Simulation of coupled pelagic-benthic ecosystem of the Yellow Sea Cold Water Mass

A one-dimensional coupled pelagic-benthic box model for the Yellow Sea Cold Water Mass （YSCWM） is developed. The model is divided into three boxes vertically according to the depths of thermocline and euphotic layer. It simulates well the oligotrophic shelf ecosystem of the YSCWM considering effects of nutrients deposition and microbial loop. Main features of vertical structure of various variables in ecosystem of the YSCWM were captured and seasonal variability of the ecosystem was well reconstructed. Calculation shows that the contribution of microbial loop to the zooplankton can reach up to 60%. Besides, input of inorganic nutrients from atmospheric deposition is an important mechanism of production in upper layer of the YSCWM when stratified.     

Community composition,abundance and biomass of zooplankton in Zhangzi Island waters,Northern Yellow Sea

Samples were collected monthly from the sea area around Zhangzi Island,northern Yellow Sea,from July 2009 to June 2010.Vertical net towing was used to examine spatial and temporal variability in zooplankton abundance and biomass.Overall,C alanus sinicus and Saggita crassa were the dominant species found during the study period,while the amphipod T hemisto gracilipes was dominant in winter and spring.Vast numbers of the ctenophore species of the genus Beroe were found in October and November.It was not possible to count them,but they constituted a large portion of the total zooplankton biomass.Zooplankton species diversity was highest in October,and species evenness was highest in April.Zooplankton abundance(non-jellyfi sh)and biomass were highest in June and lowest in August,with annual averages of 131.3 ind./m3and 217.5 mg/m3,respectively.Water temperature may be responsible for the variations in zooplankton abundance and biomass.B eroe biomass was negatively correlated with other zooplankton abundance.Longterm investigations will be carried out to learn more about the infl uence of the environment on zooplankton assemblages.     

Spatial and Temporal Variations of Pelagic Copepods in the North Yellow Sea

This study aims to analyze the spatial and temporal variations of the abundance and biodiversity of pelagic copepods and their relationships with the environmental factors in the North Yellow Sea(NYS). These variations were analyzed on the basis of the survey data of the NYS in four seasons from 2006 to 2007. A total of 31 copepod species that belong to 17 genera, 13 families and 4 orders were identified in the four seasons. Of these copepods, the species belonging to Calanoida is the most abundant component. The dominant species include Calanus sinicus, Centropages abdominalis, Paracalanus parvus, Acartia bifilosa, Oithona plumifera, and Corycaeus affinis. C. sinicus is the most important and widely distributed dominant species in all of the seasons. The dominant species have not shown any significant variation for the past 50 years. However, the richness of warm-water species increased. The abundance of copepods significantly varied among different seasons: the average abundance was higher in spring(608.2 ind m~(-3)) and summer(385.1 ind m~(-3)) than in winter(186.5 ind m~(-3)) and autumn(128.0 ind m~(-3)). Factor analyses showed a high correlation between the spatial distributions of dominant copepods and environmental parameters, and Chl-a was the most important factor that influenced the distribution of copepods. This research can provide the fundamental information related to zooplankton, especially pelagic copepods. This research is also beneficial for the long-term monitoring of zooplankton ecology in the NYS.     

Seasonal dynamics of crustacean zooplankton community structure in Erhai Lake,a plateau lake,with reference to phytoplankton and environmental factors

The seasonal dynamics of a crustacean zooplankton community in Erhai Lake was investigated from May 2010 to April 2011. In total, 11 species were recorded, including six （6 genera） cladoceran and five （5 genera） copepod species. The crustacean zooplankton densities ranged from 24.3 to 155.4 ind./L. In winter and spring, the large-bodied cladoceran Daphnia galeata dominated the crustacean plankton community. In summer and autumn, when the colonial or filamentous algae dominated the phytoplankton communities, the small-bodied species （e.g. Bosminafatalis, Ceriodaphnia quadrangular, and Mesocyclops leuckarti） replaced the large-bodied ones. One-way ANOVA and redundancy analysis revealed that community structure was dependent upon total nitrogen, total phosphorus, water temperature, transparency, and the biomass of small algae. The variation in both phytoplankton structure and environmental variables were important factors in the seasonal succession of crustacean zooplankton structure in Erhai Lake.     

