Stable isotopes in ecological studies

Abstract

Stable isotope ratio analyses at natural abundance levels are an increasingly useful tool in ecological studies, with new papers being published in nearly every issue of Oecologia and other ecological journals. In April 2004, the National Institute of Water and Atmospheric Research (NIWA) and the Institute of Geological and Nuclear Sciences (IGNS) co-hosted the fourth conference on ‘‘Applications of Stable Isotopes to Ecological Studies’’ at the Museum of New Zealand Te Papa Tongarewa, Wellington, New Zealand (http:// www.isoecol.org/previous.html). This biannual international conference brings together a wide range of biologists, physiologists, geochemists, and environmental scientists who use stable isotopes to identify and solve gaps in ecological knowledge. Topics presented at this meeting were very diverse, and included the use of stable isotope analyses in ecological management of terrestrial, marine and freshwater systems, the hydrologic cycle, the carbon cycle and primary productivity, microbial ecology, nutrient cycling, pollution ecology, precipitation analyses across broad spatial scales, terrestrial and aquatic trophic level and diet studies, bird migration studies, and palaeoecology. The need for these international meetings continues to grow since the first meeting held in 1998 in Saskatoon, Canada (Hobson and Wassenaar 1999); the next conference is planned for Belfast, Northern Ireland in August 2006 (http://www.isoecol.org). A number of contributors to the New Zealand conference jointly submitted manuscripts for review and publication in Oecologia. Having now satisfactorily completed the review process, a number of the conference contributions are published together in this issue of Oecologia. These papers highlight the diverse ecological studies discussed in New Zealand. Bird migration studies take advantage of the pronounced isotope gradients across continents (Bowen et al. 2005; Hobson et al. 2004; Pain et al. 2004). Mazerolle et al. (2005) developed the use of stable hydrogen isotopes of feather and claw material from white-throated sparrows (Zonotrichia albicollis) in order to elucidate both breeding and wintering catchment areas, an approach augmented by conventional bird-banding data. Wunder et al. (2005) provided a quantitative assessment on the utility of using isotope tracers in feathers of known origin. There is a long history of using stable isotopes in marine studies. Continuing this area of investigation, Hicks et al. (2005) investigated the contribution of marine-derived nutrients from spawning coho salmon (Oncorhynchus kisutch) to freshwater-riparian foodwebs in southcentral Alaska, and found that spawning salmon provide marine nitrogen and carbon comprising about 35% of the dietary needs of juvenile salmon. Harrod et al. (2005) examined stable isotope analyses in the evaluation of ecological plasticity in eels. Cunjak et al. (2005) showed the utility of using isotopes as trackers of fish movements, especially when combined with more traditional approaches. Isotopes are often useful tracers in ecological systems. Connolly et al. (2005) examined relationships in carbon dynamics by invertebrates in estuaries. Wissell and Fry Communicated by Jim Ehleringer