THE STRENGTH OF THE DISSOLVED OXYGEN MAXIMUM IN THE VERTICAL DISTRIBUTION OF NANSHA ISLANDS WATERS

Observation data from a cruise in the Nansha Islands, in May to June 1990, December, 1993, September to October 1994, and July, 1999, respectively, were used to develop the method presented here to indicate the existing strength of the dissolved oxygen maximum in the vertical distribution of Nansha Islands waters. Its seasonal variation and regional distribution are discussed in this paper. Analysis results showed that the distribution of the strength of dissolved oxygen maximum (DOmax-DOsur) was closely related to the upper layer circulation and the bioactivity of Nansha Islands seawater.     

Improvement of the one-dimensional Vertical Advection-diffusion Model in Seawater

The classical 1-D vertical advection-diffusion model was improved in this work.The main advantages of the improved model over the previous one are:1) The applicable condition of the 1-D model is made clear in the improved model,in that it is substantively applicable only to a vertical domain on which two end-member water masses are mixing.2) The substitution of parameter f(z) in the equation of the classical 1-D model with end-member fraction f1^z makes the model more precisely and easily solved.3) All the terms in the improved model equation have specific physical meanings,which makes the model easily understood.Practical application of the improved model to predict the vertical profiles of dissovled oxygen and micronutrients in abyssal ocean water of the North Pacific proved that the improvement of the 1-D advection-diffusion model is successful and practicable.     

A dynamic box model of bioactive elements in the southern Taiwan Strait

A dynamic box model was applied to study the characteristics of biogeochemical cycling of PO_4-P,NO_3-N,AOU,POC and PON in the southern Taiwan Strait region based on field data of the"Minnan Taiwan Bank Fishing Ground Upwelling Ecosystem Study" during the period of Dec.1987-Nov.1988.According to the unique hydrological and topographical features of the region,six boxesand three layers were considered in the model.The variation rates and fluxes of elements induced by hor-izontal current,upwelling,by diffusion,sinking of particles and biogeochemical processes were estimatedrespectively.Results further confirmed that upwellings had important effects in this region.Thenearshore upwelling areas had net input fluxes of nutrients brought by upwelling water,also had high de-pletion rates of nutrients and production rates of particulate organic matter and dissolved oxygen.Theabnormal net production of nutrients in the middle layer(10-30m) indicated the important role of bacte-ria in this high production region.Th     

FLUXES OF SEAWATER AND SOME DISSOLVED CHEMICALS IN THE BASHI STRAIT

An Acoustic Doppler Current Profiler (ADCP) was used in Nov. 1990 measure the seawaterfluxes in a southeast-northwest cross-section in the Bashi Strait to a depth of 400 m. Measuredconcentrations of dissolved oxygen (DO), phosphate (PO_4), nitrate (NO_3), silicate (SiO_2), total alkalinity(TA) and calculated total CO_2, (TCO_2) and the current speed were used to estimate the flux densities(concentration times current speed) of seawater and chemicals.The fluxes of nutrients were near zero near surface and increased with depth. For oxygen andcarbonates, the distributions of flux had structures similar to that of the curmt speed field.     

STUDY ON THE DISSOLVED OXYGEN FLUX IN THE SOUTH CHINA SEA

xiODUonONThemaoreleInent(oxygen)ofldeinthemarineeresySteInisCycledalongapartho-larrouteinWhwhthethetcanbedrawnfromtheexternlenvirDnmentintoorgan-isim,andthenberetumedtotheenvbonmentfromtheorganisrns.TheDocontentinseawatCfisinIlUentalbyorganisms,imtS,temPeratureandoxidation.So,studyonDoisoftoortanceinoasnographyastheDofluxisofgreatsignfonceinmarinebiogeochdricalcydes.'MareRIAnooMEmOorlnthisstudy,datafroml98O~l992multi-disdplinaryinvestigationsinthecenthel,northeastem,andsouthernSrswe…     

