Picophytoplankton abundance and community structure in the Philippine Sea, western Pacific

Flow cytometric determinations of the abundance distribution and community structure of picophytoplankton (i.e., Prochlorococcus spp., orange fluorescence Synechococcus spp. and picoeukaryotes) were used for samples taken from the Philippine Sea in the western tropical Pacific Ocean from September to October of 2004. A fluorescence probe was employed to detect Chlorophyll a (Chl a). Abundances of Prochlorococcus spp., orange fluorescence Synechococcus spp. and picoeukaryotes ranged from 0.1 to 58×10³ cells ml^?1, 0.38 to 17×10² cells ml^?1 and 0.42 to 26×10² cells ml^?1, respectively. Synechococcus spp. and picoeukaryotes co-occurred in relatively shallow water with the maximum abundance observed at 50 to 70 m depth, while Prochlorococcus spp. only occurred in the 70 to 200 m layer. Prochlorococcus spp. was the dominant picophytoplankton population in terms of abundance and biomass. The cell size and carbon biomass content were estimated for the three picophytoplankton groups. In addition, among the three groups of picophytoplankton, the relative contribution of red fluorescence to the total red fluorescence varied with depth. The fluorescence and light scatter properties of individual cells indicated that in the upper 100 m layer, picoeukaryotes were a major contributor to total red fluorescence, while at the depth below 100 m, Prochlorococcus spp. and Synechococcus spp. made an important contribution to the total red fluorescence.     

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) ×103 and(1.1±1.4) ×103 cells m L-1, respectively. Prochlorococcus spp.(Pro) was only found in the high-salinity brackish water with the concentration of 3.0×103 cells m L-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.     

Hydrobiological variables as a regulatory factor on the abundance of heterotrophic flagellates in an urban pond

The seasonal abundance of flagellates has been monitored over a period of 1 year from December2013 to November 2014(divided into 4 conjugative seasons namely winter, spring, summer, and autumn) in an experimental pond located in Rajshahi City Corporation area, Bangladesh. To our knowledge, this study is the first to shed light on the occurrence and possible interrelationships among heterotrophic flagellates(HF),bacteria and zooplankton in Bangladesh and the result obtained by this study will be beneficial for similar water ecosystem all over the world. Standard methods were used to determine the prescribed hydrological parameters and zooplankton cell density. Maximum HF abundance(14 346.00 cells/mL) was found in the spring and the minimum(5 215.00 cells/mL) occurred in the summer. Inverse to HF, significantly(P0.05)higher zooplankton abundance was found during the winter(782.00±47.62 cells/mL) and the lowest value was found in the autumn(448.00±39.15 cells/mL). Whereas similar to the HF, total bacterial abundance was significantly higher during the spring((2.25±1.05)×10~5 cells/mL) and lower in the summer((0.79±0.06)×105 cells/mL). Multivariate analyses(ANOSIM and MDS) have shown significant seasonal differences for cell numbers where MDS ordination plot and cluster analysis based on similarity in the genera abundance of HF revealed overlapping condition between winter and spring. Canonical correspondence analysis(CCA) also showed a distinct separation among the genera based on the prevailing hydrological situation and indicated that temperature, pH, BOD_5, and NO_3~- were the most important environmental variables in determining the observed variation in HF community structure. Among the biological factors, zooplankton showed negative but total bacteria were positively correlated with HF abundance.     

Tidal effects on diel variations of picoplankton and viruses in the Changjiang estuary

Spatial distributions and seasonal variations of picoplankton (i.e. Synechococcus spp., Prochlorococcus spp., picoeukaryotes and heterotrophic bacteria) and viruses in the Changjiang estuary have been reported in the past. However, short-term variations (e.g. at a tidal timescale) of these organisms and their regulating factors remain unclear. We determined the time-series of fluctuations of picoplankton and viruses with tide simultaneously in flow cytometry in the Changjiang estuary during a cruise in June 2006, in which a tidal model based rectangle equation was applied. The results indicate that high cell abundances of picoplankton and viruses occurred during flood tide and low cell abundances during ebb tide. The period of the surface cell abundance variations was about 13 h, suggesting the surface cell abundances in the Changjiang estuary were largely regulated by tide. However, cell abundances in middle and bottom waters varied in different periods due to influences of tidal induced physical forces such as resuspension and stratification. Therefore, tidal action is an important factor for the diel variations of picoplankton and viruses in the Changjiang estuary.     

