Using a flow cytometer (FCM) onboard the R/V Xuelong during the 24th Chinese Antarctic cruise, picoplankton community structure and biomass in the surface water were examined along the latitude and around the Antarctic Ocean. Salinity and temperature were automatically recorded and total Chl a was determined. Along the cruise, the abundance of Synechococcus, Prochlorococcus, pico-eukaryotes and heterotrophic bacteria ranged in 0.001-1.855×10⁸ ind./L, 0.000-2.778×10⁸ ind./L, 0.002-1.060×10⁸ ind./L and 0.132-27.073×10⁸ ind./L, respectively. Major oceanic distribution of Synechococcus and Prochlorococcus appeared between latitudes 30°N and 30°S. Prochlorococcus was mainly influenced by water temperature, water mass combination and freshwater inflow. Meanwhile, Synechococcus distribution was significantly associated with landing freshwater inflow. Pico-eukaryotes and heterotrophic bacteria were distributed all over the oceans, but with a relatively low abundance in the high latitudes of the Antarctic Ocean. Principal Component Analysis showed that at same latitude of Atlantic Ocean and Indian Ocean, picoplankton distribution and constitution were totally different, geographical location and different water masses combination would be main reasons.

Picoplankton distribution around the Zhangzi Island (northern Yellow Sea) was investigated by monthly observation from July 2009 to June 2010. Three picoplankton populations were discriminated by flow cytometry, namely Synechococcus, picoeukaryotes and heterotrophic prokaryotes. In summer (from July to September), the edge of the northern Yellow Sea Cold Water Mass (NYSCWM) resulting from water column stratification was observed. In the NYSCWM, picoplankton (including Synechococcus, picoeukaryotes and heterotrophic prokaryotes) distributed synchronically with extremely high abundance in the thermocline (20 m) in July and August (especially in August), whereas in the bottom zone of the NYSCWM (below 30 m), picoplankton abundance was quite low. Synechococcus, picoeukaryotes and heterotrophic prokaryotes showed similar response to the NYSCWM, indicating they had similar regulating mechanism under the influence of NYSCWM. Whereas in the non-NYSCWM, Synechococcus, picoeukaryotes and heterotrophic prokaryotes exhibited different distribution patterns, suggesting they had different controlling mechanisms. Statistical analysis indicated that temperature, nutrients (NO₃^– and PO₄^3–) and ciliate were important factors in regulating picoplankton distribution. The results in this study suggested that the physical event NYSCWM, had strong influence on picoplankton distribution around the Zhangzi Island in the northern Yellow Sea.

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 distnbution pattern of Syn and Pro was observed Possible reasons for these differences in the two marine regimes were discussed.

The investigation on community structure of standing stock of photosynthetic picoplankton:Synechococcus (Syn), Prochlorococcus (Pro) and Picoeukaryotes (Euk) and their environmental regulation mechanisms in the northern South China Sea was carried out in the summer of 1999. The results showed that the average abundances of Syn, Pro and Euk in the study sea areas were (5.0±7.6)×10⁴cell/cm³ (51%), (4.6±4.2)×10⁴ cell/cm³ (47%) and (1.8±1.1)×10³ cell/cm³ (2%) respectively, and those of their carbon biomass were (12.5±18.9) μg/dm³ (74%), (2.7±2.5) μg/dm³ (16%) and (1.7±1.0) μg/dm³ (10%). The most of high values of Syn appeared in the estuaries, coastal zone and continental shelf in the sea area to the east of Leizhou Peninsula and Hainan Island where nutrients were rich, and those appeared in the Beibu Gulfwere the second, while those appeared in continental slope and open sea were tens times lower than the above those. Its distribution in water column was mainly above the thermocline and its abundance below it sharply decreased. Two different populations of Pro were found, the surface population and deep one. The distribution pattern of the former was similar to that of Syn; while with marked difference from that of the former, the abundance and biomass of the latter markedly increased towards outer sea, continental slope and open sea where nutrients were poor; the high values in the water column mainly appeared at the bottom of euphoric zone and above the nitrocline, where it often vigorously grow. The distribution difference of Euk in the various sea areas is not as obvious as those of Syn and Pro, but it was high in coastal and shelf waters and low in continental slope and open sea. The high values in the water column were mostly appeared at the bottom of euphoric zone. This difference of distribution pattern for the three type of photosynthetic picoplankton depends on environmental effects and their ecophysiological differences.

