Dinoflagellate Sterols

Withers, Nancy W.

doi:10.1016/b978-0-12-624005-4.50010-0

Cited by 51 publications

(49 citation statements)

References 91 publications

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“…21) was easily detected, indicating a significant contribution of dinoflagellates to these sediments. Dinosterol is the most utilized biomarker for dinoflagellates even though it is a minor component in some dinoflagellate species and completely absent in others (Withers 1987;Volkman et al 1993;Leblond and Chapman 2002). Other dinoflagellate steroidal species present are the corresponding stanol, 30D 0 (dinostanol, peak No.…”

Section: Resultsmentioning

confidence: 99%

“…Composed of a skeleton of four fused rings, sterols vary in the number and position of double bonds, side chains and/or ring methylations, as well as in their stereochemistry (Volkman 1986). A subset of the sterol pool, the 4a23,24-trimethyl sterols (and particularly dinosterol, Table 1), have been proposed as dinoflagellate tracers for sedimentary organic matter (Withers 1987;Volkman et al 1999) since they are not synthesized to a significant extent by other organisms (Volkman et al 1993).…”

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confidence: 99%

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Dinosterols or dinocysts to estimate dinoflagellate contributions to marine sedimentary organic matter?

Mouradian

Panetta

Vernal³

et al. 2007

Limnology & Oceanography

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Dinosterol (4a,23,24-trimethyl-5a-cholest-22E-en-3b-ol) is frequently used as an alternative to dinoflagellate cyst (dinocyst) counting in paleoceanography to assess dinoflagellate inputs to marine sediments. However, recent studies have shown poor correlation between these two proxies in continental-margin sediments. We reevaluated the relationship and expanded it to include a suite of biogeochemical transformation products of the parent dinosterol (dinosterone, dinostanone, and dinostanol). These dinoflagellate-specific 4a,23,24-trimethyl steroidal species (S dinosterol ) are compared to dinocyst counts in sediments from the western Mexican margin (375-3,500 m). Samples were taken from subsurface (3-6 cm) and down core (16-27 cm) to reflect widely contrasting organic carbon content and redox conditions. A strong correlation was found between the sum of all dinoflagellate-derived sterols, S dinosterols , and total dinocyst counts, highlighting the importance of including diagenetic alteration products of the parent molecule when exploiting organic biomarkers in paleoceanographic studies. In low-energy environments and for well-preserved samples, such as those studied in this work, both methods provide robust, internally consistent data, suggesting that when diagenetic transformation products of dinosterol are taken into account, gas chromatography and optical microscopy could be used interchangeably to estimate dinoflagellate inputs to marine sediments.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

Dinosterols or dinocysts to estimate dinoflagellate contributions to marine sedimentary organic matter?

Mouradian

Panetta

Vernal³

et al. 2007

Limnology & Oceanography

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“…The dominant sterol(s) in diatoms varies depending on the species present, but brassicasterol (24-methylcholesta-5,22-dien-3b-ol), fucosterol (24-methylcholesta-5,24(28)-dien-3b-ol), and b-sitosterol (24-ethylcholesta-5-en-3b-ol) are common lipids of diatoms (Barrett et al 1995;Volkman et al 1998). The compound dinosterol (4a,23,24-trimethyl-5a-cholest-22-en-3b-ol) is found in many dinoflagellate species (Boon et al 1979;Withers 1983;Pirretti et al 1997) and is commonly used as a biomarker for these organisms (Robison et al 1984;Brassell et al 1987;Volkman et al 1998). The other two main algal groups in Lake Malawi, green algae and cyanobacteria, also have specific biomarkers.…”

Section: Methodsmentioning

confidence: 99%

Influence of climate change on algal community structure and primary productivity of Lake Malawi (East Africa) from the Last Glacial Maximum to present

Castañeda

Werne

Johnsona

2009

Limnology & Oceanography

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Biomarkers of aquatic algae and compound-specific carbon isotopes are used to examine past variations in algal community composition and primary productivity in Lake Malawi. We note major changes at the Pleistocene-Holocene boundary. From the Last Glacial Maximum until ,11.8 calendar years before present (kyr B.P.), Lake Malawi was characterized by either low rates of primary productivity or algal productivity that was dominated by a group other than diatoms. At the onset of the Holocene, conditions similar to those of modern Lake Malawi were initiated, with diatoms and nitrogen-fixing cyanobacteria becoming more important contributors to primary productivity. The transition at ,11.8 kyr B.P. is likely related to a shift in the dominant wind direction over Lake Malawi, resulting from a southward shift in the mean latitudinal position of the Intertropical Convergence Zone during the last glacial. Throughout the 23-kyr B.P. record, the effects of windinduced upwelling are important and may be the main control on the carbon isotopic composition of algal lipids through delivery of 13 C-depleted CO 2 , derived from organic matter decomposition in deeper waters, to the photic zone. Relationships are also suggested between thermal stratification and primary productivity, with cool conditions at ,12 and 8 kyr B.P. resulting in weaker thermal stratification and increased primary productivity. The opposite situation occurs at 4.9 kyr B.P., when significantly warmer temperatures and decreased algal productivity are observed. Thus, in lentic systems such as Lake Malawi the major influence of climate on algal ecology appears to be through feedbacks in physical circulation mechanisms.

