Stable nitrogen isotopic ratios of sinking particles and sediments from the northern Indian Ocean

Gaye-Haake, Birgit; Lahajnar, Niko; Emeis, Kay–Christian; Unger, Daniela; Rixen, Tim; Suthhof, A.; Ramaswamy, V.; Schulz, Hartmut; Paropkari, A.L.; Guptha, M.V.S.; Ittekkot, V.

doi:10.1016/j.marchem.2005.02.001

Cited by 131 publications

(98 citation statements)

References 63 publications

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“…Montoya, 1999;Struck et al, 2001;Meyers and Bernasconi, 2005;Arnaboldi and Meyers, 2006). The δ 15 N in nonsapropel sediments thus are similar to pelagic sediments world wide that range from 5 to 15‰ (Holmes et al, 1996;Holmes et al, 1997;Gaye-Haake et al, 2005). The δ 15 N of sediments integrates the isotopic composition of the assimilated nitrate source, biological fractionation, foodweb dynamics, and isotope fractionation during sediment diagenesis (McClelland and Valiela, 1998;Voss et al, 2005;Altabet, 2007;Fry, 2007;Dähnke et al, 2008).…”

Section: Introductionmentioning

confidence: 81%

“…Interestingly, present-day suspended matter, sinking particles and deep-water nitrate in the EMS all have light δ 15 N similar to the δ 15 N of sapropel S1. 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: 99%

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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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Section: Introductionmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

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

2010

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“…Isotopic fractionation during nitrogen uptake results in an increase of the d 15 N of the substrate as well as the produced organic matter as nutrients become depleted during a progressing plankton bloom (Altabet, 1996) (Altabet et al, 1999;Lourey et al, 2003;Smith et al, 2002). However, a strong isotopic imprint is probably restricted to degradation processes in the deep sea; near shore and slope sediments showed no significant d 15 N increase in sediments compared to sinking particles which was probably related to faster burial and oxygen depletion in the sediments (Altabet et al, 1999;Gaye-Haake et al, 2005). Kara Sea trap samples with higher d 15 N values were, generally, less degraded (see 3.2. and 4.3.)…”

Section: Relation Of Fluxes To Ice Cover Light Availability and Rivementioning

confidence: 97%

Particulate matter fluxes in the southern and central Kara Sea compared to sediments: Bulk fluxes, amino acids, stable carbon and nitrogen isotopes, sterols and fatty acids

Gaye

Fahl

Kodina

et al. 2007

Continental Shelf Research

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The Kara Sea is one of the arctic marginal seas strongly influenced by fresh water and river suspension. The highly seasonal discharge by the two major rivers Yenisei and Ob induces seasonal changes in hydrography, sea surface temperature, ice cover, primary production and sedimentation. In order to obtain a seasonal pattern of sedimentation in the Kara Sea, sediment traps were deployed near the river mouth of the Yenisei (Yen) as well as in the central Kara Sea (Kara) within the framework of the German-Russian project ''Siberian River run-off; SIRRO''. Two and a half years of time-series flux data were obtained between September 2000 and April 2003 and were analyzed for bulk components, amino acids, stable carbon and nitrogen isotopes as well as sterols and fatty acids.Sediment trap data show that much of the annual deposition occurred under ice cover, possibly enhanced by zooplanktonic activity and sediment resuspension. An early bloom of ice-associated algae in April/May occurred in the polynya area and may have been very important to sustain the life cycles of higher organisms after the light limitation of the winter months due to no/low insolation and ice cover. The strong river input dominated the months June-August in the southern part of the Kara Sea. The central Kara Sea had a much shorter productive period starting in August and was less affected by the river plumes. Despite different time-scales of sampling and trapping biases, total annual fluxes from traps were in the same order of magnitude as accumulation rates in surface sediments. Terrestrial organic carbon accumulation decreased from 10.7 to 0.3 g C m À2 a À1 from the riverine source to the central Kara Sea. Parallel to this, preservation of marine organic matter decreased from 10% to 2% of primary productivity which was probably related to decreasing rates of sedimentation. r

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“…We thus do not separate denitrification from anammox in the context of this paper and just state that both are tied to oxygen deficient waters. A possible bias on the use of 15 N/ 14 N ratios as a proxy for denitrification intensity is the differential degradation of proteinaceous biological products under oxic and anoxic conditions (Gaye-Haake et al 2005;Lehmann et al 2002). Several studies suggested that the d 15 N ratio of material deposited under suboxic to anoxic conditions is lower than that of material deposited under oxic conditions.…”

Section: Nutrient Abundance/denitrification Proxy: Nitrogen Isotopic mentioning

confidence: 99%

Variability in upwelling intensity and nutrient regime in the coastal upwelling system offshore Namibia: results from sediment archives

Emeis

Struck

Leipe

et al. 2007

Int J Earth Sci (Geol Rundsch)

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The coastal upwelling system offshore Namibia is ideally suited to address a focal question of the Integrated Marine Biogeochemistry and Ecosystem Research Programme: what are the mechanisms that drive long-term changes in ecosystems? Considerable interannual variability in climatic forcing is indicated by long time series of meteorological and remote sensing observation; these accompany considerable interannual to interdecadal changes in the upwelling intensity over the last 100 years, as well as a centennial trend. On longer time scales, the only archives available are sediment records spanning the late Holocene. To decipher the sediment record, we mapped surface-sediment patterns of proxies for physical (sea surface temperature/SST from alkenone unsaturation indexes) and nutrient (d 15 N on bulk sedimentary N) variables. Their present-day surface-sediment patterns outline the coastal upwelling cells and filaments and associated high productivity area. Analysed in an array of dated sediment cores, the spatial patterns of SST suggest long-term ([100 years) variability in the location and intensity of individual upwelling cells. The patterns of d 15 N outline an area of intense denitrification near the coast, and advection of water with low-oxygen concentrations in the undercurrent from the North. d 15 N exhibits considerable downcore variability, in particular over the last 50 years. The variability appears to be governed by differences in extent of denitrification and thus of the shelf oxygen balance, which appears to have deteriorated in the last 50 years. Together, the data suggest that SST and denitrification conditions have remained in the narrow bounds outlined by today's patterns in surface sediments, but that spatially small variability in upwelling intensity and make-up of upwelling feed waters induced considerable changes in the lower trophic levels of the coastal upwelling ecosystem over the last 6,000 years. Attempts to correlate proxy records from sediments with observational time series and regional climate reconstructions were not successful, possibly because annual to interannual environmental signals are erased in the process of sediment formation.

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Stable nitrogen isotopic ratios of sinking particles and sediments from the northern Indian Ocean

Cited by 131 publications

References 63 publications

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

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

Particulate matter fluxes in the southern and central Kara Sea compared to sediments: Bulk fluxes, amino acids, stable carbon and nitrogen isotopes, sterols and fatty acids

Variability in upwelling intensity and nutrient regime in the coastal upwelling system offshore Namibia: results from sediment archives

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