西部瀬戸内海におけるFlowCAM^®を用いた現場赤潮監視

抄録

The harmful dinoflagellate Karenia mikimotoi is responsible for extensive red tides in the western part of the Seto Inland Sea and causes severe fish-kills. There is great demand by fishermen for a red tide monitoring system covering wide areas, however, manual sampling and microscopy-based detection used in the current monitoring system is time intensive, and makes wide-area surveys almost impossible. In this study, we applied FlowCAM to enumerate K. mikimotoi occurrences in the field and compared the results with conventional microscope counting. The field surveys were carried out in Suo-Nada, Iyo-Nada, and Beppu Bay in June and July from 2010 to 2012. No significant difference was found in the quantification results obtained by both methods at rather low density occurrences of K. mikimotoi (<10 cells mL^-1). However FlowCAM was more advantageous in enumerating mid-density occurrences (<100 cells mL^-1) which are critical for monitoring the status of forthcoming red tides. Furthermore, images captured by FlowCAM allowed identification of what seems to be a characteristic phenomenon in which diatoms are usually scarce prior to red tides of K. mikimotoi.