BIOGEOCHEMICAL BEHAVIOR OF NUTRIENTS AND THEIR FLUXES IN THE MINJIANG RIVER ESTUARY

IMRODUcTlONThe577km1ongMinjiangRiver,thelongestriverinFujianProvinceofChina,hasa6O992km2drainagebasin.Thewaterdischargeislarge(meaninyearsis198Om/s).TheannualrunofffromtheMinjiangRiveris5.84xlOlom,WhichismorethanthatoftheHuangheRiver,andranksthirdintheannualrunoffofmaorChineseriversWhang,l994).SimdentnutrientSfromtheMinjiangRivertotheseaisanarisa-ryconditionforthefonnationandcontinuingexistenceoftheMindongFisheryGroundandtheMihahongFisheryGround.Inthendingareaofriverwaterwithseaw…     

Influential factors on the exchange rate of dissolved inorganic nutrients at the sediment-water interface in Jiaozhou Bay, China

Incubation experiments are carried out to study the exchange rates of dissolved inorganic nutrients including silicate, phosphate, ammonium, nitrite, and nitrate (vSiO3-Si, vPO4-P, vNH4-N, vNO2-N and vNO3-N) at the sediment-water interface in the Jiaozhou Bay. Major factors influencing the exchange rates are discussed in detail, which include the dissolved inorganic nutrient concentrations in porewater (Cpw), water and clay contents, and grain size of the sediments (CH2O, Cclay and GSsed). The results may provide insight into the dynamics of nutrient transport and the environmental capacity of nutrients in Jiaozhou Bay, and should be beneficial to solving the problems caused by excessive nutrient input this area.     

Influential factors on the exchange rate of dissolved inorganic nutrients at the sediment-water interface in Jiaozhou Bay,China

Incubation experiments are carried out to study the exchange rates of dissolved inorganic nutrients including silicate, phosphate, ammonium, nitrite, and nitrate （^vSiO3-Si,^vPO4-P, ^vNH4-N, ^vNO2-N and ^vNO3-N） at the sediment-water interface in the Jiaozhou Bay. Major factors influencing the exchange rates are discussed in detail, which include the dissolved inorganic nutrient concentrations in porewater （Cpw）, water and clay contents, and grain size of the sediments （CH2O, Cclay and GSsed）. The results may provide insight into the dynamics of nutrient transport and the environmental capacity of nutrients in Jiaozhou Bay, and should be beneficial to solving the problems caused by excessive nutrient input this area.     

Effects of temperature and dissolved oxygen content on oxygen consumption rate of Chinese prawn, giant tiger prawn and giant freshwater prawn

INTRODUCnON-WatertemperatheanddissolvedoxygenareimportantenvironmentalfactorsinthegmwthanddevelOPmntofaqUaticorgAnsms.ThereareInanPublishedstUdiesontheox-.ygenconsUInPtionrate(OCR)oftheprawn')(WangJim,l986;WangDanghenetal-,199l;ZangWeilingetal-,l992,l993),buttheydidnotcontalndetailedinfonnaionabouttheeffectoftemPerabeontheOCR-ThePresentstudydetendnedtheOCRofju-venilesofChineseprawn,gianttiserprawnandgiantfreshwaterprawnthatwererearedatdifferenttemperatllresforaboutaweekattheCaoj…     

Vertical properties of nutrients and oxygen under tempeuature-salinity structure of the Bering Basin in July 1999

The China R/V Xuelong went on the first Arctic scientific cruise, and we obtained 271 hydro-chemical samples from 22 deep-sea stations in the Bering Basin in late July, 1999. Here we describe vertical properties of silicate [Si] , dissolved inorganic nitrogen [DIN] or [N] (nitrate plus ammonium plus nitrite) , phosphate [P] and oxygen [ O2 ] in seawater under potential temperature-salinity structure. The seasonal stratification in the summer and the water exchanges of the North Pacific Ocean over the Bering Basin resulted in that the four layers of vertical structure with two thermoclines may be found. Vertical [Si] and [N] and [P] profiles show that the nutrients are consumed mainly in ≤50 m and the order of deficient nutrients is [Si] the first, [N] the second and [P] the third. The [N] and [P] increase with depth downward to about 500 m and then both decrease, but the [Si] increases from 150 m to 2000 m or the bottom. In ≥ 150 m the [ O2 ] decreases, which is related with both [P] and [N] increasin     

