Extensive marine anoxia during the terminal Ediacaran Period

Zhang, Feifei; Xiao, Shuhai; Kendall, Brian; Romaniello, Stephen J.; Cui, Huan; Meyer, Mike; Gilleaudeau, Geoffrey J.; Kaufman, Alan J.; Anbar, Ariel D.

doi:10.1126/sciadv.aan8983

Cited by 141 publications

(125 citation statements)

References 97 publications

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“…The spike‐sample mixtures were evaporated to dryness and taken up in 3N HNO 3 . Uranium was purified using the UTEVA method for isotopic analysis (Brennecka et al, ; Chen et al, ; Kendall et al, ; Romaniello et al, ; Weyer et al, ; Zhang, Algeo, Cui, et al, ; Zhang, Algeo, Romaniello, et al, ; Zhang, Romaniello, et al, ; Zhang, Xiao, et al, ). All samples were put through UTEVA resin twice in order to completely remove matrix ions.…”

Section: Methodsmentioning

confidence: 99%

“…Because the duration of the SE (>8 Myr; Minguez & Kodama, ) is significantly longer than the residence time of U in the SE ocean (<0.5 Myr), we use a simple steady‐state isotopic mass balance model combined with the measured δ 238 U data to assess changes in the size of the anoxic U sink and the implications for the areal extent of anoxic bottom waters (see Zhang, Xiao, et al, for details):

{normalδ}^{238} {normalU}_{input} = false(f_{anoxic} \times δ^{238} U_{anoxic} false) + false(f_{other} \times δ^{238} U_{other} false)

\begin{matrix} {normalδ}^{238} {normalU}_{seawater} \\ = {normalδ}^{238} {normalU}_{input} - \frac{A_{anoxic} * k_{anoxic} * {normalΔ}_{anoxic} + false(A_{ocean} - A_{anoxic} false) * k_{other} * {normalΔ}_{other} false)}{A_{anoxic} * k_{anoxic} + false(A_{ocean} - A_{anoxic} false) * k_{other}} \end{matrix}

where δ 238 U input , δ 238 U anoxic , and δ 238 U other , and δ 238 U seawater denote the U isotopic compositions of riverine input, anoxic sink, all other sedimentary sinks, and seawater, respectively. The variables f anoxic and f other represent the fraction of total U removed to the respective sinks, Δ anoxic and Δ other represent the isotope fractionation factor between seawater and the respective sinks, A anoxic and A ocean denote anoxic seafloor area and seafloor area of the world ocean, and k anoxic and k other represent the area‐weighted first‐order removal rate constants for each of the respective sinks.…”

Section: Near‐modern Levels Of Ocean Oxygenation During the Shuram Eventmentioning

confidence: 99%

“…Recent studies provide evidence that an episode of extensive marine anoxia during the terminal Ediacaran Period may have contributed to the decline of the Ediacara biota (Tostevin et al, ; Wei et al, ; Zhang, Xiao, et al, ). However, the cause of the rise of the Ediacara biota during the middle Ediacaran Period remains a subject of intensive debate.…”

Section: Introductionmentioning

confidence: 99%

“…The U isotope system ( 238 U/ 235 U, denoted as δ 238 U) measured in carbonate sedimentary rocks is a more direct probe of global ocean redox conditions and can be used to place quantitative constraints on the extent of global redox changes (Brennecka, Herrmann, Algeo, & Anbar, ; Clarkson et al, ; Elrick et al, ; Lau et al, ; Tostevin et al, ; Wei et al, ; Zhang, Algeo, Cui, et al, ; Zhang, Algeo, Romaniello, et al, ; Zhang, Romaniello, et al, ; Zhang, Xiao, et al, ). The power of U isotopes as a global proxy derives from the fact that in the modern ocean U has a long residence time, ~500 kyr (Dunk, Mills, & Jenkins, ), and hence, δ 238 U is uniform in the open ocean (e.g., Tissot & Dauphas, ).…”

