title: Picoplankton and virioplankton abundance and community structure in Pearl River Estuary and Daya Bay, South China.
abstract: By using flow cytometry techniques, we investigated the abundance and composition of the heterotrophic prokaryotes, virioplankton and picophytoplankton community in the Pearl River Estuary and Daya Bay in the summer of 2012. We identified two subgroups of prokaryotes, high nucleic acid (HNA) and low nucleic acid (LNA), characterized by different nucleic acid contents. HNA abundance was significantly correlated with larger phytoplankton and Synechococcus (Syn) abundance, which suggested the important role of organic substrates released from primary producers on bacterial growth. Although LNA did not show any association with environmental variables, it was a vital component of the microbial community. In contrast to previous studies, the total virioplankton concentration had a poor relationship with nutrient availability. The positive relationship between large-sized phytoplankton abundance and the V-I population confirmed that V-I was a phytoplankton-infecting viral subgroup. Although the V-II group (bacteriophages) was dominant in the virioplankton community, it was not related with prokaryotic abundance, which indicated factors other than hosts controlling V-II abundance or the uncertainty of virus-host coupling. With respect to the picophytoplankton community, our results implied that river input exerted a strong limitation to Syn distribution in the estuary, while picoeukaryotes (Euk) were numerically less abundant and showed a quite different distribution pattern from that of Syn, and hence presented ecological properties distinct from Syn in our two studied areas.
authors.affiliation: Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China; South China Sea Environmental Monitoring Center, South China Sea Branch of the State Oceanic Administration, Guangzhou 510310, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Zhixin
authors.initials: Z
authors.lastname: Ni
authors.affiliation: Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China. Electronic address: xphuang@scsio.ac.cn.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Huang
authors.affiliation: Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China. Electronic address: zhangxia@scsio.ac.cn.
authors.forename: Xia
authors.initials: X
authors.lastname: Zhang
mesh_terms: D001435:Bacteriophages / Q000302:isolation & purification*; D044822:Biodiversity; D002681:China; D004784:Environmental Monitoring / Q000379:methods*; D005434:Flow Cytometry; D010839:Phytoplankton / Q000302:isolation & purification*; D011387:Prokaryotic Cells / Q000166:cytology; D045483:Rivers / Q000382:microbiology*; D012623:Seawater / Q000382:microbiology*; D014871:Water Microbiology
keywords: Community composition; Flow cytometry; Picoplankton; Virioplankton