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| Titel |
Biogeochemistry of a large and deep tropical lake (Lake Kivu, East Africa: insights from a stable isotope study covering an annual cycle |
| VerfasserIn |
C. Morana, F. Darchambeau, F. A. E. Roland, A. V. Borges, F. Muvundja, Z. Kelemen, P. Masilya, J.-P. Descy, S. Bouillon |
| 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 ; 12, no. 16 ; Nr. 12, no. 16 (2015-08-19), S.4953-4963 |
| Datensatznummer |
250118068
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| Publikation (Nr.) |
 copernicus.org/bg-12-4953-2015.pdf |
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| Zusammenfassung |
| During this study, we investigated the seasonal variability of the
concentration and the stable isotope composition of several inorganic and
organic matter (OM) reservoirs in the large, oligotrophic and deep tropical
Lake Kivu (East Africa). Data were acquired over 1 year at a fortnightly
temporal resolution. The δ13C signature of the dissolved inorganic
carbon (DIC) increased linearly with time during the rainy season, then
suddenly decreased during the dry season due to vertical mixing with
13C-depleted DIC waters. The δ13C signature of the particulate
organic carbon pool (POC) revealed the presence of a consistently abundant
methanotrophic biomass in the oxycline throughout the year. We also noticed a
seasonal shift during the dry season toward higher values in the
δ15N of particulate nitrogen (PN) in the mixed layer and
δ15N-PN was significantly related to the contribution of
cyanobacteria to the phytoplankton assemblage, suggesting that rainy season
conditions could be more favourable to atmospheric nitrogen-fixing
cyanobacteria. Finally, zooplankton were slightly enriched in 13C
compared to the autochthonous POC pool, and the δ15N signature of
zooplankton followed well the seasonal variability in δ15N-PN,
consistently 3.0 ± 1.1 ‰ heavier than the PN pool.
Together, δ13C and δ15N analysis suggests that
zooplankton directly incorporate algal-derived OM in their biomass, and that
they rely almost exclusively on this source of OM throughout the year in
general agreement with the very low allochthonous OM inputs from rivers in
Lake Kivu. |
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