Simultaneous δ¹⁵N, δ¹³C and δ³⁴S measurements of low‐biomass samples using a technically advanced high sensitivity elemental analyzer connected to an isotope ratio mass spectrometer

Abstract

Conventional simultaneous CNS stable isotope abundance measurements of solid samples usually require high sample amounts, up to 1 mg carbon, to achieve exact analytical results. This rarely used application is often impaired by high C:S element ratios when organic samples are analyzed and problems such as incomplete conversion into sulphur dioxide occur during analysis. We introduce, as a technical innovation, a high sensitivity elemental analyzer coupled to a conventional isotope ratio mass spectrometer, with which CNS-stable isotope ratios can be determined simultaneously in samples with low carbon content (<40 microg C corresponding to approximately 100 microg dry weight). The system includes downsized reactors, a temperature program-controlled gas chromatography (GC) column and a cryogenic trap to collect small amounts of sulphur dioxide. This modified application allows for highly sensitive measurements in a fully automated operation with standard deviations better than +/-0.47 per thousand for delta15N and delta34S and +/-0.12 per thousand for delta13C (n = 127). Samples collected from one sampling site in a Baltic fjord within a short time period were measured with the new system to get a first impression of triple stable isotope signatures. The results confirm the potential of using delta34S as a stable isotope tracer in combination with delta15N and delta13C measurements to improve discrimination of food sources in aquatic food webs.

Mercury in gray wolves (Canis lupus) in Alaska: Increased exposure through consumption of marine prey

“…Carbon and nitrogen isotopes are two measures that have been used to demonstrate marine resource utilization in populations (Adams et al, 2010), as δ 13 C and δ 15 N increase with the marine content of diet (Hilderbrand et al, 1996). The additional measurement of δ 34 S was implemented in this study, since it can further aid in differentiating between the dietary contributions of marine and terrestrial resources (Crawford, McDonald, and Bearhop, 2008; Hansen, Burmeister, and Sommer, 2009). Our isotope analyses strengthen the contention that marine resources are contributing to the diets of coastal wolves in Alaska.…”

“…Stable isotope analysis is an integrated approach used to improve the overall understanding of food-webs (Hansen, Burmeister, and Sommer, 2009). Stable carbon (C)-, nitrogen (N)-, and sulfur (S)-isotopic compositions, in particular, have been widely recognized as established proxies of the trophic architecture.…”

Stable isotopes dissect aquatic food webs from the top to the bottom

“…The majority of food-web studies are limited to carbon and nitrogen isotopes because of their ease of measurement, and to larger-sized organisms that can be physically separated and then analyzed by CF-IRMS. Recent improvements in technology now allow the measurement of δ 13 C, δ 15 N and δ 34 S simultaneously on small samples (Hansen et al, 2009). This will enable more accurate and complete reconstruction of food-web interactions.…”

Simultaneous analysis of δ13C, δ15N and δ34S ratios uncovers food web relationships and the trophic importance of epiphytes in an eelgrass Zostera marina community

“…Epiphytes obtain sulphur mostly from seawater sulphate while seagrass leaves (Kharlamenko et al 2001, Moncreiff & Sullivan 2001 at least partially obtain their sulphur from the interstitial waters of the sediment. The δ 34 S stable isotope value of sulphate in the water column is 21 ‰ (Grey & Deines 2005), compared to δ 34 S values of 1 ‰ of reduced sulphur (H 2 S − ) derived from depleted sediment pore water (Hansen et al 2009). The trophic shift for sulphur is assumed to be negligible (McCutchan et al 2003, Michener & Kaufman 2007.…”