Sources of carbon and nitrogen in modern planktonic foraminifera: the role of algal symbionts as determined by bulk and compound specific stable isotopic analyses

Ocean warming increases the incidence of coral bleaching, which reduces or eliminates the nutrition corals receive from their algal symbionts, often resulting in widespread mortality. In contrast to extensive knowledge on the thermal tolerance of coral-associated symbionts, the role of the coral host in bleaching patterns across species is poorly understood. Here, we applied a Bayesian analysis of carbon and nitrogen stable isotope data to determine the trophic niche overlap between corals and their symbionts and propose benchmark values that define autotrophy, heterotrophy, and mixotrophy. The amount of overlap between coral and symbiont niche was negatively correlated with polyp size and bleaching resistance. Our results indicated that as oceans warm, autotrophic corals lose their competitive advantage and thus are the first to disappear from coral reefs.

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Seasonal trends in the stable isotopic composition of snow and meltwater runoff in a subarctic catchment at Okstindan, Norway

Hydrology Research ◽

10.2166/nh.2004.0009 ◽

2004 ◽

Vol 35 (2) ◽

pp. 119-137 ◽

Cited By ~ 12

Author(s):

S.D. Gurney ◽

D.S.L. Lawrence

Keyword(s):

Isotopic Composition ◽

Mean Value ◽

Mean Values ◽

Stable Isotopic Composition ◽

Meltwater Runoff ◽

Stable Isotopic ◽

The Mean ◽

The Difference ◽

Δ18o And Δd

Seasonal variations in the stable isotopic composition of snow and meltwater were investigated in a sub-arctic, mountainous, but non-glacial, catchment at Okstindan in northern Norway based on analyses of δ18O and δD. Samples were collected during four field periods (August 1998; April 1999; June 1999 and August 1999) at three sites lying on an altitudinal transect (740–970 m a.s.l.). Snowpack data display an increase in the mean values of δ18O (increasing from a mean value of −13.51 to −11.49‰ between April and August), as well as a decrease in variability through the melt period. Comparison with a regional meteoric water line indicates that the slope of the δ18O–δD line for the snowpacks decreases over the same period, dropping from 7.49 to approximately 6.2.This change points to the role of evaporation in snowpack ablation and is confirmed by the vertical profile of deuterium excess. Snowpack seepage data, although limited, also suggest reduced values of δD, as might be associated with local evaporation during meltwater generation. In general, meltwaters were depleted in δ18O relative to the source snowpack at the peak of the melt (June), but later in the year (August) the difference between the two was not statistically significant. The diurnal pattern of isotopic composition indicates that the most depleted meltwaters coincide with the peak in temperature and, hence, meltwater production.

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Temperature affects carbon and nitrogen stable isotopic signatures of aquatic plants

Aquatic Sciences ◽

10.1007/s00027-021-00794-8 ◽

2021 ◽

Vol 83 (2) ◽

Author(s):

Peiyu Zhang ◽

Xianghong Kong ◽

Elisabeth S. Bakker ◽

Jun Xu ◽

Min Zhang

Keyword(s):

Aquatic Plants ◽

Isotopic Signatures ◽

Carbon And Nitrogen ◽

Stable Isotopic

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The Role of Faults in Groundwater Circulation before and after Seismic Events: Insights from Tracers, Water Isotopes and Geochemistry

Water ◽

10.3390/w13111499 ◽

2021 ◽

Vol 13 (11) ◽

pp. 1499

Author(s):

Davide Fronzi ◽

Francesco Mirabella ◽

Carlo Cardellini ◽

Stefano Caliro ◽

Stefano Palpacelli ◽

...

Keyword(s):

