Abstract
Mesoscale eddies exhibit unique properties, compared with surrounding water, due to their unique physical processes. There is uncertainty over the physical and biological coupling of warm-core eddies.  Our goal was to reveal how warm eddies affect microbial communities (nanoflagellates, bacteria, picophytoplankton, and viruses) during the propagation of anticyclonic warm eddies in the Pacific Ocean. Furthermore, top-down and bottom-up control factors affecting these communities were examined. A difference in the grazing pressure between inside and outside warm eddy affects microbial interactions, as hypothesized here. To explain how grazers affect microbial communities,
successive seven-day microcosm experiments were conducted in the eddy core (EC) and outside the eddy (OE). Our findings show that at surface waters, Synechococcus spp. was the most abundant picophytoplankton in EC samples. Synechococcus spp. abundances in OE samples were higher than in EC samples at other depths, with maximum values at 60 m above the deep chlorophyll maximum (DCM). Furthermore, Prochlorococcus spp. dominated in EC samples from the surface to 100 m, with the highest abundance at 100
m. Furthermore, the vertical variation in nanoflagellate, bacterial, and viral abundances also showed that EC surface water samples had significantly higher abundances than OE
samples. The results of OE microcosm experiments indicate that regenerated nutrients and carbon availability regulate bacteria and picophytoplankton growth. Furthermore, the convergence effect may drive zooplankton and nanoflagellates toward the core of EC regions, resulting in increased bacterial and picophytoplankton grazing rates.

warm eddys,nanoflagellates,bacteria,picophytoplankton,viruses