Reconstruction of carbon and nitrogen stable isotope in baleen whale earplugs.

Changes in sea surface temperature, pH, and stratification have been reported to alter nutrient availability and resulted in a shift in phytoplankton community composition and size structure as well as ocean biogeochemistry over time. An empirical understanding of changes in the marine ecosystem and the ocean’s biogeochemical cycles through time requires a time-series dataset that spans years to decades. Biological time series datasets provide an unparalleled opportunity to investigate regional and global changes in the marine environment. Baleen whales are long-lived sentinel species and an integral part of the marine ecosystem. Interestingly, baleen whales have earplugs, a keratin-rich matric that is capable of recording and archiving the life history of an individual whale. Combining age estimates with elemental and molecular measurements from individual earplugs results in the reconstruction of chemicals and hormones in baleen whales with six-months resolution dating back 100 years. The objective of this dissertation is to reconstruct lifetime δ13C and δ15N profiles (i.e., birth to death) earplugs and investigate years to decadal changes in the ocean ecosystem and individual foraging and feeding ecology. Reconstructed δ13C and δ15N profiles from baleen whale earplugs (N = 17, n = 950 laminae) in this study provide the first recorded birth to death stable isotope profiles for baleen whales. These longitudinal profiles reveal changes in both individual whale behavior such as possible shifts in foraging location and/or trophic level as well as ecosystem-level changes that could be associated with the Suess effect and/or long-term changes in biogeochemical cycling.