Compositional characteristics of sediment from Jiaozhou Bay in North China and the implication to the provenance

Rare earth elements(REEs)can be used to trace source materials and identify their provenances,because of significant conservation and immobility during chemical alteration processes after erosion of materials from the provenance.This study focused on the temporal variation of REEs for columnar sediments from the mouth of Jiaozhou Bay in North China to understand the potential controls for the geochemical variations of sediments.Through extraction experiments,we identified that the residual fraction is the main host for REEs compared with other fractions(i.e.,exchangeable and carbonate fraction,easily reducible oxides fraction,reducible oxides fraction,magnetite fraction).REE ratios(e.g.,La_(N)/Sm_(N)and La_(N)/Yb_(N);N:normalized by chondrite)lack correlations with grain size or the chemical index of alteration(CIA),which is correlated with major elements.All these indicate that these REE variations reflect the varying contribution of source materials from different provenances instead of grain size or chemical weathering effects.REE ratios(e.g.,La_(N)/Sm_(N)and La_(N)/Yb_(N))remain relatively constant until the depth of roughly 40 cm(equivalent to the year 1995),and show obvious changes beyond this depth.Compared REE characteristics of Jiaozhou Bay with those of neighboring rivers and bedrocks,the relative contributions of Dagu River-Jiaolai River,and Licun River may have been increased during the sedimentary processes,which could be caused by the construction of reservoir and related change of aquaculture(e.g.,rapid accumulation of organic materials).

Establishing environmental background values of selected trace elements and environmental quality assessment of fi negrained sediments in the Jiaozhou Bay catchment,China

With the development of economy,the impact of human activities on ecological environment is increasing,and environmental protection work is important.Trace elements(Co,Ni,Cu,Pb,Zn,Cd,Cr,and Sc)in surface fi ne-grained sediment samples from the Jiaozhou Bay catchment were selected to evaluate their 2015 environmental background values and the environmental quality.Using statistical analysis,the environmental background values(ranges)of Sc,Co,Ni,Cu,Pb,Zn,Cd,and Cr were calculated,being 13.1(10.8-15.4),12.4(8.6-16.2),32.0(22.9-41.2),29.6(13.5-64.9),24.1(13.0-44.6),77.6(38.5-156.5),0.07(0.02-0.20),and 82.5(66.5-104.0)mg/kg,respectively.The enrichment factor,contamination factor,and pollution load index were used to evaluate the pollution status of the Jiaozhou Bay catchment.The environmental background values of most elements are higher than those of the upper continental crust and lower than those of global shale.At present,the pollution in the eastern Jiaozhou Bay is much higher than that in the western part.The results shall be helpful for future management for trace element pollution monitoring in the Jiaozhou Bay catchment.

The effects of spring-neap tide on the phytoplankton community development in the Jiaozhou Bay, China

The development of the phytoplankton community was studied in the Jiaozhou Bay during the spring to neap tide in August2001, through three cruises and a 15 d continuous observation. This investigation indicates that diatom cell abundance increasedsharply following the end of a spring tide, from 9 cells/cm3 to a peak of 94 cells/cm3. The dominant species composition andabundance show a quick species sequence from spring to neap tide, and the dominant species at the start phase is Skeletomenacostatum, then changes to Chaetoceros curvisetus, finally it changes to Eucampia zodiacus. Silicate concentration increasesduring spring tide, as a result of nutrient replenishment from the watersediment interface, its initial average concentration inneap tide is 1.39 mmol/dm3 and reached the peak average concentration of 8.40 mmol/dm3 in spring tide. But the nitrogenconcentration dropped due to dilution by the low nitrogen seawater from the Huanghai Sea, its initial average concentration inneap tide is 67 mmol/dm3 and decreased to the average concentration of 54 mmol/dm3 in spring tide. The degree of siliconlimitation was decreased and phytoplankton, especially diatoms, responds immediately after nutrient replenishment in thewater column. Skeletonmea costatum, as one of the dominant species in the Jiaozhou Bay, shows a quicker response tonutrient availability than Eucampia zodiacus and Chaetoceros curvisetus. It is proposed that dominant species compositionand water column stability synchronously determine the development of phytoplankton summer blooms in the Jiaozhou bay.

