Qinhuangdao coastal waters have been frequently hitting by nano-and pico-eukaryotic phytoplankton(NPEP)blooms and green tides(macroalgal blooms)in the recent decade.However,understanding about the impacts of environme...Qinhuangdao coastal waters have been frequently hitting by nano-and pico-eukaryotic phytoplankton(NPEP)blooms and green tides(macroalgal blooms)in the recent decade.However,understanding about the impacts of environmental factors and the green tides on the NPEP assemblages in this area is limited.In this study,the composition of NPEP assemblages and their variations were analyzed via amplicon sequence variants(ASVs)assay based on amplicon high-throughput sequencing data with the 18S V4 region as a targeted gene in the Qinhuangdao green-tide area during the green tide.Consequently,average NPEP effective sequences and ASVs of 178000 and 200 were obtained from each sample,respectively.Although there were 25 classes,110 genera,and 97 species of NPEP were identified and annotated,the proportions of annotated ASVs at genus and species levels were only 44.7%and 17.8%,respectively.The NPEP communities had a seasonal succession from diatom-dominated to dinoflagellate-dominated.During the three investigations,Skeletonema,Karlodinium,and Gonyaulax were the most dominant genera in May,August,and September,respectively.Species diversity and the abundance of NPEP communities could be increased by a high content of dissolved organic nitrogen(DON)and dissolved organic phosphorus(DOP)but inhibited by low dissolved inorganic phosphorus content.The outbreak of green tides could alter the composition and content of nutrients and accelerate the succession of the NPEP communities from diatom-dominated to dinoflagellate-dominated under the background of a seasonal increase in seawater temperature.These results preliminarily revealed the impacts of the recurrent occurrences of green tides on the NPEP assemblages in the Qinhuangdao green-tide area exhibiting high DON content and dissolved inorganic nitrogen/phosphorus ratio.展开更多
Dynamics of major picoplankton groups, Synechococcus (Syn), Prochlorococcus (Pro), picoeukaryotes (Euk) and heterotrophic bacteria (Bact) was investigated by flow cytometry for the first time in the Nansha Islands are...Dynamics of major picoplankton groups, Synechococcus (Syn), Prochlorococcus (Pro), picoeukaryotes (Euk) and heterotrophic bacteria (Bact) was investigated by flow cytometry for the first time in the Nansha Islands area in the South China Sea. Averaged over the whole investigation area, depth-weighted integrated cell abundance (DWA) of Syn, Pro, Euk and Bact was 1.6 (0.4-5.7)×103, 5.4 (0.1-7.3)×104, 0.7 (0.2-2.2)×103, and 2.3 (1.4-3.2)×105 cells/mL respectively. Picoautotrophic cell abundance was low in the northwest part of the Nansha Islands where surface water temperature was low and the upper mixed layer was shallow. Concurrently, a surface maximum vertical distribution pattern was observed in this area. While in the southeast and east zones where temperatures were relatively higher and nitraclines were deeper, picoplankton is abundant and a subsurface maximum around 50-75 m is observed. Coupling of horizontal and vertical distribution patterns of picoplankton abundance and hydrological status was found, suggesting a strong influence of currents and water column structure on picoplankton distribution in the investigation area. Contrary to that in the shelf water in the East China Sea, the relationship between Pro and Bact in the Nansha Islands area in the South China Sea was not significantly negative but weakly positive. Moreover, a similar distribution pattern of Syn and Pro was observed. Possible reasons for these differences in the two marine regimes were discussed.展开更多
基金Supported by the National Key R&D Program of China(No.2019YFC14079000)the National S&T Basic Resources Investigation Program of China(No.2018FY100206)from the Ministry of Science and Technology(MoST)。
文摘Qinhuangdao coastal waters have been frequently hitting by nano-and pico-eukaryotic phytoplankton(NPEP)blooms and green tides(macroalgal blooms)in the recent decade.However,understanding about the impacts of environmental factors and the green tides on the NPEP assemblages in this area is limited.In this study,the composition of NPEP assemblages and their variations were analyzed via amplicon sequence variants(ASVs)assay based on amplicon high-throughput sequencing data with the 18S V4 region as a targeted gene in the Qinhuangdao green-tide area during the green tide.Consequently,average NPEP effective sequences and ASVs of 178000 and 200 were obtained from each sample,respectively.Although there were 25 classes,110 genera,and 97 species of NPEP were identified and annotated,the proportions of annotated ASVs at genus and species levels were only 44.7%and 17.8%,respectively.The NPEP communities had a seasonal succession from diatom-dominated to dinoflagellate-dominated.During the three investigations,Skeletonema,Karlodinium,and Gonyaulax were the most dominant genera in May,August,and September,respectively.Species diversity and the abundance of NPEP communities could be increased by a high content of dissolved organic nitrogen(DON)and dissolved organic phosphorus(DOP)but inhibited by low dissolved inorganic phosphorus content.The outbreak of green tides could alter the composition and content of nutrients and accelerate the succession of the NPEP communities from diatom-dominated to dinoflagellate-dominated under the background of a seasonal increase in seawater temperature.These results preliminarily revealed the impacts of the recurrent occurrences of green tides on the NPEP assemblages in the Qinhuangdao green-tide area exhibiting high DON content and dissolved inorganic nitrogen/phosphorus ratio.
文摘Dynamics of major picoplankton groups, Synechococcus (Syn), Prochlorococcus (Pro), picoeukaryotes (Euk) and heterotrophic bacteria (Bact) was investigated by flow cytometry for the first time in the Nansha Islands area in the South China Sea. Averaged over the whole investigation area, depth-weighted integrated cell abundance (DWA) of Syn, Pro, Euk and Bact was 1.6 (0.4-5.7)×103, 5.4 (0.1-7.3)×104, 0.7 (0.2-2.2)×103, and 2.3 (1.4-3.2)×105 cells/mL respectively. Picoautotrophic cell abundance was low in the northwest part of the Nansha Islands where surface water temperature was low and the upper mixed layer was shallow. Concurrently, a surface maximum vertical distribution pattern was observed in this area. While in the southeast and east zones where temperatures were relatively higher and nitraclines were deeper, picoplankton is abundant and a subsurface maximum around 50-75 m is observed. Coupling of horizontal and vertical distribution patterns of picoplankton abundance and hydrological status was found, suggesting a strong influence of currents and water column structure on picoplankton distribution in the investigation area. Contrary to that in the shelf water in the East China Sea, the relationship between Pro and Bact in the Nansha Islands area in the South China Sea was not significantly negative but weakly positive. Moreover, a similar distribution pattern of Syn and Pro was observed. Possible reasons for these differences in the two marine regimes were discussed.
