Program

Abstract:

Picoplankton groups (Prochlorococcus, Synechococcus, picoeukaryotes, and heterotrophic bacteria) respond differently to the phytoplankton bloom events which are common but complex phenomenon in coastal ecosystems. To understand the variations of picoplankton abundances during bloom, the distribution of picoplankton in the Taiwan Bank, South China Sea was investigated using flow cytometry during diatom Thalassiosira diporocyclus bloom in March, 2016. The results indicated that the abundance of picophytoplankton (Prochlorococcus, Synechococcus, and picoeukaryotes) decreased within the bloom area which was co-affected by temperature, nutrients, and mixing condition. The abundance of heterotrophic bacteria showed no significant difference between the bloom and non-bloom areas which was associated with chlorophyll a. We found two sub-groups of heterotrophic bacteria: high- and low-nucleic acid content (HNA and LNA) bacteria. HNA was dominated in the bloom area while LNA was dominated in the non-bloom area. Among the picoplankton components, HNA represented the highest (61.1%) carbon biomass in the bloom area while picoeukaryotes represented the highest (37.6%) in the non-bloom area. It was likely that heterotrophic bacteria, especially HNA, played an essential role during the diatom bloom.

Keywords: diatom bloom, Taiwan Bank, picoplankton abundance, ecological role