Kinetic fractionation of stable carbon and nitrogen isotopes during peptide bond hydrolysis: Experimental evidence and geochemical implications

Silfer, J.A.; Engel, Michael H.; Macko, Stephen A.

doi:10.1016/0009-2541(92)90003-n

Cited by 82 publications

(84 citation statements)

References 32 publications

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“…When degradation continues, more of the less susceptible (and isotopically depleted) material is degraded and the residual sediment material is enriched. It has also been shown that hydrolysis of proteins (Bada et al 1989;Silfer et al 1992) and bacterial biosynthesis (Macko and Estep 1984) might Table 2. R 2 values for the correlation for the observed changes in d 13 C and d 15 N compared to different organic matter quality parameters of the initial material (i.e., the surface varve).…”

Section: Discussionmentioning

confidence: 99%

Decadal diagenetic effects on δ¹³C and δ¹⁵N studied in varved lake sediment

Gälman

Rydberg

Bigler

2009

Limnology & Oceanography

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To assess the long-term (27 yr) effects of sediment aging on stable carbon and nitrogen isotope values (d 13 C and d 15 N), we used a collection of eight freeze cores of annually laminated (varved) lake sediment collected from 1979 to 2007 in Nylandssjö n (northern Sweden). Previous research has shown that 20-23% of carbon and 35% of nitrogen is lost in 27 yr. Material from specific years was compared in the cores, e.g., d 13 C and d 15 N of the surface varve of the 1979 core was followed in cores retrieved in 1980, 1989, 1993, 2002, 2004, and 2006. d 13 C increased by 0.4-1.5% during the first 5 yr. After this initial increase, only minor fluctuations were recorded. There is a good correlation between the magnitude in d 13 C changes and the initial carbon and nitrogen concentrations, indicating that the initial sediment composition is important for the 13 C fractionation. d 15 N gradually decreased by 0.3-0.7% over the entire 27-yr period. The lack of correlation with the initial sediment composition and the gradual decrease in d 15 N indicates a microbial control on d 15 N change. The diagenetic changes in the stable isotope values that occur in Nylandssjö n are small, but of the same magnitude as the down-core variation in the varves deposited . Diagenetic effects should be considered when d 13 C and d 15 N are used to study organic matter sources or paleoproductivity, especially when dealing with recent trends or small changes. Based on our findings, diagenetic effects for d 13 C are observed during the first 5-10 yr, whereas no delimitation can be recommended for d 15 N.

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Section: Discussionmentioning

confidence: 99%

Decadal diagenetic effects on δ¹³C and δ¹⁵N studied in varved lake sediment

Gälman

Rydberg

Bigler

2009

Limnology & Oceanography

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“…If N 2 serves as a N source, the ␦ 15 N value of the bulk organic matter may be significantly lowered because isotope fractionation associated with N 2 fixation is small compared to photosynthesis (Fogel and Cifuentes 1993 and references therein) and the ␦ 15 N of dissolved N 2 is close to 0‰. Lastly, the ␦ 15 N value for POM can be altered by microzooplankton grazing, microbial decompositional processes, and protein hydrolysis (Silfer et al 1992;Hoch et al 1996). On the basis of several marine studies (e.g., Altabet 1988;Freudenthal et al 2001), microbial degradation has traditionally been considered to enrich 15 N in the residual organic matter; the evidence, however, is conflicting (Libes and Deuser 1988;Lehmann et al 2002).…”

Section: N In the Epilimnion: Reliable Indicator Of Nitrate Utilizatimentioning

confidence: 99%

Seasonal variation of the δC and δN of particulate and dissolved carbon and nitrogen in Lake Lugano: Constraints on biogeochemical cycling in a eutrophic lake

