Spatial and temporal variations of Synechococcus and picoeukaryotes in the Taiwan Strait,China

The size-fractionated phytoplankton biomass, and the spatial and temporal variations in abundance of Synechococcus (SYN) and picoeukaryotes (PEUK) were measured in the Taiwan Strait during three cruises (August 1997, February-March 1998, and August 1998). The results show that picophytoplankton and nanophytoplankton dominate the phytoplankton biomass, in average of 38% and 40%, respectively. SYN and PEUK varied over time in abundance and carbon biomass, greater in summer than in winter, in range of (7.70–209.2)×106 and (0.75–15.4)×106 cells/cm2 in the abundance, and 1.93–52.3 and 1.57–32.4 μgC/cm2 in the carbon biomass, for SYN and PEUK, respectively. The horizontal distributions of both groups were diurnal but heterogeneous in abundance, depending on the groups and layer of depths. Temperature is the key controlling factor for picophytoplankton distribution (especially in winter) in the Strait.

Bacterioplankton, Picoeukaryotes and Synechococcus Distribution Associated with Seagrass in South Coast of Hainan Island, China

Seagrass ecosystem is a potential bank for carbon sink. In the paper, we compared the distribution of bacterioplankton, picoeukaryotes and Synechococcus in seagrass ecosystem in Xincun Bay and coral ecosystem in Sanya Bay and found that quantity of bacterioplankton was higher in seagrass ecosystem, and picoeukaryotes had similar distribution pattern with that of bacterioplankton. However, quantity of Synechococcus distribution was higher in coral ecosystem and higher in Sanya Bay. Comparing the unit of quantity of bacterioplankton, picoeukaryotes and Synechococcus in Xincun Bay with that of Sanya Bay, open sea of the South China Sea and Indian Ocean, results showed that the highest quantity of bacterioplankton was in Xincun Bay, and the lowest was in open sea of the South China Sea. The quantity of picoeukaryotes had the similar pattern with that of bacterioplankton. Pattern of Synechococcus quantity was different, which was the highest in Sanya Bay. These results indicated that seagrass ecosystem was more suitable for bacterioplankton and picoeukaryotes growth.

Standing stock and community structure of photosynthetic picoplankton in the northern South China Sea

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)×104 cell/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) ?滋g/dm3 (74%), (2.7±2.5) ?滋g/dm3 (16 %) and (1.7±1.0) ?滋g /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 Gulf were 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 euphotic 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 euphotic zone. This difference of distribution pattern for the three type of photosynthetic picoplankton depends on environmental effects and their ecophysiological differences.

Spatial and temporal variation of picoplankton distribution in the Yellow Sea, China

Seven surveys were carried out in April, September, October, December 2006 and March, May, August 2007 in the Yellow Sea, China. Variations in the spatial and temporal distribution of Synechococcus, picoeukaryotes and heterotrophic bacteria are quantified using flow cytometry. Synechococcus and heterotrophic bacteria are most abundant from late spring to autumn, while picoeukaryotes concentration is high in spring. Synechococcus and heterotrophic bacteria concentrated high in the northwest part of the Yellow Sea in spring and autumn, while picoeukaryotes distributed evenly over the whole study area except for a small frontal zone in the coastal area on the west （in spring） and central Yellow Sea （in autumn）. Under mixing conditions, the vertical distribution of the three picoplankton groups showed a well-mixed pattern. Upon a well-established stratification, the maximum abundance of picoplankton occurred above the mixed layer depth （-30 m）. Cell sizes of Synechococcus and picoeukaryotes were estimated by converting forward scatter signals （FSC） from cytometry analysis to cell diameter, showing the results of 0.65-0.82 um for Synechococcus and 0.85-1.08 um for picoeukaryotes. The average integrated carbon biomasses ranged 15.26-312.62 mgC/m2 for Synechococcus, 18.54-51.57 mgC/m2 for picoeukaryotes, and 402.63-818.46 mgC/m2 for heterotrophic bacteria. The distribution of Synechococcus and heterotrophic bacteria was temperature dependent, and picoplankton presence was poor in the Yellow Sea Cold Water Mass.

Picoplankton distribution in different water masses of the East China Sea in autumn and winter

Abstract Picoplankton distribution was investigated in different water masses of the East China Sea in November, 2006 and February, 2007. The autumn and winter cruises crossed three major water masses： the coastal water mass （CWM）, the mixed water mass （MWM）, which forms on the continental shelf, and the Kuroshio water mass （KWM）. Picoplankton composition was resolved into four main groups by flow cytometry, namely Synechococcus, Prochlorococcus, picoeukaryotes, and heterotrophic bacteria. The average abundances of Synechococcus, picoeukaryotes, and heterotrophic bacteria were （0.63＋ 10.88）~ 103, （1.61＋1.16）x103, （3.39~1.27）x105 cells/mL in autumn and （6.45~8.60）x103, （3.23~2.63）x103, （3.76~1.37）x 105 cells/mL in winter, respectively. Prochlorococcus was not found in the CWM and seldom observed in surface samples in either season. However, Prochlorococcus was observed in the MWM and KWM （approximately 103 cells/mL） in both auttman and winter. Synechococcus distribution varied considerably among water masses, with the highest levels in KWM and lowest levels in CWM. The depth-averaged integrated abundance of Synechococcus was approximately 5-fold higher in KWM than in CWM, which may be due primarily to water temperature. In the MWM, Synechococcus was resolved as two subgroups; the presence of both subgroups was more common in autumn. Picoeukaryote abundance varied less among water masses than Synechococcus, and heterotrophic bacteria depth-averaged integrated abundance exhibited the smallest seasonal variations with respect to water mass. Correlation analysis showed that relationships between picoplankton abundances and environmental factors （temperature, nutrients, and chlorophyll a） differed among the three water masses, suggesting that the three water masses have different effects on picoplankton distribution （particularly Synechococcus）.