During spring and autumn of 2006, the investigations on abundance, carbon biomass and distribution of picoplankton were carried out in the southern Huanghai Sea (Yellow Sea, sHS). Three groups of picoplankton-Synechococcus (Syn), Picoeukaryotes (PEuk) and heterotrophic bacteria (BAC) were identified, but Prochlorococcus (Pro) was undetected. The average abundance of Syn and PEuk was lower in spring (5.0 and 1.3×10³ cells/cm³, respectively) than in autumn (92.4 and 2.7×10³ cells/cm³, respectively), but it was opposite for BAC (1.3 and 0.7×10⁶ cells/cm³ in spring and autumn, respectively). And the total carbon biomass of picoplankton was higher in spring (37.23±11.67) mg/m³ than in autumn (21.29±13.75) mg/m³. The ratios of the three cell abundance were 5:1:1 341 and 30:1:124 in spring and autumn, respectively. And the ratios of carbon biomass of them were 5:7:362 and 9:4:4 in spring and autumn, respectively. Seasonal distribution characteristics of Syn, PEuk, BAC were quite different from each other. In spring, Syn abundance decreased in turn in the central waters (where phytoplankton bloom in spring occurred), the southern waters and inshore waters of the Shandong Peninsula (where even Syn was undetected); the high values of PEuk abundance appeared in the central and southern waters and the inshore of the Shandong Peninsula; the abundance of BAC was nearly three order of magnitude higher than that of photosynthetic picoplankton, and high values appeared in the central waters. In autumn, Syn abundance in central waters was higher than that in surrounding waters, while for PEuk abundance, it decreased in turn in the inshore waters of the Shandong Peninsula, the southern waters and the central waters; BAC presented a complicated blocky type distribution. Sub-surface maximum of each group of picopalnkton appeared in both spring and autumn. Compared with the available literatures concerning the studied area, the range of Syn abundance was larger, and the abundance of BAC was higher. In addition, the conversion factors for calculating picoplanktonic carbon biomass were discussed, with the conversion factors which are different from previous studies in the same surveyed waters. The result of regression analysis showed that there was distinct positive correlation between BAC and photosynthetic picoplankton in spring (r=0.61, P <0.001), but no correlation was found in autumn.

The biomass and size fraction of phytoplankton in terms of chlorophyll a (Chl a) was measured during four cruises conducted in April, July, October 2013 and January 2014 in mariculture area, the Sanggou Bay, China. Results show that total Chl a levels in the surface seawater of the Sanggou Bay generally range from 0.10 to 20.46 μg/L, with an average value of 2.13 μg/L. Nano-phytoplankton was the most important size-fraction and accounted for about 65.1% of total Chl a. In order to evaluate the importance of the "protozoan trophic link" for energy transfer from the microbial loop to filter-feeding feeders, Zhikong scallop Chlamys farreri was then offered a natural planktonic community as potential prey. Results show that scallops obtained carbon source from natural plankton with the rate of 11 033.05 μg/(g·d). Protists (nanoflagellates and ciliates) were the dominant source of carbon retained by scallop (48.78%). The microbial loop provided 58.45% of the carbon source for farmed scallops. These results indicate that the microbial loop represent a valuable trophic resource in mariculture system of the Sanggou Bay.

