Wave Characteristics at the South Part of the Radial Sand Ridges of the Southern Yellow Sea

Based on one-year wave field data measured at the south part of the radial sand ridges of the Southern Yellow Sea, the wave statistical characteristics, wave spectrum and wave group properties are analyzed. The results show that the significant wave height （H1/3） varies from 0.15 to 2.22 m with the average of 0.59 m and the mean wave period （Tmean） varies from 2.06 to 6.82 s with the average of 3.71 s. The percentage of single peak in the wave spectra is 88.6 during the measurement period, in which 36.3% of the waves are pure wind waves and the rest are young swells. The percentage with the significant wave height larger than 1 m is 12.4. The dominant wave directions in the study area are WNW, W, ESE, E and NW. The relationships among the characteristic wave heights, the characteristic wave periods, and the wave spectral parameters are identified. It is found that the tentative spectral model is suitable for the quantitative description of the wave spectrum in the study area, while the run lengths of the wave group estimated from the measured data are generally larger than those in other sea areas.

One century record of contamination by polycyclic aromatic hydrocarbons and polychlorinated biphenyls in core sediments from the southern Yellow Sea

Sixteen polycyclic aromatic hydrocarbons （PAHs） and 28 polychlorinated biphenyls （PCBs） were measured at a 2-cm interval in a core sample from the middle of the southern Yellow Sea for elucidating their historical variations in inflow and sources. The chronology was obtained using the ^210Pb method. PAHs concentrations decreased generally with depth and two climax values occurred in 14-16 cm and 20-22 cm layers, demonstrating that the production and usage of PAHs might reach peaks in the periods of 1956-1962 and 1938-1944. The booming economy and the navy battles of the Second World War might explain why the higher levels were detected in the two layers. The result of principal component analysis （PCA） revealed that PAHs were primarily owing to the combustion product. Down-cored variation of PCB concentrations was complex. Higher concentrations besides the two peaks being the same as PAHs were detected from 4 to 8 cm, depositing from 1980 to 1992, which probably resulted from the disposal of the out-dated PCB-containing equipment. The average Cl percentage of PCBs detected was similar to that of the mixture of Aroclor 1254 and 1242, suggesting they might origin from the dielectrical and heat-transfer fluid. The total organic carbon （TOC） content played a prevalent role in the adsorption of high molecular weight PAHs （≥ring）, while no obvious relationship among total PCBs, the concentration of congeners, and TOC was found.

Long-term nutrient variation trends and their potential impact on phytoplankton in the southern Yellow Sea,China

The concentration and composition of nutrients,such as N,P,and Si,respond to biogeochemical processes and in turn,impact the phytoplanktons'community structure and primary production.In this study,historical data was systematically analyzed to identify long-term variations in nutrient trends,red tide frequency,phytoplankton community abundance,and dominant species succession in the southern Yellow Sea(SYS).Results showed that N/P concentration ratios dramatically increased as a function of increasing dissolved inorganic nitrogen concentrations,and Si/N concentration ratios were generally larger than 1,indicating that N limitation morphed to P limitation and potentially to Si limitation,which impacted the phytoplankton community.Furthermore,inter-annual trends over the past 50 years show that phytoplankton community abundance has been higher in spring and summer,relative to autumn and winter.Moreover,with respect to red tide frequency,diatom abundance gradually decreased,while that of dinoflagellates gradually increased.Dominant species succession showed that the phytoplankton community exhibited an evident tendency to transform from diatoms to dinoflagellates.These research results clearly depict the presence of an important correlation between the phytoplankton community and nutrient structure in the SYS.

Phytoplankton communities and its controlling factors in summer and autumn in the southern Yellow Sea, China

The phytoplankton water samples were collected in two multidisciplinary investigations which were carried out during summer（June） and autumn（November to December） of 2011. Phytoplankton species composition and abundance data were accomplished by Uterm？hl method. The phytoplankton community was dominated by diatoms and dinoflagellates in the southern Yellow Sea（YS） in summer and autumn. In summer, Paralia sulcata and Prorocentrum dentatum were the predominated species, the cell abundance ranged from 0.074 to 107.733×103 cells/L with an average of 9.057×103 cells/L. Two phytoplankton high abundance appeared in northwest part of the survey area and the Changjiang River Estuary, respectively. In autumn, Par. sulcata became the predominant species, and the phytoplankton cell abundance ranged from 1.035×103 to 8.985×103 cells/L, the average was 3.263×103 cells/L. The phytoplankton abundance in surface layer presented the homogeneous distributions. Canonical Correspondence Analysis（CCA） method was applied for discovering the relationship between environmental factors and the common found phytoplankton species. The responses of phytoplankton to nutrients were varied between summer and autumn. The abundance of most predominant species, Par. sulcata was strongly correlated to temperature and salinity in autumn, but not the case in summer.