Distributions of Picophytoplankton and Phytoplankton Pigments Along a Salinity Gradient in the Changjiang River Estuary, China

We investigated the abundance of different picophytoplankton groups and the phytoplankton pigment ratio in relation to environmental factors such as nutrients and suspended solids along a salinity gradient in the Changjiang River Estuary.The average numbers of Synechococcus spp.（Syn） and picoeukaryotes （Euk） were （2.7 ±5.1）×l03 and （1.1±1.4）×l03 cells mL-1,respectively.Prochlorococcus spp.（Pro） was only found in the high-salinity brackish water with the concentration of 3.0× 10^3 cells mL-1.Syn and Euk numbers both tended to increase offshore and Syn showed a larger variation in cell abundance than Euk.The contribution of picophytoplankton to total phytoplankton biomass increased with increasing salinity and decreasing nutrient concentrations from the estuary to the open ocean.The response of different picophytoplankton groups to environmental variables was different.Water temperature was more important in its control over Euk than over Syn,while nutrients were more important in their influence over Syn than over Euk.Phytoplankton pigment ratios were different in the three different ecological zones along the salinity gradient （i.e.,freshwater zone with 0-5 range,fresh and saline water mixing zone with 5-20 range,and high-salinity brackish water zone with 20-32 range）,where three different phytoplankton communities were discovered,suggesting that phytoplankton pigment ratios can be considered as a complementary indicator of phytoplankton community structure in the Changjiang River Estuary.

Seasonal Variations of Picoeukaryote Community Structure in Zhoushan Fishing Ground,East China Sea

Picoeukaryotes(<2-3μm)are major oceanic primary producers and play a crucial role for the functioning of marine ecosystems.However,the community structure of such communities remains poorly understood,especially in the East China Sea(ECS).We investigated the seasonal variations of abundance and diversity of picoeukaryotes,and recorded environmental variables,along a transect in Zhoushan Fishing Ground.High-throughput sequencing was used for sequencing the V4-V5 variable region within the 18S rRNA gene to analyze genetic diversity and relative abundance of picoeukaryotes.A total of 40 phyla,68 classes,99 orders,126 families,and 140 genera were observed.The estimated richness and diversity indices were both higher in each season.The composition and dominant picoeukaryotes changed significantly at the class level with the seasons alternating.Basidiomycota,Ciliophora,Ascomycota and Cryptomonadales were observed throughout the year.The Linear Discriminant Analysis(LDA)revealed the predominant discriminant taxa of four seasonal groups.Redundancy analysis(RDA)showed that NO2^−and salinity played very important roles to picoeukaryotes for all the spring samples and DS5 sample in winter,PO4^3−and pH affected mostly picoeukaryotes for winter samples and autumn samples.

ECOLOGICAL STUDY OF PICOPLANKTON IN NORTHERN SOUTH CHINA SEA

Abundance, carbon biomass and composition of picoplankton along a transect (fromthe Pearl River estuary to Dongsha Island) in the northern South China Sea were measured by flow cytom-etry (FCM); and the vertical structure, composition variation, relationship between heterotrophic and au-totrophic picoplankton as well as the controlling mechanism of diel variation were studied. Results showedthat along the horizontal direction, both Synechococcus (SYN) and picoeukaryote (PEUK) were highest inabundance and dominated autotrophic picoplankton in the Pearl River estuary, but decreased

Distribution Pattern of Photosynthetic Picoplankton and Heterotrophic Bacteria in the Northern South China Sea

The environmental regulation of plcoplankton distribution in the northern South China Sea was examined In winter and summer of 2004. The average abundance of Synechococcus, Prochlorococcus, and heterotrophlc bacteria was lower In winter （30, 21, and 780×10^3 cells/cm^3, respectively） than In summer （53, 85, and 1 090×10^3 cells/cm^3, respectively）, but the seasonal pattern was opposite for plcoeukaryotlc phytoplankton （4 500 and 3 200 cells/cm^3 In winter and summer, respectively）. Synechococcus, picoeukaryotes, and bacteria were most abundant in the nutrient-rich coastal zone and continental shelf, but Prochlorococcus was most abundant In the continental slope and open ocean. The vertical distribution of each photosynthetic group and heterotrophlc bacteria changed between the two seasons. Synechococcus populations with apparently different phycoerythrobilin content occurred at many stations In the summer. In addition, two different populations of Prochlorococcus were found： （i） small, weakly fluorescing cells in the surface layer; and （ii） larger, strongly fluorescent cells In the deep layer. The distribution pattern of photosynthetic plcoplankton and heterotrophlc bacteria depends on environmental effects and their ecophyslologlcal differences. The distribution of Synechococcus appeared to be related to nutrient availability, whereas the distribution of Prochlorococcus appeared to be limited by temperature. Synechococcus was the only plcophytoplankton with a consistent strong relationship with bacteria.