Organic Marine Geochemistry - American Chemical Society

3 Sedimentary Lipids and Polysaccharides As Indicators for Sources of Input, Microbial Activity, and Short-Term Diagenesis

Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on May 28, 2018 | https://pubs.acs.org Publication Date: April 21, 1986 | doi: 10.1021/bk-1986-0305.ch003

J. W. de Leeuw Department of Chemistry and Chemical Engineering, Delft University of Technology, De Vries van Heystplantsoen 2, 2628RZDelft, The Netherlands

Organic compounds present i n recent marine sediments reflect the biochemical composition of the overlying water column as well as the in situ benthic activity. Suites of sedimentary compounds are also considered as starting compounds i n chemical diagenetic pathways. Samples from several locations have been analyzed (e.g. the Namibian Shelf (S.W.-Africa), the Black Sea, Solar Lake (N. Sinai) and the Gavish Sabkha (S. Sinai)). Selected groups of sedimentary compounds such as sterols, 4-methylsterols, hydroxy fatty acids, carotenoids, long chain unsaturated methyl- and ethylketones, sterolethers, long chain 1,15-diols and 15-keto-monools, tocopherols, thiophenes and polysaccharides are discussed. These compounds have been selected i n such a way that attention can be paid to the origin of sedimentary compounds, how they reflect the composition of the living communities in the overlying water column and the sediment i t s e l f , to symbiotic relationships, to microbial activity and to early diagenetic processes.

One of the ultimate goals i n organic geochemistry is the detailed reconstruction of the environment of deposition using organic matter characteristics. Organic molecules isolated from sediment samples and subsequently identified carry information about their biological origin or about the state of diagenesis of the sediment or both. Therefore scientists working i n the molecular organic geochemistry field have used and s t i l l use terms like biomarkers, chemical fossils, biological markers, geochemical fossils, guide molecules, biotracers, etc. to indicate the information content of individual organic compounds or suites of sedimentary organic compounds. Due to recent developments in the organic geochemistry of recent sediments i n particular, these terms can be rather confusing and i t is no longer clear what kind of information content of the organic molecules is being referred to. Therefore i t is necessary to reevaluate the "marker concept in organic geochemistry. 11

0097-6156/ 86/ 0305-0033S08.25/ 0 © 1986 American Chemical Society

Sohn; Organic Marine Geochemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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ORGANIC MARINE GEOCHEMISTRY