Influence of Sea Surface Temperature on Outbreak of Ulva prolifera in the Southern Yellow Sea,China

In this study,using Moderate Resolution Imaging Spectroradiometer(MODIS)satellite images and environmental satellite CCD images,the spatio-temporal distribution of Ulva prolifera in the southern Yellow Sea during the period of 2011–2018 was extracted and combined with MODIS Level3 Photosynthetically Active Radiation(PAR)product data and Earth System Research Laboratory(ESRL)Sea Surface Temperature(SST)data to analyze their influences on the growth and outbreak of Ulva prolifera.The following conclusions were drawn:1)comprehensive analysis of Ulva prolifera distribution during the eight-year period revealed that the coverage area of Ulva prolifera typically exhibited a gradually increasing trend.The coverage area of Ulva prolifera reached a maximum of approximately 1714.21 km^2 during the eight-year period in late June 2015.The area affected by Ulva prolifera fluctuated.In mid-July 2014,the area affected by Ulva prolifera reached a maximum of approximately 39020.63 km^2.2)The average growth rate of Ulva prolifera was positive in May and June but negative in July.During the outbreak of Ulva prolifera,the SST in the southern Yellow Sea tended to increase each month.The SST anomaly and average growth rate of Ulva prolifera were positively correlated in May(R^2=0.62),but not significantly correlated in June or July.3)The variation trends of PAR and SST were approximately the same,and the PAR during this time period maintained a range of 40–50 mol/(m^2·d),providing sufficient illumination for the growth and outbreak of Ulva prolifera.In addition,the abundant nutrients and suitable temperature in the sea area near northern Jiangsu shoal resulted in a high growth rate of Ulva prolifera in May.In summary,the outbreak of Ulva prolifera was closely related to the environmental factors including SST,nutrients,and PAR.Sufficient nutrients and suitable temperatures resulted in a fast growth rate of Ulva prolifera.However,under poor nutrient conditions,even more suitable temperatures were not sufficient to trigger an outbreak of Ulva prolifera.

Distribution of phytoplankton in the East China Sea and the southern Yellow Sea in spring in relation to environmental variables and dimethylsulfide compounds

The coastal ecosystems are highly sensitive to climate change and are usually influenced by variations in phytoplankton communities and water physiochemical factors.In the present study,the phytoplankton community,chlorophyll a(Chl a)and their relationships with environmental variables and dimethylsulfide(DMS)and dimethylsulfoniopropionate(DMSP)were investigated in spring 2017(March 24 to April 16)in the East China Sea(26.0°-33.0°N,120.0°-128.0°E)and southern Yellow Sea(31.0°-36.0°N,120.0°-125.0°E).The spatial distributions of phytoplankton species composition and cell density were investigated by qualitative and quantitative methods and were compared with historical data to study phytoplankton species succession in the survey area.The results showed that there were 275 phytoplankton species belonging to 90 genera and 6 phyla in the survey area,of which 208 species belonged to 62 genera of Bacillariophyta and 56 species belonged to 20 genera of Pyrrophyta.The dominant phytoplankton species were Skeletonema dohrnii,Chaetoceros vanheurckii and Prorocentrum donghaiense.The phytoplankton cell densities ranged from 0.06×10^(4)cells/L to 418.73×10^(4)cells/L,with an average value of 21.46×10^(4)cells/L.In spring,the average ratio of Bacillariophyta/Pyrrophyta was41.13 for the entire study area.The areas with high phytoplankton cell density were mainly distributed in the northern South Yellow Sea and offshore waters of the East China Sea.According to a canonical correspondence analysis among phytoplankton and environmental parameters,the water Chl a concentrations were notably consistent with phytoplankton cell density(P<0.001),and both showed significant negative correlations with salinity and nitrite(P<0.05)and significant positive correlations with dissolved oxygen and pH(P<0.001).There was a significant positive correlation between diatom(both in cell density and in dominant species)and DMS(P<0.05),which indicated that diatoms play a greater role in DMS production in this investigated area.