Studies on growth rate and grazing mortality rate by microzooplankton of size-fractionated phytoplankton in spring and summer in the Jiaozhou Bay,China

Dilution experiments were performed to examine the growth rate and grazing mortality rate of size-fractionated phytoplankton at three typical stations, inside and outside the bay, in the spring and summer of 2003 in the Jiaozhou Bay, China. In spring, the phytoplankton community structure was similar among the three stations, and was mainly composed of nanophytoplankton, such as, Skeletonema costatum and Cylindrotheca closterium. The structure became significantly different for the three stations in summer, when the dominant species at Stas A, B and C were Chaetoceros curvisetus, Pseudo-nitzschia delicatissima, C. affinis, C. debilis, Coscinodiscus oculus-iridis and Paralia sulcata respectively. Tintinnopsis beroidea and T. tsingtaoensis were the dominant species in spring, whereas the microzooplankton was apparently dominated by Strombidium sp. in summer. Pico- and nanophytoplankton had a relatively greater growth rate than microzooplankton both in spring and summer. The growth rate and grazing mortality rate were 0.18~0.44 and 0.12~1.47 d-1 for the total phytoplankton and 0.20~0.55 and 0.21~0.37 d-1 for nanophytoplankton in spring respectively. In summer, the growth rate and grazing mortality rate were 0.38~0.71 and 0.27~0.60 d-1 for the total phytoplankton and 0.11~1.18 and 0.41~0.72 d-1 for nano- and microphytoplankton respectively. The carbon flux consumed by microzooplankton per day was 7.68~39.81 mg/m3 in spring and 12.03~138.22 mg/m3 in summer respectively. Microzooplankton ingested 17.56%~92.19% of the phytoplankton standing stocks and 31.77%~467.88% of the potential primary productivity in spring; in contrast, they ingested 34.60%~83.04% of the phytoplankton standing stocks and 71.28%~98.80% of the potential primary productivity in summer. Pico- and nanophytoplankton appeared to have relatively greater rates of growth and grazing mortality than microphytoplankton during the experimental period. The grazing rate of microzooplankton in summer was a little bit greater than that in spring because of the relatively higher incubation temperature and different dominant microzooplankton species. Microzooplankton preferred ingesting nanophytoplankton to microphytoplankton in spring, while they preferred ingesting picophytoplankton to nanophytoplankton and microphytoplankton in summer. Compared with the results of dilution experiments performed in various waters worldwide, the results are in the middle range.

Organic carbon source and burial during the past one hundred years in Jiaozhou Bay,North China

Organic carbon （OC）, total nitrogen （TN）, and ^210Pb in core sediment were measured to quantify the burial of organic carbon and the relative importance of allochthonous and autochthonous contributions during the past one hundred years in Jiaozhou Bay, North China. The core sediment was dated using ^210Pb chronology, which is the most promising method for estimation of sedimentation rate on a time scale of 100-150 years. The variation of the burial flux of organic carbon in the past one hundred years can be divided into the following three stages： （1） relatively steady before 1980s; （2） increasing rapidly from the 1980s to a peak in the 1990s, and （3） decreasing from the 1990s to the present. The change is consistent with the amount of solid waste and sewage emptied into the bay. The OC：TN ratio was used to evaluate the source of organic carbon in the Jiaozhou Bay sediment. In the inner bay and bay mouth, the organic carbon was the main contributor from terrestrial sources, whereas only about half of organic carbon was contributed from terrestrial source in the outer bay. In the inner bay, the terrestrial source of organic carbon showed a steady change with an increase in the range of 69%-77% before 1990 to 93% in 2000, and then decreased from 2000 because of the decrease in the terrestrial input. In the bay mouth, the percentage of organic carbon from land reached the highest value with 94% in 1994. In the outer bay, the sediment source maintained steady for the past one hundred years.