Annual cycle and budgets of nutrients in the Bohai sea

The environmental problems in the Bohai Sea have become more serious in the last decade. High nutrient concentration contributes much to it. A Sino-German cooperation program has been carried out to improve the understanding of the ecosystem by observations and modelling. A three-dimensional ecosystem model, coupled with a physical transport model, is adopted in this study. The simulation for the year 1982 is validated by the data collected in 1982/1983. The simulated annual mean nutrient concentrations are in good agreement with observations. The nutrient concentrations in the bohai Sea, which are crucial to the algal growth, are high in winter and low in summer. There are depletion from spring to summer and elevation from autumn to winter for nutrients. The nutrients’ depletion is a response to the consumption of the phytoplankton bloom in spring. Internal recycle and external compensation affect the nutrient cycle. Their contributions to the nutrient budgets are discussed based on the simulated results. Production and respiration are the most important sink and source of nutrients. The process of photosynthesis consumes 152 kilotons-P and 831.1 kilotons-N while respiration releases 94.5 kilotons-P and 516.6 kilotons-N in the same period. The remineralization of the detritus pool is an important source of nutrient regeneration, It can compensate 23 percent of the nutrient consumed by the production process. The inputs of phosphates and nitrogen from rivers are 0.55 and 52.7 kilotons respectively. The net nutrient budget is −3.05 kilotons-P and 31.6 kilotons-N.     

A new carbon and oxygen balance model based on ecological service of urban vegetation

The application of human induced oxygen consumption and carbon emission theory in urban region was summed up and on this base a new model of urban carbon and oxygen balance (UCOB) was constructed by calculating the carbon and oxygen fluxes. The purpose was to highlight the role of vegetation in urban ecosystems and evaluate the effects of various human activities on urban annual oxygen consumption and carbon emission. Hopefully,the model would be helpful in theory to keep the regional balance of carbon and oxygen,and provide guidance and support for urban vegetation planning in the future. To test the UCOB model,the Jimei District of Xiamen City,Fujian Province,China,a very typical urban region,was selected as a case study. The results turn out that Jimei′s vegetation service in oxygen emission and carbon sequestration could not meet the demand of the urban population,and more than 31.49 times of vegetation area should be added to meet the whole oxygen consumption in Jimei while 9.60 times of vegetation area are needed to meet the carbon sequestration targets. The results show that the new UCOB model is of a great potential to be applied to quantitative planning of urban vegetation and regional eco-compensation mechanisms.     

Study on kinetics of cathodic reduction of dissolved oxygen in 3.5% sodium chloride solution

Electrochemical reduction of dissolved oxygen in seawater on metals is of great importance for corrosion studies. The present paper studied cathodic reduction of dissolved oxygen on Q235 carbon steel in 3. 5% sodium chloride(NaCl)solutions by cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS), rotating disk electrode(RDE)and rotating ring-disk electrode(RRDE). The cyclic voltammetric results demonstrated the cathodic process on Q235 carbon steel in O2-saturated 3. 5% NaCl solution contains three reactions:dissolved oxygen reduction, iron oxides reduction and hydrogen evolution. The peak potential of oxygen reduction reaction(ORR)is-0. 85 V vs Ag/AgCl, 3 molL-1 KCl. The E1S results indicated that the ORR occurring on Q235 carbon steel is a 4-electron process and that no finite diffusion is caused by the intermediate of H2O2 produced by ORR. The RDE and RRDE voltammograms confirmed the EIS results and it was found that the number of transferred electrons for ORR was nearly 4, I. E. , dissolved oxygen reduced to water.     

Occurrence and distribution of dissolved tellurium in Changjiang River estuary

With the implementation of the GEOTRACES program, the biogeochemical cycle and distribution of tellurium （Te） in marine environments are becoming increasing environmental concerns. In this study, the concentration of dissolved Te in the Changjiang （Yangtze） River estuary and nearby waters was determined in May 2009 by hydride-generation atomic fluorescence spectrometry to elucidate the abundance, dominant species, distribution, and relationship with environmental factors. Results show that： （1） dissolved Te was low owing to its low abundance in the Earth＇s crust, high insolubility in water, and strong affinity to particulate matter; （2） Te（IV） and Te（VI） predominated in surface water. Te（VI） was the dominant species in bottom water, and Te（IV） was the minor species; （3） Horizontally, resulting from low phytoplankton metabolism and the weak reduction from Te（VI） to Te（IV） in the shore, Te（IV） was concentrated in the central zone instead of the coastal region. However, Te（VI） was abundant near the mouth of the Changjiang River where the Changjiang water is diluted and in the area to the south where the Taiwan Warm Current invaded. In the adsorption-desorption process, Te（IV） was negatively related to suspended paniculate matter （SPM）, indicating that it was adsorbed by particulate matter. While for Te（VI）, the positive correlation with SPM suggested that it was desorbed from the solid phase. In the estuary, dissolved Te had a negative correlation to salinity. However, it deviated from the dilution line in high-salinity regions due to the invasion of the Taiwan Warm Current and the mineralization of organic matter. The relationship between Te（IV） and SPM nutrients indicated that it was more bioavailable and more related to phosphorus than to nitrogen. Progress in the field is slow and more research is needed to quantify the input of Te to the estuary and evaluate the biochemical role of organisms.     

