HR: 0800h
AN: PP21C-1570    [Abstracts]
TI: Sr/Ca Ratios of Vaceletia: Implication for Biocalcification Mechanisms of Sclerosponges
AU: * Haase-Schramm, A
EM: ahaase@ifm-geomar.de
AF: IFM-GEOMAR, Wischhofstr. 1-3, Kiel, 24148 Germany
AU: Boehm, F
EM: fboehm@ifm-geomar.de
AF: IFM-GEOMAR, Wischhofstr. 1-3, Kiel, 24148 Germany
AU: Eisenhauer, A
EM: aeisenhauer@ifm-geomar.de
AF: IFM-GEOMAR, Wischhofstr. 1-3, Kiel, 24148 Germany
AU: Garbe-Schoenberg, D
EM: dgs@gpi.uni-kiel.de
AF: Institut für Geowissenschaften Christian-Albrechts-Universität, Olshausenstr. 40, Kiel, 24118 Germany
AU: Reitner, J
EM: jreitne@gwdg.de
AF: Geobiologie, GZG, Goldschmidtstr. 3, G 37077 Germany
AU: Woerheide, G
EM: gert.woerheide@geo.uni-goettingen.de
AF: Geobiologie, GZG, Goldschmidtstr. 3, G 37077 Germany
AB: Sclerosponges have been established as reliable proxy recorders for several environmental parameters like the radiocarbon and stable carbon isotopic composition, lead concentration, temperature and salinity of ambient water. Specifically, Sr/Ca ratios in skeletons of the Caribbean species Ceratoporella nicholsoni have been shown to record water temperatures with a very high precision. In order to study the variability of strontium incorporation and its temperature dependence in the skeletons of different sclerosponge species, we investigated the Sr/Ca ratios of various specimens of Vaceletia crypta and Vaceletia sp. from different sites and water depths in the Pacific. We determined Sr/Ca ratios and their temperature dependence in Vaceletia skeletons and compared them with published data of Ceratoporella and Astrosclera, inorganic aragonite and ooids. The Sr/Ca-temperature relation in Vaceletia and Ceratoporella is identical within errors (-0.1mmol/mol/K) and stronger than in inorganic aragonites and corals. The distribution coefficient of Sr/Ca in aragonite relative to sea water is similar in Ceratoporella and inorganic aragonite, however it is higher in Vaceletia, Astrosclera and ooids. The sclerosponges Ceratoporella, Vaceletia and Astrosclera precipitate the bulk of skeletal aragonite extracellularly as synvivo-diagenetic, epitactic overgrowth, in carbon and oxygen isotopic equilibrium with ambient sea water. Thus sea water derived carbonate ions are incorporated into the skeleton without biologic modifications. In contrast, the observed interspecific differences of skeletal cation ratios indicate an incorporation process, which involves the biologically controlled modification of the sea water ion composition. I. e. sclerosponges use a calcification mechanism that does not affect carbonate anions, but selectively incorporates certain cations.
DE: 1055 Organic and biogenic geochemistry
DE: 4808 Chemical tracers
DE: 4954 Sea surface temperature
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005