Strontium to calcium ratios in the marine gastropod Conus ermineus: Growth rate effects and temperature calibration

Abstract

[1] Here we investigate the potential of Sr/Ca ratios in the marine gastropod Conus ermineus for reconstructing seawater temperatures. We present annually resolved records of Sr/Ca and d18 O for four shells collected alive from the Flower Garden Banks National Marine Sanctuary in the Gulf of Mexico. Our results show that variations in Sr/Ca and d18 O covary with the in situ seasonal temperature cycle. Sr/ Ca and temperature are positively correlated, in contrast with the inverse relationship found in inorganically precipitated aragonite. The seasonal Sr/Ca variability is superimposed on a long-term trend of increasing Sr/Ca with age. Both the seasonal and long-term ontogenetic changes in Sr/Ca are associated with variations in growth rate, defined here as the shell linear extension rate (LER); the seasonal variability in LER is superimposed on a long-term decrease with ontogeny. Thus the covariance of Sr/Ca ratios with temperature and LER suggests that Sr incorporation is likely driven by temperature influence on growth rate, rather than by thermodynamic effects. Unlike the seasonal variability, the ontogenetic effect is characterized by inverse covariation between Sr/Ca and LER, suggesting that Sr/Ca variability is not controlled by growth rate alone, but probably by two different biomineralization mechanisms, one related to temperature and the other related to age. We use the seasonal Sr/Ca signal of four shells to construct a temperature calibration. To minimize the ontogenetic effects, we separate the records into juvenile and adult growth stages and calculate the Sr/Ca-temperature (T) relationships: Juvenile: Sr/Ca (mmol mol the seasonal estimates reflects the high variability among specimens. To reduce the uncertainty on seasonal temperatures, we propose combining records from multiple shells to generate an average temperature record. The potential of this approach needs, however, to be validated in other locations.

Portable x-ray fluorescence in sourcing prehistoric whelk shell artifacts

“…These results are consistent with previous shell source analyses and work (e.g., Chave, 1954, Lerman, 1965Sosdian et al, 2006) that have suggested a positive relationship between the incorporation of strontium into shells and the water temperature of the growing environment among some gastropod mollusk species. On average, mean annual surface temperatures in the Gulf of Mexico are warmer than those along the Atlantic coast.…”

Cenozoic seawater Sr/Ca evolution

“… h Data sources: K01, Kobashi et al [2001]; S06, Sosdian et al [2006]; G08, Gentry et al [2008]; T10, Tao and Grossman [2010]; T12, Tao [2012]; S13, this paper; T13, Tao et al (submitted manuscript, 2012); GUD, E. L. Grossman (unpublished data, 2002); TUD, K. Tao (unpublished data, 2011). …”

“…Several studies have shown that mollusc shell Sr/Ca is controlled by ambient solution and could provide a record of Sr/Ca sw [ Buchardt and Fritz , 1978; Lorens and Bender , 1980]. Temperature and growth rate also modify Sr/Ca in modern and fossil marine gastropods [ Purton et al , 1999; Sosdian et al , 2006; Gentry et al , 2008; Tripati et al , 2009]. These relationships have been used in a study of turritellid gastropods to suggest that between 64 and 37 Ma, Sr/Ca sw was higher than today [ Tripati et al , 2009], in contrast with results based on other biogenic and abiogenic proxies [ Lear et al , 2003; Coggon et al , 2010; Balter et al , 2011].…”

Shifting Baselines in Antarctic Ecosystems; Ecophysiological Response to Warming in Lissarca miliaris at Signy Island, Antarctica

“…During faster crystal growth rates, near-surface migration of ions, which expel impurities, are less efficient and an increase in strontium replacement of calcium ions might be expected [38]. Strontium has also been found to be correlated with temperature indirectly by increased growth rates in marine gastropods [39]. The increased ratios of strontium in the shells of L. miliaris are therefore likely to be linked to the increased growth rates observed, although other abiotic influences may also affect this relationship.…”