Heterotrophic bacterial flora in aquaculture area around Xuejiadao

From Oct., 1999 to Oct., 2000, the heterotrophic bacterial flora in the aquaculture area around Xuejiadao was investigated. The result shows that the populations of the heterotrophic bacteria are heavier in summer and autumn than those in winter and spring. The average populations in seawater, sediment, the surface of seaweed and the surface of fish are 1.4×10⁴cfu mL⁻¹, 5.4×10⁶cfu g⁻¹, 1.5×10⁶cfu g⁻¹ and 1.8×10³cfu cm⁻², respectively. A total of 301 strains were isolated, among them 259 were Gram-negative. All the Gram-negative bacteria belong to 13 genera and some genera of Enterobacteriaceae. The communities of bacteria are slightly different among the samples. In the body surface of fish, Genus vibrio is dominant. In the remaining samples, dominant genus is Aeromonas.     

Estimation of ecological water requirements based on habitat response to water level in Huanghe River Delta, China

In recent years,wetland ecological water requirements (EWRs) have been estimated by using hydrological and functional approaches,but those approaches have not yet been integrated for a whole ecosystem.This paper presents a new method for calculating wetland EWRs,which is based on the response of habitats to water level,and determines water level threshold through the functional integrity of habitats.Results show that in the Huanghe (Yellow) River Delta water levels between 5.0 m and 5.5 m are required to maintain the functional integrity of the wetland at a value higher than 0.7.One of the dominant plants in the delta,Phragmites australis,tolerates water level fluctuation of about ± 0.25 m without the change in wetland functional integrity.The minimum,optimum and maximum EWRs for the Huanghe River Delta are 9.42×106 m3,15.56×106 m3 and 24.12×106 m3 with water levels of 5.0 m,5.2 m and 5.5 m,corresponding to functional integrity indices of 0.70,0.84 and 0.72,respectively.A wetland restoration program has been performed,which aims to meet these EWRs in attempt to recover from losses of up to 98% in the delta's former wetland area.     

Simultaneous estimates ofsynechococcus spp. Growth and grazing mortality rates in the English Channel

The marine chroococooid phycoerythrin-containingSynechococcus spp. cyanobacterium has been implicated as a substantial component of the photosynthetic picoplankton in the ocean. Although its importance as food source for heterotrophic nanoplankton is now recognized, information about the cycling ofSynechococcus biomass and its diel pattern is limited and study methodology varies among authors. The selective metabolic inhibitor method was used to simultaneously estimate growth and grazing disappearance rates ofSynechococcus in the English Channel where growth rates ranged from 0.25 to 0.72/d (mean ±SD=0.51±0.17/d) and grazing mortality rates ranged from 0.19 to 0.64/d (mean ±SD=0.48±0.17/d). Size-fractionated experiments demonstrated that up to 70% ofSynechococcus disappearance could be attributed to grazers going through a 2 μm Nuclepore filter.Synechococcus grazing mortality rates (mean=0.74 ±0.25/d) during the day were always higher than that (mean=0.2±0.20/d) during the night, while growth rates showed no clear diel pattern. A positive correlation was observed between growth rates andin situ temperature ranging from 9 to 17°C, while in contrast grazing was independent of temperature. The close similatiry between average growth and grazing rates suggests a rapid recycling ofSynechococcus biomass in English Channel coastal waters.     

Distribution patterns of chlorophyll <Emphasis Type="Italic">a</Emphasis> in spring and autumn in association with hydrological features in the southern Yellow Sea and northern East China Sea

Two field studies were conducted to measure pigments in the Southern Yellow Sea (SYS) and the northern East China Sea (NECS) in April (spring) and September (autumn) to evaluate the distribution pattern of phytoplankton stock (Chl a concentration) and the impact of hydrological features such as water mass, mixing and tidal front on these patterns. The results indicated that the Chl a concentration was 2.43±2.64 (Mean ± SD) mg m^?3 in April (range, 0.35 to 17.02 mg m^?3) and 1.75±3.10 mg m^?3 in September (from 0.07 to 36.54 mg m^?3) in 2003. Additionally, four areas with higher Chl a concentrations were observed in the surface water in April, while two were observed in September, and these areas were located within or near the point at which different water masses converged (temperature front area). The distribution pattern of Chl a was generally consistent between onshore and offshore stations at different depths in April and September. Specifically, higher Chl a concentrations were observed along the coastal line in September, which consisted of a mixing area and a tidal front area, although the distributional pattern of Chl a concentrations varied along transects in April. The maximum Chl a concentration at each station was observed in the surface and subsurface layer (0–10 m) for onshore stations and the thermocline layer (10–30 m) for offshore stations in September, while the greatest concentrations were generally observed in surface and subsurface water (0–10 m) in April. The formation of the Chl a distributional pattern in the SYS and NECS and its relationship with possible influencing factors is also discussed. Although physical forces had a close relationship with Chl a distribution, more data are required to clearly and comprehensively elucidate the spatial pattern dynamics of Chl a in the SYS and NECS.     