The distribution of dissolved aluminum in the Yellow and East China Seas

Water samples containing dissolved aluminum were collected from the Yellow and East China Seas in October-November 2000. The average concentrations of dissolved AI in the Yellow Sea （YS） and East China Sea （ECS） were 0.042 and 0.056 μ molL^-1, respectively. The concentration of dissolved aluminum decreased gradually across the continental shelf. The lower concentrations appeared in the YS cold water center and in the bottom layer at the shelf edge of the ECS, where they were 0.016 and 0.011 μmolL^-1, respectively. The distribution of dissolved Al was controlled by physical mixing processes rather than biological uptake processes. The impact of different water masses along the PN transect was calculated based on the mass balance model. The results show that the impact of the Changjiang River was mainly concentrated on the coastal area and the top thermocline water on the ECS shelf, where the impact percentage decreased from 12.6% to 1.1% in the surface water, while the contribution of the Kuroshio water was dominant on the ECS shelf in this survey, increasing from 77.6% to 97,8% along the PN transect from the Changjiang River Estuary to the Ryukyu Islands. It is concluded that aluminum can serve as a proper tracer for studying the impact of Changjiang terrestrial matter on the ECS shelf water.     

Effect of dissolved oxygen on swimming ability and physiological response to swimming fatigue of whiteleg shrimp (Litopenaeus vannamei)

The swimming endurance of whiteleg shrimp(Litopenaeus vannamei, 87.66 mm ± 0.25 mm, 7.73 g ± 0.06 g) was examined at various concentrations of dissolved oxygen(DO, 1.9, 3.8, 6.8 and 13.6 mg L-1) in a swimming channel against one of the five flow velocities(v1, v2, v3, v4 and v5). Metabolite contents in the plasma, hepatopancreas and pleopods muscle of the shrimp were quantified before and after swimming fatigue. The results revealed that the swimming speed and DO concentration were significant factors that affected the swimming endurance of L. vannamei. The relationship between swimming endurance and swimming speed at various DO concentrations can be described by the power model(ν·tb = a). The relationship between DO concentration(mg L-1) and the swimming ability index(SA∫ 9000I), defined as SAI =vdt( cm), can be described as SAI = 27.947 DO0.137(R2 = 0.9312). The 0level of DO concentration directly affected the physiology of shrimp, and exposure to low concentrations of DO led to the increases in lactate and energetic substrate content in the shrimp. In responding to the low DO concentration at 1.9 mg L-1 and the swimming stress, L. vannamei exhibited a mix of aerobic and anaerobic metabolism to satisfy the energetic demand, mainly characterized by the utilization of total protein and glycogen and the production of lactate and glucose. Fatigue from swimming led to severe loss of plasma triglyceride at v1, v2, and v3 with 1.9 mg L-1 DO, and at v-11 with 3.8, 6.8 and 13.6 mg L DO, whereas the plasma glucose content increased significantly at v3, v4 and v5 with 3.8 and 6.8 mg L-1 DO, and at v5 with 13.6 mg L-1 DO. The plasma total protein and hepatopancreas glycogen were highly depleted in shrimp by swimming fatigue at various DO concentrations, whereas the plasma lactate accumulated at high levels after swimming fatigue at different velocities. These results were of particular value to understanding the locomotory ability of whiteleg shrimp and its physiological changes, further contributing to the improvement of capture and rearing technique.     

