Variations in the distributions and isotopic composition of alkenones in Black Sea particles and sediments

doi:10.1016/0146-6380(92)90043-W

Organic Geochemistry

Volume 19, Issues 1–3, December 1992, Pages 277-285

https://doi.org/10.1016/0146-6380(92)90043-W Get rights and content

Abstract

Concentrations, unsaturation index (U₃₇^k) and isotopic compositions of individual alkenones were measured for samples of suspended particulate organic matter (POM), sediment trap and sedimentary organic matter from the Black Sea. In general, temperatures estimated from U₃₇^k are lower than actual sea surface temperatures, indicating existing calibrations may not be appropriate for alkenones in the Black Sea. Specifically, there is a lack of agreement among U₃₇^k values calculated with and without the concentration of the C_37:4 alkenone which lead to significant differences in temperatures estimated using the available calibrations. The more unsaturated alkenones in suspended POM with high water column residence times may be degraded preferentially, resulting in the observed increase with depth of U₃₇^k values. The σ¹³C of individual alkenones in suspended particles decrease with increased unsaturation. However, there is no correlation between temperature inferred from U₃₇^k and the isotopic composition of individual alkenones. Isotopic compositions of the C_37:4 alkenone are apparently independent of more saturated isomers. Although the overall pattern of the σ¹³C of higher molecular weight alkenones (C₃₈, C₃₉) with depth in the water column is similar to that of that of the di- and tri-unsaturated C₃₇ alkenones, isotopic compositions of individual isomers range several permil. Variation in the isotopic compositions of alkenones may be due to differences either in the biological sources for or mechanisms for removal of alkenones in organic matter suspended in the waters of the Black Sea.

References (42)

J.M. Hayes et al.
Compound-specific isotopic analyses: A novel tool for reconstruction of ancient biogeochemical processes
M.E.L. Kohnen et al.
Origin and diagenetic transformations of C₂₅ and C₃₀ highly branched isoprenoid sulphur compounds: further evidence for the formation of organically bound sulphur during early diagnesis
Geochim. Cosmochim. Acta
(1990)
P.M. Kroopnick
The distribution of ¹³C in the world oceans
Deep-Sea Res.
(1985)
J.W. de Leeuw et al.
On the occurrence and structural identification of long chain unsaturated ketones and hydrocarbons in sediments
I.N. McCave
Vertical flux of particles in the ocean
Deep-Sea Res.
(1975)
F.G. Prahl et al.
Further evaluation of long-chain alkenones as indicators of paleoceanographic conditions
Geochim. Cosmochim. Acta
(1988)
G.H. Rau et al.
The relationship between σ¹³C of organic matter and [CO₂(aq)] in ocean surface water: Data from a JGOFS site in the northeast Atlantic Ocean and a model
Geochim. Cosmochim. Acta
(1992)
J.A. Rechka et al.
Characterization of alkenone temperature indicators in sediments and organisms
E.L. Sikes et al.
Use of the alkenone unsaturation ratio U₃₇^k to determine past sea surface temperatures: core-top SST calibrations and methodology considerations
Earth Planet. Sci. Lett.
(1991)
J.S. Sinninghe-Damsté et al.
Quenching of labile functionalised lipids by inorganic sulphur species: evidence for the formation of sedimentary organic sulphur compounds at the early stages of diagenesis
Geochim. Cosmochim. Acta
(1989)

J.R. Volkman et al.

Novel unsaturated straight-chain C₃₇C₃₉ methyl and ethyl ketones in marine sediments and a coccolithophore Emiliania huxleyi

J.R. Volkman et al.

Long-chain alkenes and alkenones in the marine coccolithophorid Emiliania huxleyi

Phytochemistry

(1980)

S.C. Brassell et al.

Molecular stratigraphy: a new tool for climatic assessment

Nature

(1986)

P.A. Cranwell

Long-chain unsaturated ketones in recent lacustrine sediments

Geochim. Cosmochim. Acta

(1985)

G.J. Demaison et al.

Anoxic environments and oil source bed genesis

AAPG Bull.

(1980)

K.H. Freeman

The carbon isotopic composition of individual compounds from ancient and modern depositional environments

Ph.D. dissertation, Indiana University

(1991)

K.H. Freeman et al.

Fractionation of carbon isotopes by phytoplankton and estimates of Ancient CO₂ levels

Global Biogeochem. Cycles

(1992)

K.H. Freeman et al.

