Nitrogen cycle perturbations linked to metazoan diversification during the early Cambrian

Xu, Dongtao; Wang, Xinqiang; Shi, Xiaoying; Tang, Dongjie; Zhao, Xiangkuan; Liu, Feng; Song, Huyue

doi:10.1016/j.palaeo.2019.109392

Cited by 30 publications

(14 citation statements)

References 93 publications

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“…In anoxic basins, NH 4 + may be the dominant N species and serve as the main N source to living primary producers (Higgins et al, 2012; Papineau et al, 2009; Xu et al, 2020; Yang et al, 2019). Where NH 4 + is replete, photoautotrophs in the photic zone that preferentially uptake 14 N during NH 4 + assimilation could cause an enrichment in 15 N in the residual NH 4 + pool (Papineau et al, 2009; Stüeken, 2013).…”

Section: Discussionmentioning

confidence: 99%

“…Nitrogen isotope compositions (δ 15 N) were analyzed for 60 samples from organic‐rich calcareous mudstone, shale, and argillaceous limestone at the State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Wuhan) (CUG), following previously described procedures (Xu et al, 2020). Fresh sample chips without any weathering surface and visible veins were ground into powders below 200 mesh in an agate mortar.…”

Section: Methodsmentioning

confidence: 99%

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Coupled Nitrate and Phosphate Availability Facilitated the Expansion of Eukaryotic Life at Circa 1.56 Ga

Wang

Shi

et al. 2020

JGR Biogeosciences

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Recent geochemical and paleontological studies have revealed a significant ocean oxygenation episode and an evolutionary leap of eukaryotes at the onset of the Mesoproterozoic. However, the potential role of nitrogen availability and its interaction with other nutrients in these environmental and biological events have not been investigated. Here we present an integrated study of nitrogen isotopes (δ 15 N), organic carbon isotopes (δ 13 C org ), and major and trace element concentrations from Member III of the Gaoyuzhuang Formation in the central North China Craton where the earliest macroscopic multicellular eukaryotic fossils were reported. The enrichments of redox-sensitive elements (Mo, U, and V), coupled with Mo-U covariations, δ 13 C org , and I/(Ca + Mg), indicate that the Gaoyuzhuang Member III in the study area was deposited in largely suboxic-anoxic environments with ephemeral occurrences of euxinia. These data reinforce previous inferences of a strongly redox stratified ocean during the early Mesoproterozoic, but a pulsed oxygenation event may have resulted in deepening of the chemocline. The high δ 15 N values from the study section are interpreted as a result of aerobic N cycling and the presence of a fairly stable nitrate pool in the surface oxic layer, possibly due to the combined effects of oxygenation and low primary productivity. Increased availability of nitrate could have contributed to the expansion of eukaryotic life at this time. However, our data also suggest that nitrate alone was not the only trigger. Instead, this evolutionary leap was likely facilitated by multiple environmental factors, including a rise in O 2 levels and increasing supplies of phosphorus and other bio-essential trace elements.Plain Language Summary The oldest macroscopic eukaryotes (algae) first appeared in ancient oceans about 1.56 billion years ago. Before that, only simple and microscopic fossils have been discovered. The reason behind this evolutionary leap is, however, still puzzling scientists. Here we use multiple proxies to study the change of nutrient and oxygen levels during this critical period. Our results demonstrate the availability of the nutrient nitrogen (in form of nitrate) in the oxic surface ocean owing largely to restrictive consumption by organic carbon decomposition, providing favorable N substance for bio-utilization. Furthermore, we also found evidence for the joint increase of O 2 level, seawater phosphorus, and some bio-essential trace elements along with the occurrence of these earliest algae. Our study provides important clues for untangling the triggers of biological innovation at circa 1.56 Ga.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Coupled Nitrate and Phosphate Availability Facilitated the Expansion of Eukaryotic Life at Circa 1.56 Ga

