtidal were the `subtidal beds' ofZostera marinaL before the occurence of the wasting disease in the early 1930's? Netherlands Journal of Aquatic Ecology 30, 99±106.

de Leeuw, J.W., Rijpstra, W.I.C., Nienhuis, P.H., 1995. Free and bound fatty acid and hydroxy fatty acids in the living and decomposing eelgrassZostera marinaL. Organic Geo-chemistry 23, 721±728.

(11)

multiple linear regression. Continental Shelf Research 17, 761±778.

Michaelis, H., 1971. Ohba T, TuÈxen R, Die Zostera -gesell-schaften der NiedersaÈchsischen watten. Forschungstelle Norderney, Jahresbericht 1969 (11), 87±100.

MuÈller, P.J., Kirst, G., Ruhland, G., Von Storch, I., Rosell-MeleÂ, A., 1998. Calibration of the alkenone paleo-temperature indexUk0

37 based on core-tops from the eastern South Atlantic and the global ocean (60N±60S).

Geochi-mica et CosmochiGeochi-mica Acta 62 (10), 1757±1772.

Oudemans, C.A.J.A., Conrad, J.F.W., Maats Jr., P., Bouricius, L.J., 1870. Verslag der Staatscommissie in zake de wier-maaierij. Verslag aan de Koning over de Openbare Werken in het jaar 1869, Algemene Landsdrukkerij, 's-Gravenhage, pp. 199±231.

Philippart C.J.M., 1994. Europhication as a possible cause of decline in the seagrassZostera noltiiof the Dutch Wadden Sea. Thesis, University Wageningen, p. 4.

Prahl, F.G., Wakeham, S.G., 1987. Calibration of unsaturation patterns in long-chain ketone compositions for paleo-temperature assessment. Nature 330, 367±369.

Reigersman C.J.A., Houben G.F.H. and Havinga B., 1939. Rapport omtrent den invloeden de wierziekte op den achter-uitgang van de wierbedrijven.

Ridderinkhof, H., Zimmerman, J.T.F., Philippart, M.E., 1990. Tidal exchange between the North Sea and Dutch Wadden Sea and mixing time scales of the tidal basins. Netherlands Journal of Sea Research 25, 331±350.

Rohmer, M., Bisseret, P., Neunlist, S., 1992. The hopa-noids, prokaryotic triterpenoids and precursors of ubi-quitous molecular fossils. In: Moldowan, J.M., Albrecht, P., Philp, R.P. (Eds.), Biological Markers in Sediments and Petroleum,Prentice Hall. Englewood Cli€s, NJ, pp. 1±17.

Santos, V., Billett, D.S.M., Rice, A.L., Wol€, G.A., 1994. Organic matter in deep-sea sediments from the Porcupine

Abyssal Plain in the north-est Atlantic Ocean. 1 Ð Lipids. Deep-Sea Research 41, 787±819.

Shimizu, Y., Alam, M., Kobayashi, A., 1976. Dinosterol, the major sterol with a unique side chain in the toxic dino-¯agellate, Gonyaulax tamarensis. Journal of the American Chemical Society 98, 1059±1060.

Short, F.T., Ibelings, B.W., Den Hartog, C., 1988. Comparison of a current eelgrass disease to the wasting disease in 1930s. Aquatic Botany 30, 295±304.

Spies, R.B., Andresen, B.D., Rice Jr., D.W., 1987. Benzthia-zoles in estuarine sediments as indicators of street runo€. Nature 327, 697±699.

Volkman, J.K., Barratt, S.M., Blackburn, S.I., Sikes, E.L., 1995. Alkenones in Gephyrocapsa oceanica: implications for studies of paleoclimate. Geochimica et Cosmochimica Acta 59, 513±520.

Volkman, J.K., Eglinton, G., Corner, E.D.S., Sargent, J.R., 1980. Novel unsaturated straight-chain C37±C39methyl and

ethyl ketones in marine sediments and a coccolithophore

Emiliania huxleyi. In: Douglas, A.G., Maxwell, J.R. (Eds.), Advances in Organic Geochemistry 1979. Pergamon Press, Oxford, pp. 219±227.

Weering, T.C.E., Berger, G.W., Okkels, E., 1993. Sediment transport, resuspension and acumulation rates in the north-eastern Skagerrak.. Marine Geology 111, 269±285.

Witbaard, R., Klein, R., 1994. Long-term trends on the e€ects of the southern North Sea beamtrawl ®shery on the bivalve molluscArctica islandicaL (Mollusca, bivalvia). ICES Jour-nal of Marine Science 51, 99±105.

Withers, N., 1983. Dino¯agellate sterols. In: Scheuer, P.J. (Ed.), Marine Natural Products. Chemical and Biological Perspectives, Vol. 5. Academic Press, New York, pp. 87±130. Yunker, M.B., Macdonald, R.W., Veltkamp, D.J., Cretney, W.J., 1995. Terrestrial and marine biomarkers in a seasonally ice-covered Arctic estuary Ð integration of multivariate and biomarker approaches. Marine Chemistry 49, 1±50.

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