Combining otolith elemental signatures with multivariate analytical models to verify the migratory pattern of Japanese Spanish mackerel(Scomberomorus niphonius) in the southern Yellow Sea

Japanese Spanish mackerel,Scomberomorus niphonius,is a commercially important,highly migratory species that is widely distributed throughout the northwestern Pacific region.However,its life history and migratory patterns are only partially understood.This study used otolith chemistry to investigate the migratory pattern of S.niphonius in the southern Yellow Sea,an important fishing ground.Transverse sections of otoliths from 15 age-1 spawning or spent individuals,comprising up to one complete migration cycle,were analyzed from the core to the margin by using laser ablation inductively coupled plasma mass spectrometry.The ratios of the element to Ca were integrated with microstructural analysis to produce age-related elemental profiles.Combining multielemental analysis of otolith composition with multivariate analytical models,we quantified structural changes in otolith chemistry profiles.Results revealed there were diverse changing patterns of otolith chemistry profiles for detected elements and the elements of Na,Mg,Sr and Ba were important for the chronological signal.Five clusters were identified through chronological clustering,representing the five life stages from the early stage to the spawning stage.Variation of Ba:Ca ratio was most informative,showing a step-decreasing pattern in the first four stages and a rebound in the spawning stage.These results support the hypothesized migratory pattern of S.niphonius:hatching and spending their early life in the coastal sandy ridges system of the southern Yellow Sea,migrating northeastward and offshore for feeding during juvenile stage,aggregating in early October and migrating outward to the Jeju Island for wintering,and returning to the coastal waters for spawning.This study demonstrated the value of life-history related otolith chemistry profiles combined with multivariate analytical models was a means to verify the migration patterns of S.niphonius at regional scales with potential application in fisheries assessment and management.

Temporal variations of dimethylsulfide and dimethylsulfoniopropionate in the southern Yellow Sea in spring and autumn

Temporal distributions of dimethylsulfide（DMS） and dimethylsulfoniopropionate（DMSP） were studied in the southern Yellow Sea（SYS） during April and September 2010. The mean concentrations（range） of DMS, dissolved and particulate DMSP（DMSPd and DMSPp） in the surface waters in spring are 1.69（0.48–4.92）, 3.18（0.68–6.75）and 15.81（2.82–52.33） nmol/L, respectively, and those in autumn are 2.80（1.33–5.10）, 5.45（2.19–11.30） and 30.63（6.24–137.87） nmol/L. On the whole, the distributions of DMS and DMSP in spring are completely different from those in autumn. In the central part of the SYS, the concentrations of DMS and DMSP in spring are obviously higher than those in autumn, but the opposite situation is found on the south of 34°N, which can be attributed to the differences in nutrients and phytoplankton biomass and composition between spring and autumn. Besides,the seasonal variations of water column stability and the Changjiang diluted water also have significant impact on the distributions of DMS and DMSP in spring and autumn on the south of 34°N. DMS and DMSPp concentrations coincide well with chlorophyll a（Chl a） levels in the spring cruise, suggesting that phytoplankton biomass may play an important role in controlling the distributions of DMS and DMSPp in the study area. Annual DMS emission rates range from 0.015 to 0.033 Tg/a（calculated by S）, respectively, using the equations of Liss and Merlivat（1986） and Wanninkhof（1992）. This result implies a significant relative contribution of the SYS to the global oceanic DMS fluxes.

Distributions and sea-to-air fluxes of volatile halocarbons in the southern Yellow Sea and the East China Sea