Lehmann

Bernasconi

McKenzie

et al. 2004

Limnology & Oceanography

188

190

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We determined the ␦ 13 C and ␦ 15 N of water-column particulate organic matter (POM), dissolved inorganic carbon, and nitrate, together with water chemistry and phytoplankton biomass and species composition every month in eutrophic Lake Lugano. As primary productivity increased during spring, the ␦ 13 C of photic-zone POM increased from Ϫ34‰ to Ϫ24‰. This 13 C enrichment reflects decreasing C-isotope fractionation between organic and inorganic carbon pools in response to decreasing surface water [CO 2 (aq)]. Variations in the ␦ 15 N of surface-water POM (ϩ2‰ to ϩ8‰) collected during the productive period were attributed to isotope effects associated with nitrate uptake, nitrogen fixation, and mixing of different organic matter sources. The apparent N-isotope enrichment () associated with nitrate assimilation varied with ϭ Ϫ1.0‰ Ϯ 0.9 for diatoms and ϭ Ϫ3.4‰ Ϯ 0.4 for green algae. The mechanisms controlling the N-isotopic composition of surface-water nitrate include the combined processes of nitrate assimilation, nitrification, mixing of water masses, and external nitrate loading. There was no consistent relation between the ␦ 15 N of POM, the ␦ 15 N of nitrate, and the nitrate concentration in surface waters. Low ␦ Stable carbon and nitrogen isotope measurements of autochthonous material from aquatic environments have proven to be a powerful tool to better understand biologically driven carbon and nitrogen cycles. Such studies helped to assess the sources and cycling of organic matter (e.g., Cifuentes et al. 1988;Bernasconi et al. 1997;Huon et al. 2002) and to identify microbial processes (e.g., Ostrom et al. 1997;Brandes et al. 1998). Through the carbon and nitrogen stable isotope analysis of sediments, insights may be gained into the trophic evolution of lakes, provided that the processes controlling isotope fractionation during organic matter synthesis and degradation are well understood. For example, the C-isotopic composition of lacustrine organic matter has been used as a proxy indicator for primary productivity, pCO 2 (aq) and CO 2 versus HCO uptake (Hollander and McKenzie Ϫ 3 1991;Ostrom et al. 1997; Hodell and Schelske1998).Variations in the isotopic composition of organic and inorganic nitrogen species in aquatic environments can be re-

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“…Assuming that this indicates significant N 2 -fixation in the modern EMS, Sachs and Repeta (1999) proposed that the S1-situation was similar to the present-day situation, and that the low δ 15 N in S1 is due to the preservation of the original δ 15 N signature of sedimenting newly fixed N. Preservation may play an important role because sedimentary δ 15 N is known to become enriched during OM degradation resulting from preferential loss of 15 N depleted compounds (Altabet, 1996;Freudenthal et al, 2001;Gaye-Haake et al, 2005). Although exact mechanisms remain unknown, kinetic isotope fractionation during protein hydrolysis (Bada et al, 1989;Silfer et al, 1992) and deamination (Macko and Estep, 1984) very likely cause this enrichment.…”

Section: Introductionmentioning

confidence: 95%

Diagenetic control of nitrogen isotope ratios in Holocene sapropels and recent sediments from the Eastern Mediterranean Sea

2010

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Abstract. The enhanced accumulation of organic matter in Eastern Mediterranean sapropels and their unusually low δ 15 N values have been attributed to either enhanced nutrient availability which led to elevated primary production and carbon sequestration or to enhanced organic matter preservation under anoxic conditions. In order to evaluate these two hypothesis we have determined Ba/Al ratios, amino acid composition, N and organic C concentrations and δ 15 N in sinking particles, surface sediments, eight spatially distributed core records of the youngest sapropel S1 (10-6 ka) and older sapropels (S5, S6) from two locations. These data suggest that (i) temporal and spatial variations in δ 15 N of sedimentary N are driven by different degrees of diagenesis at different sites rather than by changes in N-sources or primary productivity and (ii) present day TOC export production would suffice to create a sapropel like S1 under conditions of deepwater anoxia. This implies that both enhanced TOC accumulation and 15 N depletion in sapropels were due to the absence of oxygen in deep waters. Thus preservation plays a major role for the accumulation of organic-rich sediments casting doubt on the need of enhanced primary production for sapropel formation.

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Kinetic fractionation of stable carbon and nitrogen isotopes during peptide bond hydrolysis: Experimental evidence and geochemical implications

Cited by 82 publications

References 32 publications

Decadal diagenetic effects on δ¹³C and δ¹⁵N studied in varved lake sediment

Decadal diagenetic effects on δ¹³C and δ¹⁵N studied in varved lake sediment

Seasonal variation of the δC and δN of particulate and dissolved carbon and nitrogen in Lake Lugano: Constraints on biogeochemical cycling in a eutrophic lake

Diagenetic control of nitrogen isotope ratios in Holocene sapropels and recent sediments from the Eastern Mediterranean Sea

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Kinetic fractionation of stable carbon and nitrogen isotopes during peptide bond hydrolysis: Experimental evidence and geochemical implications

Cited by 82 publications

References 32 publications

Decadal diagenetic effects on δ13C and δ15N studied in varved lake sediment

Decadal diagenetic effects on δ13C and δ15N studied in varved lake sediment

Seasonal variation of the δC and δN of particulate and dissolved carbon and nitrogen in Lake Lugano: Constraints on biogeochemical cycling in a eutrophic lake

Diagenetic control of nitrogen isotope ratios in Holocene sapropels and recent sediments from the Eastern Mediterranean Sea

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Decadal diagenetic effects on δ¹³C and δ¹⁵N studied in varved lake sediment

Decadal diagenetic effects on δ¹³C and δ¹⁵N studied in varved lake sediment