Wang

Shi

et al. 2020

JGR Biogeosciences

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“…Modeled results indicate that δ 15 N data from the Ediacaran Doushantuo Formation show contrasting distributions before and during the Shuram excursion (Figure 7). High δ 15 N values from the lower-middle Doushantuo Formation prior to the Shuram excursion have been attributed to incomplete denitrification that preferentially removed light 14 N from the ocean (Kikumoto et al, 2014;Ader et al, 2014;Wang et al, 2017Wang et al, , 2018Chen et al, 2019;Lan et al, 2019;Xu et al, 2020). The decrease of δ 15 N associated with the Shuram excursion was previously interpreted as partial assimilation of NO 3 − from an expanding nitrate pool in response to a rise of oxygen levels in the ocean-atmosphere system, implying that dissolved P rather than N was the limiting nutrient during the excursion interval (Kikumoto et al, 2014;Nishizawa et al, 2019).…”

Section: Feedback Between Nitrogen and Carbon Cyclesmentioning

confidence: 99%

“…750 Ma to 570 Ma, spanning from the Tonian through the Cryogenian to the middle Ediacaran (Ader et al, 2014). Particularly, after the deglaciation of the Marinoan Snowball Earth, which represented a global sea level rise, δ 15 N remains high for at least 60 Myr or even longer until the onset of the Shuram excursion (Xiang et al, 2018;Chen et al, 2019;Xu et al, 2020). Further, from the Ediacaran to early Cambrian the ocean was characterized by predominately anoxic environments with multiple short-term oxygenation events (Sahoo et al, 2016;Li et al, 2018).…”

Section: Feedback Between Nitrogen and Carbon Cyclesmentioning

confidence: 99%

“…Coupled nitrate (NO 3 − ) reduction and the oxidation of organic matter through denitrification would result in the transformation of 12 C-enriched organic carbon to inorganic carbon, and the preferential release of light 14 N to the atmosphere, thereby elevating the δ 15 N in the fixed N pool and lowering the δ 13 C of the dissolved inorganic carbon pool (Sigman et al, 2009;Kump et al, 2011). Further, the remineralization of organic matter in the oceans would release the organic-bound N into seawater with limited nitrogen isotopic fractionation (−1 to +2‰, Ader et al, 2016;Stüeken et al, 2016), which could serve as new nutrient N source to fuel productivity (Higgins et al, 2012;Xu et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

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Feedback Between Carbon and Nitrogen Cycles During the Ediacaran Shuram Excursion

Wang

Shi

et al. 2021

Front. Earth Sci.

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The middle Ediacaran Period records one of the deepest negative carbonate carbon isotope (δ13Ccarb) excursions in Earth history (termed the Shuram excursion). This excursion is argued by many to represent a large perturbation of the global carbon cycle. If true, this event may also have induced significant changes in the nitrogen cycle, because carbon and nitrogen are intimately coupled in the global ocean. However, the response of the nitrogen cycle to the Shuram excursion remains ambiguous. Here, we reported high resolution bulk nitrogen isotope (δ15N) and organic carbon isotope (δ13Corg) data from the upper Doushantuo Formation in two well-preserved sections (Jiulongwan and Xiangerwan) in South China. The Shuram-equivalent excursion is well developed in both localities, and our results show a synchronous decrease in δ15N across the event. This observation is further supported by bootstrapping simulations taking into account all published δ15N data from the Doushantuo Formation. Isotopic mass balance calculations suggest that the decrease in δ15N during the Shuram excursion is best explained by the reduction of isotopic fractionation associated with water column denitrification (εwd) in response to feedbacks between carbon and nitrogen cycling, which were modulated by changes in primary productivity and recycled nutrient elements through remineralization of organic matter. The study presented here thus offers a new perspective for coupled variations in carbon and nitrogen cycles and sheds new light on this critical time in Earth history.

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Nitrogen isotope stratigraphy of the Early Cambrian successions in the Tarim Basin: Spatial variability of nitrogen cycling and its implication for paleo-oceanic redox conditions

Zhu,

Li,

et al. 2024

Acta Geochim

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Nitrogen cycle perturbations linked to metazoan diversification during the early Cambrian

Cited by 30 publications

References 93 publications

Coupled Nitrate and Phosphate Availability Facilitated the Expansion of Eukaryotic Life at Circa 1.56 Ga

Coupled Nitrate and Phosphate Availability Facilitated the Expansion of Eukaryotic Life at Circa 1.56 Ga

Feedback Between Carbon and Nitrogen Cycles During the Ediacaran Shuram Excursion

Nitrogen isotope stratigraphy of the Early Cambrian successions in the Tarim Basin: Spatial variability of nitrogen cycling and its implication for paleo-oceanic redox conditions

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