Numerical Simulation of Water Exchange Characteristics of the Jiaozhou Bay Based on A Three-Dimensional Lagrangian Model

Based on theory of three-dimensional hydrodynamics, an Euler-Lagrangian particle model is established to study the transport and water exchange capability in the Jiaozhou Bay. The three-dimensional hydrodynamic model, driven by tide and wind, is used to study the effects of wetting and drying of estuarine intertidal flats by the dry-wet grid technology based on the Estuarine, Coastal and Ocean Model （ECOM）. The particle model includes the advection and the diffusion processes, of which the advection process is simulated with a certain method, and the diffusion process is simulated with the random walk method. The effect of the intertidal zone, the turbulent diffusion and the timescales of the water exchange are also discussed. The results show that a moving boundary model can simulate the transport process of the particle in the intertidal zone, where the particles are transported for a longer distance than that of the stationary result. Simulations with and without the turbulent random walk show that the effect of turbulent diffusion is very effective at spreading particles throughout the estuary and speeding up the particle movement. The spatial distribution of residence time is given to quantify the water exchange capability that has very important ramifications to water quality. The effect of wind on the water exchange is also examined and the southeasterly wind in summer tends to block the water exchange near the northeast coast, while the northerly wind in winter speeds up the transport process. These results indicate that the Lagrangian particle model is applicable and has a large potential to help understanding the water exchange capability in estuaries, which can also be useful to simulate the transport process of contaminant.

Evolution of nutrient structure and phytoplankton composition in the Jiaozhou Bay ecosystem

The inventories of nutrients in the surface water and large phytoplankton(>69 μm) were analyzed from the data set of JERS ecological database about a typical coastal waters, the Jiaozhou Bay, China, from 1960s for N, P and from 1980s for Si. By examining long term changes of nutrient concentration, calculating stoichiometric balance, and comparing diatom composition, Si limitation of diatom production was found to be more possible. The possibility of Si limitation was from 37% in 1980s to 50% in 1990s. Jiaozhou Bay ecosystem is becoming serious eutrophication, with notable increase of NO 2 N, NO 3 N and NH 4 N from 0 1417 μmol/L, 0 5414 μmol/L, 1 7222 μmol/L in 1960s to 0 9551 μmol/L, 3 001 μmol/L, 8 0359 μmol/L in late 1990s respectively and prominent decrease of Si from 4 2614 μmol/L in 1980s to 1 5861 μmol/L in late 1990s; the nutrient structure is controlled by nitrogen; the main limiting nutrient is probably silicon; because of the Si limitation the phytoplankton community structure has changed drastically.

Geochemical records of phosphorus in Jiaozhou Bay sediments—Impli-cations for environmental changes in recent hundred years

Phosphorus is a key element and plays an important role in global biogeochemical cycles. The evolution of sedimentary environment is also influenced by phosphorus concentrations and fractions as well as phosphate sorption characteristics of the marine sediments. The geochemical characteristics of phosphorus and their environmental records were presented in Jiaozhou Bay sediments. Profiles of different forms of phosphorus were measured as well as the roles and vertical distributions of phosphorus forms in response to sedimentary environment changes were investigated. The results showed that inorganic phosphorus （IP） was the major fraction of total phosphorus （TP）; phosphorus which is bound to calcium, iron and occluded phosphorus, as well as the exchangeable phosphorus were the main forms of IP, especially calcium - phosphorus, including detrital carbonate-bound phosphorus （Det- P） and authigenic apatite-bound phosphorus （ACa- P）, are the uppermost constituent of IP in Jiaozhou Bay sediments. Moreover, the lead-210 chronology technology was employed to estimate how much phosphorus was buried ultimately in sediments. And the research showed that the impacts of human activities have increased remarkably in recent years especially between the 1980s and 2000. According to research, the development of Jiaozhou Bay environment in the past hundred years can be divided into three stages ： （ 1 ） before the 1980s characterized by the relatively low sedimentation rate, weak land-derived phosphorus inputs and low anthropogenic impacts; （2） from the 1980s to around 2000, accelerating in the 1990s, during which high sedimentation rates, high phosphorus abundance and burial fluxes due to the severe human activities impacted on the whole environmental system ; （ 3 ） after 2000, the period of the improvement of environment, the whole system has been improved including the decreasing sedimentation rates, concentration and the burial fluxes of phosphorus.