Evidence from carbon isotopic measurements for diverse origins of sedimentary hydrocarbons

Nature

(1990)

G.E. Friederich et al.

Bottle and pump cast data from the 1988 Black Sea expedition

Monterey Bay Aquarium Research Institute Technical Report 90-3

(1990)

B. Fry et al.

Stable isotope studies of the carbon, nitrogen and sulfur cycles in the Black Sea and the Cariaco Trench

Deep-Sea Res.

(1992)

C. Goyet et al.

The carbonate system in the Black Sea

Deep-Sea Res.

(1992)

Cited by (106)

Carbonate dissolution and environmental parameters govern coccolith vs. alkenone abundances in surface sediments from the northwest North Atlantic
2021, Marine Micropaleontology
We determined the abundances and concentrations of coccoliths and alkenones in 66 surface sediment samples from the northwest North Atlantic to evaluate the role that surface ocean temperature, salinity, sea-ice cover, and productivity have on the regional distribution of these two biological remains produced by haptophytes in the photic zone. In areas with sea-ice cover of more than 1 month per year, coccolith and alkenone concentrations in sediments are extremely low to nil. Elsewhere, the distribution of coccolith taxa generally displays strong relationships to water temperature, salinity, and productivity. Coccolithus pelagicus is associated with low summer sea-surface temperatures (<8°C) and relatively high summer sea-surface salinities (>33.5), whereas Helicosphaera carteri seems to follow the path of the North Atlantic Drift. The distribution of Emiliania huxleyi, the dominant alkenone producer, is not strongly correlated with that of alkenones. Calcite dissolution in shelf sediments could explain the occurrence of alkenones in the absence of coccoliths but alkenone production by non-calcifying haptophytes seems to also exert some control on alkenone concentrations in surface sediments, thus blurring alkenone abundance links to coccolithophorid production and their relative preservation.
Severe late Miocene droughts affected western Eurasia
2021, Global and Planetary Change
Citation Excerpt :
All warming events observed in the Panagia section are accompanied by carbonate deposition (Palcu et al., 2021), suggesting coeval changes in the chemistry and circulation of the basin. The δ13CC37 values from Panagia (−26.5‰ to −20.5‰) are close to global upper Miocene values (−25‰ to −21‰) (e.g. Pagani et al., 1999), yet somewhat different to those measured in the recent Black Sea (−26‰ to −29‰) (e.g. Freeman and Wakeham, 1992). Important is the 3‰ decrease in δ13CC37alkenones (Fig. 3D, Supplementary Table 3) between 9.66 and 9.28 Ma, that parallels an increase in δ2HC37 up to −126‰, a value typical for evaporative conditions.
A large and highly dynamic aquatic system called Paratethys governed important elements of the middle and late Miocene (15.97–5.33 Ma) hydrology in western Eurasia. So far, the impact of the vast Paratethys water body on the Eurasian climate, however, is not yet understood. Here we apply biomarker analyses coupled to compound-specific hydrogen and carbon isotope data to track changes in sea surface temperature, mean annual air temperature, hydrological budget and vegetation changes to reconstruct long-term western Eurasian climate conditions between 12.7 and 7.65 Ma in the Black Sea region. Biomarker data from Panagia (Russia) indicate the presence of three exceptionally evaporative intervals peaking at 9.65, 9.4 and 7.9 Ma. These peaks in evaporation relate to aridity, parallel increasing fire activity and are associated with changes in vegetation. Carbon isotope and pollen data support the evidence of an increase in C₄ plants associated with these dry intervals. At 9.66 Ma, alkenone producing algae appear in the basin and thrive for the subsequent two million years. Cumulative fluctuations in both hydrology and surface temperature of Paratethys might have enhanced rainfall seasonality in western Eurasia as a response to changes in evaporation over the Paratethys basin. Our combined data suggest a strong regional imprint on overall climate patterns, dominated by basin dynamics causing Paratethys volume and surface reduction. Collectively, the presented biomarker results provide evidence of severe droughts affecting the late Miocene circum-Paratethys region, leading to a direct impact on the evolution of biota in the basin and its surroundings.
New insights into environmental controls on the occurrence and abundance of Group I alkenones and their paleoclimate applications: Evidence from volcanic lakes of northeastern China
2019, Earth and Planetary Science Letters
The distinctive long-chain alkenones (LCAs) produced by Group I Isochrysidales from freshwater and oligohaline lakes have great potential for quantitative paleotemperature reconstructions. The widespread application of sedimentary Group I LCAs, however, is hampered by an incomplete understanding of the environmental controls on the occurrence of Group I LCAs in freshwater lakes. The correspondence between Group I LCA concentrations and pH (6.2–8.5) in northern Alaskan freshwater lakes (Longo et al., 2016) suggests that Group I Isochrysidales may preferentially thrive in freshwater lakes with high pH. Here, we systematically study LCA distributions, haptophyte-specific 18S rDNA sequences, and concentrations of major ions and trace elements in 18 freshwater volcanic lakes in northeastern China with an extended pH range from 7.17 to 9.99. We find that 11 of the 18 lakes examined contain Group I LCAs and the corresponding DNA sequences of their producers. Our DNA results indicate that the dominant alkenone producer in all 11 lakes is closely related to the Group I Greenland OTU 5 genotype, with the exception of two anthropogenically impacted lakes where small numbers of Group II sequences are found. Statistical analyses indicate that the highest concentrations of Group I LCAs are found in oligotrophic freshwater lakes with pH ranging from ∼7.3 to 8.8. We find that elevated concentrations of certain trace elements may lead to the disappearance of Group I LCAs despite lake water falling within the optimal pH range. Together with previously published Group I LCA data from the temperature calibration in Northern Hemisphere freshwater lakes (Longo et al., 2018), we find, for the first time, that Group I R3b (R3b = C_37:3b/(C_38:3bEt + C_37:3b)) values are most sensitive to winter temperature changes when mean winter temperature is higher than $\sim - 20 ° C$ . Our results suggest that the freshwater volcanic lakes in northeastern China are highly valuable targets for paleotemperature reconstructions using Group I LCAs.
