Stable carbon isotope and C/N geochemistry of coastal wetland sediments as a sea‐level indicator

Khan, Nicole S.; Vane, Christopher H.; Horton, Benjamin P.

doi:10.1002/9781118452547.ch20

Cited by 55 publications

(65 citation statements)

References 96 publications

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“…Ranges of d 13 C ratios and C/N values from different sources of organic material found in intertidal environments. This figure was modified from Lamb et al (2006) and Khan et al (2015). (226.0 and 230.0%; Chmura & Aharon, 1995), Potentilla spp.…”

Section: Live and Dead Foraminiferal Distributions In Bandon Marsh Anmentioning

confidence: 99%

“…The sample thickness and volume for foraminiferal analysis allows comparisons with similar studies (e.g., Scott & Medioli, 1978;Jennings & Nelson, 1992;Horton et al, 1999;Kemp et al, 2009). The geochemical samples were immediately refrigerated (,4uC) in darkness to limit microbial activity and prevent photo-oxidation of the organic components (Khan et al, 2015). All inter-annual and seasonal foraminiferal and geochemical data, and grain-size data, can be found in the supplementary material (Appendices 2 and 3).…”

Section: Sampling Strategymentioning

confidence: 99%

“…Recently, the stable carbon isotopic composition (d 13 C%) and carbon to nitrogen (C/N) ratio of bulk sediment in intertidal environments have been tested to discern whether these geochemical indicators could be used in a similar way as foraminiferal assemblages to reconstruct relative sea-level changes (Kemp et al, 2012;Engelhart et al, 2013b;Khan et al, 2015). These and other studies (e.g., Chmura & Aharon, 1995;Lamb et al, 2007;Kemp et al, 2010) have shown that the d 13 C values from marsh sediment correspond well with marsh elevation and hence the degree of tidal inundation (Wilson et al, 2005a, b), a variable that strongly influences the distribution of plants and the botanical composition of intertidal sediment.…”

Section: Introductionmentioning

confidence: 99%

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Annual and Seasonal Distribution of Intertidal Foraminifera and Stable Carbon Isotope Geochemistry, Bandon Marsh, Oregon, Usa

Milker

Horton

Vane

et al. 2015

The Journal of Foraminiferal Research

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We investigated the influence of inter-annual and seasonal differences on the distribution of live and dead foraminifera, and the inter-annual variability of stable carbon isotopes (d 13 C), total organic carbon (TOC) values and carbon to nitrogen (C/N) ratios in bulk sediments from intertidal environments of Bandon Marsh (Oregon, USA). Living and dead foraminiferal species from 10 stations were analyzed over two successive years in the summer (dry) and fall (wet) seasons. There were insignificant inter-annual and seasonal variations in the distribution of live and dead species. But there was a noticeable decrease in calcareous assemblages (Haynesina sp.) between live populations and dead assemblages, indicating that most of the calcareous tests were dissolved after burial; the agglutinated assemblages were comparable between constituents. The live populations and dead assemblages were dominated by Miliammina fusca in the tidal flat and low marsh, Jadammina macrescens, Trochammina inflata and M. fusca in the high marsh, and Trochamminita irregularis and Balticammina pseudomacrescens in the highest marsh to upland. Geochemical analyses (d 13 C, TOC and C/N of bulk sedimentary organic matter) show no significant influence of inter-annual variations but a significant correlation of d 13 C values (R = 20.820, p , 0.001), TOC values (R = 0.849, p , 0.001) and C/N ratios (R = 0.885, p , 0.001) to elevation with respect to the tidal frame. Our results suggest that foraminiferal assemblages and d 13 C and TOC values, as well as C/N ratios, in Bandon Marsh are useful in reconstructing paleo sea-levels on the North American Pacific coast.

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Section: Live and Dead Foraminiferal Distributions In Bandon Marsh Anmentioning

confidence: 99%

Section: Sampling Strategymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Annual and Seasonal Distribution of Intertidal Foraminifera and Stable Carbon Isotope Geochemistry, Bandon Marsh, Oregon, Usa

Milker

Horton

Vane

et al. 2015

The Journal of Foraminiferal Research

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“…The d 13 C of OM was used to distinguish between allochthonous (marine) and autochthonous (terrestrial) OM sources that differ greatly with respect to substrate quality and degradability (Khan et al 2015). The d 13 C of OM was used to distinguish between allochthonous (marine) and autochthonous (terrestrial) OM sources that differ greatly with respect to substrate quality and degradability (Khan et al 2015).…”

Section: Substrate Quality Of Soil Organic Matter and Plant Biomassmentioning

confidence: 99%

“…We assayed enzymes involved in both C and N cycling in order to relate EEAs to potential differences in substrate sources and quality in grazed vs. ungrazed marshes. Here, autochthonous and allochthonous sources of OM with large differences in substrate quality (Khan et al 2015) contribute to different amounts to the total soil-or sediment-OM pool, thus shaping the microbial community structure (Fagervold et al 2014). Quantifying the decomposition of different OM types as well as major decomposer groups separately could be particularly relevant to understand decomposition processes in coastal ecosystems.…”

