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.

中文翻译：

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世界上最大的热带湖泊维多利亚湖的溶解有机物组成和反应性

我们报告了从东非大湖维多利亚湖收集的样本中获得的溶解有机碳 (DOC) 浓度和溶解有机质 (DOM) 组成（稳定碳​​同位素特征、吸收和荧光特性）的数据集。样品是在 2018-2019 年沿测深梯度（海湾到开阔水域）收集的，在三个对比季节：长雨季、短雨季和旱季，分别对应于明显的水柱混合状态、分层、半分层和混合状态. 基于三维激发-发射矩阵 (EEM) 确定了来自平行因子分析 (PARAFAC) 的八种 DOM 成分，这些成分聚合为三组主要成分（微生物类腐殖质、陆生腐殖质类、蛋白质类）。在空间上，与更深的近海水域相比，生产力更高的海湾的 DOM 浓度更高（海湾的荧光强度和 DOC 分别高约 80% 和约 30%）。季节性地，DOM 池从混合状态下的类蛋白质组分转变为半分层状态下的微生物类腐殖质组分，以及分层状态下的陆地类腐殖质组分。这表明来自浮游植物的原生 DOM 脉冲发生在湖泊混合时，这增加了溶解无机养分的可用性。随后，在以下半分层制度中对这种新鲜生产的本土 DOM 进行了微生物处理。在开阔水域，在分层制度期间，由于前一个混合季节产生的不稳定和新鲜的 DOM 存量被消耗，因此只剩下陆生难降解 DOM 成分。在海湾中，分层制度期间高陆地耐火 DOM 可能另外是由于来自径流的外来 DOM 输入。在全湖范围内，背景难降解DOM可能主要来自降水，其次是河流输入。