MEPS 467:47-59 (2012)  -  DOI: https://doi.org/10.3354/meps09945

ABSTRACT: Stable isotopes of carbon (δ¹³C) and nitrogen (δ¹⁵N) were used to examine trophic structures in an arctic marine food web at small and large spatial scales. Twelve species, from primary consumers to Greenland shark, were sampled at a large spatial scale near the west and east coasts of Greenland. There was a significant positive latitudinal effect on δ¹⁵N values, which varied by 2 to 5‰ over the sample range. This latitudinal pattern was also illustrated by the negative correlation between the productive open-water period and baseline δ¹⁵N values. At a smaller spatial scale, 8 species from the Nuuk Fjord were compared with species sampled in waters immediately offshore. All values of δ¹⁵N and δ¹³C (except for Calanus finmarchicus) were more enriched inshore than offshore. The use of C. finmarchicus δ¹⁵N and δ¹³C values as a baseline explained a portion of the spatial variability in isotopes, attributing some of the variation to physical and biological sources. Hence, significant differences in isotopic signatures on both large and small spatial scales were less related to food web structure than to different physical and biological properties of the water masses. Accordingly, the results illustrate the importance of spatial variability when interpreting trophic structure from stable isotopes.

KEY WORDS: δ¹⁵N · δ¹³C · Greenland · Latitudinal effects · Marine food web · Ecohydrography ·  Isoscapes