Article (Scientific journals)
Dissolved organic matter composition and reactivity in Lake Victoria, the World’s largest tropical lake
Deirmendjian, Loris; Lambert, Thibault; Morana, Cédric et al.
2020In Biogeochemistry, 150 (0), p. 61-83
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Abstract :
[en] We report a data set of dissolved organic carbon (DOC) concentration and dissolved organic matter (DOM) composition (stable carbon isotope signatures, absorption and fluorescence properties) obtained from samples collected in Lake Victoria, a large lake in East Africa. Samples were collected in 2018-2019 along a bathymetric gradient (bays to open waters), during three contrasting seasons: long rainy, short rainy and dry, which corresponded to distinctly water column mixing regimes, respectively, stratified, semi-stratified and mixed regimes. Eight DOM components from parallel factor analysis (PARAFAC) were identified based on three-dimensional excitation–emission matrices (EEMs), which were aggregated into three main groups of components (microbial humic-like, terrestrial humic-like, protein-like). Spatially, the more productive bays were characterized by higher DOM concentration than deeper more offshore waters (fluorescence intensity and DOC were ~80% and ~30% higher in bays, respectively). Seasonally, the DOM pool shifted from protein-like components during the mixed regime to microbial humic-like components during the semi-stratified regime and to terrestrial humic-like components during the stratified regime. This indicates that pulses of autochthonous DOM derived from phytoplankton occurred when the lake was mixing, which increased the availability of dissolved inorganic nutrients. Subsequently, this freshly produced autochthonous DOM was microbially processed during the following semi-stratified regime. In the open waters, during the stratified regime, only terrestrial refractory DOM components remained because the labile and fresh stock of DOM created during the preceding mixed season was consumed. In the bays, the high terrestrial refractory DOM during the stratified regime may be additionally due to the allochthonous DOM input from the runoff. At the scale of the whole lake, the background refractory DOM probably comes mainly from precipitation and followed by river inputs.
Research center :
FOCUS - Freshwater and OCeanic science Unit of reSearch - ULiège
Disciplines :
Aquatic sciences & oceanology
Author, co-author :
Deirmendjian, Loris 
Lambert, Thibault
Morana, Cédric ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Chemical Oceanography Unit (COU)
Bouillon, Steven
Descy, Jean-Pierre ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Chemical Oceanography Unit (COU)
Okello, William
Borges, Alberto  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Chemical Oceanography Unit (COU)
Language :
English
Title :
Dissolved organic matter composition and reactivity in Lake Victoria, the World’s largest tropical lake
Publication date :
01 July 2020
Journal title :
Biogeochemistry
ISSN :
0168-2563
eISSN :
1573-515X
Publisher :
Springer, Netherlands
Volume :
150
Issue :
0
Pages :
61-83
Peer reviewed :
Peer Reviewed verified by ORBi
Name of the research project :
LAVIGAS
Funders :
F.R.S.-FNRS - Fonds de la Recherche Scientifique [BE]
Available on ORBi :
since 01 July 2020

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