Microphytoplankton community structure of a Cochlodinium polykrikoides bloom in the Tongyeong coastal waters of South Korea using morphological and 454 pyrosequencing

Abstract

Massive phytoplankton blooms such as the annual Cochlodinium polykrikoides proliferation in the Tongyeong coastal waters (TCW) of South Korea have a significant influence on planktonic community structure and food web dynamics. Additionally, fish farms in the TCW are severely damaged by Harmful algal blooms, particularly C. polykrikoides. Although the ecology of the TCW is relatively complex, it has been reasonably well studied across two decades of monitoring, including morphological observations of its planktonic organisms. Our objective was to study the under-explored phytoplankton diversity using morphological and 454 pyrosequencing methods. During C. polykrikoides summer bloom, the phytoplankton biomass increased by threefold while its composition decreased in size. The operational taxonomic units (OTUs) in 454 pyrosequencing analysis decreased by half and corresponded with results of the morphological analysis. At the genus level, pyrosequencing revealed the diatoms Chaetoceros, Skeletonema, Thalassiosira, Ditylum, and Leptocylindrus, and the dinoflagellates Akashiwo, Alexandrium, and Cochlodinium, which were highest in abundance. Fluctuating monthly patterns of Skeletonema, Leptocylindrus, Akashiwo, and Cochlodinium in morphological and 454 pyrosequencing results correlated significantly. Although morphological data were more detailed for diatoms than for other groups, 454 pyrosequencing and morphological resu, fish farms in the TCW are severely damaged by Harmful algal blooms, particularly C. polykrikoides. Although the ecology of the TCW is relatively complex, it has been reasonably well studied across two decades of monitoring, including morphological observations of its planktonic organisms. Our objective was to study the under-explored phytoplankton diversity using morphological and 454 pyrosequencing methods. During C. polykrikoides summer bloom, the phytoplankton biomass increased by threefold while its composition decreased in size. The operational taxonomic units (OTUs) in 454 pyrosequencing analysis decreased by half and corresponded with results of the morphological analysis. At the genus level, pyrosequencing revealed the diatoms Chaetoceros, Skeletonema, Thalassiosira, Ditylum, and Leptocylindrus, and the dinoflagellates Akashiwo, Alexandrium, and Cochlodinium, which were highest in abundance. Fluctuating monthly patterns of Skeletonema, Leptocylindrus, Akashiwo, and Cochlodinium in morphological and 454 pyrosequencing results correlated significantly. Although morphological data were more detailed for diatoms than for other groups, 454 pyrosequencing and morphological resu