Seasonal variations of dimethylsulfide (DMS) and dim-ethylsulfoniopropionate (DMSP) in the sea-surface microlayer and subsurface water of Jiaozhou Bay and its adjacent area

The distributions of DMS and its precursor dimethylsulfoniopropionate, in both dissolved （DMSPd） and particulate fractions （DMSPp） were determined in the sea-surface microlayer and corresponding subsurface water of the Jiaozhou Bay, China and its adjacent area in May and August 2006. The concentrations of all these components showed a clear seasonal variation, with higher concen- trations occurring in summer. This can be mainly attributed to the higher phytoplankton biomass observed in summer. Simultaneously, the enrichment extents of DMSPd and DMSPp in the mi- crolayer also exhibited seasonal changes, with higher values in spring and lower ones in summer. Higher water temperature and stronger radiant intensity in summer can enhance their solubility and photochemical reaction in the microlayer water, reducing their enrichment factors （the ratio of concentration in the microlayer to that in the corresponding subsurface water）. A statistically significant relationship was found between the microlayer and subsurface water concentrations of DMS, DMSP and chlorophyll a, demonstrating that the biogenic materials in the microlayer come primarily from the underlying water. Moreover, our data show that the concentrations of DMSPp and DMS were significantly correlated with the levels of chlorophyll a, indicating that phytoplankton biomass might play an important role in controlling the distributions of biogenic sulfurs in the study area. The ratios of DMS/chlorophyll a and DMSPpchlorophyll a varied little from spring to summer, suggesting that there was no obvious change in the proportion of DMSP producers in the phytoplankton community. The mean sea-to-air flux of DMS from the study area was estimated to be 5.70 μmol/（m^2·d）, which highlights the effects of human impacts on DMS emission.

Dissolved inorganic carbon and CO_(2) fluxes across Jiaozhou Bay air-water interface

On the basis of data collected in the Jiaozhou Bay in June and July 2003, the DIC distribution in seawater is studied, and an average air-sea flux of CO2 is estimated. The results show that the content of DIC inside the bay is markedly higher than outside the bay in June, but the content of DIC outside the bay is markedly higher than inside the bay in July. The trend of DIC distribution inside the bay is similar, viz. the content is the maximum in the northeast, then decreases gradually toward the west, and the content is the minimum in the west. The total trend of vertical distribution is to increase gradually from surface to bottom. This characteristic of DIC distribution is determined by Jiaozhou Bay hydrology and there is a close relation between DIC and particulate N,P. Average CO2flux across the air-sea interface is 0.55 mol/(m2-a) in June and 0.72 mol/(m2-a) in July. Jiaozhou Bay is considered as a net annual source for atmospheric CO2 in June and July, and the total CO2 flux from seawater into atmosphere is about 740t in June and 969 t in July.

The morphological and phylogenetic characterization for the dinoflagellate Margalefidinium fulvescens (=Cochlodinium fulvescens) isolated from the Jiaozhou Bay, China

The dinoflagellate genus Margalefidinium has been split from Cochlodinium as a new genus recently and Margalefidiniumfulvescens is one of the five Margalefidinium species. Margalefidiniumfulvescens is toxic and has been reported from the coastal waters of USA, Canada, Mexico, China, Japan, Indonesia, Korea, Pakistan and Spain. Here we provide the morphological and phylogenetic characterization for an isolate of it from the Jiaozhou Bay, Qingdao, China. Our results showed that the vegetative cells were subspherical to ellipsoidal, 34-60 pm in length, and 19-41 pm in width. Both single cell forms and colonies in chains of 2, 4, or 8 cells were observed in cultures, but chain forms with 2 or 4 cells were observed more often in the field samples. The cingulum was rather deep, encircling the cell approximately twice, but the sulcus was rather narrow, surrounding the cell about one turn. The nucleus was spherical and located at the central epicone. The chloroplasts were granular, brownish, and scattered peripherally. An orange pigmented body also appeared in the epicone. The apical groove appeared vase-like as previously described. Under epi-fluorescence microscopy, a pumpkin-like structure was clearly observed, in which cells were embedded. Cells were observed to exit from the structure, which led us to a hypothesis that the structure may provide cells a shelter to avoid predation or to respond to other stresses. The phylogenetic analyses based on partial LSU rDNA sequences indicated that M. fulvescens from the Jiaozhou Bay was grouped with M. fulvescens populations from other origins and closely related to the clade ofM. polykrikoides. Our morphological observations and phylogenetic analyses together confirmed the presence of M. fulvescens in China and our monitoring has also observed the species dominant in the dinoflagellate community of the Jiaozhou Bay in the early autumn of 2015, which alerted us to continually monitor this bloom-forming species in the region.

