Application of a pulse-amplitude-modulation (PAM) fluorometer reveals its usefulness and robustness in the prediction of Karenia mikimotoi blooms: A case study in Sasebo Bay, Nagasaki, Japan

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• 作者：Shota Higo^a ; ¹ ; Maung-Saw-Htoo-Thaw^a ; Toshifumi Yamatogi^b ; Naoya Ishida^c ; Sou Hirae^b ; Kazuhiko Koike^a ; ^{kazkoike@hiroshima-u.ac.jp}
• 关键词：Karenia mikimotoi ; PAM fluorometer ; Fv/Fm ; Electron transport rate (ETR) ; Red tide
• 刊名：Harmful Algae
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：61
• 期：Complete
• 页码：63-70
• 全文大小：2441 K
• 卷排序：61

文摘

Red tides of Karenia mikimotoi blooms have severely impacted marine fish culture in Japanese waters, however, blooms cannot be accurately predicted because they are controlled by a combination of numerous spontaneous environmental parameters, including unknown parameters. Nevertheless, these parameters must eventually control photosynthesis and result in growth, and measuring the photosynthetic activities of this species may be useful for predicting blooms. In this study, K. mikimotoi blooms were predicted in Sasebo Bay, Nagasaki, Japan, in 2014 and 2015 by measuring the maximum quantum yield (Fv/Fm) and relative photochemical electron transport rate (ETR) using pulse-amplitude-modulation (PAM) fluorometers (a cuvette-type and a microscopy-type fluorometer). In 2014, a raphidophycean Heterosigma akashiwo bloom initially dominated at the end of May and was followed by a K. mikimotoi bloom. This change was previously characterized by a decrease in the Fv/Fm of H. akashiwo and an increase in K. mikimotoi. In 2015, a moderate K. mikimotoi bloom was detected at the beginning of the survey and was predicted to increase thereafter based on the population’s high Fv/Fm and ETR values. Additionally, these values were highest in the mid-deeper layer, as expected for K. mikimotoi, which prefers lower light intensities in the water column. In both years, blooms of K. mikimotoi were replaced by Prorocentrum dentatum, and these successions were initially recognized by PAM fluorometer measurements. These dinoflagellate blooms eventually vanished due to massive diatom blooms, which were accelerated by nutrient inputs from rivers after heavy precipitation. Furthermore, the activation of these diatom populations was also primarily detected based on their Fv/Fm and ETR increases, especially in the surface layer. Again, this location is expected because diatoms prefer high light intensity. In this study, it was found that various environmental factors influenced the Fv/Fm and ETR values, especially light and nutrient stresses, and these values served as useful proxies for the phytoplankton physiological status. These values could be used to predict the blooming or succession of phytoplankton.