Analysis of phytoplankton community change according to continuous observation pattern of chlorophyll-a concentration

Abstract

To understand the changes in chlorophyll-a concentration and phytoplankton community in Tongyeong coastal waters, South Korea, we continuously monitored chlorophyll-a concentration using a fluorescence sensor from July 29 to September 28, 2017(62 days) and from July 19 to September 7, 2018 (51 days). Furthermore, phytoplankton analyses were conducted periodically to monitor changes in dominant species affected by variations in chlorophyll-a concentrations. In the presented study, chlorophyll-a concentrations increased rapidly three times in 2017(event 1~3) and twice in 2018(event 4, 5). During the event 1(August 6 to 14, 2017) and 4(July 29 to August 6, 2018), rapid and repeated increase pattern of chlorophyll-a concentration during 14:00 to 16:00 pm were the result of the diel vertical migration of Alexandrium affine and Cochlodinium polykrikoides(the dominant species during each peak) in 2017 and 2018, respectively. During event 2(August 24 to 30, 2017), 3(September 12 to 17, 2017) and 5(August 11 to 18, 2018), increases in chlorophyll-a concentration were caused by diatoms(common species: Chaetoceoros curvisetus, Skeletonema marinoi-dohrnii complex, Psuedonitzschia spp. Etc.). Unlike event 1 and 4, we did not observe any characteristic changes such as vertical migration during these events. Therefore, the continuous monitoring of chlorophyll-a concentrations using a real-time detection device, such as a fluorescen017(62 days) and from July 19 to September 7, 2018 (51 days). Furthermore, phytoplankton analyses were conducted periodically to monitor changes in dominant species affected by variations in chlorophyll-a concentrations. In the presented study, chlorophyll-a concentrations increased rapidly three times in 2017(event 1~3) and twice in 2018(event 4, 5). During the event 1(August 6 to 14, 2017) and 4(July 29 to August 6, 2018), rapid and repeated increase pattern of chlorophyll-a concentration during 14:00 to 16:00 pm were the result of the diel vertical migration of Alexandrium affine and Cochlodinium polykrikoides(the dominant species during each peak) in 2017 and 2018, respectively. During event 2(August 24 to 30, 2017), 3(September 12 to 17, 2017) and 5(August 11 to 18, 2018), increases in chlorophyll-a concentration were caused by diatoms(common species: Chaetoceoros curvisetus, Skeletonema marinoi-dohrnii complex, Psuedonitzschia spp. Etc.). Unlike event 1 and 4, we did not observe any characteristic changes such as vertical migration during these events. Therefore, the continuous monitoring of chlorophyll-a concentrations using a real-time detection device, such as a fluorescen