Chemical Oceanography Unit, University of Liège, Liège, Belgium.
Department of Hydrobiology, Federal University of São Carlos, 13565-905 São Carlos, São Paulo, Brazil.
Sci Total Environ. 2014 Mar 1;473-474:178-88. doi: 10.1016/j.scitotenv.2013.12.036. Epub 2013 Dec 24.
Phytoplankton biomass and primary production in tropical large lakes vary at different time scales, from seasons to centuries. We provide a dataset made of 7 consecutive years of phytoplankton biomass and production in Lake Kivu (Eastern Africa). From 2002 to 2008, bi-weekly samplings were performed in a pelagic site in order to quantify phytoplankton composition and biomass, using marker pigments determined by HPLC. Primary production rates were estimated by 96 in situ (14)C incubations. A principal component analysis showed that the main environmental gradient was linked to a seasonal variation of the phytoplankton assemblage, with a clear separation between diatoms during the dry season and cyanobacteria during the rainy season. A rather wide range of the maximum specific photosynthetic rate (PBm) was found, ranging between 1.15 and 7.21 g carbong(-1)chlorophyll ah(-1), and was best predicted by a regression model using phytoplankton composition as an explanatory variable. The irradiance at the onset of light saturation (Ik) ranged between 91 and 752 μE m(-2)s(-1) and was linearly correlated with the mean irradiance in the mixed layer. The inter-annual variability of phytoplankton biomass and production was high, ranging from 53 to 100 mg chlorophyll am(-2) (annual mean) and from 143 to 278 g carbon m(-2)y(-1), respectively. The degree of seasonal mixing determined annual production, demonstrating the sensitivity of tropical lakes to climate variability. A review of primary production of other African great lakes allows situating Lake Kivu productivity in the same range as that of lakes Tanganyika and Malawi, even if mean phytoplankton biomass was higher in Lake Kivu.
浮游植物生物量和初级生产力在热带大湖中有不同的时间尺度变化，从季节到世纪。我们提供了一个数据集，其中包含了基伍湖（东非）连续 7 年的浮游植物生物量和生产力数据。从 2002 年到 2008 年，在一个浮游生物站点进行了两周一次的采样，以使用高效液相色谱法确定的标记色素来量化浮游植物的组成和生物量。通过 96 次现场（14）C 培养来估计初级生产力速率。主成分分析表明，主要的环境梯度与浮游植物组合的季节性变化有关，在旱季期间有明显的硅藻分离，在雨季期间有蓝藻分离。发现最大比光合作用速率（PBm）的范围相当宽，范围在 1.15 到 7.21 克碳每克叶绿素 ah（-1）之间，并且最好通过使用浮游植物组成作为解释变量的回归模型来预测。光饱和起始时的辐照度（Ik）范围在 91 到 752 μE m（-2）s（-1）之间，并且与混合层中的平均辐照度呈线性相关。浮游植物生物量和生产力的年际变异性很大，范围在 53 到 100 毫克叶绿素 am（-2）（年平均值）和 143 到 278 克碳 m（-2）y（-1）之间。季节性混合的程度决定了年生产力，表明热带湖泊对气候变化的敏感性。对其他非洲大湖初级生产力的综述使基伍湖的生产力处于与坦噶尼喀湖和马拉维湖相同的范围内，即使基伍湖的平均浮游植物生物量更高。
