Temperature dependence of δ 18 O in otolith of juvenile Japanese sardine: Laboratory rearing experiment with micro-scale analysis

Grain‐scale stable carbon and oxygen isotopic variations of the international reference calcite, IAEA‐603

“…9 The development of advanced high-precision micromilling systems (e.g., New Wave/Merchantek MicroMill ® ; 10 Izumo-web/ GEOMILL326 11 ) has made it possible to obtain very small (submicrogram) samples of carbonate, and the isotopic compositions of small (<100 μg) samples of biogenic carbonate such as fish otoliths and molluscs can be used for high-resolution reconstruction of paleoenvironments. [12][13][14][15] In addition, the isotopic compositions of single microfossil specimens, such as foraminiferal tests (<50 μg), are being used as new environmental and paleoecological proxies. [16][17][18][19][20] To ensure the reliability of microscale isotopic analyses of carbonate, grain-scale δ 13 C and δ 18 O variations in the IAEA-603 new international reference material must be examined.…”

Combining microvolume isotope analysis and numerical simulation to reproduce fish migration history

“…This is crucial information to understand the environmental conditions necessary for fish to survive, providing clues on how environmental variabilities are driving fish population fluctuations. Because otolith δ 18 O is generally recognized as temperature dependent (Høie, Otterlei, & Folkvord, 2004;Kim et al, 2007;Kitagawa et al, 2013;Sakamoto et al, 2017;Storm-Suke, Dempson, Reist, & Power, 2007), the method presented here will notably improve the knowledge on the survival and migration ecology of early life stages of numerous fish species.…”

“…Salinity was converted into seawater δ 18 O using a regression between seawater δ 18 O and salinity in the habitat of the Japanese sardine (Equation 1, see Section ). Otolith δ 18 O was then calculated by substituting seawater δ 18 O and temperature into the equation for the relationship among otolith δ 18 O, temperature, and seawater δ 18 O recently proposed for the Japanese sardine (Sakamoto et al., ; δ otolith –δ seawater = −0.18* T + 2.69). The agreement of the calculated δ 18 O for the required period was computed by substituting the calculated otolith δ 18 O value into a probability density function of normal distribution N (δ 18 O analysed , 0.18).…”

“…Otolith δ 18 O was measured using a continuous-flow isotope ratio mass spectrometry system (MICAL3c with IsoPrime 100) at the National Institute of Technology, Ibaraki College. This system allows analysis of δ 18 O from sub-microgram carbonate samples (>0.2 μg) with high precision and accuracy (Ishimura, Tsunogai, & Gamo, 2004;Ishimura et al, 2008;Kitagawa et al, 2013;Nishida & Ishimura, 2017;Oda et al, 2016;Sakamoto et al, 2017). Otolith powders reacted with phosphoric acid at 25°C, and the released CO 2 was purified and then introduced into the mass spectrometer.…”

“…Recently, however, the analysing system MICAL3c has been developed. This system requires 1/100 of the sample quantity required for conventional mass spectrometry (Ishimura, Tsunogai, & Nakagawa, 2008;Nishida & Ishimura, 2017), thereby allowing an accurate analysis of narrow growth increments in small otoliths (Sakamoto et al, 2017). Despite this drastic technical improvement, interpreting otolith δ 18 O values to estimate fish migration history remains difficult.…”