Application study of coupled model between reservoir organic pollutant BOD5-DO and temperature

The BOD5-DO (Biochemical Oxygen Demand in five days and Dissolved Oxygen) are important indexes that reflect the organic pollution extent of water,but the variation of the indexes is closely related with water temperature.The study on the coupled mathematical model reflecting the BOD5-DO with temperature is the key to reveal the mechanism of the migration and distribution of BOD5-DO in the water.The authors presented 1-D mathematical model for the three variables in vertical direction,and gave accurate solution for the equations under steady state,the relation among the variables and the method for solving BOD5-DO concentrations at different depth and temperature.     

Transfort of oxygen,nutrients and carbonates by the Kuroshio Current

Measured concentrations of dissolved oxygen, phosphate, silicate, total alkalinity and calculated total CO₂ in a section between 121° E and 125° E across the Kuroshio near 22° N off Taiwan and the geostrophic velocity were used to estimate the gross transport of oxygen, nutrients and carbonates. The flux of dissolved oxygen is 6.7×10⁶ mol/s northward and 0.9×10⁶ mol/s southward. The net flux equals 5.8×10⁶ mol/s down-stream. The northward flux of phosphate is 22.6×10³ mol/s; the southward flux is 1.4×10³ mol/s. The net phosphate flux is 21.2×10³ mol/s northward. The flux of silicate is 967×10³ northward and 59×10³ mol/s southward; the net transport is 908×10³ mol/s down-stream. The flux of alkalinity is 75.5×10⁶ mol/s northward, and 10.8×10⁶ mol/s southward, the net flux is 64.7×10⁶ mol/s northward. For total CO₂ the transport is 73.4×10⁶ mol/s northward and 10.8×10⁶ mol/s southward, or a net transport of 62.6×10⁶ mol/s horthward.     

Spatial distribution characteristics of surface tidal currents in the southwest of Taiwan Strait

This study was conducted on the spatial distribution characteristics of surface tidal currents in the southwestern Taiwan Strait based on the quasi-harmonic analysis of current data obtained by two high frequency surface wave radar (HFSWR) systems. The analysis shows that the tidal current pattern in the southwestern Taiwan Strait is primarily semi-diurnal and influenced significantly by shallow water constituents. The spatial distribution of tidal current ellipses of M₂ is probably affected by the interaction between two different systems of tide wave, one from the northern mouth of Taiwan Strait and the other from the Bashi Channel. The directions of the major axes of M₂ tidal current ellipses coincide roughly with the axis of the Taiwan Strait. The spatial distribution of the magnitudes of the probable maximum current velocity (PMCS) shows gradual increase of the velocity from northeast to southwest, which is in accordance with the spatial distribution of the measured maximum current velocity (MMCS). The directions of the residual currents are in accordance with the direction of the prevailing monsoon wind at the Taiwan Strait and the direction of the Taiwan warm current during summer. The bathymetry also shows a significant effect on the spatial distribution characteristics of tidal currents.     

Dissolved oxygen distribution and O2 fluxes across the sea-air interface in East China Sea waters

This study on the sectional and vertical distribution of dissolved oxygen (DO) and the O₂ fluxes across the sea-air interface in East China Sea (ESC) waters shows that the waters were in steady state and that the difference of DO was great in upper and bottom waters in Apr. 1994; but that seawater mixing was strong and the difference of DO was small in upper and bottom waters in Oct. 1994. The above conclusions were specially obvious in continental shelf waters under 100 m. The DO maximum in subsurface layer waters appeared only at several stations and in general the DO in the waters decreased with depth. The horizontal distributions of O₂ fluxes across the sea-air interface appeared in stripes in Leg 9404 when most regions covered were supersaturated with O₂ seawater to air flux was large, and that on section No. 1 was 1.594 L/m²·d. The horizontal distribution of O₂ fluxes across the sea-air interface appeared lumpy in Leg 9410, when most regions covered were unsaturated with O₂·O₂ was dissolved from air to seawater, and the fluxes were 0.819 L/m²·d on section No. 1 in Leg 9310, 0.219 L/m²·d in Leg 9410. The main reasons for DO change in surface layer seawater were the mixture of upper and bottom layer water, and the exchange of O₂ across the sea-air interface. The variation of DO by biological activity was only 20% of total change of DO. Contribution No. 2716 from Institute of Oceanology, Chinese Academy of Sciences.