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2 Annales Universitatis Mariae Curie-Sklodowska, sectio AAA – Physica

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δ37Cl of waters from the Akyatan lagoon, Turkey

100%

Pelc A. , Lécuyer C. , Bodergat A.-M. , Hałas S.

We report the first δ37Cl data for surface waters of the Akyatan lagoon, Turkey, from 12 stations sampled over the period 2005 to 2006. The recorded variation of δ37Cl values is fairly small, from -0.4 to +0.6 ‰ vs. SMOC, though the environmental conditions were highly variable seasonally. The salinity of the studied waters varied from 2.8 to 95 g/L and the δD vs. δ18O plot significantly departures from the World Meteoric Water Line (WMWL) with a slope of 5.43±0.19. Chlorine isotopes indicate a weak positive correlation between δ37Cl and δD of water and its salinity. This may be due to mixing between seawater and distinct sources of freshwater. The small spread of obtained δ37Cl results demands enhanced precision of analysis and careful sample preparation.

Carbon and oxygen isotope variability among foraminifera and ostracod carbonated shells

75%

Fourel F. , Martineau F. , Emoke Tóth E. , Görög A. , Escarguel G. , Lécuyer C.

This study investigates the effect of biological and environmental inter-individual variability on the meaning of d18O and d13C values acquired on small carbonated shells. First we present data obtained with a MultiPrep automated carbonate system on small sample sizes of a homogeneous carbonate material: Carrara marble. This demonstrates the capacities of the analytical system to reliably run small amounts of carbonates even down to 10 mg. Then we present two data sets obtained on real fossil samples of various size (sensu number of individual organisms) calibrated against the NBS19 carbonate standard. Both datasets evidence a clear trend of between-biological sample standard deviation increase for both d18O and d13C measurements when the number of pooled specimens per sample decreases. According to the results obtained from a systematic study of a geologically homogeneous sample of coeval fossil Elphidium foraminifera, we estimate that there is 95% of chances to reach between-biological sample standard deviation values higher than 1.02‰ (d18O) and 1.45‰ d13C) based on single-cell measurements. Such values are one order of magnitude higher than the instrumental standard deviations associated with these stable isotope ratios. Conversely, a minimum of 35 (d18O) and 44 (d13C) pooled specimens of Elphidium appears necessary to reach a between-sample standard deviation £ 0.25‰ with a probability of 95%. Such biological intrinsic and irreducible variability between coeval individuals, and thus samples, clearly questions the interest for single-cell analyses, more precisely, for coastal marine species, such as Elphidium, subject to many environmental changes during their life-time. Indeed, strong variations in salinity or temperature, as well as biogenic fractionation, could influence the isotopic composition of an individual specimen. Results might be less problematic for an average community including several tests. This paper underlines uncertainties linked to specific environments in which selected organisms live, especially for paleoceanographic or paleoclimatic reconstruction purposes where secular oxygen and carbon isotope variations typically range from 0.5 to 1.5‰.