Seasonal and depth variations in molecular and isotopic alkenone composition of sinking particles from the western North Pacific

Yamamoto, Masanobu; Shimamoto, Akifumi; Fukuhara, Tatsuo; Naraoka, Hiroshi; Tanaka, Yuichiro; Nishimura, Akira

doi:10.1016/j.dsr.2007.05.012

Cited by 27 publications

(18 citation statements)

References 50 publications

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“…The alknone concentration and sinking flux also showed strong seasonal variability 166 in traps at each depth (Yamamoto et al, 2007). The alkenone concentration and sinkingflux increased abruptly in mid-March-April, showed multiple maxima in spring to fall.…”

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confidence: 92%

“…5d; Yamamoto et al, 2007), which showed parallel 491 changes at each depth. The U K' 37 -based temperature decreased gradually after October 492 during the low alkenone flux period, abruptly decreased in April at the beginning of the 493 high alkenone flux period, was minimized in April-May, and then increased until 494 September.…”

Section: Seasonal Variation In Tex 86 478mentioning

confidence: 99%

“…BP) using 204 CALIB4.3 software and the marine98 calibration data set (Stuiver and Reimer, 1993) 205 with a 400-year global reservoir correction (Yamamoto et al, 2007). 206 207…”

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confidence: 99%

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Glycerol dialkyl glycerol tetraethers and TEX86 index in sinking particles in the western North Pacific

Yamamoto

Shimamoto²,

Fukuhara³

et al. 2012

Organic Geochemistry

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temperature was lower than the SST from May to December and corresponded to the 30 temperature at the thermocline, whereas it was higher than the SST from December to 31May. The annual average sinking flux of the GDGTs decreased with increasing depth. 32The GDGT half-depth, the depth range over which half of the GDGT is lost, was 33 calculated to be 3108-3349 m, implying that GDGTs were well preserved during 34 sinking in the water column. The flux-weighted average TEX 86 -based temperatures 35were constant with depth and roughly corresponded to mean annual SST. These findings 36 support a previously proposed hypothesis that the GDGTs produced in surface waters 37 are preferentially delivered to the deeper water column by grazing and repackaging in 38 larger particles. The constant TEX 86 at different depths indicates that TEX 86 is not 39 affected by degradation in the water column. The preservation efficiency of GDGTs was 40 1.0-1.3% at the water-sediment interface. Despite the significant degradation of the 41GDGTs, there was a small difference in TEX 86 levels between sinking particles and the 42 surface sediment. 43 44

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confidence: 92%

Section: Seasonal Variation In Tex 86 478mentioning

confidence: 99%

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Glycerol dialkyl glycerol tetraethers and TEX86 index in sinking particles in the western North Pacific

Yamamoto

Shimamoto²,

Fukuhara³

et al. 2012

Organic Geochemistry

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“…We predicted a possible increase in the U 37 K ' -derived temperature when the onset 297 of alkenone production was delayed based on the one-year sediment-trap data of the 298 flux-weighted U 37 K ' -derived temperature at 39˚N, 147˚E in 1998 (Site WCT-2; 299 Yamamoto et al, 2007). The delay in the onset of alkenone production by 1 month 300 (early May onset) induced only a 0.1˚C rise and delays 2 (early June), 3 (late June), 4 301 (late July), 5 (late August), or 6 (late September) months resulted in a total increase in 302 U 37 K ' -derived temperatures of 0.7˚C, 0.9˚C, 2.1˚C, 2.2˚C, and 2.5˚C, respectively (Fig.…”

Section: N; Harada Et Al 2006b) 296mentioning

confidence: 99%

Biomarker records from core GH02-1030 off Tokachi in the northwestern Pacific over the last 23,000 years: Environmental changes during the last deglaciation

Inagaki

Yamamoto

Igarashi³

et al. 2009

J Oceanogr

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19We investigated marine and terrestrial environmental changes at the northern 20 Japan margin in the northwestern Pacific during the last 23,000 years by analyzing 21 biomarkers (alkenones, long-chain n-alkanes, long-chain n-fatty acids, and 22 lignin-derived materials) in Core GH02-1030. The U 37 K ' -derived temperature in the last 23 2 glacial maximum (LGM) centered at 21 ka was ~10˚C, which was 2˚C lower than the 24 core-top temperature (~12˚C). This small temperature drop does not agree with pollen 25 evidence of a large air temperature drop (more than 4˚C) in the Tokachi area. This 26 disagreement might be attributed to a bias of U 37 K ' -derived temperature within 2.5˚C by 27 a seasonal shift in alkenone production. The U 37 K ' -derived temperature was significantly 28 low during the last deglaciation. Because this cooling was significant in the 29Kuroshio-Oyashio transition zone, the temperature drops are attributable to the 30 southward displacement of the Kuroshio-Oyashio boundary. Abundant lignin-derived 31 materials, long-chain n-alkanes and long-chain n-fatty acids indicate a higher 32 contribution of terrigenous organic matter from 17 to 12 ka. This phenomenon might 33 have resulted from an enhanced coastal erosion of terrestrial soils due to marine 34 transgression and/or an efficient inflow of higher plant debris to river waters from 17 to 35 12 ka. 36 37

