Algae blooms are of considerable concern in freshwater lakes and reservoirs worldwide. In-situ Chlorophyll a (Chl-a) fluorometers are widely used for rapid assessments of algae biomass. However, accurately converting Chl-a fluorescence to an equivalent concentration is challenging due to natural variations in the relationship as well as nonphotochemical quenching (NPQ) which occurs commonly in surface waters during daytime. This study is based on water quality data from a freshwater lake from October 2018 to December 2020. Initial analysis of sonde Chl-a fluorescence and laboratory extracted Chl-a concentrations shows that the two data sets exhibit a nonlinear relationship with positive correlation and significant errors. A bias correction method was next developed based on (1) concurrent sonde measurements of other water quality parameters (to account for nonlinearities) and (2) a bias correction approach for nonphotochemical quenching effects in surface waters. The new Chl-a model exhibits much improved accuracy, with a root mean square error (RMSE) less than 0.95 µg/L. The new method facilitates accurate Chl-a characterization in freshwater lakes and reservoirs based on readily obtainable in-situ fluorescence sonde measurements.

全球淡水湖泊和水库中的藻类大量繁殖引起了相当大的关注。原位叶绿素a(Chl-a) 荧光计广泛用于藻类生物量的快速评估。然而，由于关系的自然变化以及白天在地表水中常见的非光化学淬灭 (NPQ)，将 Chl-a 荧光准确转换为等效浓度具有挑战性。本研究以某淡水湖2018年10月至2020年12月水质数据为基础，对探测器 Chl-a 荧光和实验室提取的 Chl-a 浓度进行初步分析，表明两组数据呈非线性关系，正相关且误差显着. 接下来开发了一种偏差校正方法，其基础是 (1) 其他水质参数的并发探测器测量（以解释非线性）和 (2) 地表水中非光化学猝灭效应的偏差校正方法。新的 Chl-a 模型的精度大大提高，均方根误差 (RMSE) 小于 0.95 µg/L。新方法基于容易获得的原位荧光探测器测量，促进了淡水湖泊和水库中 Chl-a 的准确表征。