Allochthonous inputs from grass-dominated wetlands support juvenile salmonids in headwater streams: evidence from stable isotopes of carbon, hydrogen, and nitrogen

Expanding the Isotopic Toolbox: Applications of Hydrogen and Oxygen Stable Isotope Ratios to Food Web Studies

“…Prior to the use of δ 2 H values, C stable isotopes were principally used as a marker for these studies. In some locales, δ 13 C values differ sufficiently between terrestrial and aquatic end members to distinguish these energy inputs (Rosenfeld and Roff, 1992;Junger and Planas, 1994;Doucett et al, 1996;Grey et al, 2001;Dekar et al, 2011), but there is not sufficient resolution in δ 13 C values for doing so in other cases (France, 1995;Finlay et al, 1999Finlay et al, , 2002Finlay et al, , 2010 FIGURE 2 | Hydrogen isotope values are a useful tracer of land-to-water and water-to-land nutrient flow as a result in δ 2 H value differences between aquatic and terrestrial primary producers. The offset between δ 2 H water and δ 2 H producer ( H , Equation 1) is typically larger for aquatic primary producers (excluding macrophytes) than for terrestrial vegetation.…”

“…These range from simple linear mixing models, such as IsoSource, that do not necessarily incorporate complexities such as variability in isotope values, hierarchical variance structure, and discrimination factors, to fully Bayesian mixing models that permit more flexibility and may incorporate some or all of these features. There are several off-the-shelf Bayesian models and packages available (see Phillips et al, 2014), but biologists in this field have mainly used SIAR (Dekar et al, 2011;Berggren et al, 2014;Roach and Winemiller, 2015;Stenroth et al, 2015) and MixSIR (Evans, 2012). Note that SIAR development has halted and the new MixSIAR GUI (graphical user interface) provides a collaboration between SIAR and MixSIR, while the mixing model components of SIAR are still available as an R package called simmr.…”

“…Any of these mixing models may also incorporate C and/or N isotopes in addition to those of H (Jardine et al, 2009;Cole et al, 2011;Dekar et al, 2011;Solomon et al, 2011;Batt et al, 2012Batt et al, , 2015Cole and Solomon, 2012;Evans, 2012;Wilkinson et al, 2013a;Berggren et al, 2014;Stenroth et al, 2015;Voigt et al, 2015). Because the biogeochemical controls on each of the elements are different, in many cases it can be more powerful to use the multiple tracers together to resolve contributions of potential nutrient sources (Jardine et al, 2009;Cole et al, 2011;Soto et al, 2013a; The trophic levels of a simple food chain with declining numbers of individuals at higher levels was the early vision for a food web that Charles Elton showed in his classical book for animal ecology (Elton, 1927).…”

Fish reduce habitat coupling by a waterbird: evidence from combined stable isotope and conventional dietary approaches

“…13 C values than typical aquatic sources (Peterson and Fry 1987), but the d 13 C signatures are not necessarily distinct enough to be fully efficient in resolving energy sources of different origin (Beaudoin et al 2001;Doucett et al 2007;Dekar et al 2012). In our study, leaf beetles representing the land-water ecotone were clearly the least 13 C-depleted source; frogs, however, most of which live in terrestrial environments (except the reproductive period), did not significantly differ from higher-level aquatic consumers such as dytiscids.…”

“…Hart and Lovvorn 2002;Bond and Jones 2009). The most recent developments to enhance separation of allochthonous and autochthonous sources by using deuterium isotope ratios (d 2 H) are promising, but still little is known of trophic fractionation of 2 H for aquatic consumers and the contribution of environmental water to consumer signatures (Doucett et al 2007;Jardine et al 2009;Dekar et al 2012). While SIA can be a valuable method to partition energy flow in freshwater ecosystems, our study confirms that it should be complemented by conventional techniques both to ensure that all important resources are included in the endmember selection and to provide independent evidence (e.g.…”