The sources and composition of organic matter in sediments of the Jiaozhou Bay：implications for environmental changes on a centennial time scale

The Jiaozhou Bay is characterized by heavy eutrophication that is associated with intensive anthropogenic activities. Four core sediments from the Jiaozhou Bay are analyzed using bulk technologies, including sedimentary total organic carbon（TOC）, total nitrogen（TN）, the stable carbon（δ13C） and nitrogen（δ15 N） isotopic composition to obtain the comprehensive understanding of the source and composition of sedimentary organic matter and further shed light on the environmental changes of the Jiaozhou Bay on a centennial time scale.Results suggest that the TOC and TN concentrations increase in the upper core, having indicated a probable eutrophication process since the 1920 s in the inner bay and the 2000 s in the bay mouth. The TOC and TN concentrations outside the bay have also changed since 1916 owing to the variation of terrigenous input.Considering TOC/TN ratio, δ13 C and δ15 N, it can be concluded there is a mixture of terrigenous and marine organic matter sources in the study area. A simple two end-member（terrigenous and marine） mixing model usingδ13 C indicats that 45%–79% of TOC in the Jiaozhou Bay is from the marine source. The environmental changes of the Jiaozhou Bay are recorded by geochemical proxies, which are influenced by the intensive anthropogenic activities（e.g., extensive use of fertilizers, and discharge of sewage） and climate changes（e.g., rainfall）.

Cycling of phosphorus in the Jiaozhou Bay

Dissolved inorganic phosphorus （DIP ）,dissolved organic phosphorus （DOP ）,particulate inorganic phosphorus （P IP ） and particulate organic phosphorus （P OP ） in the Jiaozhou Bay （JZB） and its adjacent major rivers were analyzed during 2001–2003.DIP was the major form of dissolved phosphorus in JZB,representing 62%–83% of the total dissolved phosphorus （T DP ）,and the P IP concentration generally exceeded the P OP concentration.The concentrations of phosphorus were higher in the north than in the south of the bay,which were related to the fluvial input and water exchange rate.The dissolved phosphorus concentrations were higher in the autumn and spring than in the summer,while the seasonal variation of particulate phosphorus showed opposite pattern.The distribution of phosphorus is mainly affected by the growth of phytoplankton,desorption/adsorption of DIP from and to particulates,and anthropogenic activities.A preliminary phosphorus budget was established.In JZB,riverine input and water exchange flow between JZB and the Huanghai （Yellow） Sea are the major sources of phosphorus,followed by industrial and domestic waste transport,and then atmospheric deposition.Phosphorus burial efficiency is estimated to be 91%.About 52.2 × 10 6 mol/a of phosphorus were assimilated by phytoplankton,of which about 68% was recycled in the water column and sediment.

Bacterial and cyanobacterial diversities determined by T-RFLP analyses in the Jiaozhou Bay

The methods of DAPI staining epifluorescence microscopy and T-RFLP analysis were used to analyze the microbial abundance and diversity in surface seawater sampled from 12 stations inside and outside of the Jiaozhou Bay during a survey on 12 and 13 September 2004. The abundance of total microbes is in the range of 10^6～ 10^7 cells/cm^3, similar to those of most semi-enclosed bays in the temperate areas in the world. The highest microbial densities occur in the northeastern part of the Jiaozhou Bay, around the mouths of Loushan and Licun Rivers and the Hongdao aquacultural farming areas, suggesting that the degree and characteristics of pollutions, along with geographical and hydrological effects, may be important determinants affecting the abundance and distribution of bacteria in the Jiaozhou Bay. Bacterial communities inside and outside of the Jiaozhou Bay can be grouped into three classes based on T-RFLP patterns and cluster analyses. Stations at the water channel of the bay mouth and outside, such as D1, D3, D5, D6 and D7, are grouped together to stand for the outside bacterial community interacting with the environment outside of the Jiaozhou Bay. Stations of the innermost side of the Jiaozhou Bay, such as A3, A5, B2 and Y1, are grouped together to stand for the residential bacteria community. Stations C1, C3 and CA are grouped together and may stand for the transitional bacterial assemblage between the residential community and the outside community. However, there is no such a defined relationship for the case of cyanobacterial diversity, indicating the fact that cyanobacteria are more flexible and adaptable to all kinds of conditions.