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“…More studies [30][31][32][33] have documented that nutrientlimitation (either nitrate or phosphate) and Fe-limitation control the cell growth rate and thus affect isotopic fractionation. On the other hand, many field observations and laboratory experiments [34][35][36] have repeatedly shown strong evidence on isotopic depletion (negative shift) of alkenones during transport/recycling. Interpretations on isotopic alterations of alkenones during transport/recycling have been controversial and various hypothesized mechanisms have not been clarified.…”

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confidence: 99%

Impact of Biogeochemical Cycling of Phytoplankton-Produced Lipid Compounds in Ocean Systems on Paleoceanographic Records Buried in Sediments

Sun¹

2012

J Marine Sci Res Dev

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Deciphering historic records buried in ancient marine sediments is critically important for understanding the past and current changes in environmental and climate conditions of the earth. Many molecular approaches, including phytoplankton-produced lipid compounds and their stable isotopic compositions, have been developed to conduct this mission [1][2][3][4]. Applications of these approaches are based on a presumption that once these chemical and isotopic signals are generated by phytoplankton in surface water, they remain intact until ultimate burial in sediments. However, most (>95%) phytoplankton-produced organic compounds are recycled by biological and biogeochemical processes in water and surface sediments [5][6][7][8]. Therefore, a logical question has been raised on whether or how these molecular signals are altered during transport/recycling processes.The first example is the record of paleo-surface water temperature using alkenone-based index Uk-37' [9,10]. Although the variability in the Uk-37' index is largely dependent on the temperature in surface water at which the algae grow, other factors have been recognized to affect the index. For example, cell growth rate or growth stage may play a role along with temperature in controlling the unsaturation degree of alkenones [11]. Alkenones are disproportionally synthesized by Prymnesiophyceae cells either as membrane compounds or as metabolic energy storage compounds during different growth stages [12,13], leading to potential deviations (up to 3°C) in the estimated temperature [14][15][16][17]. Grazing activities of zooplankton and benthic fauna seem to have little impact on alkenone degradation [18][19][20], but microbial processes play a dominating role in alkenone degradation [21,22]. Contrasting effects of microbial degradation of alkenones on the Uk-37' index have been observed in different systems or under different environmental conditions, which are likely due to involvement of different microorganisms [23], different degrading reactions [24], and variable redox conditions [25].The second example is to determine paleo-CO 2 level using alkenone δ 13 C signals, based on a presumption that isotopic composition of one single alkenone compound preserved in sediments is linked to carbon isotopic fractionation (ε p ) of phytoplanktonic organic matter while a simple linear relationship exists between CO 2 concentration and the (ε p ) [26,27]. This simple linear relationship was challenged by a finding that cell growth rate also affects isotopic fractionation of phytoplankton organic matter and the (ε p ) is strongly related to the ratio of growth rate to CO 2 concentration (μ/C e ) rather than [CO 2 ] alone [28,29]. More studies [30][31][32][33] have documented that nutrientlimitation (either nitrate or phosphate) and Fe-limitation control the cell growth rate and thus affect isotopic fractionation. On the other hand, many field observations and laboratory experiments [34][35][36] have repeatedly shown strong evidence on isotopic depletion (negative shif...

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Seasonal and depth variations in molecular and isotopic alkenone composition of sinking particles from the western North Pacific

Cited by 27 publications

References 50 publications

Glycerol dialkyl glycerol tetraethers and TEX86 index in sinking particles in the western North Pacific

Glycerol dialkyl glycerol tetraethers and TEX86 index in sinking particles in the western North Pacific

Biomarker records from core GH02-1030 off Tokachi in the northwestern Pacific over the last 23,000 years: Environmental changes during the last deglaciation

Impact of Biogeochemical Cycling of Phytoplankton-Produced Lipid Compounds in Ocean Systems on Paleoceanographic Records Buried in Sediments

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