Distributions and sea-to-air fluxes of five kinds of volatile halocarbons（VHCs） were studied in the southern Yellow Sea（SYS） and the East China Sea（ECS） in November 2007. The results showed that the concentrations of 1,1,1-trichloroethane（C2H3Cl3）, 1,1-dichloroethene（C2H2Cl2）, 1,1,2-trichloroethene（C2HCl3）, trichloromethane（CHCl3） and tetrachloromethane（CCl4） in the surface water were 0.31–4.81, 2.75–21.3, 1.21–17.1, 5.02–233 and 0.045–4.47 pmol/L, respectively, with the average values of 1.89, 12.20, 6.93, 60.90 and 0.33 pmol/L. On the whole, the horizontal distributions of C2H3Cl3, C2H2Cl2 and CCl4 were affected mainly by anthropogenic activities, while C2HCl3 and CHCl3 were influenced by biological factors as well as anthropogenic activities. In the study area, the concentrations of VHCs（except C2HCl3） exhibited a decreasing trend from inshore to offshore sites, with the higher values occurring in the coastal waters. The sea-to-air fluxes of C2H3Cl3, C2HCl3, CHCl3 and CCl4 were calculated to be-56.00–（-5.68）,-7.31–123.42, 148.00–1 309.31 and-83.32–（-1.53） nmol/（m2·d）, respectively, with the average values of-6.77, 17.14, 183.38 and-21.27 nmol/（m2·d）. Our data showed that the SYS and ECS in autumn was a sink for C2H3Cl3 and CCl4, while it was a source for C2HCl3 and CHCl3 in the atmosphere.

Differences in planktonic ciliate spatial distribution in spring and autumn in the southern Yellow Sea

Seasonal variation of marine plankton spatial distribution is important in understanding the biological processes in the ocean.In this study,we studied spatial distribution of planktonic ciliate abundance and biomass in the central deep area（station depth greater than 60 m） and the coastal shallow area（station depth less than 60 m） of the southern Yellow Sea（32°–36.5°N,121°–125°E） in spring（April） and autumn（October–November） of 2006.Our results showed that both ciliate abundance and biomass in the surface waters were higher in spring（（1 490±2 336）ind./L;（4.11±7.81） μg/L） than in autumn（（972±823） ind./L;（1.11±1.18） μg/L,calculated by carbon）.Ciliate abundance and biomass in the surface waters of the coastal shallow area were similar in spring and autumn.However,in the central deep area,those values were much higher in spring（（1 878±2 893） ind./L;（5.99±10.10）μg/L） than in autumn（（738±373） ind./L;（0.74±0.76） μg/L）.High values of ciliate abundance and biomass occurred in the central deep area in spring and in the coastal shallow area in autumn.Mixotrophic ciliate Laboea strobila was abundant in the central deep area in spring,when a phytoplankton bloom occurred.However,in autumn,L.strobila was abundant in the coastal shallow area.Boreal tintinnid Ptychocyli obtusa was found in spring.Both L.strobila and P.obtusa were concentrated in the surface waters when their abundance was more than 1 000 ind./L.Peaks of these species were in the subsurface waters when their abundance was less than 400 ind./L.This study showed that both high abundance and biomass of ciliates occurred in different areas in southern Yellow Sea seasonally.

Increased diversity and environmental threat of harmful algal blooms in the Southern Yellow Sea,China

Harmful algal blooms(HABs)in the Southern Yellow Sea(SYS)have shown a trend of increasing diversity and detrimental ef fects.While the Bohai Sea,East China Sea,and South China Sea have experienced a high incidence of HABs since the 1980s,the Yellow Sea provides a relatively healthy ecological environment in which fewer HABs have been documented before the 21s t century.Yet largescale blooms of the green macroalga Ulva prolifera(so-called“green tides”)have occurred annually since 2007 in the Yellow Sea.Six people were poisoned and one person died in Lianyungang in 2008 due to ingestion of algal toxins.Moreover,the Yellow Sea experienced co-occurrence of harmful red tides,green tides,and golden tides in 2017.This combination of events,rare worldwide,indicates the potential for further deterioration of the marine environment in the Yellow Sea,which may be related to climate change,aquaculture,and other human activities.Using the SYS as an example,we collected data of the frequency and scale of HABs over the years,as well as that of marine algal toxins,and analyzed the trend in the diversity of HABs in the SYS,to explore the causes and impacts of HABs,as well as the interrelationships among dif ferent types of HABs,including harmful red tides,green tides,and golden tides.We also attempted to improve our understanding of HAB evolution under the influence of global climate change and intensified human activities.

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 to9 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 (4137.1×103ind m 3) >spring (3940.4×103ind m 3) >winter (3010.6×103ind m 3) >autumn (340.8×103ind 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.