Section: Introductionmentioning

confidence: 99%

“…The power of U isotopes as a global proxy derives from the fact that in the modern ocean U has a long residence time, ~500 kyr (Dunk, Mills, & Jenkins, ), and hence, δ 238 U is uniform in the open ocean (e.g., Tissot & Dauphas, ). Although the concentration and residence time of U in seawater would both be reduced during times of expanded marine anoxia, studies suggest that the U isotope composition of open ocean seawater was likely uniform even during periods of expanded anoxia (Clarkson et al, ; Zhang, Algeo, Romaniello, et al, ; Zhang, Xiao, et al, ). Seawater δ 238 U varies with redox conditions because the reduction of dissolved U(VI) to U(IV), which is immobilized in anoxic sediments, results in a large and detectable change in δ 238 U (0.6‰–0.85‰), favoring the 238 U over 235 U in the reduced species (Andersen et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Global marine redox changes drove the rise and fall of the Ediacara biota

et al. 2019

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The role of O2 in the evolution of early animals, as represented by some members of the Ediacara biota, has been heavily debated because current geochemical evidence paints a conflicting picture regarding global marine O2 levels during key intervals of the rise and fall of the Ediacara biota. Fossil evidence indicates that the diversification the Ediacara biota occurred during or shortly after the Ediacaran Shuram negative C‐isotope Excursion (SE), which is often interpreted to reflect ocean oxygenation. However, there is conflicting evidence regarding ocean oxygen levels during the SE and the middle Ediacaran Period. To help resolve this debate, we examined U isotope variations (δ238U) in three carbonate sections from South China, Siberia, and USA that record the SE. The δ238U data from all three sections are in excellent agreement and reveal the largest positive shift in δ238U ever reported in the geologic record (from ~ −0.74‰ to ~ −0.26‰). Quantitative modeling of these data suggests that the global ocean switched from a largely anoxic state (26%–100% of the seafloor overlain by anoxic waters) to near‐modern levels of ocean oxygenation during the SE. This episode of ocean oxygenation is broadly coincident with the rise of the Ediacara biota. Following this initial radiation, the Ediacara biota persisted until the terminal Ediacaran period, when recently published U isotope data indicate a return to more widespread ocean anoxia. Taken together, it appears that global marine redox changes drove the rise and fall of the Ediacara biota.

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Section: Methodsmentioning

confidence: 99%

{normalδ}^{238} {normalU}_{input} = false(f_{anoxic} \times δ^{238} U_{anoxic} false) + false(f_{other} \times δ^{238} U_{other} false)

\begin{matrix} {normalδ}^{238} {normalU}_{seawater} \\ = {normalδ}^{238} {normalU}_{input} - \frac{A_{anoxic} * k_{anoxic} * {normalΔ}_{anoxic} + false(A_{ocean} - A_{anoxic} false) * k_{other} * {normalΔ}_{other} false)}{A_{anoxic} * k_{anoxic} + false(A_{ocean} - A_{anoxic} false) * k_{other}} \end{matrix}

Section: Near‐modern Levels Of Ocean Oxygenation During the Shuram Eventmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Global marine redox changes drove the rise and fall of the Ediacara biota

et al. 2019

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The Ediacaran‐Cambrian Transition

Kaufman

2018

Geophysical Monograph Series

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Why can insects not biosynthesize cholesterol?

Haas

Kim

Stanley

2022

Arch Insect Biochem Physiol

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Two aspects of insect lipid biochemistry differ from the mammalian background. In one aspect, nearly a hundred years ago scientists demonstrated that the polyunsaturated fatty acid (PUFAs), linoleic acid (LA; 18:2n-6) is an essential nutrient in the diets of all mammals that have been studied in that regard. An unknown number of insect species are able to biosynthesize LA de novo. Some species take the biosynthesized LA into fatty acid elongation/desaturation pathways to produce other PUFAs, 18:3n-6, 20:3n-6 and 20:4n-6. A couple of species use the de novo produced LA to biosynthesize prostaglandins and other eicosanoids, shortlived signal moieties that mediate important physiological actions in immunity and reproduction. Insects differ from mammals, also, in their lack of genes that encode enzymes acting in biosynthesis of cholesterol. Insects require dietary cholesterol to meet their cellular, physiological, developmental, and reproductive needs. Looking at a broader view of invertebrate biochemistry, most protostomes lost all or most genes involved in cholesterol biosynthesis. The massive gene loss occurred during the Ediacaran Period, which lasted 96 million years, from the end of the Cryogenian Period (635 million years ago; MYA) to the beginning of the Cambrian Period (538.6 MYA). The key point here is that the inability to biosynthesize cholesterol is not limited to insects; it occured in most protostomes. We address the protostome need and benefits of acquiring exogenous sterols.

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Extensive marine anoxia during the terminal Ediacaran Period

Abstract: Extensive marine anoxia in the terminal Ediacaran ocean was associated with the decline of the Ediacara biota.

Cited by 141 publications

References 97 publications

Global marine redox changes drove the rise and fall of the Ediacara biota

Global marine redox changes drove the rise and fall of the Ediacara biota

The Ediacaran‐Cambrian Transition

Why can insects not biosynthesize cholesterol?

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