Exploring the use of historic cuttlebones as archives of environmental and biological change

Context Isotopic markers in the hard parts of marine animals can unearth long-lasting records of biological and environmental change, but have rarely been studied in modern coleoid cephalopods. Aims We aimed to explore how cuttlebones from historic archieves can be used as archives of enviornmental and biological change. Methods We first collated the first historic archive of Ascarosepion apama cuttlebones. Cuttlebones were obtained from museums, research repositories and private collections, spanned six decades, and represented multiple sites around southern Australia. We analysed carbon (δ13C) and oxygen (δ18O) isotopic ratios in each cuttlebone and used generalised additive models (GAM) and linear regression models to assess temporal and spatial trends in δ13C and δ18O values. Key results We found that spatial trends overrode temporal trends, and that δ13C and δ18O values in carbonate were strong geographical predictors. However, we observed temporal changes in δ13C and δ18O values in cuttlebones collected from a discreet oceanographic region where more cuttlebones were available. Conclusions These temporal changes were possibly linked to a changing climate, and specifically, ocean warming and the increase in atmospheric carbon, otherwise known as the Suess effect. Implications This study has highlighted both the challenges and benefits of using novel carbonate archives to reconstruct biological and environmental change in marine ecosystems.