CHAPTER 5 . Organic Matter Preservation: Lipid Behavior from Plankton to Sediments
135
C 3T + C 38 -alkenones), bacterial (cis-vaccenic acid [18:1(07], iso+anteiso-15:0 acids [br15 fas], bisnorhopane and squalene), or vascular plant (n-nonacosane [C29], hexade canol [28ROH] and hexacosanoic acid [26faJ) origins. All compounds in this suite,
regardless of source, clearly exhibited markedly decreasing fluxes with increasing depth
(Fig. 5.6). There were no absolute flux increases below the ocean surface to the extent
that would unambiguously indicate significant amounts of net secondary production
at depth. Nor were there significant inputs of biomarkers via lateral advection. 24Ethylcholest-5-en-3j3-ol has traditionally been ascribed to vascular plant sources
(Huang and Meinschein 1979), but its abundance in many plankton (Volkman 1986)
and a stable carbon isotopic composition of -24%0 for these EqPac samples indicates
a predominately marine source.
On the other hand, there were significantly different behaviors among these biomarkers when distributions were scaled based on their relative abundances in the
sample set (Fig. 5.7). This approach further classifies the biomarkers into subcategories based on their behavior, in addition to source. Three of the seven planktonic
biomarkers (22:6W3 pufa, 16ROH, and 28~5.24(28) had maximal abundances in the upper 100 m where planktonic production is highest. Cholest -5-en -313 -01 (27 ~5) was most
abundant in the 1000 m trap, while the remaining three planktonic compounds (29~5,
30~22, and alkenones) had enhanced abundances in the sediments. The four bacterial
markers (18:1W7, br-15 fas, bisnorhopane and squalene) and the three vascular plant
biomarkers (n-C29, 28ROH and 26fa) were most abundant in sediments.
o
8 0 ~
o 8 8 0
d d
d
d
d
0
0
0
Plankton rWIL.JWJIIO...J.W-:::;~~~M1
105 m trap
1000mtrap
3500 mtrap
0-1 em sed
22:6 pufa
-B16ROH
.. ~ ..
28(5,24(28))
·····0····
27(5)
-*- 30(22)
_ .. -
29(5)
-...
alkenones
Flux (mg m-2 dol)
0 0 0
q
0
0 0
0
0
0
d
d
~
I!
,:
I!
I!
,:
I!
I!
,:
**
/ i ./
I !
I :
" i !
. '
0
d d
0
18:1w7fa
--br-15 fas
.... 0-...
bisnorhopane
-_ .. -_ .
squalene
-*-.
0 0
0
0
0 0 0
oq 0 0
~o
d
d
0
d
I
I
I
I
I
I
I
. . 3ft
:11
! f "
i i i
!! :
Ii I
I i I
~
11/
I !I
! ;
d
0
C29
... -0-...
28ROH
---.-_.
26 fa
-*-.
Fig. 5.6. Fluxes for selected biomarkers in EqPac samples from the equator station (docosahexaenoic
acid [22:6(1)3 pufa], hexadecanol [16ROH], 28-methr,lcho!esta-5,24(28)-dien-3/3-0! [2M 5 ,24(28)], cholest5-en-3/3-ol [27Ll5], 24-ethylcho!est-5-en-3/3-ol [29Ll], 4a,23,24-trimethylcholest-22E-en-3/3-ol [30Ll 22 ],
C3T +C38-aikenones, cis-vaccenic acid [18:1(1)7], iso+anteiso-15:0 acids [br-15 fas], bisnorhopane,squaiene,
n-nonacosane [C29], hexadecanol [28ROH], hexacosanoic acid [26fa])
0
0