Phase Evolution of Holocene Paleoenvironmental Changes in the Southern Yellow Sea: Benthic Foraminiferal Evidence from Core CO2

Assemblages of benthic foraminifera in a sediment core(C02)near the western margin of the southern Yellow Sea Mud were studied to decipher the phase evolution of Holocene paleoenvironmental changes associated with the Holocene marine transgression.It appears that during the early Holocene(11.2 10.1 kyr BP),the faunal was dominated by low salinity and shallow water species Cribrononion subincertum,Buccella frigida and Ammonia beccarii,reflecting a near coast depositional environment.A rapid increase of the relative abundance of Ammonia compressiuscula between 10.1 9.3 kyr BP indicates that the sea level rose rapidly during that time period.From 9.3 7.7 kyr BP,the benthic foraminiferal assemblage was dominated by high percentage of A.compressiscula,suggesting that the sea level was relatively stable.An obvious transition of benthic foraminifera,from the A.compressiuscula-dominated assemblage to an Ammonia ketienziensis-dominated assemblage,occurred between 7.7 6.2 kyr BP,possibly corresponding to a second sea level rapid rise period in the Yellow Sea during the Holocene.This transition may correspond to the gradually strengthened Yellow Sea warm current(YSWC)and finally is established the modern-type circulation in the Yellow Sea.It may also mark the formation of the Yellow Sea cold bottom water(YSCBW)during that period.Since then,the benthic foraminiferal assemblage based on core C02 was dominated by typical YSCBW species,A.ketienziensis,Astrononion italicum and Hanzawaia nipponica,at 6.2 4 kyr BP.A non-deposition period occurred since 4 kyr BP,which possibly related to the hydrology changes caused by the East Asia monsoon.The two obvious benthic foraminiferal transitions recorded in core C02 during the early and middle Holocene provide evidence that the Yellow Sea has undergone a two-phase rapid sea level rise during the Holocene marine transgression.

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.

Seasonal variation in abundance, diel vertical migration and body size of pelagic tunicate Salpa fusiformis in the Southern Yellow Sea

Mass occurrence of Salpa fusiformis was observed in the Southern Yellow Sea in May and June 2007. In order to investigate its population recruitment and environmental adaptation, temporal variation of abundance, diel vertical migration (DVM) and length frequency distribution of both aggregate and solitary forms were studied with samples collected from eight months during September 2006 to August 2007. S. fusiformis presented in six months other than September and October 2006, and average abundance of aggregate and solitary forms peaked in June and May, respectively. In December, aggregate forms were absent in the bottom layer and performed irregular DVM from surface to 50 m depth, while solitary forms was too scarce to perform diel vertical distribution analysis. Both aggregate and solitary forms presented reverse DVM in May and June. They migrated upwards during daytime and concentrated in surface layer at sunset. The bimodal distribution of aggregate forms was found in April and the average size was largest in this month. In other months, the smaller aggregate forms (1-5 mm) dominated in populations except for May, when the modal size ranged from 2 to 8 mm. The average size of solitary forms was largest in December, followed by April. The skewed nomal distribution of solitary forms was found in May and June, with the modal size of 2-7 mm and 5-13 mm, respectively.

Tidal current observation in the southern Yellow Sea in the summers of 2001 and 2003

Direct current observations in the Yellow Sea interior are very scarce due to intense fishing and trawling activities. Most previous studies on tides in the area were based on coastal measurements or satellite altimeter sea levels and have not been rigorously compared with direct measurements. In this paper, tidal currents are studied with current profiles from three bottom-moored Sontek Acoustic Doppler Profilers (ADPs) deployed in the southern Yellow Sea in summer of 2001 and 2003. The measured current series were dominated by tidal currents. Maximum velocities are between 40–80 cm/s at the mooring stations. M2 current is the most dominant primary tidal constituent, while MS4 and M4 are the most significant shallow water tides with much smaller amplitudes than the primary tides.

Observation of Currents in the Southern Yellow Sea in the Summers of 2001 and 2003

Long term current observations in the southern Yellow Sea are very scarce because of the intense fishing and trawling activities. Most of the previous studies on tides and circulation were not rigorously validated with direct current measurements. In this study, tidal and sub-tidal currents were examined using current profiles from three bottom-moored Sontek Acoustic Doppler Profilers (ADPs) deployed in the southern Yellow Sea in the summers of 2001 and 2003. The measured current time series were dominated by tidal currents. The maximum velocities were between 40–80 cm s-1 at the mooring stations. The M2 current was the dominant primary tidal constituent, while the MS4 and M4 components produced the most significant shallow water tidal currents with much weaker amplitudes. The measured mean sub-tidal velocities were less than 5 cm s-1. The mean flows in the lower layer implied that an anti-cyclonic circulation pattern might exist in the deeper central Yellow Sea. However, the previously expected cyclonic circulation pattern in the upper layer was not clearly shown by the observations.

