Feedback Between Carbon and Nitrogen Cycles During the Ediacaran Shuram Excursion

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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Stable isotopes of carbon and nitrogen in the study of avian and mammalian trophic ecology

Canadian Journal of Zoology ◽

10.1139/z99-165 ◽

2000 ◽

Vol 78 (1) ◽

pp. 1-27 ◽

Cited By ~ 727

Author(s):

Jeffrey F Kelly

Keyword(s):

Stable Isotopes ◽

Stable Isotope ◽

Carbon Isotope ◽

Isotope Ratio ◽

Trophic Ecology ◽

Nitrogen Isotope ◽

Isotope Ratios ◽

Food Chains ◽

Stable Isotope Ratios ◽

Carbon And Nitrogen

Differential fractionation of stable isotopes of carbon during photosynthesis causes C4 plants and C3 plants to have distinct carbon-isotope signatures. In addition, marine C3 plants have stable-isotope ratios of carbon that are intermediate between C4 and terrestrial C3 plants. The direct incorporation of the carbon-isotope ratio (13C/12C) of plants into consumers' tissues makes this ratio useful in studies of animal ecology. The heavy isotope of nitrogen (15N) is preferentially incorporated into the tissues of the consumer from the diet, which results in a systematic enrichment in nitrogen-isotope ratio (15N/14N) with each trophic level. Consequently, stable isotopes of nitrogen have been used primarily to assess position in food chains. The literature pertaining to the use of stable isotopes of carbon and nitrogen in animal trophic ecology was reviewed. Data from 102 studies that reported stable-isotope ratios of carbon and (or) nitrogen of wild birds and (or) mammals were compiled and analyzed relative to diet, latitude, body size, and habitat moisture. These analyses supported the predicted relationships among trophic groups. Carbon-isotope ratios differed among species that relied on C3, C4, and marine food chains. Likewise, nitrogen-isotope ratios were enriched in terrestrial carnivorous mammals relative to terrestrial herbivorous mammals. Also, marine carnivores that ate vertebrates had nitrogen-isotope ratios that were enriched over the ratios of those that ate invertebrates. Data from the literature also indicated that (i) the carbon-isotope ratio of carnivore bone collagen was inversely related to latitude, which was likely the result of an inverse relationship between the proportion of carbon in the food chain that was fixed by C4 plants and latitude; (ii) seabirds and marine mammals from northern oceans had higher nitrogen-isotope ratios than those from southern oceans; (iii) the nitrogen-isotope ratios of terrestrial mammals that used xeric habitats were higher than the ratios of those that used mesic habitats, indicating that water stress can have important effects on the nitrogen-isotope ratio; (iv) there was no relationship between body mass and nitrogen-isotope ratio for either bone collagen or muscle of carnivores; and (v) there was linear covariation between stable-isotope ratios of carbon and nitrogen in marine food chains (but not in terrestrial C3 or C4 food chains), which is likely a product of increases in carbon-isotope ratio with trophic level in marine food chains. Differences in stable-isotope composition among trophic groups were detected despite variation attributable to geographic location, climate, and analytical techniques, indicating that these effects are large and pervasive. Consequently, as knowledge of the distribution of stable isotopes of carbon and nitrogen increases, they will probably become an increasingly important tool in the study of avian and mammalian trophic ecology.

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Isotopic Evidence for Diet in the Seventeenth-Century Colonial Chesapeake

American Antiquity ◽

10.2307/3557036 ◽

2003 ◽

Vol 68 (1) ◽

pp. 129-139 ◽

Cited By ~ 14

Author(s):

Douglas H. Ubelaker ◽

Douglas W. Owsley

Keyword(s):

Seventeenth Century ◽

Carbon Isotope ◽

Nitrogen Isotopes ◽

Dietary Diversity ◽

Stable Carbon Isotope ◽

Isotope Analysis ◽

Nitrogen Isotope ◽

Stable Carbon ◽

Carbon And Nitrogen ◽

American Colonies

Excavations of colonial period sites in Maryland and Virginia have produced human remains dating to the seventeenth century. In this study, we analyze stable isotopes of carbon and nitrogen from these remains to explore aspects of the diets of the individuals represented. Analyses of both stable carbon and nitrogen isotopes were conducted on preserved protein while stable carbon isotope analysis was also conducted on preserved biological apatite. Carbon isotope values (δ13N‰) ranged from -10.5 to -20.5 for collagen and -5.1 to -12.5 for bioapatite. Nitrogen isotope values (δ15N‰) ranged from 9.9 to 14.4. The data suggest dietary diversity among the individuals examined. Three factors contribute to this diversity: the availability of maize, variation in immigration histories of the individuals, and the differing lengths of time they spent in the American colonies.

