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| Titel |
Manganese content records seasonal upwelling in Lake Tanganyika mussels |
| VerfasserIn |
D. Langlet, L. Y. Alleman, P.-D. Plisnier, H. Hughes, L. André |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 4, no. 2 ; Nr. 4, no. 2 (2007-03-15), S.195-203 |
| Datensatznummer |
250001618
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| Publikation (Nr.) |
 copernicus.org/bg-4-195-2007.pdf |
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| Zusammenfassung |
| Biogenic productivity of Lake Tanganyika is highly dependent on seasonal
upwellings of cold, oxygen-depleted, nutrient-rich deep waters. We investigated the shell of freshwater
bivalve Pleiodon spekii as a geochemical archive of these periodic hydrological changes
tuned by the monsoon regime. The results of a three-year-long limnological
and geochemical survey of the coastal waters performed on the dissolved and
particulate fractions were compared to LA-ICP-MS profiles of Mn in five
aragonitic shells from the same lake location. Three shells present very
similar Mn/Ca profiles dominated by a peak that matched the concomitant
increase of Mn and chlorophyll a in surface waters during the 2002 upwelling,
while a shell collected during 2003 dry season detect both 2002 and 2003
upwelling events. Larger shells showing an extremely reduced growth display
more than 8 Mn/Ca peaks suggesting at least an 8-year-record of seasonal
changes in water composition. We postulate that Mn/Ca in shells record the
conjunction of an increase of biological activity with supplied of dissolved
Mn and nutriments in coastal waters, resulting in an enhanced assimilation
of biogenic Mn-rich particles. By combining the most recent generation of
laser ablation system and the powerful High Resolution ICP-MS, the spatial
resolution could be improved down to 5 to 10 µm crater size and end up
in a better constrain of the relative variations of the annual Mn peaks.
Such an approach on P. spekii from Lake Tanganyika has definitively a great
potential to provide recent and past records on primary productivity
associated with the monsoon climate system. |
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