Open AccessThe Giant Pacific Oyster ( Crassostrea gigas ) as a modern analog for fossil ostreoids: Isotopic (Ca, O, C) and elemental (Mg/Ca, Sr/Ca, Mn/Ca) proxies
Author(s) -
Ullmann Clemens V.,
Böhm Florian,
Rickaby Rosalind E.M.,
Wiechert Uwe,
Korte Christoph
Publication year - 2013
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1002/ggge.20257
Subject(s) - crassostrea , geology , isotopes of oxygen , trace element , δ18o , isotope , stable isotope ratio , oyster , isotopes of carbon , seawater , paleontology , mineralogy , oceanography , environmental chemistry , chemistry , geochemistry , total organic carbon , physics , quantum mechanics
Modern analogs are an essential part of palaeoclimate studies, because they provide the basis for the understanding of geochemical signatures of fossils. Ostreoids are common in many sedimentary sequences and because of their fast growth, high temporal resolution sampling of past seasonal variability is possible. Here, two shell structures of modern Giant Pacific Oysters ( Crassostrea gigas ), the chalky substance and foliate layers, have been sampled for trace element distributions (Mg, Sr, Mn) and stable isotope variability (C, O, Ca). Oxygen isotopes exhibit a clear seasonal signature. Mean carbon isotope values of different oysters agree within 0.1‰, but ontogenic variability is complicated by shell growth patterns and potential small vital effects. The calcium isotope ratios are found to be constant throughout ontogeny within analytical precision at a value of δ 44/40 Ca = 0.68 ± 0.16‰ (2 sd) SRM–915a which is consistent with other bivalve species. Calcium isotope ratios in oyster shell material might thus be a possible proxy for palaeo seawater calcium isotope ratios. Element/Ca ratios are significantly higher in the chalky substance than in the foliate layers and especially high Sr/Ca and Mn/Ca ratios are observed for the first growth season of the oysters. Mg/Ca ratios in the chalky substance show a negative correlation with δ 18 O values, compatible with a temperature dependence, whereas this correlation is absent in the foliate layers. Seasonal changes of Sr/Ca are controlled by metabolic processes, whereas for Mn/Ca an additional environmental control is evident.