Examining the response of top marine predators to ecological change using stable isotope proxies

• Main Author: Hanson, Nora N
• Format: Dissertation
• Language: English
• Published: University of St Andrews 30.11.2012; The University of St Andrews
• Subjects: 172

Monitoring the response of upper trophic level animals to ecological change is importantto understanding the state and stability of ecosystems. Marine predatorsintegrate information over large geographical scales and are relatively long-lived; furthermore,many of these organisms are restricted to terrestrial or freshwater habitatsat certain times during their life history and are accessible to researchers. This thesisinvestigated the response of marine predators to ecological change at a varietyof spatial and temporal scales using stable isotope ratio methods with the aims ofdeveloping meaningful proxies, or indices, of variability in marine ecosystems.The first study explored the intrinsic (i.e. ontogenetic) and extrinsic (i.e. environmental)factors important to modulating variation in the stable isotope ratios ofC and N in tooth dentin of male Antarctic fur seals (Arctocephalus gazella) in theSouthern Ocean. In the second study, long-term records of variation in δ15Nδ13C values of Atlantic salmon (Salmo salar) scales and grey seal (Halichoerus grypus)tooth dentin provided evidence for large-scale climate forcing across the easternNorth Atlantic. In the following study, a more detailed examination of intra- andinter-individual stable isotope variation in Atlantic salmon within a single year wasundertaken in an attempt to better understand recent declines in somatic conditionof these fish.The last two studies were concerned with the development of high resolution samplingof fish otoliths using secondary mass spectrometry (SIMS) and the applicationof this technique to reconstructing the thermal and metabolic histories of individualAtlantic salmon from intra-otolith δ13C and δ18O values.Stable isotope proxies can be used to document shifts in trophic dynamics andanimal movement that may be associated with ecological change. Using multipletissues, elements and species, such studies provide unique monitoring tools at arange of spatial and temporal scales.