The carbon isotopic composition of marine phytoplankton varies significantly with growth conditions. Aqueous CO2 concentration [CO2] and algal growth rate (m) have been suggested to be important factors determining isotope fractionation («p). Here we examine «p of the coccolithophorid Emiliania huxleyi in relation to CO2 concentration and light conditions in dilute batch cultures. Cells were in...

Sulfur compounds in intermediate valence states, for example elemental sulfur, thiosulfate, and tetrathionate, are important players in the biogeochemical sulfur cycle. However, key understanding about the pathways of oxidation involving mixed-valance state sulfur species is still missing. Here we report the sulfur and oxygen isotope fractionation effects during the oxidation of tetrathionate (...

Stable isotope analysis is an important tool for characterising food web structure; however, interpretation of isotope data can often be flawed. For instance, lipid normalisation and trophic fractionation values are often assumed to be constant, but can vary considerably between ecosystems, species and tissues. Here, previously determined lipid normalisation equations and trophic fractionation ...

he efficiency of photosynthesis continues to interest biochemists, biologists, and plant physiologists. Scientists interested in CO2 uptake are concerned about the extent to which the uptake rate is limited by such factors as stomatal diffusion and the chemistry of the CO2 absorption process. The fractionation of carbon isotopes that occurs during photosynthesis is one of the most useful techni...

Ab initio molecular dynamics and quantum chemistry techniques are used to calculate the structure, vibrational frequencies, and carbon-isotope fractionation factors of the carbon dioxide component [CO(2)(m)] of soil (oxy)hydroxide minerals goethite, diaspore, and gibbsite. We have identified two possible pathways of incorporation of CO(2)(m) into (oxy)hydroxide crystal structures: one in which ...

Sulfur isotope fractionation during dissimilatory sulfate reduction has been conceptually described by the widely accepted Rees model as related to the stepwise reduction of sulfate to sulfide within the cells of bacteria. The magnitude of isotope fractionation is determined by the interplay between different reduction steps in a chain of reactions. Here we present a revision of Rees’ model for...

We have developed a technique for cultivation of chemolithoautotrophs under high hydrostatic pressures that is successfully applicable to various types of deep-sea chemolithoautotrophs, including methanogens. It is based on a glass-syringe-sealing liquid medium and gas mixture used in conjunction with a butyl rubber piston and a metallic needle stuck into butyl rubber. By using this technique, ...

Stable Zn isotopes are fractionated in roots and leaves of plants. Analyses demonstrate that the heavy Zn isotopes are enriched in the root system of plants with respect to shoots and leaves as well as the host soil, but the fractionation mechanisms remain unclear. Here we show that the origin of this isotope fractionation is due to a chemical isotope effect upon complexation by Zn malates and ...

the upper cretaceous carbonate sequence of ab-deraz formation is well exposed in the kopet- dagh basin. this formation comprises marly limestone and three chalky limestone units. chalky limestone of ab-deraz formation is mainly composed of calcareous dinoflagellate (pithonellid calcispher), cocolithofore and planktonic foraminifera. carbon and oxygen stable isotopes analysis of the third chalky...

Non-traditional stable isotopes have increasingly been applied to studies of igneous processes including planetary differentiation. Equilibrium isotope fractionation of these elements in silicates is expected to be negligible at magmatic temperatures (δ(57)Fe difference often less than 0.2 per mil). However, an increasing number of data has revealed a puzzling observation, e.g., the δ(57)Fe for...