Ontogenetic isotopic variation in foraminifera: Implications for palaeo proxy

The oxygen isotopic composition (δ 1 8 O) of Marginopora kudakajimaensis (Foraminiferida) is found to differ by 0.5‰ among the individuals living under similar physico-chemical conditions. The δ 1 8 O variation along the growth direction (ontogeny) is much higher, ranging between 1.5 and 2.5‰. In comparison, the ontogenetic variation in carbon isotopes (δ 1 3 C) is relatively small. The range and standard deviation of ontogenetic δ 1 8 O decrease progressively for deeper water species. There is no such systematic change in δ 1 3 C values. The study suggests that as palaeo proxy, the isotopic data not only require correct species discrimination but also a good understanding of the palaeobiology of the species.

[1]  K. Seto,et al.  Oxygen and carbon isotopic variation in co-existing larger foraminifera from a reef flat at Akajima, Okinawa, Japan , 2004 .

[2]  A. Mitra,et al.  Distribution of Larger Foraminifera in the Reef Sediments of Akajima, Okinawa, Japan , 2003 .

[3]  H. Nishi,et al.  Population dynamics of Marginopora kudakajimensis Gudmundsson (Foraminifera: Soritidae) in the Ryukyu Islands, the subtropical northwest Pacific , 2000 .

[4]  H. Spero,et al.  Size-related isotopic trends in some Maastrichtian planktic foraminifera: methodological comparisons, intraspecific variability, and evidence for photosymbiosis , 1999 .

[5]  D. Lea,et al.  Experimental determination of stable isotope variability in Globigerina bulloides: implications for paleoceanographic reconstructions , 1996 .

[6]  K. Billups,et al.  Reconstructing the stable isotope geochemistry and paleotemperatures of the equatorial Atlantic during the last 150,000 years: Results from individual foraminifera , 1996 .

[7]  T. Anderson,et al.  Stable Isotopes of Oxygen and Carbon and their Application to Sedimentologic and Paleoenvironmental Problems , 1983 .

[8]  G. Wefer,et al.  Stable isotopes in recent larger foraminifera , 1981 .

[9]  W. Berger,et al.  Stable Isotopes in Benthic Foraminifera: Seasonal Variation in Large Tropical Species , 1980, Science.

[10]  J. Erez.  Vital effect on stable-isotope composition seen in foraminifera and coral skeletons , 1978, Nature.

[11]  J. Duplessy,et al.  Individual isotopic fractionation of carbon and oxygen in benthic foraminifera , 1973 .

[12]  J. Duplessy,et al.  Differential Isotopic Fractionation in Benthic Foraminifera and Paleotemperatures Reassessed , 1970, Science.