The oxygen isotope ratios （δ18O） preserved in marine sediments have been widely used to reconstruct past ocean temperatures. However, there remain significant uncertainties associated with this method, owing to ass...The oxygen isotope ratios （δ18O） preserved in marine sediments have been widely used to reconstruct past ocean temperatures. However, there remain significant uncertainties associated with this method, owing to assumptions about the δ18O of ancient seawater which affects the temperature inferred from sediment δ18O records. In this study, oxygen isotope compositions of phosphate in teeth and bones from five different modem cetacean species, including sperm whale, pygmy sperm whale, short-finned pilot whale, killer whale, and Cuvier＇s beaked whale, and three fossil whales were determined. The data were used to assess whether the oxygen isotope ratios of biogenic phosphate （δ18Op） from cetaceans are a reliable proxy for the oxygen isotopic composition of ocean water （δ18Ow）. The δ18Op values of modem cetaceans range from 15.5 ‰ to 21.3 ‰, averaging （19.6 ‰ ±0.8 ‰） （n = 136）.Using a greatly expanded global cetacean δ18Op dataset, the following regression equation is derived for cetaceans： δ18Ow = 0.95317 （4-0.03293） δ18Op- 17.971 （＋0.605）, r = 0.97253. The new equation, when applied to fossil teeth and bones, yielded reasonable estimates of ancient seawater δ18Ow values. Intra-tooth isotopic variations were observed within individual teeth. Among the selected species, the killer whale （O. orca） has largest intra-tooth δ18Op preference and migratory the lowest δ18Op values and the variation, reflecting its habitat behavior. The results show that oxygen isotope analysis of phosphate in cetacean teeth and dense ear bones provides a useful tool for reconstructing the oxygen isotopic composition of seawater and for examining environmental preferences （including migratory behavior） of both modem and ancient whales.展开更多
基金supported by US National Science Foundation Cooperative Agreement No.DMR-1157490 and the State of Floridathe State of Florida.The Stable Isotope Lab was established with grants from the US National Science Foundation(EAR-0824628EAR-0517806 and EAR-0236357)
文摘The oxygen isotope ratios （δ18O） preserved in marine sediments have been widely used to reconstruct past ocean temperatures. However, there remain significant uncertainties associated with this method, owing to assumptions about the δ18O of ancient seawater which affects the temperature inferred from sediment δ18O records. In this study, oxygen isotope compositions of phosphate in teeth and bones from five different modem cetacean species, including sperm whale, pygmy sperm whale, short-finned pilot whale, killer whale, and Cuvier＇s beaked whale, and three fossil whales were determined. The data were used to assess whether the oxygen isotope ratios of biogenic phosphate （δ18Op） from cetaceans are a reliable proxy for the oxygen isotopic composition of ocean water （δ18Ow）. The δ18Op values of modem cetaceans range from 15.5 ‰ to 21.3 ‰, averaging （19.6 ‰ ±0.8 ‰） （n = 136）.Using a greatly expanded global cetacean δ18Op dataset, the following regression equation is derived for cetaceans： δ18Ow = 0.95317 （4-0.03293） δ18Op- 17.971 （＋0.605）, r = 0.97253. The new equation, when applied to fossil teeth and bones, yielded reasonable estimates of ancient seawater δ18Ow values. Intra-tooth isotopic variations were observed within individual teeth. Among the selected species, the killer whale （O. orca） has largest intra-tooth δ18Op preference and migratory the lowest δ18Op values and the variation, reflecting its habitat behavior. The results show that oxygen isotope analysis of phosphate in cetacean teeth and dense ear bones provides a useful tool for reconstructing the oxygen isotopic composition of seawater and for examining environmental preferences （including migratory behavior） of both modem and ancient whales.