The paper deals with the studies on the cell abundance,the composition of dominant species,size fractionated biomass and productivity of phytoplankton,new production,the environmentally restricted mechanism in the Prydz Bay and the adjacent Indian sector of the Southern Ocean during the austral summer 1998/1999.The results showed that there was marked feature of spatial zonation in the sea areas investigated.In the Prydz Bay and its adjacent continental shelf,the biomass and productivity of phytoplankton were high; those of continental slope and open ocean area were obviously low.The nutrient concentration had opposite distribution trend,due to the consumption of phytoplankton.It mainly affected by the vertical stability of water column,grazing pressure of zooplankton,temperature and light etc.The results of size-fractionation showed that the average contribution of netplankton to total chlorophyll a in studied sea areas was 52.2%,those of nano-and picoplankton were 29.4% and 18.4%,respectively.The average contribution of netplankton to total primary production was 52.4%,those of nano-and picoplankton were 28.7% and 18.9%,separately.It is same as previous conclusion that the contribution of picoplankton to productivity is slightly larger than that to biomass of phytoplankton communities.The average new production and f-ratio were 230.6 mg/(m²·d) and 0.43,respectively.

An important goal in ocean colour remote sensing is to accurately detect different phytoplankton groups with the potential uses including the validation of multi-phytoplankton carbon cycle models; synoptically monitoring the health of our oceans, and improving our understanding of the bio-geochemical interactions between phytoplankton and their environment. In this paper a new algorithm is developed for detecting three dominant phytoplankton size classes based on distinct differences in their optical signatures. The technique is validated against an independent coupled satellite reflectance and in situ pigment dataset and run on the 10-year NASA Sea viewing Wide Field of view Sensor (SeaWiFS) data series. Results indicate that on average 3.6% of the global oceanic surface layer is dominated by microplankton, 18.0% by nanoplankton and 78.4% by picoplankton. Results, however, are seen to vary depending on season and ocean basin.

The primary production and chlorophyll a concentration of picoplankton (0.2~2 μm), nanoplankton (2~20 μm) and microplankton (20~200 μm) are described in the northeastern Pacific Ocean near the Hawaii Islands during the six survey cruises from 1996 to 2003:DY85-4, DY95-7, DY95-8, DY95-10, DY105-11 and DY105-12.14. The primary production of carbon was in range from 76.8 to 191.9 mg/(m²·d) with an average of 116.1 mg/(m²·d) in the east region, and from 73.1 to 222.5 mg/(m²·d) with an average of 127.1 mg/(m²·d) in the west region, similar to the other oligotrophic regions of the Pacific Ocean investigated. The chlorophyll a concentration was about 0.1 mg/m³ from the surface to the 50 m depth, about 0.2~0.4 mg/m³ from 50 to 100 m, and gradually decreased below the 100 m depth. The picoplankton accounted for more than 70% of the total chlorophyll a in the upper layer (surface to 125 m), but it decreased to less than 50% in depth below 125 m. The nanoplankton and microplankton combined only accounted for less than 30% of the total chlorophyll a in the upper layer, but showed a more even vertical distribution.

The distribution of the abundance of phytoplankton, chlorophyll a (Chl.a) concentration and primary productivity in the Beibu Gulf were observed from May 23 to June 4, 1994.The results show that there were marked featares of spatial zonation in the survey area due to the differences between the geographic environment and the hydrological conditions.Chlorophyll a and primary productivity were higher in the inshore than in the middle area and higher in the north than in the south of the Beibu Gulf.The average concentration of Chl.a, primary productivity and the abundance of phytoplankton were 0.94±0.45 μg/dm³, 351±172 mg/(m²·d) (C) and 0.97×10⁴-10.050×10⁴ ind./m³ in the area, respectively.There were 176 species belonging to 4 phyla and 56 genera based on microscope identification.The results of the size-fractionation show that the contribution of nanoplankton and picoplankton was 77% to total Chl.a and 91% to total primary productivity, which proved their importance to phytoplankton communities in the Beibu Gulf.