MEPS 692:185-194 (2022)  -  DOI: https://doi.org/10.3354/meps14067

ABSTRACT: Stable isotope ratios have proven a valuable tool to investigate marine mammal ecology, including diet, distribution, and migratory movements. While most studies have focused on δ¹⁵N and δ¹³C values, δ³⁴S values have been little used because their pattern of variation and tissue dynamics remain unclear. We examined the sequential variation of δ¹⁵N, δ¹³C, and δ³⁴S values along the baleen plates from fin whales occurring off West Iceland in summer. All baleen plates exhibited fluctuations along their growing axis. A significant synchronic correlation was found between δ¹⁵N and δ³⁴S values, while the relation of these values to the δ¹³C value was highly variable and inconsistent. These results were similar to those obtained in previous studies of Greenland bowhead whales, although the pattern of the oscillations in fin whales showed an increase in values during winter, while those of bowhead whales showed a decrease. Although seasonal variations in food intake and the associated cycles of protein synthesis and catabolism may have played a role in such fluctuations and the observed differences between species, we suggest that the main driver for the δ³⁴S fluctuations reflected in baleen plates is the variation of local baselines between winter and summer grounds. This suggests ample potential for using δ³⁴S values to study migratory movements and destinations of marine megafauna, provided that the geographic variation in δ³⁴S baselines is clarified.

KEY WORDS: Baleen whale · Iceland · Stable isotope covariation · Baleen plate · Migration · Nitrogen · Carbon · Sulfur