Long-term variability of the sharp thermocline in the Yellow and East China Seas

Based on observed temperature data since the 1950s, long-term variability of the summer sharp thermocline in the Yellow Sea Cold Water Mass (YSCWM) and East China Sea Cold Eddy (ECSCE) areas is examined. Relationships between the thermocline and atmospheric and oceanic forcing were investigated using multiyear wind, Kuroshio discharge and air temperature data. Results show that: 1) In the YSCWM area, thermocline strength shows about 4-year and 16-year period oscillations. There is high correlation between summer thermocline strength and local atmospheric temperature in summer and the previous winter; 2) In the ECSCE area, interannual oscillation of thermocline strength with about a 4-year period (stronger in El Ni o years) is strongly correlated with that of local wind stress. A transition from weak to strong thermocline during the mid 1970s is consistent with a 1976/1977 climate shift and Kuroshio volume transport; 3) Long-term changes of the thermocline in both regions are mainly determined by deep layer water, especially on the decadal timescale. However, surface water can modify the thermocline on an interannual timescale in the YSCWM area.     

DISTRIBUTION AND POPULATION DYNAMICS OF PARACALANUS PARVUS, PARACALANUS CRASSIROSTRIS, AND ACARTIA BIFILOSA (COPEPODA, CALANOIDA) IN THE BOHAI SEA

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Seasonal variations of several main water masses in the southern Yellow Sea and East China Sea in 2011

The seasonal variations of several main water masses in the southern Yellow Sea (SYS) and East China Sea (ECS) in 2011 were analyzed using the in-situ data collected on four cruises. There was something special in the observations for the Yellow Sea Warm Current (YSWC), the Yellow Sea Cold Water Mass (YSCWM) and the Changjiang Diluted Water (CDW) during that year. The YSWC was confirmed to be a seasonal current and its source was closely associated with the Kuroshio onshore intrusion and the northerly wind. It was also found that the YSCWM in the summer of 2011 occupied a more extensive area in comparison with the climatologically-mean case due to the abnormally powerful wind prevailing in the winter of 2010 and decaying gradually thereafter. Resulting from the reduced Changjiang River discharge, the CDW spreading toward the Cheju Island in the summer of 2011 was weaker than the long-term mean and was confined to flow southward in the other seasons. The other water masses seemed normal without noticeable anomalies in 2011. The Yellow Sea Coastal Current (YSCC) water, driven by the northerly wind, flowed southeastward as a whole except for its northeastward surface layer in summer. The Taiwan Warm Current (TWC) was the strongest in summer and the weakest in winter in its northward movement. The Kuroshio water with an enhanced onshore intrusion in autumn was stable in hydrographic features apart from the seasonal variation of its surface layer.     

Changes in the small-jellyfish community in recent decades in Jiaozhou Bay, China

We used long term monitoring data to evaluate changes in abundance and species dominance of small-jellyfish (collected with zooplankton net whose bell diameter was less than 5 cm) between 1991 and 2009 in the Jiaozhou Bay, China. Zooplankton samples were vertically towed with conical plankton net from near-bottom to surface, identified microscopically, and mapped in time-space using Grapher 7.0 and Surfer 8.0. Results show that the abundance of small-jellyfish throughout the bay had been increasing during 2001-2009 on average of 15.2 ind./m 3 , almost 5 times higher than that between 1991 and 2000. The occurrence of peak abundance shifted from spring to summer after 2000, and two peaks appeared in spring and summer, respectively, after 2005. Both the abundance and the frequency of blooms of small-jellyfish increased after 2000 in the bay. In addition, the biodiversity of jellyfish has increased significantly in recent years with a change in dominant species. Several new dominant species appeared after 2000, including Rathkae octopunctata in winter, Phialidium hemisphaericum in spring, summer, and autumn, Phialucium carolinae in spring, and Pleurobrachia globosa in summer and autumn, while some previous dominant species throughout the 1990s (Eirene ceylonensis, Zanclea costata, Lovenella assimilis, and Muggiaea atlantica) were no longer dominant after 2000. The abundance of small-jellyfish was positively correlated with the density of dinoflagellates, and the abundance of zooplankton. We believe that the changes in smalljellyfish abundance and species composition were the result of eutrophication, aquaculture and coastal construction activities around the bay. Concurrently, seawater warming and salinity decrease in recent decades promoted the growth and reproduction of small-jellyfish in the bay.     

