Nitrogen isotopic analysis of carbonate-bound organic matter in modern and fossil fish otoliths

Assimilation of nitrogen and carbon isotopes from fish diets to otoliths as measured by nanoscale secondary ion mass spectrometry

“…This technical limitation restricted the use of NanoSIMS to measure the δ 15 N values of artificially 15 N‐spiked otoliths. Nitrogen contributes less than 0.2 wt% of the otolith, which makes high‐precision analysis by an ion probe very difficult. Furthermore, otolith organic materials are heterogeneously interlaced within the CaCO 3 structure .…”

“…[28][29][30] The high δ 15 N values of spot measurements for otoliths 1, 2 and 4 varied by >500‰ within and between fishes and by approximately otoliths. Nitrogen contributes less than 0.2 wt% of the otolith, 14,16,17 which makes high-precision analysis by an ion probe very difficult.…”

“…In addition, the chemical composition, such as stable isotope ratios, of otoliths also provides valuable information on fish ecology . The carbonate‐bound nitrogen isotopic compositions of organic materials in fish otoliths may record information on the food sources, diet changes and trophic levels of fishes . However, a fundamental understanding of otolith nitrogen stable isotopes remains limited and the isotopic assimilation of δ 15 N compositions from diets to otoliths has rarely been investigated.…”

“…New approaches have recently been developed to measure the organic carbon and nitrogen isotopes of fish otoliths . The otolith mass required for the analysis of otolith δ 15 N composition has been greatly reduced from 100 to 2 mg .…”

Fractionation of otolith nitrogen stable isotopes measured by peroxodisulfate oxidation‐bacterial conversion and isotope ratio mass spectrometry

“…Atmospheric N 2 O concentration is very low, which reduces the risk of atmospheric contamination and greatly increases the signal‐to‐noise ratio when purified N 2 O is measured in the samples . The bacterial conversion method has been recently used to measure otolith δ 15 N values using 3–4 mg otolith powders collected from ancient and modern fish otoliths …”