Disentangling the biological and environmental control of M. edulis shell chemistry

Abstract

[1] Blue mussel individuals (Mytilus edulis) were cultured at four different salinities (17, 20, 29, and 34). During the course of the experiment, temperature was gradually increased from 6°C to 14°C. Mg/Ca and Sr/Ca ratios of the shell calcite portions produced during the 9 weeks of experimental treatment as well parts that were precipitated before the treatment phase were measured by laser ablation-multicollectorinductively coupled plasma-mass spectrometry. Mg/Ca ratios show a positive correlation with temperature for individuals cultured at salinity 29 and 34 (Mg/Ca (mmol/mol) ∼ (0.2-0.3)*T (°C)), while for individuals cultured at low salinities (17, 20) no trend was observed. Sr/Ca ratios were not affected by temperature but strongly by salinity. The data show very strong biological influence ("individual differences" and "physiological variability") on elemental ratios (79% on Mg/Ca and 41% on Sr/Ca) in M. edulis calcite. The results challenge the use of blue mussel shell data as environmental proxies.

Calcium carbonate veins in ocean crust record a threefold increase of seawater Mg/Ca in the past 30 million years

“…On the other hand, Sr incorporation in 421 mollusc shells is known to be strongly controlled by physiological processes (e.g. 422 Elliot et al, 2009;Heinemann et al, 2011). We conclude that much more research is 423 necessary to resolve the discrepancies between reconstructions of seawater chemistry 424 derived from different fossil shells and from CCVs.…”

The 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

“…The strong, negative, correlation of Mg/ Ca ratios with 18 O values of the chalky substance (r 2 ¼ 0.60) indicates that Mn/Ca ratios is controlled largely by temperature, pointing to Mg/Ca ratios in the chalky substance of C. gigas as a promising proxy for temperatures. Mg/Ca temperature proxies using bivalve calcite [e.g., Vander Putten et al, 2000;Ford et al, 2010;Heinemann et al, 2011;Schöne et al, 2011;Freitas et al, 2012] can be interesting for environmental reconstructions, if the covariations of Mg/Ca with temperature are very strong. Further studies, including 18 O measurements of ambient water and using environmental data with better time resolution might show, if the chalky substance of C. gigas is suitable for such reconstructions.…”

The influence of temperature and seawater carbonate saturation state on <sup>13</sup>C-<sup>18</sup>O bond ordering in bivalve mollusks

“…Subsequently fossil mollusks have been widely used as an archive of past environmental change and seawater chemistry (Keith et al, 1964;Killingley and Berger, 1979;Grossman and Ku, 1986;Veizer et al, 1999;Tripati et al, 2001;Tripati and Zachos, 2002;Ivany et al, 2008;Wanamaker et al, 2011;Taviani and Zahn, 1998). However it has proven challenging to develop robust independent paleothermometers in mollusk carbonate; for example, approaches using trace element partitioning (Mg / Ca, Sr / Ca) into mollusk shell carbonate are often hampered by strong biological controls and high inter-and intra-specimen variability (Dodd, 1965;Lorens and Bender, 1980;Klein et al, 1996;Gillikin et al, 2005;Freitas et al, 2006Freitas et al, , 2008Freitas et al, , 2009Heinemann et al, 2011;Wanamaker et al, 2008). Therefore it has not yet been possible to reliably partition the contributions of temperature and seawater δ 18 O to bivalve mollusk carbonate δ 18 O with a high level of confidence in environments where both parameters could be expected to vary.…”