5:15 PM - 6:45 PM
[BPT02-P03] Effects of pre-treatment on the isotopic composition of structural carbonates in teleost fish teeth
Keywords:Biomineralization, Proxy, Fish, Teeth
The oxygen (δ18O) and carbon (δ13C) stable isotope ratio of structural carbonates in vertebrate teeth provide environmental and eco-physiological information. The teeth of teleost fishes, mainly composed of phosphate, are relatively resistant to diagenetic alteration and can retain original information when fishes have inhabited. In addition, fish teeth are relatively abundant in post-Cenozoic marine sediments, making them a valuable tool for providing environmental and eco-physiological information about marine organisms at higher trophic levels. In general, isotopic analysis of teeth requires the removal of contamination by organic matter and other non-target materials. However, the effect of different pre-treatments for organic matter removal on the isotope ratios of structural carbonates in modern teleost fish teeth has not yet been verified.
In this study, the effects of different pre-treatment methods on isotope ratios were examined by testing three different reagents for organic matter removal from the teeth of the Half-smooth golden pufferfish (Lagocephalus spadiceus), which have big teeth and is common in the Indo-West Pacific region. Sodium hypochlorite (NaClO) solution, hydrogen peroxide (H2O2) solution, and ethanol (C2H5OH) were used as reagents considered effective in removing organic matter. After soaking the teeth samples in these reagents for several days, samples were powdered and analyzed for δ18O and δ13C.
The treatment with H2O2 solution and ethanol did not significantly change δ18O values (mean: -0.23‰, n = 10; -0.57‰, n = 6, respectively) compared to the analytical error (0.67‰, 0.31‰). On the contrary, treatment with NaClO solution induced a more significant decrease in δ18O values (-3.96‰, n = 9) compared to the analytical error (0.67‰), which might reflect the δ18O of water in the solution. The effect of all three pre-treatment on δ13C was almost equivalent (H2O2: -0.76‰, n = 10; ethanol: -0.60‰, n = 6; NaClO -0.36‰, n = 9) to analytical error (0.46‰, 0.15‰, 0.46‰, respectively).
The results suggest that pre-treatment with NaClO solution is not a suitable method for removing organic matter from fish teeth. Although the effects of the other two pre-treatments on isotope ratios were minor, treatment with H2O2 solution was considered preferable because only fat removal was expected by the ethanol treatment.
In this study, the effects of different pre-treatment methods on isotope ratios were examined by testing three different reagents for organic matter removal from the teeth of the Half-smooth golden pufferfish (Lagocephalus spadiceus), which have big teeth and is common in the Indo-West Pacific region. Sodium hypochlorite (NaClO) solution, hydrogen peroxide (H2O2) solution, and ethanol (C2H5OH) were used as reagents considered effective in removing organic matter. After soaking the teeth samples in these reagents for several days, samples were powdered and analyzed for δ18O and δ13C.
The treatment with H2O2 solution and ethanol did not significantly change δ18O values (mean: -0.23‰, n = 10; -0.57‰, n = 6, respectively) compared to the analytical error (0.67‰, 0.31‰). On the contrary, treatment with NaClO solution induced a more significant decrease in δ18O values (-3.96‰, n = 9) compared to the analytical error (0.67‰), which might reflect the δ18O of water in the solution. The effect of all three pre-treatment on δ13C was almost equivalent (H2O2: -0.76‰, n = 10; ethanol: -0.60‰, n = 6; NaClO -0.36‰, n = 9) to analytical error (0.46‰, 0.15‰, 0.46‰, respectively).
The results suggest that pre-treatment with NaClO solution is not a suitable method for removing organic matter from fish teeth. Although the effects of the other two pre-treatments on isotope ratios were minor, treatment with H2O2 solution was considered preferable because only fat removal was expected by the ethanol treatment.