Preferential Flow ◽

Central Italy ◽

Tracer Tests ◽

Integrated Approach ◽

Fault System ◽

Tectonic Structures ◽

Fault Systems ◽

Isotopic Analyses ◽

Before And After

The interaction between fluids and tectonic structures such as fault systems is a much-discussed issue. Many scientific works are aimed at understanding what the role of fault systems in the displacement of deep fluids is, by investigating the interaction between the upper mantle, the lower crustal portion and the upraising of gasses carried by liquids. Many other scientific works try to explore the interaction between the recharge processes, i.e., precipitation, and the fault zones, aiming to recognize the function of the abovementioned structures and their capability to direct groundwater flow towards preferential drainage areas. Understanding the role of faults in the recharge processes of punctual and linear springs, meant as gaining streams, is a key point in hydrogeology, as it is known that faults can act either as flow barriers or as preferential flow paths. In this work an investigation of a fault system located in the Nera River catchment (Italy), based on geo-structural investigations, tracer tests, geochemical and isotopic recharge modelling, allows to identify the role of the normal fault system before and after the 2016–2017 central Italy seismic sequence (Mmax = 6.5). The outcome was achieved by an integrated approach consisting of a structural geology field work, combined with GIS-based analysis, and of a hydrogeological investigation based on artificial tracer tests and geochemical and isotopic analyses.

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Role of carbon and nitrogen in the improvement of corrosion resistance of new powder metallurgy Co-Cr-Mo alloys

Corrosion Reviews ◽

10.1515/corrrev-2019-0109 ◽

2020 ◽

Vol 38 (3) ◽

pp. 273-286 ◽

Cited By ~ 1

Author(s):

Cristina Garcia-Cabezon ◽

Celia Garcia-Hernandez ◽

Maria L. Rodriguez-Mendez ◽

Gemma Herranz ◽

Fernando Martin-Pedrosa

Keyword(s):

Mechanical Properties ◽

Corrosion Resistance ◽

Powder Metallurgy ◽

Nitrogen Content ◽

Powder Metallurgy Technique ◽

Carbon And Nitrogen ◽

Physiological Conditions ◽

Carbon And Nitrogen Content ◽

Astm F75

AbstractMicrostructural changes that result in relevant improvements in mechanical properties and electrochemical behavior can be induced using different sintering conditions of ASTM F75 cobalt alloys during their processing using powder metallurgy technique. It has been observed that the increase in carbon and nitrogen content improves corrosion resistance and mechanical properties as long as the precipitation of carbides and nitrides is avoided, thanks to the use of rapid cooling in water after the sintering stage. In addition, the reduction of the particle size of the powder improves hardness and resistance to corrosion in both acid medium with chlorides and phosphate-buffered medium that simulates the physiological conditions for its use as a biomaterial. These results lead to increased knowledge of the role of carbon and nitrogen content in the behavior displayed by the different alloys studied.

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Stable isotopes in planktonic and benthic foraminifera from Arctic Ocean surface sediments

Canadian Journal of Earth Sciences ◽

10.1139/e88-066 ◽

1988 ◽

Vol 25 (5) ◽

pp. 701-709 ◽

Cited By ~ 17

Author(s):

A. E. Aksu ◽

G. Vilks

Keyword(s):

Surface Water ◽

Arctic Ocean ◽

Sea Water ◽

Ocean Surface ◽

The Arctic ◽

Size Fractions ◽

Isotopic Compositions ◽

Isotopic Analyses ◽

Stable Isotopic ◽

Surface Water Salinity

Oxygen and carbon isotopic analyses have been performed on the tests of Planulina wuellerstorfi and three size fractions of sinistral Neogloboquadrina pachyderma recovered from 33 Arctic Ocean surface-sediment samples. Stable isotopic compositions of N. pachyderma are found to be dependent on the test size: larger specimens show considerable enrichment in both δ18O and δ18C. The difference between the isotopic compositions of the 63–125 and 125–250 μm size fractions in N. pachyderma can be explained by biogenic fractionation effects during foraminiferal test growth. Larger (250–500 μm) N. pachyderma displayed accretions of secondary calcite, i.e., the outermost shell contained significant amounts of inorganically precipitated magnesium calcite. Thus, larger foraminifera may not be suited for down-core stable isotopic studies. There is a difference of ~2‰ between δ18O values of surface samples from the eastern and western Arctic Ocean, reflecting large differences between surface-water salinity in these regions. Therefore, oxygen isotopic data may have limited use as a chronostratigraphic tool in down-core studies in the Arctic Ocean, but we can use them to infer past variations in surface-water salinities. Planulina wuellerstorfi also showed depletions of both δ18O and δ18C in its calcite tests relative to calcite precipitated in isotopic equilibrium with ambient sea water; these depletions ranged from −0.8 to −0.9‰ in δ18Oand −1.2 to −0.9‰ in δ18C. This taxon is found to deposit its shell very close to the δ18C of ΣCO2 of bottom waters.

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