Annual variation in Calanus sinicus abundance and population structure in the northern boundary area of the Yellow Sea Cold Water Mass

The Yellow Sea Cold Water Mass （YSCWM） was suggested as an over-summering site of the dominant copepod species Calanus sinicus in coastal Chinese seas. Population abundance and structure were investigated by monthly sampling along three transects across the northern boundary of the YSCWM during 2009-2010. Results show that thermal stratification existed from June to October and that the vertical thermal difference increased with depth. Generally, total abundance was lowest in October and highest in June, and the female/male sex ratio was highest in February and lowest in August. Evident spatial differences in abundance were observed during the existence of the YSCWM. In June, total abundance averaged 158.8 ind/m~ at well-stratified stations, and 532.1 ind/m3 at other stations. Similarly, high abundances of 322.0 and 324.4 ind/m3 were recorded from July to August inside the YSCWM, while the abundance decreased from 50.4 to 1.9 ind/m3 outside the water mass. C. sinicus distribution tended to even out over the study area in September when the YSCWM disappeared. We believe that the YSCWM may retard population recruitment in spring and preserve abundant cohorts in summer. The summer population was transported to neritic waters in autumn. In addition to low temperatures, stable vertical structure was also an essential condition for preservation of the summer population. C. sinicus can survive the summer in marginal areas in high abundance, but the population structure is completely different in terms of C5 proportion and sex ratio.     

Studies of community structure and seasonal dynamics of planktonic copepods in saline-alkaline ponds

Abstracts Species abundance and seasonal succession of copepods in saline-alkaline ponds were studied in Zhaodian Fish Farm, Gaoqing County, Shandong Province, from 5 April 1997 to 1 September 1998. The results indicated that in the conditions of salinity ranging from 1.36 to 20 g/L, total alkalinity changing from 2.4 to 7.2 mmol/L and pH 8-9, zooplankton in saline-alkaline ponds was composed of freshwater salt-tolerated species or halophile species, some of which are halobiont species and usually occurs in freshwater. In our study, copepods were predominant in many fish-culture ponds and all control ponds without fishes in spring, late autumn and early winter. Dominant species of copepods were Sinocalanus tenellus, Cyclops vicinus, Thermocyclops taihokuensis. The biomass of copepods in the control ponds without fishes was higher than that of the fish-culture ponds.     

The sensitivity of numerical simulation to vertical mixing parameterization schemes: a case study for the Yellow Sea Cold Water Mass

The vertical mixing parameterization scheme,by providing the effects of some explicitly missed physical processes and more importantly closing the energy budgets,is a critical model component and therefore imposes significant impacts on model performance.The Yellow Sea Cold Water Mass(YSCWM),as the most striking and unique phenomenon in the Yellow Sea during summer,is dramatically affected by vertical mixing process during its each stage and therefore seriously sensitive to the proper choice of parameterization scheme.In this paper,a hindcast of YSCWM in winter of 2006 was implemented by using the Regional Ocean Modeling System(ROMS).Three popular parameterization scheme s,including the level2.5 Mellor-Yamada clo sure(M-Y 2.5),Generic Length Scale clo sure(GL S) and K-Profile Parameterization(KPP),were tested and compared with each other by conducting a series of sensitivity model experiments.The influence of different parameterization scheme s on modeling the YSCWM was then carefully examined and assessed based on these model experiments.Although reasonable thermal structure and its seasonal variation were well reproduced by all schemes,considerable differences could still be found among all experiments.A warmer and spatially smaller simulation of YSCWM,with very strong the rmocline,appeared in M-Y 2.5 experiment,while a spatially larger YSCWM with shallow mixed layer was found in GLS and KPP schemes.Among all the experiments,the discrepancy,indicated by core temperature,appeared since spring,and grew gradually by the end of November.Additional experiments also confirmed that the increase of background diffusivity could effectively weaken the YSCWM,in either strength or coverage.Surface wave,another contributor in upper layer,was found responsible for the shrinkage of YSCWM coverage.The treatment of wave effect as an additional turbulence production term in progno stic equation was shown to be more superior to the strategy of directly increasing diffusivity for a coastal region.     

