Beyond the bi-plot: State of the art approaches to using stable isotopes and biomarkers in marine trophic and spatial ecology

Dr. Rachel Jeffreys, (Liverpool), Dr. Clive Trueman (Southampton) 

Stable isotope and biomarker (e.g. fatty acids, pigments and amino acids) analyses are now routinely used to reconstruct trophic interactions and nutrient flux in terrestrial and marine ecosystems. Stable isotope and biomarker approaches can be used to address questions over a wide range of ecological and spatial scales ranging from reconstructing individual behaviour to deriving metrics of ecosystem function. Analyses of long lived organisms, or archived historic samples can yield time series data suitable for assessing ecosystem responses to anthropogenic change.

In recent years the field of isotope ecology has benefitted from several technological and conceptual advances, challenging some widely held assumptions about fundamental processes in isotope ecology, and changing the types of ecological questions addressed. Compound-specific isotope analyses provide subtle tools for testing the physiological processes underpinning trophic fractionation, while also providing new methods to track nutrient sources throughout food webs in unprecedented detail. Spatially explicit isotope datasets reveal strong systematic geographic gradients in the isotopic composition of marine primary production that complicate conventional diet analyses. However, the development of predictive spatial isotope models also provides new tools to reconstruct geographic origin and animal movements. Emerging data analysis methods allow for uncertainty to be considered explicitly in diet source approaches, and draw attention to the importance of individual variation in the form of the isotopic niche.

While these techniques, approaches and datasets provide exciting new opportunities, the increasing complexity of the field and rapid rate of publication calls for increased communication of these new insights both within the field and more broadly to the marine science community.

We welcome presentations utilising bulk or compound-specific stable isotope and biomarker approaches, or conceptual biogeochemical models to address questions related to marine trophic and spatial ecology ranging from microbes to top predators and from individual behaviour to global ecosystem function.