Stable Isotope Ecology

Abstract

Stable isotope geochemistry has proved to be an extremely useful tool in elucidating many ecological problems, with stable isotope ecology comprising the theme of a series of international conferences ( http://www.isoecol.org ). Stable isotopes can be used as biological tracers in the following ways: (i) to identify sources, for instance in determining the identity of basal carbon in a food web; (ii) to distinguish sources, for example to determine whether a breeding animal is using local resources or its own reserves; (iii) to quantify relative inputs in a system, for example determining the proportions of different prey items to a consumer's diet. When utilized carefully, stable isotope geochemistry provides some advantages over conventional methods, and provides an additional device for the ecologist. The following article provides a short reference for ecologists considering the inclusion of stable isotope analysis as part of their methodology. Key concepts: Stable isotopes are useful tracers of ecological processes. Carbon stable isotopes are useful for tracing carbon sources and plant physiology. Nitrogen stable isotope ratios in animal tissues are useful indicators of trophic level. Combined carbon and nitrogen isotope ratios in animal tissues elucidate food webs and trophic niche. Hydrogen and oxygen isotope ratios in animals reflect those of local precipitation.

Ontogenetic variation in diet and habitat of Irrawaddy dolphins (Orcaella brevirostris) in the Gulf of Thailand and the Andaman Sea

“…); fish, birds, crustaceans, and cephalopods (DeNiro and Epstein , Peterson and Fry , Caut et al . ); and terrestrial mammals and birds), Δ 15 N = 3.22‰ (SD = 0.30) and Δ 13 C = 0.95‰ (SD = 0.53) (henceforth IDF1) ( e.g ., DeNiro and Epstein , Minagawa and Wada , France and Peters , Newton , Caut et al . ).…”

“…, Hobson , Knoff et al . , Newton ), and may indicate whether individuals are generalist or specialist foragers (Hobson and Sease , Walker and Macko , Knoff et al . ).…”

Critical issues with cryogenic extraction of soil water for stable isotope analysis

“…Recent studies have shown that the isotopic ratios of suction lysimeter waters differ from cryogenically extracted waters (Brooks et al ., ; Figueroa‐Johnson et al ., ; Landon et al ., ; Zhao et al ., ). While there is of course a large literature on isotopes in plant ecophysiology (see review articles of Adams and Grierson, ; Dawson et al ., ; Newton, ), there has been rather little comment on the techniques we use to extract low mobility waters in soils. Physically, we distinguish between water held at suctions less than field capacity (mobile water) and water held at suctions greater than field capacity – usually referred to as plant available water or tightly bound water (Huntington, ).…”

Dietary variation within and between populations of northeast Atlantic killer whales, Orcinus orca, inferred from δ13C and δ15N analyses

“…The analysis of naturally occurring variation in the ratio of isotopes of elements within the tissues of an organism has become a powerful tool for ecologists and has been used to address a range of questions including studying differences in the diet between individuals, sex/age classes, and populations; studying migration patterns and geographic range; and studying life history strategies (Hobson 1999, Hobson E473 and Wassenaar 1999, Newsome et al 2010, Newton 2010. Stable isotope studies comparing the ratios of nitrogen ( 15 N/ 14 N) and carbon ( 13 C/ 12 C) can be particularly informative for comparing differences in diet, trophic position and geographic range (Hobson and Wassenaar 1999, Newsome et al 2010, Newton 2010. This is because of a stepwise enrichment of 15 N with each increase in trophic level, which reflects differences in fractionation between synthesis and excretion.…”