F i g u r e 1 s c h e m a t i c a l l y shows an approach by which sedimentary o r g a n i c m o l e c u l e s a r e c o n s i d e r e d as i n f o r m a t i o n c a r r i e r s , how the v a r i o u s k i n d s o f i n f o r m a t i o n c o n t e n t s can be d i s c r i m i n a t e d and how t h e assembled i n f o r m a t i o n i s e v a l u a t e d . The d i f f e r e n t ways by which t h e i n f o r m a t i o n content i s e x p r e s s e d a r e s h o r t l y d i s c u s s e d h e r e a f t e r . S t r u c t u r e s . S t r u c t u r a l f e a t u r e s such as the s k e l e t o n , the s t e r e o c h e m i c a l c o n f i g u r a t i o n and the n a t u r e o f f u n c t i o n a l groups o f i n d i v i d u a l compounds can be h i g h l y i n f o r m a t i v e . I f the s t r u c t u r e s encountered a r e i d e n t i c a l o r r e f l e c t an o r i g i n from n a t u r a l l y o c c u r r i n g compounds, the degree o f i n f o r m a t i o n i s determined by t h e uniqueness o f the o c c u r r e n c e i n the n a t u r a l environment which i n i t s t u r n i s determined by the uniqueness o f the b i o s y n t h e t i c machinery o f a c e r t a i n group o f organisms. Well-known examples a r e the extended hopanoids (J_), d i n o s t e r o l (2) and the v e r y l o n g u n s a t u r a t e d ketones 03). Sometimes the s t r u c t u r e s o f the sedimentary o r g a n i c m o l e c u l e s as such do n o t o c c u r i n the b i o s p h e r e b u t a r e (based on s p e c i f i c s t r u c t u r a l f e a t u r e s ) e a s i l y t r a c e d back t o n a t u r a l p r e c u r s o r s w h i c h are n o t e n t i r e l y unique f o r c e r t a i n groups o f organisms. I n t h i s case the s t r u c t u r a l i n f o r m a t i o n can be used t o u n r a v e l d i a g e n e t i c pathways and t o determine t h e degree o f d i a g e n e s i s o f the sediment under study. Examples h e r e o f a r e s t e r o i d hydrocarbons such as s t e r e n e s , d i a s t e r e n e s , s p i r o s t e r e n e s , s t e r a n e s , d i a s t e r a n e s and aromatized s t e r o i d s which a l l r e f l e c t s p e c i f i c b i o c h e m i c a l and c h e m i c a l t r a n s f o r m a t i o n s o f the o r i g i n a l l y p r e s e n t s t e r o l s 04). I f t h e s t r u c t u r a l f e a t u r e s s t i l l r e f l e c t s t r u c t u r e s o f unique n a t u r a l compounds, then they c o n t a i n b o t h i n f o r m a t i o n about t h e i r s p e c i f i c n a t u r a l o r i g i n and d i a g e n e t i c a l pathways. Examples h e r e o f a r e t h e extended hopanes, 4m e t h y l d i a s t e r e n e s , s t e r a n e s and c e r t a i n d i t e r p e n e s 05). D i s t r i b u t i o n patterns. A d i s t r i b u t i o n pattern of a c e r t a i n class of compounds can be h i g h l y i n f o r m a t i v e i n s e v e r a l a s p e c t s , w h i l e t h e i n d i v i d u a l components do n o t have any i n f o r m a t i o n c o n t e n t . The most common example t o i l l u s t r a t e t h i s type o f i n f o r m a t i o n content a r e nalkane p a t t e r n s observed i n sediment e x t r a c t s and o i l s . I f t h e envelope o f n-alkanes maximizes i n t h e C 2 7 - C 3 1 range and t h e r e i s a s t r o n g odd even predominance, an o r i g i n from h i g h e r p l a n t waxes i s assumed. Based on e x a c t l y t h e same d i s t r i b u t i o n p a t t e r n one a l s o can conclude t h a t the sediment has n o t undergone severe d i a g e n e s i s . I f the n-alkane p a t t e r n s a r e smooth w i t h o u t any odd over even predominance o n l y some g e n e r a l c o n c l u s i o n s can be made about t h e degree o f m a t u r a t i o n . An even over odd predominance o f n-alkanes c a n o c c u r i n sediments o r o i l s which o r i g i n a t e from h y p e r s a l i n e d e p o s i t i o n a l environments ( 6 ) . Mode o f o c c u r r e n c e . I t i s o n l y i n r e c e n t y e a r s t h a t i n some o r g a n i c geochemical i n v e s t i g a t i o n s a t t e n t i o n has been p a i d t o the f a c t t h a t o r g a n i c m o l e c u l e s i n sediments ( e s p e c i a l l y i n r e c e n t sediments) o c c u r i n d i f f e r e n t modes (e.g. Λ JO · S i n c e m o l e c u l e s i n organisms a r e p r e s e n t as such o r as p a r t s o f l a r g e r s t r u c t u r a l e n t i t i e s i t i s a g a i n the uniqueness o f the b i o s y n t h e t i c machinery i n s p e c i f i c groups o f organisms which determines the v a r i o u s modes by w h i c h the m o l e c u l e s are p r e s e n t i n the c e l l s . To b e n e f i t from t h i s p o t e n t i a l source o f i n f o r m a t i o n p r e s e n t i n l i v i n g systems s e q u e n t i a l o r s p e c i f i c procedures t o i s o l a t e s u i t e s o f o r g a n i c m o l e c u l e s from sediment


3.

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Sedimentary Lipids and Polysaccharides

