Raw absorbance and fluorescence measurements of water samples during Nodularia spumigena 2021 bloom event on Lake Bante in Wilhelmshaven, Germany

Water sampling was conducted from the shoreline of Lake Bante in Wilhelmshaven, Germany. A very dense Nodularia spumigena bloom was taking place on the day of sampling 16 August 2021. Samples were kept in the dark and stored at 4 °C until further analyses were conducted. First the samples were pre-filtered through Whatman GF/F filters with a 0.7 µm mesh. Further filtration was done using Whatman Nuclepore Track-Etch 0.2 µm pore size membranes within 72 hours after field sampling. Sample filtrate was diluted using deionized water at a ratio 1:4 to mitigate inner filter effect and detector saturation. Excitation-emission matrices (EEMs) and absorbance measurements were done using a Horiba Aqualog benchtop fluorometer. Sample filtrate was placed in a 1 cm quartz cuvette that had been pre-rinsed 3 times before each measurement.

本研究于德国威廉港班特湖（Lake Bante）岸线开展水体采样。2021年8月16日采样当日，湖体正暴发高密度泡沫节球藻（Nodularia spumigena）水华。采集的样本于避光条件下以4℃冷藏保存，直至后续分析环节。首先将样本通过孔径0.7μm的沃特曼（Whatman）GF/F滤膜进行预过滤；野外采样后72小时内，再采用孔径0.2μm的沃特曼Nuclepore Track-Etch径迹蚀刻滤膜完成二次过滤。为缓解内滤效应与检测器饱和问题，以1:4的比例用去离子水对样本滤液进行稀释。采用堀场（Horiba）Aqualog台式荧光分光光度计开展激发发射矩阵（Excitation-emission matrices, EEMs）与吸光度检测。将样本滤液装入1cm光程石英比色皿中，该比色皿需在每次测量前预冲洗3次。