Seasonal variability of thermocline in the Yellow Sea

Based on the MASNUM wave-tide-circulation coupled numerical model, seasonal variability of thermocline in the Yellow Sea was simulated and compared with in-situ observations. Both simulated mixed layer depth (MLD) and thermocline intensity have similar spatial patterns to the observations. The simulated maximum MLD are 8 m and 22 m, while the corresponding observed values are 13 m and 27 m in July and October, respectively. The simulated thermocline intensity are 1.2℃/m and 0.5℃/m in July and October, respectively, which are 0.6℃/m less than those of the observations. It may be the main reason why the simulated thermocline is weaker than the observations that the model vertical resolution is less precise than that of the CTD data which is 1 m. Contours of both simulated and observed thermocline intensity present a circle in general. The wave-induced mixing plays a key role in the formation of the upper mixed layer in spring and summer. Tidal mixing enhances the thermocline intensity. Buoyancy-driven m     

Effects of Liaoning Hongyanhe Nuclear Power Plant on the Zooplankton Community in Summer of 2017

To evaluate the effects of the Hongyanhe Nuclear Power Plant on the zooplankton community in the surrounding seawater during summer, multiple environmental factors and zooplankton distribution along the east coast of Liaodong Bay were investigated in the summer of 2017. In particular, the influences of seawater temperature, salinity, and chlorophyll a(Chl a) on the zooplankton community were analyzed. Zooplankton abundances and Chl a concentrations along the east coast of Liaodong Bay showed an initial increase followed by a decrease from July to September. During the three months, the zooplankton abundance was the highest(8116.70 ind m~(-3)) in August. The Shannon-Wiener index showed a downtrend from July to September, with the average value falling from 1.65 in July to 1.50 in September. Calanus sinicus, Paracalanus parvus, copepodid, and bivalve larvae were the dominant species/groups in the three months. The effects of the nuclear power plant's outlet on the environment factors were mainly reflected in the increased seawater temperature. Redundancy analysis showed that the zooplankton community was jointly affected by seawater temperature, salinity and Chl a concentration, and the degree of this impact varied monthly. The impact of seawater temperature on the zooplankton community was stronger than that of salinity. The primary impact of the Hongyanhe Nuclear Power Plant on the structure and distribution of the zooplankton community in the surrounding seawater during the summer was increased seawater temperature, which caused a reduction in the abundance of dominant species/groups.     

SPECIES COMPOSITION, HORIZONTAL DISTRIBUTION AND SEASONAL SUCCESSION OF PHYTOPLANKTON IN THE CHANNEL FROM DONGTING LAKE TO THE CHANGJIANG RIVER, CHINA

The species composition, horizontal distribution and seasonal succession of the phyto-plankton at five sampling stations in the channel between Dongting Lake and the Changjiang River, China were studied from May 1995 to December 1997. A total of 416 taxa were observed; diatoms comprised the most diverse taxonomic group representing 58.2 % of the total species. The β-mezotrophic indicators were 92 taxa or 22 % of the total, the a-mezotrophic or α, β-eutrophic indicators decreased distinctly to 20 taxa or 4.8 % of the total. The species number and composition of various phyla were approximately similar at Stations 1, 2, 3 and 4, but at Station 5 the number of species was the minimum and the ratio of diatoms to total phytoplankton in the number of species was the highest. In seasonal succession of the phytoplank-ton species, the number was the highest in May and June, lower in December, January, March and July in the channel. The dominant species were different in different months. The ratio of diatoms species number to blue green algae and green algae species number diminished gradually from winter to summer and autumn, and then increased gradually from autumn to winter and early spring in the annual cycle. Margalef, Simpson and Shannon—Weaver diversity indices changed in different months, their values were higher in winter, lower in summer. Nygaard‘s diatoms quotients were lower in winter, then in spring and autumn, higher in summer. These results indicated that the water quality was the best in winter, better in spring and autumn than in summer. The relationship between the structure of the phytoplankton communi-ty and the water environmental quality was discussed.     