Trophic interactions, ecosystem structure and function in the southern Yellow Sea

The southern Yellow Sea is an important fishing ground, providing abundant fishery resources. However, overfishing and climate change have caused a decline in the resource and damaged the ecosystem. We developed an ecosystem model to analyze the trophic interactions and ecosystem structure and function to guide sustainable development of the ecosystem. A trophic mass-balance model of the southern Yellow Sea during 2000-2001 was constructed using Ecopath with Ecosim software. We defined 22 important functional groups and studied their diet composition. The trophic levels of fish, shrimp, crabs, and cephalopods were between 2.78 and 4.39, and the mean trophic level of the fisheries was 3.24. The trophic flows within the food web occurred primarily in the lower trophic levels. The mean trophic transfer efficiency was 8.1%, of which 7.1% was from primary producers and 9.3% was from detritus within the ecosystem. The transfer efficiency between trophic levels II to III to IV to V to >V was 5.0%, 5.7%, 18.5%, and 19.7%-20.4%, respectively. Of the total flow, phytoplankton contributed 61% and detritus contributed 39%. Fishing is defined as a top predator within the ecosystem, and has a negative impact on most commercial species. Moreover, the ecosystem had a high gross efficiency of the fishery and a high value of primary production required to sustain the fishery. Together, our data suggest there is high fishing pressure in the southern Yellow Sea. Based on analysis of Odum's ecological parameters, this ecosystem was at an immature stage. Our results provide some insights into the structure and development of this ecosystem.

Distribution of Sediment Chloroplastic Pigments in the Southern Yellow Sea,China

The distribution of sediment chloroplastic pigments (Chl-a, i.e. chlorophyll a and Pha-a, i.e. phaeophorbide a)in the Southern Yellow Sea of China was studied. Samples were collected from four cruises in January and June 2003, and January and June 2004. The results show that the vertical distribution of Chl-a and Pha-a in the sediment layers 0-2cm, 2-5 cm and 5-8 cm, follows a stable ratio, 5:3:2. The average ratio of Pha-a to Chl-a in sediment is 2.83. Spearman 2-tailed rank correlation analysis shows that Chl-a and Pha-a contents in each sediment layer have a highly significant correlation.The average contents of Chl-a and Pha-a in the sediment of the 0-8cm layer in the investigated area are 0.31-0.47μgg-1 and 1.28-1.40 μgg-1 sediment (dry weight), respectively. The average Chl-a and Pha-a contents in sediment are higher in summer than in winter. ANOVA analysis shows that there is a highly significant variation among the Chl-a contents (P = 0.002＜ 0.01) of the four cruies, but this is not true for the case of Pha-a content (P = 0.766 ＞0.05). The average Chl-a and Phaa contents in the 2 sediment layers (0-2cm and 2-5cm) have significant or highly significant correlations with organic matter (OM), median diameter (Mdφ), silt plus clay percentage in the January 2003 cruise. In the June 2003 cruise, the average Chl-a content in the 3 sediment layers (0-2 cm, 2-5 cm, and 5-8 cm) has a significant correlation with meiofauna biomass,and Pha-a content has highly significant correlations with water depth, bottom water temperature, OM and MdC. The contents of Chl-a and Pha-a are lower than those in estuaries and intertidal areas, but close to those in the same area studied previously.

Grain-size related nitrogen distribution in southern Yellow Sea surface sediments

Forty-eight surface sediments of the southern Yellow Sea are separated into three grain-size frac- tions. Four forms of extractable nitrogen (nitrogen in ion-exchangeable form (Nie), nitrogen in weak-acid ex- tractable form (Nwa), nitrogen in strong-alkali extractable form (Nsa) and nitrogen in strong-oxidant form (Nso)) are obtained by the sequential extraction. The results show that the contents and the distributions of the extract- able nitrogen in the southern Yellow Sea surface sediments are closely related to sediment grain size. The distri- butions of Nie, Nso and total nitrogen (TN) present positive correlations with fine particles content, while Nwa and Nsa does not have such correlation. The net contents of all the forms of nitrogen increase with sediment grain size finer.