High- and low-latitude forcing on the south Yellow Sea surface water temperature variations during the Holocene
2019, Global and Planetary Change
Sea surface temperature (SST) of the modern Yellow Sea (YS) is sensitive to forcing by both the East Asian monsoon and the North Pacific western boundary current, however, detailed mechanisms for explaining the Holocene SST evolution remains to be understood. Here we present two decadal sampling resolution alkenone SST records from the south YS spanning the last 8.9 kyr to understand forcing mechanisms on different timescales. The results show that the two sites from the south YS experienced SST variations on millennial timescale, displaying mean high values of 16.5 °C (A03-B) and 15.2 °C (YS01) from 7.7 to 5.9 ka, followed by low values of 16.4 °C (A03-B) and 14.8 °C (YS01) from 5.9 to 2.9 ka, then by high values of 16.9 °C (A03-B) and 15.5 °C (YS01) from 2.9 to 0.6 ka. After the entrance of the YS Warm Current at about 7.5 ka, evolution of the south YS SSTs paralleled the pattern of the main Kuroshio Current intensity, i.e., low (high) SST coeval with weak (strong) Kuroshio Current, suggesting that millennial-scale SST variations in the south YS were primarily controlled by the Kuroshio Current. Superimposing on the millennial variations, seven abrupt centennial-scale cold events were observed during the Holocene, with SST oscillations broadly coeval with those of North Atlantic ice-rafted detritus and East Asian winter monsoon rather than SSTs from the Okinawa Tough and Indo-Pacific warm pool. Hence, we propose that the East Asian winter monsoon was the top-down conveyor transmitting North Atlantic cooling signals to the south YS on centennial timescale. Thus, our study reveals both high- and low-latitude climate forcing on the evolution of the south YS SST during the Holocene, with low-latitude forcing on millennial-scale and high-latitude forcing on centennial-scale.
Factors influencing <sup>14</sup>C concentrations of algal and archaeal lipids and their associated sea surface temperature proxies in the Black Sea
2016, Geochimica et Cosmochimica Acta
Understanding the preservation and deposition history of organic molecules is crucial for the understanding of paleoenvironmental information contained in their abundance ratios such as U^k′₃₇ and TEX₈₆ used as proxies for sea surface temperature (SST). Based on their relatively high refractivity, alkenones and glycerol dialkyl glycerol tetraethers (GDGTs) can survive postdepositional processes like lateral transport, potentially causing inferred SSTs to be misleading. Likewise, selective preservation of alkenones and GDGTs may cause biases of the SST proxies themselves and can lead to decoupling of both proxy records. Here we report compound-specific radiocarbon data of marine biomarkers including alkenones, GDGTs, and low molecular weight (LMW) n-fatty acids from Black Sea sediments deposited under different redox regimes to evaluate the potentially differential preservation of both biomarker classes and its effect on the SST indices U^k′₃₇ and TEX₈₆. The decadal Δ¹⁴C values of alkenones, GDGTs, and LMW n-fatty acids indicate similar preservation under oxic, suboxic, and anoxic redox regimes and no contribution of pre-aged compounds, e.g., by lateral supply. Moreover, similar ¹⁴C concentrations of crenarchaeol, alkenones, and LMW n-fatty acids imply that the thaumarchaeotal GDGTs preserved in these sediments are produced in the euphotic zone rather than in subsurface/thermocline waters. However, we observe biomarker-based SSTs that strongly deviate (ΔSST up to 8.4 °C) from in situ measured mean annual SSTs in the Black Sea. This is not due to redox-dependent differential biomarker preservation as implied by their Δ¹⁴C values and spatial SST pattern. Since contributions from different sources can largely be excluded, the deviation of the U^k′₃₇ and TEX₈₆ proxy-derived SSTs from in situ SSTs requires further study of phylogenetic and other yet unknown environmental controls on alkenone and GDGT lipid distributions in the Black Sea.
Recurrent phases of drought in the upper Miocene of the Black Sea region
2015, Palaeogeography, Palaeoclimatology, Palaeoecology
Since the Miocene the Black Sea proved to be highly sensitive to fluctuations in the hydrological cycle because of its recurrent restricted connections with the open ocean and the location between the dry Mediterranean and more humid higher northern latitudes. Although the Black Sea formed one of the foci of the 1975 Deep Sea Drilling Project Leg 42B, robust tools to reconstruct past changes in its hydrological cycle were lacking at that time. Here we revisit the sedimentary succession (Hole 380A) and determined compound-specific carbon (δ¹³C) hydrogen isotope ratios (δD) of terrestrial and aquatic biomarkers to investigate changes in the hydrological budget of the Black Sea during the late Miocene. The δ¹³C and δD isotopic composition of n-alkanes as well as alkenones and palynology indicate large environmental changes in the Black Sea and/or in the sources of the water entering the Black Sea during the late Miocene. The δD of alkenones, showing an enrichment of more than 80‰ at the end of the Miocene, implies a major shift in basin hydrology, possibly resulting in severely increased salinity. These changes in δD composition of the alkenones coincide with both with sharp shifts in reconstructed sea surface temperature and palynological assemblages. Two intervals with negative water budget were identified, most likely caused by enhanced evaporation. The older and longer dry/evaporative phase predates the Maeotian/Pontian boundary (regional stages) at ~ 6.1 Ma. The younger drying phase corresponds to the Messinian Salinity Crisis. This shift to highly evaporative conditions is related to a similar shift previously observed in a Messinian (Pontian) sedimentary succession from the Taman Peninsula (Russia). These recurrent dry phases likely reflect regional climatic shifts over a significantly larger area around the Black Sea area during the upper Miocene.