Abundance and Biomass of Benthic Bacteria in Jiaozhou Bay, China

The abundance and biomass of benthic heterotrophic bacteria were investigated for the 4 typical sampling stations in the northern muddy part of Jiaozhou Bay, estuary of the Dagu River, raft culturing and nearby areas of Huangdao in March, June, August and December, 2002. The abundance and biomass range from 0.98×10⁷ to 16.87×10⁷ cells g⁻¹ sediment and 0.45 to 7.08 μg C g⁻¹ sediment, respectively. Correlation analysis showed that heterotrophic bacterial abundance and biomass are significantly correlated to water temperature (R=0.79 and 0.83, respectively,P<0.01).     

Temporal and spatial variations of abundance of phycocyanin- and phycoerythrin-rich <Emphasis Type="Italic">Synechococcus</Emphasis> in Pearl River Estuary and adjacent coastal area

Three surveys were carried out in Pearl River Estuary and adjacent coastal area in May, August, and November, 2013, to investigate the temporal and spatial variations of abundance of phycoerythrin-rich Synechococcus (PE-rich SYN) and phycocyanin-rich Synechococcus (PC-rich SYN). The effects of environmental factors on the alternation of the different Synechococcus groups were also elucidated. PE-rich SYN was detected in three surveys, whereas PC-rich SYN was detected in May and August, but not in November. The highest abundances of PE-rich SYN and PC-rich SYN were recorded in August and May, with mean values of 74.17×10³ and 189.92×10³ cells mL^?1, respectively. From May to November, the relative abundance of PE-rich SYN increased, whereas that of PC-rich SYN declined. PE-rich and PC-rich SYN presented similar horizontal distributions with high abundance in the southern estuary in May, and in the western estuary in August. The abundances of PE-rich and PC-rich SYN were high at 27–32°C and salinity of 10–20. PC-rich SYN was not detected at < 24°C, and PC:PE-rich SYN decreased in abundance with salinity increase. When less than 20 mg L^?1, suspended particulate matter (SPM) was helpful for Synechococcus growth. PE-rich SYN decreased in abundance when the concentration of dissolved inorganic nitrogen increased in May and November, and the concentration of phosphate increased in November. However, PC-rich SYN abundance and nutrients showed no correlation. Principal component analysis and regression analysis indicated that PE-rich SYN significantly correlated with the principal components that were affected by environmental factors.     

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 μm for Synechococcus and 0.85–1.08 μm for picoeukaryotes. The average integrated carbon biomasses ranged 15.26–312.62 mgC/m2 for Synechococcus, 18.54–61.57 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.     

Annual variations of biogenic element contents of manila clam (Ruditapes philippinarum) bottom-cultivated in Jiaozhou Bay,China