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Extensive primary production promoted the recovery of the Ediacaran Shuram excursion

Nature Communications ◽

10.1038/s41467-021-27812-5 ◽

2022 ◽

Vol 13 (1) ◽

Author(s):

Fuencisla Cañadas ◽

Dominic Papineau ◽

Melanie J. Leng ◽

Chao Li

Keyword(s):

Primary Production ◽

Nitrogen Isotope ◽

Systematic Difference ◽

Depositional Environments ◽

Concentration Data ◽

Carbon And Nitrogen ◽

Earth History ◽

Carbon Isotope Excursion ◽

C And N ◽

Raman Spectral Data

AbstractMember IV of the Ediacaran Doushantuo Formation records the recovery from the most negative carbon isotope excursion in Earth history. However, the main biogeochemical controls that ultimately drove this recovery have yet to be elucidated. Here, we report new carbon and nitrogen isotope and concentration data from the Nanhua Basin (South China), where δ13C values of carbonates (δ13Ccarb) rise from − 7‰ to −1‰ and δ15N values decrease from +5.4‰ to +2.3‰. These trends are proposed to arise from a new equilibrium in the C and N cycles where primary production overcomes secondary production as the main source of organic matter in sediments. The enhanced primary production is supported by the coexisting Raman spectral data, which reveal a systematic difference in kerogen structure between depositional environments. Our new observations point to the variable dominance of distinct microbial communities in the late Ediacaran ecosystems, and suggest that blooms of oxygenic phototrophs modulated the recovery from the most negative δ13Ccarb excursion in Earth history.

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Compound-Specific Stable Isotope Analysis of Amino Acids in Pelagic Shark Vertebrae Reveals Baseline, Trophic, and Physiological Effects on Bulk Protein Isotope Records

Frontiers in Marine Science ◽

10.3389/fmars.2021.673016 ◽

2021 ◽

Vol 8 ◽

Author(s):

Sarah Magozzi ◽

Simon R. Thorrold ◽

Leah Houghton ◽

Victoria A. Bendall ◽

Stuart Hetherington ◽

...

Keyword(s):

Amino Acids ◽

Stable Isotope ◽

Carbon Isotope ◽

Trophic Ecology ◽

Carbon Isotopic Composition ◽

Nitrogen Isotope ◽

Essential Amino Acids ◽

Carbon And Nitrogen ◽

Isotope Data ◽

Bulk Tissue

Variations in stable carbon and nitrogen isotope compositions in incremental tissues of pelagic sharks can be used to infer aspects of their spatial and trophic ecology across life-histories. Interpretations from bulk tissue isotopic compositions are complicated, however, because multiple processes influence these values, including variations in primary producer isotope ratios and consumer diets and physiological processing of metabolites. Here we challenge inferences about shark tropho-spatial ecology drawn from bulk tissue isotope data using data for amino acids. Stable isotope compositions of individual amino acids can partition the isotopic variance in bulk tissue into components associated with primary production on the one hand, and diet and physiology on the other. The carbon framework of essential amino acids (EAAs) can be synthesised de novo only by plants, fungi and bacteria and must be acquired by consumers through the diet. Consequently, the carbon isotopic composition of EAAs in consumers reflects that of primary producers in the location of feeding, whereas that of non-essential amino acids (non-EAAs) is additionally influenced by trophic fractionation and isotope dynamics of metabolic processing. We determined isotope chronologies from vertebrae of individual blue sharks and porbeagles from the North Atlantic. We measured carbon and nitrogen isotope compositions in bulk collagen and carbon isotope compositions of amino acids. Despite variability among individuals, common ontogenetic patterns in bulk isotope compositions were seen in both species. However, while life-history movement inferences from bulk analyses for blue sharks were supported by carbon isotope data from essential amino acids, inferences for porbeagles were not, implying that the observed trends in bulk protein isotope compositions in porbeagles have a trophic or physiological explanation, or are suprious effects. We explored variations in carbon isotope compositions of non-essential amino acids, searching for systematic variations that might imply ontogenetic changes in physiological processing, but patterns were highly variable and did not explain variance in bulk protein δ13C values. Isotopic effects associated with metabolite processing may overwhelm spatial influences that are weak or inconsistently developed in bulk tissue isotope values, but interpreting mechanisms underpinning isotopic variation in patterns in non-essential amino acids remains challenging.

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