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“…Further evidence that the high %C29 steranes should be interpreted cautiously comes from the fact that there are no systematic differences between the platform and pelagic sections, even when comparing sections with similar thermal maturity. Marine inputs are clearly significant at all sites, despite the relatively low %C27 and %C28 values, indicated in particular by the occur rence of dinosterane derived from dinoflagellates (Withers, 1983). Dinosterane occurs in several samples in concentrations comparable to those of steranes (XF samples), is absent in others (CAB and PN samples, , and is one of the most abun dant hydrocarbons in CAU-24.…”

Section: Om Sources and Environmental Conditionsmentioning

confidence: 99%

Organic geochemistry, stable isotopes, and facies analysis of the Early Aptian OAE—New records from Spain (Western Tethys)

Quijano

Jiménez

Pancost

et al. 2012

Palaeogeography, Palaeoclimatology, Palaeoecology

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The Early Aptian Oceanic Anoxic Event (OAEla) is a time interval characterized by increased organic carbon accumulation in marine sediments, notable sedimentary and biotic changes, and abrupt carbon-isotope excursions indicative of significant major palaeoenvironmental changes linked to a perturbation in the global carbon cycle. Here we present the study of four sections recording the OAEl a (Early Aptian) in Spain, which are located in two broad basins respectively located in the South and the North of Iberia: the Southern Iberian Palaeomargin (Carbonero, La Frontera and Cau sections) and the Basque-Cantabrian Basin (Puentenansa section), which represent depositional settings ranging from shallow marine (distal ramp -Cau-and drowned platform -Puentenansa-) to pelagic environments (Carbonero, La Frontera). Biomarker compositions, C-isotope profiles, biostratigraphic data and fades analysis from the four sections are correlated and integrat ed. The C-isotope curves all present a clear negative excursion followed by a positive shift. The integration of the C-isotope curves with the biostratigraphic data has been used to correlate the studied sections and to ten tatively identify the eight segments formerly proposed from the Alpine domain, and subsequently identified in sections worldwide. Four main groups of compounds are present in all sections: n-alkanes, isoprenoids, hopanes and steranes. n-Alkanes and acyclic isoprenoids (pristane and phytane) are dominant in most samples.The hopanes are represented by a range ofC27 to C35 components, with the specific isomers varying amongst the sections due to differences in thermal maturity. Steranes ocrur as a range of C27, C28 and C29 isomers, whereas diasteranes only occur in the most thermally mature section (Carbonero). Other compounds of interest include gammacerane and dinosterane. Differences in thennal maturity appear to be the first order control on different biomarker assemblages amongst the studied sections. The Carbonero section is thermally mature, whereas the nearby La Frontera and Cau sections are immature. Puentenansa has intermediate values. Organic matter is de rived from a range of terrestrial, marine and bacterial sources. The dominance of the C29 sterane isomers in all sections suggests a strong contribution from higher plants. The presence of gammacerane indicates water col umn stratification, and high C2g/C30 hopane ratios suggest anoxia at the water/sediment interface, respectively.Sedimentologic analysis also suggests anoxic conditions during sedimentation, but evidence for strong and per sistent water column anoxia is equivocaL The correlation of the sections reveals that sedimentation of organic-rich fades started earlier in pelagic and later in the shallow marine settings, which can be related to an expansion of the favorable conditions for organic matter accumulation and preservation from deep marine waters to shallower platform environments during the development ofOAEla.

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Dinoflagellate Sterols

Cited by 51 publications

References 91 publications

Dinosterols or dinocysts to estimate dinoflagellate contributions to marine sedimentary organic matter?

Dinosterols or dinocysts to estimate dinoflagellate contributions to marine sedimentary organic matter?

Influence of climate change on algal community structure and primary productivity of Lake Malawi (East Africa) from the Last Glacial Maximum to present

Organic geochemistry, stable isotopes, and facies analysis of the Early Aptian OAE—New records from Spain (Western Tethys)

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