气候变化领域集成服务门户(CCPortal): Chemocline collapse in Lake Kivu as an analogue for nitrogen cycling during Oceanic Anoxic Events

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DOI	10.1016/j.epsl.2020.116459
	Chemocline collapse in Lake Kivu as an analogue for nitrogen cycling during Oceanic Anoxic Events
	Uveges B.T.; Junium C.K.; Scholz C.A.; Fulton J.M.
发表日期	2020
ISSN	0012821X
卷号	548
英文摘要	One of the outstanding issues in the study of nutrient dynamics during Oceanic Anoxic Events (OAEs) is the preservation of 15N-depleted nitrogen isotope signals, which are not observed in analogous modern environments. The favored mechanism for δ15N values below 0‰ is utilization of excess ammonium derived from underlying anoxic waters by primary producers. However, there are few modern examples available for testing this hypothesis, due to the overall well-oxygenated state of modern oceans. Here, we present sedimentary δ13Corg and δ15Nbulk data, as well as pigment biomarker ratios, from the sediments of Lake Kivu, a meromictic lake in East Africa. This system serves as a potential analogue for the development of strongly depleted δ15Nbulk in OAE black shales. We focus on intervals of organic carbon enrichment (sapropels) that are interpreted to have been the result of lake water column mixing events. Sediment δ13Corg and δ15Nbulk decrease by up to 6 and 4‰ respectively near the base of sapropel layers. These negative excursions provide evidence for the mixing of 13C-depleted dissolved inorganic carbon and ammonium in excess of photosynthetic need, derived from the deeper anoxic basin of the lake. Support of this model is also provided by photosynthetic pigment biomarkers which show significant fluctuations in phototrophic ecology consistent with water column mixing and changes in nutrient status. Further evidence for the shallowing of the chemocline during sapropel deposition is found in the presence of bacteriochlorophyll derivatives produced by phototrophic sulfide oxidizers. © 2020 Elsevier B.V.
关键词	chemocline nitrogen cycle Oceanic Anoxic Events pigment biomarkers stable isotopes
英文关键词	Biomarkers; Mixing; Nitrogen; Nutrients; Organic carbon; Sulfur compounds; Well testing; Bacteriochlorophylls; Carbon enrichment; Dissolved inorganic carbon; Nitrogen isotopes; Oceanic Anoxic Event; Photosynthetic pigments; Primary producers; Water column mixing; Lakes; anoxic conditions; biomarker; carbon isotope; deposition; lacustrine deposit; meromictic lake; nitrogen cycle; nitrogen isotope; sapropel; water column; East African Lakes; Lake Kivu
语种	英语
来源期刊	Earth and Planetary Science Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/202942
作者单位	Department of Earth Sciences, Syracuse University, 900 South Crouse Avenue, Syracuse, 13244, United States; Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, United States; Department of Geosciences, Baylor University, One Bear Place #97354, Waco, TX 76798, United States
推荐引用方式 GB/T 7714	Uveges B.T.,Junium C.K.,Scholz C.A.,et al. Chemocline collapse in Lake Kivu as an analogue for nitrogen cycling during Oceanic Anoxic Events[J],2020,548.
APA	Uveges B.T.,Junium C.K.,Scholz C.A.,&Fulton J.M..(2020).Chemocline collapse in Lake Kivu as an analogue for nitrogen cycling during Oceanic Anoxic Events.Earth and Planetary Science Letters,548.
MLA	Uveges B.T.,et al."Chemocline collapse in Lake Kivu as an analogue for nitrogen cycling during Oceanic Anoxic Events".Earth and Planetary Science Letters 548(2020).