Variability of Settling Particles Fluxes and Isotopic Composition (δ13C and δ15N) from Material Trapped in Coastal Reefs of Abrolhos Bank, Eastern Brazilian Shelf

Elemental and isotopic ratios (C/N, δ13C, δ15N) of sediment samples captured by PVC traps in eight stations along the coastal reefs of the Abrolhos region, Brazil, were analyzed. The study area is characterized by the influence of continental sediments on biogenic sediments. The highest δ13C values were found in the Sebastião Gomes (second shallower station), with average values close to -15‰ in all sampling periods. The isotopic ratio of carbon and nitrogen indicates that the organic matter analyzed has marine origin, with signature features of oceanic regions. The highest C/N ratio average value of 8.29 occurred in Nova Viçosa (the southernmost station and one of the shallowest) during the spring, in other seasons the average value was close to 7 in all periods. Although the values of C/N indicate a significantly marine contribution, δ15N values suggest that N series recycling processes are frequent during the time that the material remained in the environment. The results will provide a baseline for future environmental monitoring and studies on changes in sediment composition in an important set of coastal coral reefs.

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Soil organic carbon and nitrogen sequestration and turnover in aggregates under subtropical leucaena–grass pastures

Soil Research ◽

10.1071/sr18016 ◽

2018 ◽

Vol 56 (6) ◽

pp. 632 ◽

Cited By ~ 4

Author(s):

Kathryn Conrad ◽

Ram C. Dalal ◽

Ryosuke Fujinuma ◽

Neal W. Menzies

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Soil Organic Carbon ◽

Soil Aggregates ◽

Soil Mass ◽

Δ13c And Δ15n ◽

Organic C ◽

Carbon And Nitrogen ◽

Nitrogen Sequestration ◽

C And N

Stabilisation and protection of soil organic carbon (SOC) in macroaggregates and microaggregates represents an important mechanism for the sequestration of SOC. Legume-based grass pastures have the potential to contribute to aggregate formation and stabilisation, thereby leading to SOC sequestration. However, there is limited research on the C and N dynamics of soil organic matter (SOM) fractions in deep-rooted legume leucaena (Leucaena leucocephala)–grass pastures. We assessed the potential of leucaena to sequester carbon (C) and nitrogen (N) in soil aggregates by estimating the origin, quantity and distribution in the soil profile. We utilised a chronosequence (0–40 years) of seasonally grazed leucaena stands (3–6 m rows), which were sampled to a depth of 0.3 m at 0.1-m intervals. The soil was wet-sieved for different aggregate sizes (large macroaggregates, >2000 µm; small macroaggregates, 250–2000 µm; microaggregates, 53–250 µm; and <53 µm), including occluded particulate organic matter (oPOM) within macroaggregates (>250 µm), and then analysed for organic C, N and δ13C and δ15N. Leucaena promoted aggregation, which increased with the age of the leucaena stands, and in particular the formation of large macroaggregates compared with grass in the upper 0.2 m. Macroaggregates contained a greater SOC stock than microaggregates, principally as a function of the soil mass distribution. The oPOM-C and -N concentrations were highest in macroaggregates at all depths. The acid nonhydrolysable C and N distribution (recalcitrant SOM) provided no clear distinction in stabilisation of SOM between pastures. Leucaena- and possibly other legume-based grass pastures have potential to sequester SOC through stabilisation and protection of oPOM within macroaggregates in soil.

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Spatial and Seasonal Variations of Sedimentary Organic Matter in a Subtropical Bay: Implication for Human Interventions

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph17041362 ◽

2020 ◽

Vol 17 (4) ◽

pp. 1362 ◽

Cited By ~ 3

Author(s):

Xuan Lu ◽

Fengxia Zhou ◽

Fajin Chen ◽

Qibin Lao ◽

Qingmei Zhu ◽

...

