-Marine chroococcoid phycoerythrin - containing Synechococcus spp. recently have been implicated as a substantial component of the photosynthetic picoplankton in the ocean. Although the importance of Synechococcus as ...-Marine chroococcoid phycoerythrin - containing Synechococcus spp. recently have been implicated as a substantial component of the photosynthetic picoplankton in the ocean. Although the importance of Synechococcus as food sources for heterotrophic nanoplankton are now recognized, the information about its cycling of biomass and diel patterns is limited and the methodology used varies according to different authors. A selective metabolic inhibitor method was used to allow simultanous estimation of both growth rates and grazing disappearance rates of Synechococcus. Results obtained in the English Channel show growth rates ranging from 0. 25 to 0. 72 d-1 with an average value of 0. 51 d -1and grazing disappearance rates ranged from 0. 21 to 0. 64 d-1 (mean = 0. 44 d-1). Offshore in the Celtic Sea of the Northeast Atlantic Ocean, both rates were lower than in the channel. The similarity between average growth and grazing rates suggests a rapid recycling of Synechococcus biomass. In diel pattern, Synechococcus grazing mortality rates were higher during the day (mean = 0. 61 d-1) than during the night (mean = 0. 21d-1) in all the experiments. A positive correlation was observed between growth rates and in situ temperature ranged from 9 to 20 ℃. Sire-fractionated experiments demonstrate that up to about 7 0 % of Synechococcus disappearance could be attributed to the grazer smaller than 2 μm in diameter. The variations of Synechococcus cell characteristics such as size and phycoerythin contents in the growth and grazing experiments were determined with a flow cytometer. The methodology recently used on estimating dynamics of Synechococcus population is reviewed.展开更多
Pico-and nano-eukaryotic plankton are important members of marine ecosystems.To understand their community structure and spatio-temporal variations in the Beibu Gulf,and to study the impact of Changjiang Nuclear Power...Pico-and nano-eukaryotic plankton are important members of marine ecosystems.To understand their community structure and spatio-temporal variations in the Beibu Gulf,and to study the impact of Changjiang Nuclear Power Plant(CNPP)located in the northwest coast of the Hainan Island on the eukaryotic plankton,we studied these issues in the coastal water near CNPP bimonthly from February 2018 to January 2019 via 18 S Illumina sequencing.The results reveal a higher genetic alphadiversity and less beta-diversity of the plankton community in small-size(0.45-5μm and 5-20μm)fractions than in large-size(20-200μm and>20μm)fractions.The small-sized phytoplankton,including Micromonas(Chlorophyta)and Minutocellus(Bacillariophyta),as well as heterotrophic plankton,including Paraphysomonas(Chrysophyceae),Ellobiopsis(Dinoflagellates),and Syndiniales(Dinoflagellates),took up a considerable proportion in eukaryotic plankton community.In addition,it showed a slight temperature increase and no significant difference in eukaryotic plankton community between the outfall of CNPP and other sampling sites,suggesting that the impact of the thermal discharge from the CNPP on local eukaryotic plankton community was limited.展开更多
文摘-Marine chroococcoid phycoerythrin - containing Synechococcus spp. recently have been implicated as a substantial component of the photosynthetic picoplankton in the ocean. Although the importance of Synechococcus as food sources for heterotrophic nanoplankton are now recognized, the information about its cycling of biomass and diel patterns is limited and the methodology used varies according to different authors. A selective metabolic inhibitor method was used to allow simultanous estimation of both growth rates and grazing disappearance rates of Synechococcus. Results obtained in the English Channel show growth rates ranging from 0. 25 to 0. 72 d-1 with an average value of 0. 51 d -1and grazing disappearance rates ranged from 0. 21 to 0. 64 d-1 (mean = 0. 44 d-1). Offshore in the Celtic Sea of the Northeast Atlantic Ocean, both rates were lower than in the channel. The similarity between average growth and grazing rates suggests a rapid recycling of Synechococcus biomass. In diel pattern, Synechococcus grazing mortality rates were higher during the day (mean = 0. 61 d-1) than during the night (mean = 0. 21d-1) in all the experiments. A positive correlation was observed between growth rates and in situ temperature ranged from 9 to 20 ℃. Sire-fractionated experiments demonstrate that up to about 7 0 % of Synechococcus disappearance could be attributed to the grazer smaller than 2 μm in diameter. The variations of Synechococcus cell characteristics such as size and phycoerythin contents in the growth and grazing experiments were determined with a flow cytometer. The methodology recently used on estimating dynamics of Synechococcus population is reviewed.
基金the National Key Research and Development Program of China(No.2019YFE0124700)the Scientific Research Foundation of Third Institute of Oceanography,MNR(No.2020017)。
文摘Pico-and nano-eukaryotic plankton are important members of marine ecosystems.To understand their community structure and spatio-temporal variations in the Beibu Gulf,and to study the impact of Changjiang Nuclear Power Plant(CNPP)located in the northwest coast of the Hainan Island on the eukaryotic plankton,we studied these issues in the coastal water near CNPP bimonthly from February 2018 to January 2019 via 18 S Illumina sequencing.The results reveal a higher genetic alphadiversity and less beta-diversity of the plankton community in small-size(0.45-5μm and 5-20μm)fractions than in large-size(20-200μm and>20μm)fractions.The small-sized phytoplankton,including Micromonas(Chlorophyta)and Minutocellus(Bacillariophyta),as well as heterotrophic plankton,including Paraphysomonas(Chrysophyceae),Ellobiopsis(Dinoflagellates),and Syndiniales(Dinoflagellates),took up a considerable proportion in eukaryotic plankton community.In addition,it showed a slight temperature increase and no significant difference in eukaryotic plankton community between the outfall of CNPP and other sampling sites,suggesting that the impact of the thermal discharge from the CNPP on local eukaryotic plankton community was limited.