Manila clam(Ruditapes philippinarum) was monthly sampled from its benthic aquaculture area in Jiaozhou Bay from May 2009 to June 2010. The annual variations of major elemental composition, organic content, fatness and element ratio of Manila clam were examined. The element removal effect of clam farming in Jiaozhou Bay was analyzed based on natural mortality and clam harvest. The results indicated that the variation trend of carbon content in shell(Cshell) was similar to that in clam(Cclam). Such a variation was higher in summer and autumn than in other seasons, which ranged from 9.10 ± 0.13 to 10.38 ± 0.09 mmol g-1 and from 11.28 ± 0.29 to 12.36 ± 0.06 mmol g-1, respectively. Carbon content of flesh(Cflesh) showed an opposite variation trend to that of shell in most months, varying from 29.42 ± 0.05 to 33.64 ± 0.62 mmol g-1. Nitrogen content of shell(Nshell) and flesh(Nflesh) changed seasonally, which was relatively low in spring and summer. Nshell and Nflesh varied from 0.07 ± 0.009 to 0.14 ± 0.009 mmol g-1 and from 5.46 ± 0.12 to 7.39 ± 0.43 mmol g-1, respectively. Total nitrogen content of clam ranged from 0.50 ± 0.003 to 0.76 ± 0.10 mmol g-1 with a falling tend except for a high value in March 2010. Phosphorus content of clam(Nclam) fluctuated largely, while phosphorus content of shell(Pshell) was less varied than that of flesh(Pflesh). Pshell varied from 0.006 ± 0.001 to 0.016 ± 0.001 mmol g-1; while Pflesh fluctuated between 0.058 ± 0.017 and 0.293 ± 0.029 mmol g-1. Pclam ranged from 0.015 ± 0.002 to 0.041 ± 0.006 mmol g-1. Carbon and nitrogen content were slightly affected by shell length, width or height. Elemental contents were closely related to the reproduction cycle. The removal amounts of carbon, nitrogen and phosphorus from clam harvest and natural death in Jiaozhou Bay were 2.92×104 t, 1420 t and 145 t, respectively. The nutrient removal may aid to reduce the concentrations of nitrogen and phosphorus, the main causes of eutrophication, and to maintain the ecosystem health of Jiaozhou Bay.     

Effects of algal concentration and initial density on the population growth of Diaphanosoma celebensis Stingelin （Crustacea, Cladocera）

The effects of algal concentration and initial density on the population growth of the estuarine cladocera,Diaphanosoma celebensis Stingelin,were evaluated in an indoor experiment.A 2 × 4 layout that included two algal concentrations(Chlorella pyrenoidosa,1 × 106 and 3 × 106 cell/mL) and four inoculation densities(100,200,300 and 400 ind./L) were established.Diaphanosoma celebensis were reared in 150 mL flasks containing 50 mL of algal medium at 22°C,under salinity of 10 and a photoperiod of 12 h L:12 h D.T...     

Seasonal variations of net-phytoplankton community structure in the southern Yellow Sea

Based on the field survey data of four cruises in 2011, all phytoplankton communities in the southern Yellow Sea (SYS) were investigated for the species composition, dominant species, abundance and diversity indices. A total of 379 species belonging to 9 phyla were identified, of which the most abundant group was Bacillariophyta (60.9%), followed by Pyrrophyta (23.7%) and Haptophyta (6.9%). The seasonal distribution of abundance was: summer (4137.1×10³ ind m^?3) > spring (3940.4×10³ ind m^?3) > winter (3010.6×10³ ind m^?3) > autumn (340.8 ×10³ ind m^?3), while the horizontal distribution showed a decreasing tendency from inshore to offshore regions. The dominant species of phytoplankton varied in different seasons. The dominant species were Thalassiosira pacifica, Skeletoema spp. and Chaetoceros cinctus in spring, Chaetoceros debbilis, Chaetoceros pseudocurvisetus and Chaetoceros curvisetus in summer, Thalassiosira curviseriata, Alexandrium catenella and Ceratium fusus in autumn, Paralia sulcata, Phaeocystis sp. and Bacillaria paradoxa in winter, respectively. In SYS, the group of temperate coastal species was the major ecotype, and the groups of the central SYS species and oceanic species were also important constituents. The average values of Shannon-Weaver diversity index (H’) and Pielou evenness index (J) were 2.37 and 0.65 respectively. The indices H’ and J in the open sea were higher than those in coastal waters. Obvious co-variation tendencies between H’ and J were observed in all but the summer cruise of this survey.     

Heterotrophic bacterial floras in industrial area and unpolluted marine environments around Qingdao

From Oct. 1999 to Oct. 2000, the heterotrophic bacterial floras in the industrial marine environment around the Qingdao Power Plant (QPP) and in the unpolluted marine environments were investigated. The results showed that the numbers of the heterotrophic bacteria around QPP were much higher than those in unpolluted environments, and the average numbers in QPP Seawater, QPP Sediment, Unpolluted Seawater and Unpolluted Sediment were 5.4×10⁴cfu(mL)⁻¹, 5.0×10⁵cfug⁻¹, 3.0×10²cfu(mL)⁻¹ and 1.3×10⁵cfug⁻¹ respectively. Totally, 118 strains were isolated from QPP and 99 of them were Gram-negative. One hundred and twenty one strains were isolated from the unpolluted environments and 104 of them were Gram-negative. All the Gram-negative bacteria belonged to 13 genera. The distribution of the bacteria was varied in different marine environments. The results showed that the unpolluted marine environments contained much more Vibrio than seawater and sediment around QPP.     