Keyword(s):

Organic Matter ◽

Surface Sediment ◽

Seasonal Variations ◽

Seasonal Changes ◽

Nitrogen Isotope ◽

Anthropogenic Influences ◽

Stable Carbon ◽

Δ13c And Δ15n ◽

Carbon And Nitrogen ◽

Induced Changes

Elemental (total organic carbon (TOC) and total nitrogen (TN)) and stable carbon and nitrogen isotope compositions (δ13C and δ15N, respectively) in the surface sediment of Zhanjiang Bay (ZJB) in spring and summer were measured to study the spatial and seasonal changes of organic matter (OM) and assess the human-induced and environment-induced changes in the area. The OM in the surface sediment of ZJB was a mixture of terrestrial and marine sources, and was dominated by marine OM (54.9% ± 15.2%). Compared to the central ZJB, the channel and coastal ZJB areas had higher δ13C and δ15N values, higher TOC and TN concentrations, and lower TOC/TN ratios, indicating higher primary productivity and higher percentages of marine OM in the latter two subregions. Mariculture activities, sewage inputs, and dredging were responsible for these phenomena. Clear seasonal variations in OM were observed in ZJB. The average proportions of terrestrial OM in summer increased by 10.2% in the ZJB channel and 26.0% in the coastal ZJB area compared with those in spring. Heavy rainfall brought a large amount of terrestrial OM into the channel and coastal ZJB areas, leading to the increase of the terrestrial OM fraction in these two subregions in summer. In summary, anthropogenic influences had a significant influence on the spatial and seasonal variations of sedimentary OM in ZJB.

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Stable isotopes reveal post-release trophodynamic and ontogenetic changes in a released finfish, mulloway (Argyrosomus japonicus)

Marine and Freshwater Research ◽

10.1071/mf09014 ◽

2010 ◽

Vol 61 (3) ◽

pp. 302 ◽

Cited By ~ 12

Author(s):

Matthew D. Taylor ◽

Debashish Mazumder

Keyword(s):

Stable Isotopes ◽

Isotopic Composition ◽

Turnover Rate ◽

Isotope Composition ◽

Wild Fish ◽

Ontogenetic Changes ◽

Nitrogen Stable Isotope ◽

Δ13c And Δ15n ◽

Carbon And Nitrogen ◽

Nitrogen Isotopic Composition

Carbon and nitrogen stable isotope ratios were analysed for hatchery-reared, recaptured and wild mulloway, Argyrosomus japonicus, to investigate temporal and growth-related changes in isotopic composition for stocked fish after release, and to evaluate changes in isotopic composition in terms of ontogenetic dietary switches. δ13C and δ15N values decreased and increased, respectively, after release. The isotope composition of released fish was distinct from wild fish until 200 days after release, but after 200 days post-release fish did not differ significantly from wild fish of similar or greater sizes. Abrupt dietary transitions from crustaceans to teleost fish (>50 cm total length (TL)) were evident in a rapid δ13C and δ15N change in wild mulloway, and δ15N was significantly greater in wild fish >65 cm TL compared with wild fish <50 cm TL. Multivariate carbon and nitrogen isotopic data were suitable for separating stocked and wild fish for up to 200 days after release, but did not separate wild fish grouped according to dietary composition. Carbon and nitrogen isotopic composition closely reflected dietary transitions and rapid adaptation by stocked mulloway to wild diets, which was evident in a high tissue turnover rate of up to 0.017 day–1. Stable isotopes are a useful tool for examining the integration of released fish into stocked ecosystems and can be used to describe convergence in the diets of wild and released fish.

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Stable Carbon and Nitrogen Isotopes in the Tidal Flat Sediments of Northern Yellow Sea

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.316-317.223 ◽

2013 ◽

Vol 316-317 ◽

pp. 223-226

Author(s):

Bao Zhan Liu ◽

Yu Liu ◽

Ying Li ◽

Hai Xia Wang

Keyword(s):

Organic Matter ◽

Tidal Flat ◽

Yellow Sea ◽

Nitrogen Isotopes ◽

Stable Carbon ◽

Terrestrial Organic Matter ◽

Δ13c And Δ15n ◽

Carbon And Nitrogen Isotopes ◽

Carbon And Nitrogen ◽

Northern Yellow Sea

Stable carbon and nitrogen compositions (δ13C, δ15N) of sedimentary organic matter were determined in the tidal flat of northern Yellow sea. The results showed that stable carbon and nitrogen isotopes compositions of the sediment samples ranged from −24.669～−19.457‰ and 2.125～7.043‰, respectively. The highest value was in St.DLD, and the lowest was in St.Z. Similar δ13C values were observed in St.H (−21.996±0.651‰) and St.P (−22.021±0.187‰), and similar δ15N values were between St.DLJ (5.502±0.223‰) and St.P (5.310±0.294‰). The δ13C and δ15N values did not show any significant regularity. The δ13C and δ15N signatures showed some fluctuation, no obvious regularity. The major source of terrestrial organic matter was from the emissions of river and human pollutant.

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