Variation of Zooplankton Ecological Group During Spring in China Estuaries

Zooplankton was major indicator species of the environment. To explore the effect of marine environment on zooplankton distribution in the coast of China, the zooplankton samples from stations in Guanhe Estuary(GE), Changjiang(Yangtze River) Estuary(CE), Oujiang Estuary(OE), Jiulongjiang Estuary(JE) and Beilun Estuary(BE)(covering 14 latitudes) in spring were surveyed and the variation of zooplankton ecological group was researched. According to the adaptability temperature, the zooplankton was divided into two ecological groups: warm-temperate species and subtropical species. The warm-temperate species was the main dominant species and subtropical species was only dominant species in BE. Calanus sinicus, a warm-temperate species, was the only dominant species in all five estuaries. From north to south, the proportion of warm-temperate species in the five estuaries gradually decreased depends on the number, were 83.33%, 48.39%, 45.00%, 43.75% and 30.43%, respectively. In contrary, the proportion of subtropical species was gradually increased. The warm-temperate species predominated over the total abundance and the percentage was whopping high in the north estuaries, including GE(96.16%), CE(95.57%), OE(97.83%) and JE(95.53%). The abundance percentage of subtropical species have remarkably higher(82.39%) in BE. Five estuaries zooplankton community was subdivided into three zooplankton groups, which were the northern warm temperate zooplankton group, the southern subtropical zooplankton group and the estuarine brackish-water group. The water temperature and coastal current of China Sea are recognized as the main factors determining the distribution and community structure of estuarine zooplankton in spring.     

Responses of Yellow Sea Cold Water Mass to Typhoon Bolaven

A two-month seabed-mounted observation(YSG1 area) was carried out in the western Yellow Sea Cold Water Mass(YSCWM) using an RDI-300 K acoustic Doppler current profiler(ADCP) placed at a water depth of 38 m in late summer, 2012. On August 2012, Typhoon Bolaven passed east of YSG1 with a maximum wind speed of 20 m s-1. The water depth, bottom temperature, and profile current velocities(including u, v and w components) were measured, and the results showed that the typhoon could induce horizontal current with speed greater than 70 cm s-1 in the water column, which is especially rare at below 20 meters above bottom(mab). The deepening velocity shear layer had an intense shear velocity of around 10 cm s-1 m-1, which indicated the deepening of the upper mixed layer. In the upper water column(above 20 mab), westward de-tide current with velocity greater than 30 cm s-1 was generated with the typhoon's onshore surge, and the direction of current movement shifted to become southward. In the lower water column, a possible pattern of eastward compensation current and delayed typhoon-driven current was demonstrated. During the typhoon, bottom temperature variation was changed into diurnal pattern because of the combined influence of typhoon and tidal current. The passage of Bolaven greatly intensified local sediment resuspension in the bottom layer. In addition, low-density particles constituted the suspended particulate matter(SPM) around 10 mab, which may be transported from the central South Yellow Sea by the typhoon. Overall, the intensive external force of the Typhoon Bolaven did not completely destroy the local thermocline, and most re-suspended sediments during the typhoon were restricted within the YSCWM.     

