Attribution of the growth of a distinct population of Synechococcus to the coverage of lateral water on an upwelling

Abstract

Upwelling water generally transports abundant nutrients to fertilize the euphotic zone and promotes larger phytoplankton to thrive. In contrast, knowledge about the composition of prokaryotic picoplankton associated with the scale of upwelling is limited. In this study, the population compositions of prokaryotic picoplankton, with particular focus on Synechococcus, under two diverse hydrographic conditions in the shelf-margin upwelling system were compared in detail. During the study period of 2009, an upwelling event was observed. In contrast to conventional upwelled water, the surface of this upwelling was covered with a thin layer of nutrient-depleted water. Although the water exchange created a low-nutrient stock environment, which fell below traditional chemical detection limits, its flux was likely sufficient to support the growth of the Synechococcus clade-II lineage. In comparison with the hydrography in 2009, no obvious upwelling occurred, and oligotrophic water primarily occupied the upper layer during the study period of 2010. The abundance of Synechococcus significantly declined to approximately half its numbers observed in 2009. While the Synechococcus clade-II were still the predominant population, their proportion in the 16S rRNA gene library decreased to approximately 50%. The remaining part was replaced with α-Proteobacteria and various heterotrophic bacteria. The results of the present study, combined with those obtained in previous studies, yield a more comprehensive understanding of the phytoplankton community dynamics in this varied ecosystem.

Spatial variation of abundant picoeukaryotes in the subtropical Kuroshio Current in winter

“…In the context of global climate change, the accelerated warming might subsequently change the flow direction and velocity of the WBC, thereby affecting the ecology and the biogeochemistry cycle of the surrounding waters (Wu, Wang, Lin, Chiang, & Wu, ; Wu et al, ; Yang et al, ). Picoplankton is highly susceptible to the environmental changes and in turn alters their community compositions or nutrition strategy to respond (Chung & Gong, ; Worden et al, ). Our study provides the first insight into the community assemblage and the annual distribution of picoeukaryotes in the subtropical Kuroshio Current.…”

Effects of the Coastal Uplift on the Kuroshio Ecosystem, Eastern Taiwan, the Western Boundary Current of the North Pacific Ocean

“…The heterotrophic bacteria were stained with the nucleic acidspecific dye SYBR R Green I (emission = 530 ± 30 nm) in a 10 4 -fold-diluted commercial solution (Molecular Probes, Eugene, OR, United States; Liu et al, 2002). Known numbers of fluorescent beads (TruCOUNT Tubes, Becton-Dickinson, Franklin Lakes, NJ, United States) were simultaneously used as an instrument internal standard (Chung and Gong, 2019;Chan et al, 2020). When applicable, cell abundances were converted to carbon units using the factors widely applied, including 53 fg C cell −1 for Prochlorococcus, 250 fg C cell −1 for Synechococcus, 2100 fg C cell −1 for picoeukaryotes, and 20 fg C cell −1 for heterotrophic bacteria (Lee and Fuhrman, 1987;Morel et al, 1993;Campbell et al, 1994;Buck et al, 1996).…”

“…Picoplankton is highly susceptible to environmental changes, including altering its community compositions and/or nutrition strategy to respond (Worden et al, 2015;Chung and Gong, 2019). In addition to increasing nutrient concentrations and phytoplankton biomass, the relative abundances and composition of picophytoplankton also changed due to the coastal uplift.…”

Seasonal Assemblages of picocyanobacteria in the subtropical segment of the Kuroshio Current

“…In this study, we focused on a more southern Kuroshio current, characterized by low available nutrients in situ. Therefore, the differences found in the abundance of Synechococcus compared with the ndings of Chung and Gong (2019) [58] could be attributed to variations in the formation of upwelling caused by the main or branch currents of the Kuroshio current system. Additionally, this study revealed the presence of Synechococcus in clade VII, clade III, and clade X.…”