Tracing Change in Marine Ecosystem Using Compound Specific Stable Isotope Analysis of Amino Acids Archived in Baleen Whale Earplug

Human activities such as carbon dioxide release from burning fossil fuels and ocean eutrophication by nutrients in runoff waters can negatively affect ocean ecosystem by increasing sea surface temperature and altering habitat and food sources. These changes can affect marine organisms at a range of trophic levels and can be traced using carbon and nitrogen stable isotope ratios associated with diet and habitat. Long-term mobility, migration and food source variability across the ocean can be reconstructed by stable isotope analysis in long-range migratory animals such as baleen whales. Whale earwax bulk stable isotopes provides a great tool to trace lifetime food-web dynamics and ecosystem changes. Reconstructed stable isotope profiles from the baleen whale earplug found in southeast Gulf of Alaska (GOA) exhibited lifetime declining trends in the both carbon and nitrogen stable isotope profiles. These declining trends could be indicative of either change in biogeochemical process impacted by increased anthropogenic CO₂ emissions to the atmosphere or ¹³C-depleted terrestrial organic matter flux to the ocean. Alternatively, changes in biological processes and ecosystem structure such as prey availability can affect C and N stable isotope composition. It is challenging to differentiate change in trophic level from baseline variability using bulk stable isotope analysis, and here we present compound-specific stable isotope analysis of trophic and source amino acids in earwax that enables us to determine the source of variability in whales and shed light on the long-term climate change impact on marine ecosystem of GOA.