35


samples a r e r e q u i r e d . Even when t h e m o l e c u l e s as such o r t h e d i s t r i b u t i o n p a t t e r n s o f c e r t a i n c l a s s e s o f compounds do n o t y i e l d much i n f o r m a t i o n , t h e i r mode o f o c c u r r e n c e might be h i g h l y i n f o r m a t i v e . S t r a i g h t c h a i n f a t t y a c i d s , f o r example, do n o t c a r r y much i n f o r m a t i o n . I f , however, i t i s a n a l y z e d w h i c h f a t t y a c i d s o c c u r f r e e , which a r e e s t e r i f i e d , o r w h i c h a r e amide bound, we c a n o b t a i n a l o t o f i n f o r m a t i o n from these compounds i n terms o f t h e i r b i o l o g i c a l o r i g i n and/or o f e a r l y s t a g e d i a g e n e t i c a l pathways. T h i s k i n d o f i n f o r m a t i o n has been used t o t r a c e back t h e o r i g i n o f a l c o h o l s and s t e r o l s i n s e v e r a l sediments ( 7 ) . T o t a l p r o f i l e s . By a n a l y s i s o f t o t a l e x t r a c t s , t o t a l h y d r o l y z a t e s o r t o t a l p y r o l y s i s p r o d u c t s , e t c . w i t h o u t any p r e s e p a r a t i o n , one c a n o b t a i n so c a l l e d t o t a l p r o f i l e s . When gas chromatography o r gas chromatography-mass s p e c t r o m e t r y a r e a p p l i e d f o r these k i n d s o f a n a l y s e s , we c a n study t o t a l p r o f i l e s o f l i p i d compounds w h i c h a r e amenable by GC. However, m o n i t o r i n g f r a c t i o n s o f sedimentary o r g a n i c m a t t e r c a n a l s o be performed by IR, NMR, UV-VIS and o t h e r s p e c t r o s c o p i c t e c h n i q u e s . I n t h i s paper we w i l l l i m i t o u r s e l v e s t o GC and GC-MS p r o f i l e s o f l i p i d f r a c t i o n s o b t a i n e d from sediments. The p r o f i l e s might be c o n s i d e r e d as b i r d ' s eye views o f t h e sedimentary o r g a n i c m a t t e r . One c a n compare r e l a t i v e c o n c e n t r a t i o n s o f i n d i v i d u a l compounds o r c l a s s e s o f compounds d i r e c t l y , and by u s i n g the above mentioned i n f o r m a t i o n contents c h a r a c t e r i z e the o r i g i n and/or d i a g e n e s i s o f t h e sediment i n terms o f r e l a t i v e c o n t r i b u t i o n s from d i f f e r e n t groups o f organisms such as h i g h e r p l a n t s v s . d i n o f l a g e l l a t e s v s . c o c c o l i t h o p h o r e s v s . b a c t e r i a . F u r t h e r m o r e , i f one observes i n these t o t a l p r o f i l e s s i m i l a r o r even i d e n t i c a l d i s t r i b u t i o n p a t t e r n s o f d i f f e r e n t c l a s s e s o f compounds, a c o r r e l a t i o n between these compound c l a s s e s must e x i s t , due t o e i t h e r the o c c u r r e n c e o f s i m i l a r p a t t e r n s i n c e r t a i n groups o f organisms o r due t o d i s t i n c t d i a g e n e t i c pathways by w h i c h one c l a s s o f compounds i s transformed t o another compound c l a s s w i t h o u t a f f e c t i n g t h e d i s t r i b u t i o n p a t t e r n s . I n t h i s way i n d i v i d u a l m o l e c u l e s o r d i s t r i b u t i o n p a t t e r n s which do n o t c o n t a i n much i n f o r m a t i o n as such are becoming i n f o r m a t i o n c a r r i e r s o f some importance. No examples o f t h i s l i n e of information are reported i n the l i t e r a t u r e . I n t h i s paper a number o f examples w i l l be g i v e n t o i l l u s t r a t e t h e above mentioned concept. F o r t h a t purpose f i r s t a c r i t i c a l e v a l u a t i o n of a s e l e c t e d p a r t o f o u r work i n D e l f t from the l a s t f i v e o r s i x y e a r s i s p r e s e n t e d . Subsequently t h e r e s u l t s o f some ongoing r e s e a r c h w i l l be d i s c u s s e d t o f u r t h e r i l l u s t r a t e the a p p l i c a t i o n o f o r g a n i c m o l e c u l e i n f o r m a t i o n e x p r e s s e d i n modes o f o c c u r r e n c e and as t o t a l p r o f i l e s o f o r g a n i c compounds from sediments. F i n a l l y t h e f i n d i n g o f new o r g a n i c s u l p h u r compounds and t h e i r p o s s i b l e s i g n i f i c a n c e s a r e r e p o r t e d . I n t h i s r e p o r t , m a i n l y d a t a from r e c e n t and s u b r e c e n t sediments a r e d i s c u s s e d . A l t h o u g h some a t t e n t i o n w i l l be g i v e n t o carbohydrates, the m a j o r i t y of the organic molecules considered here a r e l i p i d s . I t s h o u l d be n o t e d t h a t t h i s paper i s n o t a t a l l meant t o g i v e a complete r e v i e w o f o r g a n i c i n f o r m a t i o n c a r r i e r s i n sediments; the i n v e s t i g a t i o n s d i s c u s s e d a r e s e l e c t e d from o u r work a t D e l f t t o i l l u s t r a t e t h e above mentioned concept.