Section: Introductionmentioning

confidence: 99%

Top‐down control of carbon sequestration: grazing affects microbial structure and function in salt marsh soils

Mueller

Granse

Nolte

et al. 2017

Ecological Applications

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Tidal wetlands have been increasingly recognized as long-term carbon sinks in recent years. Work on carbon sequestration and decomposition processes in tidal wetlands focused so far mainly on effects of global-change factors such as sea-level rise and increasing temperatures. However, little is known about effects of land use, such as livestock grazing, on organic matter decomposition and ultimately carbon sequestration. The present work aims at understanding the mechanisms by which large herbivores can affect organic matter decomposition in tidal wetlands. This was achieved by studying both direct animal-microbe interactions and indirect animal-plant-microbe interactions in grazed and ungrazed areas of two long-term experimental field sites at the German North Sea coast. We assessed bacterial and fungal gene abundance using quantitative PCR, as well as the activity of microbial exo-enzymes by conducting fluorometric assays. We demonstrate that grazing can have a profound impact on the microbial community structure of tidal wetland soils, by consistently increasing the fungi-to-bacteria ratio by 38-42%, and therefore potentially exerts important control over carbon turnover and sequestration. The observed shift in the microbial community was primarily driven by organic matter source, with higher contributions of recalcitrant autochthonous (terrestrial) vs. easily degradable allochthonous (marine) sources in grazed areas favoring relative fungal abundance. We propose a novel and indirect form of animal-plant-microbe interaction: top-down control of aboveground vegetation structure determines the capacity of allochthonous organic matter trapping during flooding and thus the structure of the microbial community. Furthermore, our data provide the first evidence that grazing slows down microbial exo-enzyme activity and thus decomposition through changes in soil redox chemistry. Activities of enzymes involved in C cycling were reduced by 28-40%, while activities of enzymes involved in N cycling were not consistently affected by grazing. It remains unclear if this is a trampling-driven direct grazing effect, as hypothesized in earlier studies, or if the effect on redox chemistry is plant mediated and thus indirect. This study improves our process-level understanding of how grazing can affect the microbial ecology and biogeochemistry of semi-terrestrial ecosystems that may help explain and predict differences in C turnover and sequestration rates between grazed and ungrazed systems.

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Paleoenvironment change and its impact on carbon and nitrogen accumulation in the Zoige wetland, northeastern Qinghai‐Tibetan Plateau over the past 14,000 years

Zeng

Zhu

Song

et al. 2017

Geochem Geophys Geosyst

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As the largest alpine wetland and peat deposition area in China, the Zoige wetland is climatically sensitive. The organic matter (OM) in peat stores copious environmental information. Here we report new data on the organic geochemistry of a 4.5 m peat profile HY2014 from southern Zoige wetland. Based on closely spaced accelerator mass spectrometry (AMS) 14C dating, we established a high‐resolution geochronological framework beginning at 14,057 a BP. Moreover, we estimated the sedimentation flux of TOC and TN (SFs) and their influencing factors. Before 10,916 a BP, the lake shrunk and peat began to develop under cold and dry conditions, and SFs were at their lowest values due to low productivity. More OM originated from hydrophyte and marsh plants. From 10,916 to 3050 a BP, peat was widely and well developed, and the climate was warm and humid, despite a cooling and drying trend. The HY2014 profile experienced an optimum climate during 10,916 − 6000 a BP, when SFs had the highest values that benefited from high productivity, and OM mainly originated from terrestrial plants. After 3050 a BP, the climate was the coldest and driest. The high SFs over the past 2000 a BP were mainly resulted from the low decomposition rate. The plant community, primary productivity, and decomposition rate were closely linked with the temporal variation of SFs. The environment change was mainly controlled by summer solar insolation, and the Zoige wetland was significantly influenced by the Indian summer monsoon.

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Stable carbon isotope and C/N geochemistry of coastal wetland sediments as a sea‐level indicator

Cited by 55 publications

References 96 publications

Annual and Seasonal Distribution of Intertidal Foraminifera and Stable Carbon Isotope Geochemistry, Bandon Marsh, Oregon, Usa

Annual and Seasonal Distribution of Intertidal Foraminifera and Stable Carbon Isotope Geochemistry, Bandon Marsh, Oregon, Usa

Top‐down control of carbon sequestration: grazing affects microbial structure and function in salt marsh soils

Paleoenvironment change and its impact on carbon and nitrogen accumulation in the Zoige wetland, northeastern Qinghai‐Tibetan Plateau over the past 14,000 years

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