DISTRIBUTION AND POPULATION DYNAMICS OF PARACALANUS PARVUS,PRACALANUS CRASSIROSTRIS,AND ACARTIA BIFILOSA（COPEPODA,CALANOIDA）IN THE BOHAI SEA

Paracalanus parvus,Paracalanus crassirostris,and Acartia bifilosa are dominant and widely distributed in the Bohai Sea,and comprise an important part of zooplankton in terms of biomass as well as production rate.In order to understand their seasonal distribution and population dynamics,their stage-specific abundance in different months of the year were analyzed based on the never analyzed yet samples collected in 1959.The three species showed clear and remarkable seasonal variation in abundance,which maximized in spring and summer,when they formed high biomass patches or concentrations in the nearshore area.For Paracalanus parvus,two peaks were observed in the annual circle,one in June and the other in September,For Paracalanus crassirostris,one peak occurred in summer and a small one in December.The seasonal pattern of Acartia bifilosa was different in different regions.In Bohai Bay it had a two-peak pattern,with the first large peak occurring in May and the second one in October.In Laizhou Bay,a winter peak in December and January could be observed besides the spring one.The number of generations during the reproductive season for the three species was estimated based on the annual cycle in abundance and ambient temperature.     

Lipids and fatty acids in Calanus sinicus during over-summering in the southern Yellow Sea

Over-summering is a crucial period for Calanus sinicus in the southern Yellow Sea,where it is a key member of the zooplankton community.Lipids play an important role in copepod diapause,which is part of their over-summering strategy.We investigated how different fatty acids and lipid classes,including wax esters,changed during over-summering of C.sinicus during three cruises in June and August 2011 and November 2010,corresponding to the pre-,during and post-diapause periods,respectively.Large amounts of lipids were accumulated,mainly wax esters as previously found in C.finmarchicus during its diapause,and most of the storage lipids were used during over-summering.Wax ester polyunsaturated fatty acids(PUFAs) showed the most variation of the fatty acids(FAs),while the percentage composition of FAs in polar lipids was relatively stable.Selective use of wax ester PUFAs has already been shown to play important roles in the winter diapause of Calanus species in other regions,and our FA results show that this is the case for the Yellow Sea Cold Bottom Water(YSCBW) population that diapauses in summer.     

A model study on dynamical processes of phytoplankton in Laizhou Bay

A three-dimensional ecosystem model, using a PIC (Particle-In-Cell) method, is developed to reproduce the annual cycle and seasonal variation of nutrients and phytoplankton biomass in Laizhou Bay. Eight state variables, i.e., DIN (dissolved inorganic nitrogen), phosphate, DON (dissolved organic nitrogen), DOP (dissolved organic phosphorus), COD (chemical oxygen demand), chlorophyll-a (Chl-a), detritus and the zooplankton biomass, are included in the model. The model successfully reproduces the observed temporal and spatial variations of nutrients and Chl-a biomass distributions in the bay. The nutrient concentrations are at high level in winter and at low level in summer. Double-peak structure of the phytoplankton (PPT) biomass exists in Laizhou Bay, corresponding to a spring and an autumn bloom respectively. Several numerical experiments are carried out to examine the nutrient limitation, and the importance of the discharges of the Yellow River and Xiaoqinghe River. Both DIN limitation and phosphate limitation exist in some areas of the bay, with the former being more significant than the latter. The Yellow River and Xiaoqinghe River are the main pollution sources of nutrients in Laizhou Bay. During the flood season, the algal growth is inhibited in the bay with the Yellow River discharges being excluded in the experiment, while in spring, the algal growth is enhanced with the Xiaoqinghe River excluded.     

黄河入海口水域春季浮游动物群落特征研究

对2008、2009年黄河入海口水域春季浮游动物进行调查,采用香农-威纳多样性指数(Shannon-Weiner index)、Pielou均匀度指数和McNaugton优势度指数对其浮游动物群落特征进行分析。结果表明:浮游动物鉴定出6大类44种,以甲壳动物种类最多;2008年5月黄河入海口水域浮游动物多样性指数范围为0.92～2.65,均匀度变化范围为0.25～0.66;2009年5月浮游动物多样性指数范围为0.76～2.87,均匀度变化范围为0.21～0.70。黄河入海口水域浮游动物时空分布较不均匀,群落特征(包括丰度、多样性指数、均匀度和优势度等)在同一时期同一水域各采样点间差异较大,同一采样点不同年份差异显著。