Evaluation of potential productivity of woody energy crops on marginal land in China

Energy crops are a basic material in the bioenergy industry, and they can also mitigate carbon emissions and have environmental benefits when planted on marginal lands. The aim of this study was to evaluate the potential productivity of energy crops on marginal lands in China. A mechanistic model, combined with energy crop and land use characteristics, and meteorological and soil parameters, was used to simulate the potential productivity of energy crops. There were three main results. 1) The total marginal land in China was determined to be 104.78 × 10~6 ha. The 400-mm precipitation boundary line, which is the dividing line between the semi-humid and semi-arid zones in China, also divided the marginal land into shrub land and sparse forest land in the southeast and bare land, bare rock land, and saline alkali land in the northeast. 2) The total area of the marginal land suitable for planting energy crops was determined to be 55.82 × 10~6 ha, with Xanthoceras sorbifolia and Cerasus humilis mainly grown in the northern China, Jatropha curcas and Cornus wilsoniana mainly grown in the southwest and southeast, and Pistacia chinensis mainly grown in the central area, while also having a northeast-southwest zonal distribution. 3) Taking the highest yield in overlapping areas, the potential productivity of target energy crops was determined to be 32.63 × 10~6 t/yr. Without considering the overlapping areas, the potential productivity was 6.81 × 10~6 t/yr from X. sorbifolia, 8.86 × 10~6 t/yr from C. humilis, 7.18 × 10~6 t/yr from J. curcas, 9.55 × 10~6 t/yr from P. chinensis, and 7.78 × 10~6 t/yr from C. wilsoniana.     

Effect of Bacillus baekryungensis YD13 supplemented in diets on growth performance and immune response of sea cucumber (Apostichopus japonicus)

The effect of a potential probiotic on the growth performance and immune response of sea cucumber(Apostichopus japonicus) was investigated. Bacillus baekryungensis YD13 isolated from sea cucumber culturing ponds was added to sea cucumber basal feed as a probiotic in different doses(0, the control; 1×104(YD134), 1×106(YD136) and 1×108(YD138) CFU g-1 of diet), and administered orally to A. japonicus(initial mean wet weight 5.44 g ± 0.17 g). The sea cucumbers were fed in 20 aquaria, 5 each treatment, for 60 d. At the end of growth trial, 20 sea cucumbers from each treatment were challenged with Vibrio splendidus. A. japonicus in YD134 and YD136 exhibited significantly better growth performance than control(P 0.05). Five non-specific immune parameters including lysozyme, acid phosphatase, alkaline phosphatase, superoxide dismutase and catalase in coelomic fluid were measured to evaluate the immune response of A. japonicus to the probiotics. Results showed that all parameters were significantly improved when YD11 was supplemented in the dose of 1×106 CFU g-1(P 0.05). The cumulative incidence and mortality after the Vibrio splendidus challenge decreased significantly in sea cucumbers of YD136. Accordingly, 1×106 CFU g-1 of YD13 in diet was recommended for the growth promotion and immune enhancement of A. japonicus.     

Numerical Study of Water and Suspended Matter Exchange Between the Yellow Sea and the East China Sea

INTRODUCTIONTheYellowSeaandtheEastChinaSea (ECS)aremarginalseasofthenorthwestPacificandhaveexpansivecontinentalshelves .TheuniqueandstrikingfeaturesoftheYellowSeaandtheECSarethattheyhavestrongtidalcurrent;aresubjecttostrongmonsooninfluence ;andreceiveinflowfromthebiggestriverinChina ,theChangjiangRiver ;andthatthefamouswesternboundarycurrent,theKuroshio ,passesthroughtheECS ,withitsbranchesintrudingupwardintothecontinentalshelfareas.Generallyspeaking ,thewaterexchangecapacityofthe…     

THE DENSITIES OF CHANGJIANG ESTUARINE WATERS

The International Eq一lation of State of Seawater,1980 and the PraeticalSalinity Scale,1978 have been adoPted by theUNESCO江CES沼COR八APSOJoint Panel ono‘eanogral,hie Tables and Standards(JPOTS),and endorsed bythese organizati6ns(Miller‘〕and Poisson,1981;Uneseo,1981).Th已new equa-tion and the Praetieal Salinity Seale are to be used for all values Published fromJan .1,1982 .The new equation 15 aeeurate for use in all oeeanie surfaee waters,but eannot be aeeurately aPPlied to…