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| Titel |
Sr/Ca and Mg/Ca in Glycymeris glycymeris (Bivalvia) shells from the Iberian upwelling system: Ontogeny and environmental control |
| VerfasserIn |
Pedro Freitas, Christopher Richardson, Simon Chenery, Carlos Monteiro, Paul Butler, David Reynolds, James Scourse, Miguel Gaspar |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250151349
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| Publikation (Nr.) |
 EGU/EGU2017-15918.pdf |
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| Zusammenfassung |
| Bivalve shells have a great potential as high-resolution geochemical proxy archives of marine
environmental conditions. In addition, sclerochronology of long-lived bivalve species (e.g.
Arctica islandica) provides a timeline of absolutely dated shell material for geochemical
analysis that can extend into the past beyond the lifetime of single individuals through the use
of replicated crossmatched centennial to millennial chronologies. However, the
interpretation of such records remains extremely challenging and complex, with
multiple environmental and biological processes affecting element incorporation in
the shell (e.g. crystal fabrics, organic matrix, biomineralization mechanisms and
physiological processes). As a result, the effective use of bivalve shell elemental/Ca
ratios as palaeoenvironmental proxies has been limited, often to species-specific
applications or applications restricted to particular environmental settings. The
dog-cockle, Glycymeris glycymeris, is a relatively long-lived bivalve (up to 200 years) that
occurs in coarse-grained subtidal sediments of coastal shelf seas of Europe and
North West Africa. Glycymeris glycymeris shells provide a valuable, albeit not fully
explored, archive to reconstruct past environmental variability in an area lacking
sclerochronological studies due to the rarity of long-lived bivalves and lack of coral
reefs.
In this study, we evaluate the potential of Sr/Ca and Mg/Ca ratios in G. glycymeris shells
as geochemical proxies of upwelling conditions in the Iberian Upwelling System, the
northern section of the Canary Current Eastern Boundary Upwelling System. Sr/Ca and
Mg/Ca generally co-varied significantly and a clear ontogenetic, non-environmental related
change in Sr/Ca and Ba/Ca variability was observed. High Sr/Ca and Mg/Ca ratios in older
shells (> 10 years old) were found to be associated with the occurrence of growth lines
deposited during the winter reduction in shell growth. Nevertheless, Sr/Ca and Mg/Ca
variation in older shells was synchronous with contemporary environmental conditions, i.e.
upwelling intensity and salinity. The use of Sr or Mg in G. glycymeris shells as valid
geochemical environmental proxies in the Iberian Upwelling System remains complex and
requires further research to unravel environmental and physiological/biomineralization
controls.
This study was financed by the Portuguese Fundação para a Ciência e Tecnologia (FCT)
GLYCY Project (contract PTDC/AAC-CLI/118003/2010) and a sabbatical grant to
PSF (Ref: SFRH/BSAB/127786/2016), co-supported by POCH and the European
Social Fund. Funding for consumable costs was provided by Bangor University. |
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