Spatial distributions and seasonal variations of particulate phosphorus in the Jiaozhou Bay in North China

Based on the measurements of particulate phosphorus（PP） in the Jiaozhou Bay from May 2003 to April 2004,the spatial distribution,seasonal variation and biogeochemical characteristics of PP were investigated to understand the fates and roles of phosphorus in the Jiaozhou Bay ecosystem.The concentration of the total PP ranged from 0.07 to 2.09 μmol/dm3.The concentration of POP was from 0.01 to 1.83 μmol/dm3,with an average of 0.32 μmol/dm3,which accounted for 49.6% in total PP.The concentration of PIP was from 0.01 to 1.49 μmol/dm3,with an average of 0.33 μmol/dm3,which accounted for 50.4% in total PP.In general,the concentrations of PP in surface water show obvious seasonal variations in the Jiaozhou Bay.POP was the highest in spring,which derived from the accumulation of phyto-detritus and was the lowest in autumn,which was decomposed into seawaters to participate the recycle of phosphorus.PIP was the highest in spring and summer and was the lowest in autumn and winter.PIP was mainly influenced by river input in the inner bay but POP derived from autochthonous source in the outer bay.Overall,the concentrations of PP in the inner bay were higher than those in mouth and the outer bay.In the inner bay,the concentrations of PP with the area near the shore were higher than those in the center of the bay.Totally PP showed the decreasing trend with depth especially in spring and winter.The high value of PP emerged in 20 and 10 m corresponding to summer and autumn,respectively.The changes of POP showed hysteretic effect compared with the changes of Chl a in the investigated year.However,according to the change of Chl a,the second high value of POP which should be emerged in October was missing due to the remineralization of POP and participation in the recycle of phosphorus,which lead to the high concentration of orthophosphate in seawaters.

A nitrogen and phosphorus dynamic model of mesocosm pelagic ecosystem in the Jiaozhou Bay in China

A nitrogen and phosphorus dynamic model of mesocosm pelagic ecosystem was established according to the summary and synthesis of the models available, in which seven state variables （DIN, PO4-P, DON, DOP, phytoplankton, zooplankton and detritus） were included. Logically it had five modules--phytoplankton, zooplankton, dissolved inorganic nutrients, dissolved organic nutrients and detritus. The results showed that this model could simulate the variations of DIN, PO4-P, DON, DOP, POC and phytoplankton biomass in pelagic ecosystem in mesocosm properly, based on the site experiment data in the Jiaozhou Bay in the autumn of 1999 and the summer of 2000. Not only the logical structure but also the model parameters were feasible, and about 20 parameters were made to fit for the Jiaozhou Bay during the simulation. All of these are necessary to study the control mechanism of nutrients biogeochemical cycling in the Jiaozhou Bay and other China＇ s coastal waters.

Silica supply and diatom blooms in the Jiaozhou Bay, China

The variations in nutrients（molar ratios） and chlorophyll a in the Jiaozhou Bay were examined before and after a diatom bloom in a period that lasted from November 2003 to March 2004. Negative relationships between nutrient concentrations, Si/P, Si/N ratios and chlorophyll a content were found during the bloom, which reflected the relationship between nutrient concentrations, phytoplankton biomass and growth. Large increase in nutrient concentrations, particularly SiO_3-Si after the late autumn, is one of major reasons inducing the diatom bloom in winter, and the bloom was finally controlled due to SiO_3-Si depletion by phytoplankton. The bloom was mainly controlled by SiO_3-Si. Before 1998, relatively low level of SiO_3-Si kept ecological balance of eutrophication waters in the Jiaozhou Bay. In recent years, however, human activities have increased SiO_3-Si concentration, which is likely one of the primary cause for the increased diatom blooms in the Jiaozhou Bay. Therefore, it is necessary to control SiO_3-Si concentration in the Jiaozhou Bay.

