Thermal dependency of stable carbon and oxygen isotopes in fish otoliths of juvenile sardine,Sardinops melanostictus, in rearing experiments
Abstract
Stable oxygen isotope is a powerful tool for estimating temperature history recorded in fish otolith. Recently, we have been developed the method of high resolution stable carbon and oxygen isotope (δ13C and δ18O) analysis of otoliths for understanding of fish ecology and marine climate by using customized microscale isotopic analytical system (MICAL3c with IsoPrime100: Ishimura et al. 2004, 2008). MICAL3c enabled us to determine δ13C and δ18O values for small amounts of carbonate, as low as 0.2 μg, which is less than 1/100 of the amount required by conventional methods. For example, to improve the temperature estimation of otolith δ18O, Sakamoto et al. (2017) reported the otolith δ18O thermometer of Japanese sardine Sardinops melanostictus cultured at different water temperatures. In this study, we newly designed the culture experiment for evaluating the previous work which would be robust by a further experiment by using the otolith marking method (Alizarin complexone: ALC). Then we analyzed otolith δ13C and δ18O of juvenile S. melanostictus reared at the three different temperatures (14, 19, 24°C) for 60 days. In addition, we compared the otolith δ13C, temperature, and growth rate for further understanding of a metabolic effect.
We cultured 29 specimens with a flow-through experimental tank system. Before the experiment, all specimens had been treated in ALC to recognize growth area of otolith during rearing period. Carbonate powder was obtained from growth area by using a high-precision micromilling system (GEOMILL326, Izumo-web). δ18O and δ13C were determined using IsoPrime100 with MICAL3c at the National Institute of Technology, Ibaraki College, with analytical precision less than 0.1‰. From the measured δ18O values, the following relationships between water temperature (T) and aragonite-water fractionation was obtained: δ18Ootolith - δ18Oseawater = -0.16 × T + 2.56 (R2 = 0.93, P < 0.01) (N = 17) Our equation was consistent with the equation reported by Sakamoto et al. (2017). Thus, these two equations can be a useful temperature proxy evaluated by the rigorous experimental methods. The otolith δ13C values showed a significant negative correlation with temperatures and otolith growth. Thus, the physiological variation affected by water temperature might be recorded in δ13C of S. melanostictus otoliths.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPP44A..08N
- Keywords:
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- 0419 Biomineralization;
- BIOGEOSCIENCESDE: 0473 Paleoclimatology and paleoceanography;
- BIOGEOSCIENCESDE: 4924 Geochemical tracers;
- PALEOCEANOGRAPHYDE: 4994 Instruments and techniques;
- PALEOCEANOGRAPHY