36 R e s u l t s and

Discussion

T a b l e I summarizes some of the sediments of which samples have been a n a l y z e d or are b e i n g a n a l y z e d i n our group. R e s u l t s o b t a i n e d from e x t r a c t s of these sediment samples are d i s c u s s e d i n t h i s paper.


T a b l e I . Sediments I n v e s t i g a t e d Sample

Age

Location

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

0 - 2500 y r . BP very r e c e n t 6 χ 10 y r . 225 χ 10 y r . 0 - 3000 y r . BP 3000 - 7000 y r . BP Cretaceous Very r e c e n t Pleistocene/Miocene 1000 - 2500 y r . BP Miocene Very r e c e n t

North S i n a i South S i n a i N o r t h Apennines Eastern Mediterranean B l a c k Sea B l a c k Sea C e n t r a l Apennines Mediterranean W a l v i s Ridge o f f S.W.-Africa Utah The N e t h e r l a n d s

S o l a r Lake Gavish Sabkha Sarsina Sapropel S B l a c k Sea U n i t 1 B l a c k Sea U n i t 2 Livello Bonarelli Sapropels DSDP 362 Namibian S h e l f Rozel Point O i l Wadden Sea

6

3

7

F i g u r e 2 shows t h e i r g e o g r a p h i c a l p o s i t i o n , except f o r the R o z e l P o i n t o i l which comes from the U i n t a b a s i n i n U t a h , USA, and the mud samples from the Dutch Wadden Sea. The occurrence and p o s s i b l e s i g n i f i c a n c e of s e v e r a l s u i t e s of o r g a n i c compounds i s o l a t e d from a number of r e c e n t sediments have been r e p o r t e d by us over the l a s t y e a r s . F i r s t l y , r e s u l t s of t h i s work w i l l be c r i t i c a l l y e v a l u a t e d and s e c o n d l y , a few new compounds s e r i e s and a n a l y t i c a l approaches are discussed. M i d c h a i n ketones and s t e r o l e t h e r s . F i g u r e 3 shows the upper p a r t o f a T o t a l Ion C u r r e n t (TIC) t r a c e o b t a i n e d from a TLC f r a c t i o n of an e x t r a c t of the Namibian S h e l f diatomaceous ooze. Long m i d c h a i n ketones and s t e r o l e t h e r s t o g e t h e r w i t h a s e r i e s of wax e s t e r s were shown t o be p r e s e n t i n t h i s f r a c t i o n ( 9 ) . The s t e r o l e t h e r s a r e composed of common A - s t e r o l m o i e t i e s and Ce and Cg a l k y l m o i e t i e s ( I ) . 5

I A l t h o u g h these compounds are encountered i n s e v e r a l o t h e r sediments (10), t h e i r unique s t r u c t u r a l i n f o r m a t i o n cannot be v a l i d a t e d s i n c e these compounds are not ( y e t ) d i s c o v e r e d by the n a t u r a l product chemists i n l i v i n g systems. The r e p o r t e d occurrence of c h o l e s t e r y l



F i g u r e 3. Upper p a r t of t o t a l i o n c u r r e n t t r a c e of a TLC of Namibian S h e l f diatomaceous ooze sediment extract.

fraction


Η

χ m ξ

m Ο m Ο Ο

> 2

ο

>

Ο Σβ Ο

00



400

ο

•Η

> •Η

•Η Ω

.

Ε CQ

>> 03

• CJ LO < Q)

—

3 Ό bO ·Η •Η ϋ b-, AL


3.

DE LEEUW

Sedimentary Lipids and Polysaccharides

39


h e x a d e c y l e t h e r i n b o v i n e c a r d i a c muscle (11) i n d i c a t e s t h a t s t e r o l e t h e r s as such o c c u r i n n a t u r e . L o n g - c h a i n ketones as such a r e known to o c c u r i n p l a n t waxes ( 1 2 ) . I n p l a n t s they are b i o s y n t h e s i z e d v i a the c o r r e s p o n d i n g hydrocarbons and the d i s t r i b u t i o n p a t t e r n s o f t h e hydrocarbons and m i d - c h a i n ketones i n p l a n t s are t h e r e f o r e v e r y s i m i l a r and are c h a r a c t e r i z e d by a s t r o n g odd over even predominance. The m i d - c h a i n ketones p r e s e n t i n t h i s sediment e x t r a c t do not a t a l l r e f l e c t the h y d r o c a r b o n p a t t e r n and do have a s t r o n g even over odd predominance ( I I ) . 0

|M-N|

Organic Marine Geochemistry - American Chemical Society

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