 |
| Titel |
Technical Note: Silica stable isotopes and silicification in a carnivorous sponge Asbestopluma sp. |
| VerfasserIn |
K. R. Hendry, G. E. A. Swann, M. J. Leng, H. J. Sloane, C. Goodwin, J. Berman, M. Maldonado |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 11 ; Nr. 12, no. 11 (2015-06-05), S.3489-3498 |
| Datensatznummer |
250117973
|
| Publikation (Nr.) |
 copernicus.org/bg-12-3489-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| The stable isotope composition of benthic sponge spicule silica is
a potential source of palaeoceanographic information about past deep seawater
chemistry. The silicon isotope composition of spicules has been shown to
relate to the silicic acid concentration of ambient water, although existing
calibrations do exhibit a degree of scatter in the relationship. Less is
known about how the oxygen isotope composition of sponge spicule silica
relates to environmental conditions during growth. Here, we investigate the
vital effects on silica, silicon and oxygen isotope composition in
a carnivorous sponge, Asbestopluma sp., from the Southern Ocean. We
find significant variations in silicon and oxygen isotopic composition within
the specimen that are related to unusual spicule silicification. The largest
variation in both isotope systems was associated with the differential
distribution of an unconventional, hypersilicified spicule type (desma) along
the sponge body. The absence an internal canal in the desmas suggests an
unconventional silicification pattern leading to an unusually heavy isotope
signature. Additional internal variability derives from a systematic offset
between the peripheral skeleton of the body having systematically a higher
isotopic composition than the internal skeleton. A simplified silicon isotope
fractionation model, in which desmas were excluded, suggests that the lack of
a system for seawater pumping in carnivorous sponges favours a low
replenishment of dissolved silicon within the internal tissues, causing
kinetic fractionation during silicification that impacts the isotope
signature of the internal skeleton. Analysis of multiple spicules should be
carried out to "average out" any artefacts in order to produce more robust
downcore measurements. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|