The observations of seabed sediment erosion and resuspension processes in the Jiaozhou Bay in China

In estuarine and coastal areas, the seabed is in a constant process of dynamic change under marine conditions.Seabed sediment erosion and resuspension are important processes that safely control the geological environment. Field tripod observations conducted in the Jiaozhou Bay in China are reported, to investigate the effects of hydrodynamic conditions on the erosion and resuspension processes of the seabed. The observational results show that the maximum shear stress created by tidal currents can reach 0.35 N/m2, which is higher than the wave-induced shear stress during fair weather conditions. A seabed erosion frequently occurs during the flood tide, whereas a seabed deposition occurs during ebb tide. Waves can produce a bottom shear stress approximately equivalent to that induced by currents when the local wind reaches Force 4 with a speed of 5 m/s.When the wind reaches 7 m/s and the significant wave height reaches 26 cm, waves play a more significant role than currents in the dynamic processes of the seabed sediment resuspension and lead to a high value of turbidity that is approximately two to eight times higher than that in fair weather. These analyses clearly illustrate that periodic current-induced sediment erosion and resuspension are dominant in fair weather, whereas episodic high waves are responsible for significant sediment resuspension. Additional work is needed to establish a more thorough understanding of the mechanisms of sediment dynamics in the Jiaozhou Bay.

Study on the analysis and distribution of dimethylsulfoxide in the Jiaozhou Bay

A chemoreduction-purge-and-trap gas chromatographic method has been developed for the deter-mination of trace dimethylsulfoxide （DMSO） in seawater. In the analysis procedure, DMSO was first reduced to dimethylsufide （DMS） by sodium borohydride and then the produced DMS was analyzed using the purge-and-trap technique coupled with gas chromatographic separation and flame photometric detection. Under the optimum conditions, 97% DMSO was reduced in the standard solution samples with a standard deviation of 5% （n=5）. The detection limit of DMSO was 2.7 pmol of sulfur, corresponding to a concentration of 0.75 nmol/L for a 40 ml sample. This method was applied to determine the dissolved DMSO （DMSOd） and particulate DMSO （DMSOp） con- centrations in the surface seawater of the Jiaozhou Bay, and the results showed that the DMSOd and DMSOp concentrations varied from 16.8 to 921.1 nmol/L （mean：165.2 nmol/L） and from 8.0 to 162.4 nmol/L （mean： 57.7 nmol/L）, respectively. The high concentrations of DMSOp were generally found in productive regions. Consequently, a significant correlation was found between the concentrations of DMSOp and chlorophyll a, suggesting that phytoplankton biomass might play an important role in controlling the distribution of DMSOp in the bay. Moreover, in the study area, the concentrations of DMSOd were significantly correlated with the levels of DMS, implying that the production of DMSOd is mainly via photochemical and biological oxidation of DMS.

Winter Phytoplankton Assemblages of Coastal Yellow Sea Connected to Jiaozhou Bay,China

The daily species variation of phytoplankton assemblage of coastal Yellow Sea connected to Jiaozhou Bay in the sea-water around the Xiaoqingdao Island was studied for the three months of winter, 2003. A total of 79 taxa from four phyla, Bacil-lariophyta (52 species), Pyrrophyta (25 species), Chrysophyta (1 species), and Cyanophyta (1species) were determined. In general, the most important groups were Bacillariophyta and Pyrrophyta on cell abundance and species richness. In January, the dominant species was mainly composed of cosmopolitan species such as Skeletonema costatum, then it changed to cosmopolitan species Tha-lassiosira nordenskiodii in February, and finally, it recovered to Skeletonema costatum again in March. Cell abundance ranged from 1.02 to 130.71×103 cells L-1with a single peak on 6th Feb., and the average abundance was 28.11 ± 26.01×103 cells L-1 (n = 90) during the winter time. The trends of Shannon-Weiner diversity index and Pielou’s evenness index were contrary to cell abundance, whereas the species diversity and evenness were the lowest in February. Temperature and salinity were closely correlated to phytoplankton species composition and cell abundance. According to the variations of temperature and salinity, species sequence was obvious at the studied site. This implies that the phytoplankton community of inner Jiaozhou Bay would be influenced heavily by the coastal Yel-low Sea phytoplankton assemblages.