View all citing articles on Scopus

^∗: Present address: Department of Geosciences, Pennsylvania State University, University Park, PA 16802, U.S.A.

View full text

Variations in the distributions and isotopic composition of alkenones in Black Sea particles and sediments

Abstract

Geochim. Cosmochim. Acta

Deep-Sea Res.

Deep-Sea Res.

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Earth Planet. Sci. Lett.

Geochim. Cosmochim. Acta

Phytochemistry

Molecular stratigraphy: a new tool for climatic assessment

Nature

Long-chain unsaturated ketones in recent lacustrine sediments

Geochim. Cosmochim. Acta

Anoxic environments and oil source bed genesis

AAPG Bull.

The carbon isotopic composition of individual compounds from ancient and modern depositional environments

Ph.D. dissertation, Indiana University

Fractionation of carbon isotopes by phytoplankton and estimates of Ancient CO2 levels

Global Biogeochem. Cycles

Evidence from carbon isotopic measurements for diverse origins of sedimentary hydrocarbons

Nature

Bottle and pump cast data from the 1988 Black Sea expedition

Monterey Bay Aquarium Research Institute Technical Report 90-3

Stable isotope studies of the carbon, nitrogen and sulfur cycles in the Black Sea and the Cariaco Trench

Deep-Sea Res.

The carbonate system in the Black Sea

Deep-Sea Res.

Fractionation of carbon isotopes by phytoplankton and estimates of Ancient CO₂ levels