Showing papers by "Ocean University of China published in 2004"

Kuroshio intrusion and the circulation in the South China Sea

Abstract: [1] The Princeton Ocean Model is used to study the circulation in the South China Sea (SCS) and its seasonal transition. Kuroshio enters (leaves) the SCS through the southern (northern) portion of the Luzon Strait. The annually averaged net volume flux through the Luzon Strait is ∼2 Sv into the SCS with seasonal reversals. The inflow season is from May to January with the maximum intrusion of Kuroshio water reaching the western SCS during fall in compensation of summertime surface offshore transport associated with coastal upwelling. From February to April the net transport reverses from the SCS to the Pacific. The intruded Kuroshio often forms an anticyclonic current loop west of the Luzon Strait. The current loop separates near the Dongsha Islands with the northward branch continuously feeding the South China Sea Warm Current (SCSWC) near the shelf break and the westward branch becoming the South China Sea Branch of Kuroshio on the slope, which is most apparent in the fall. The SCSWC appears from December to February on the seaward side of the shelf break, flowing eastward against the prevailing wind. Diagnosis shows that the onshore Ekman transport due to northeasterly monsoon generates upwelling when moving upslope, and the particular distributions of the density and sea level associated with the cross shelf motion supports the SCSWC.

Quantification of uronic acids in tea polysaccharide conjugates and their antioxidant properties.

Abstract: A technique of high-performance liquid chromatography (HPLC) was described for the measurement of total uronic acids in tea polysaccharide conjugates. This method was applied to polysaccharide conjugate extracts obtained from green tea after most of the components that produce interference were removed. The preliminary extraction process was according to the procedure of isolation of polysaccharide conjugates. The uronic acid content of different polysaccharide conjugate fractions was quantified by HPLC on a Sugar-Pak I column with a 1.0 x 10(-)(4) mol x L(-)(1) calcium disodium ethylenediaminetetraacetic acid solution as the mobile phase and refractive index detection. The validation study showed high recoveries (>97.0%) and low coefficients of variance (<3.0%). The minimum detectable limit concentration of uronic acid was 10 microg x mL(-)(1). The analysis of a standard range of galacturonic acid concentrations (100-4000 microg x mL(-)(1)) yielded linear results. The use of the method on different polysaccharide conjugate fraction samples confirmed its effectiveness. With the high content of uronic acids in polysaccharide conjugates, the stronger reactive oxygen species scavenging activities were found.

A gap in the Indo‐Pacific warm pool over the South China Sea in boreal winter: Seasonal development and interannual variability

Abstract: [1] The Indo-Pacific warm water pool in boreal winter shows a conspicuous gap over the South China Sea (SCS) where sea surface temperature (SST) is considerably lower than over the oceans both to the west and east. The formation mechanisms for the climatology and interannual variability of SCS SST in boreal winter are investigated using a suite of new satellite measurements. The winter SCS is divided into two parts by the axis of the maximum northeasterly monsoonal winds. The positive wind curl in the southeastern half of the ocean drives a cyclonic gyre circulation in the deep basin. As its western boundary current, an intense southward flow is found south of Vietnam on the continental slope separating the Sunda Shelf to the west and the deep SCS basin to the east. This slope current exceeds 0.5 m s(-1) in speed and advects cold water from the north. This cold advection results in a distinct cold tongue in the winter SST climatology. Both the slope current and the cold tongue are strongest in November to February. This winter cold tongue displays considerable interannual variability that is highly correlated with eastern equatorial Pacific SST. In an El Nino the winter monsoon weakens, causing the SCS ocean circulation to spin down. The reduced western boundary current and its thermal advection result in a warming in the SCS winter cold tongue. Both SST variance and its correlation with the El Nino-Southern Oscillation peak along the climatological cold tongue indicate that ocean dynamics are an important player in SCS climate variability.

Mesozoic, Not Paleoproterozoic SHRIMP U-Pb Zircon Ages of Two Liaoji Granites, Eastern Block, North China Craton

Abstract: The Paleoproterozoic Jiao-Liao-Ji orogen in the North China craton is composed mainly of the Liaohe Group (and its equivalents) and the Liaoji Granites. The latter have long been considered to be Paleoproterozoic in age, but have not been precisely constrained by reliable isotopic ages. CL and BSE images reveal the existence of both magmatic and xenocrystal/inherited zircons in one rock sample each from the Dandong and Gaoliduntai granites, two major Liaoji Granite intrusions. The magmatic zircons occur as either single grains or rims surrounding or truncating xenocrystal/inherited zircon cores, and are characterized by euhedral, prismatic grains with well-developed oscillatory zoning, whereas the xenocrystal/inherited zircons occur either as cores surrounded by the igneous zircon rims, or as single grains exhibiting weakly zoned bands. The magmatic zircons yielded ages of 157.4 ± 5.7 Ma and 156.3 ± 4.8 Ma for the Dandong and Gaoliduntai granites, respectively, indicating that these two plutons were empla...

Optimal dietary protein requirement of grouper Epinephelus coioides juveniles fed isoenergetic diets in floating net cages

Abstract: Summary An experiment to determine the optimal protein requirement of grouper Epinephelus coioides juveniles was conducted in floating net cages (1.5 m × 1 m × 1.5 m). Six isoenergetic fishmeal–casein-based experimental diets containing 350–600 g kg−1 crude protein (CP) were fed to triplicate groups of 20 fish (10.7 ± 0.2 g) for 56 days. Weight gain (WG) and specific growth rate (SGR) increased with increasing dietary protein level from 350 to 450 g kg−1 and then plateaued above these levels. Feed intake (FI) showed no significant difference among fish fed more than 350 g kg−1 CP. Lowest feed conversion ratio (FCR) was found for fish fed 500 g kg−1 CP but this was not significantly different from that of fish fed the 450 and 600 g kg−1 CP. Lowest protein efficiency ratio (PER) was found for fish fed 550 and 600 g kg−1 CP. Fish fed the 600 g kg−1 CP had the highest body protein and moisture contents but the lowest body lipid content. Body ash content was unaffected by protein level for fish fed >400 g kg−1 CP. Dietary protein level had no significant effect on hepatosomatic index (HSI). Fish fed the 350 g kg−1 CP had significantly lower condition factor (CF) and viscerosomatic index (VSI). Based on broken-line regression analysis of SGR the optimal dietary protein requirement for E. coioides juveniles was determined to be close to 480 g kg−1.

Simulation of water exchange in Jiaozhou Bay by average residence time approach

Abstract: A dispersion model coupled with the Princeton Ocean Model was used to estimate the average residence time of the water in Jiaozhou Bay. The tidal simulation agreed quite well with drift experiments and water elevation observations at the Dagang tide station in the east coast of the bay. In particular, in situ measurements of 228Ra and salinity were carried out to calibrate the dispersion model. The modelled average residence time was about 52 days, ranging from less than 20 days in the deep part near the bay channel, the only passage connecting the bay to the Yellow Sea, to over 100 days in the shallow area in the northwest. The spatial difference of average residence time was controlled by tidal residual currents and the distance to the bay channel. The modelled tidal exchange rate was uneven in the bay, and consistent with 228Ra observations. The temporal evolution of the passive tracer accords with the evolution of the rain fraction after the rainstorm in August 2001.

Photochemical degradation of dimethyl phthalate by Fenton reagent

Abstract: The photochemical degradation of dimethyl phthalate (DMP) in water was investigated under a variety of reaction conditions using hydrogen peroxide and Fe 2+ (Fenton reagent) as oxidant. All experiments were conducted under artificial UV light (high pressure Hg lamp). Fenton reagent vigorously enhanced the photo-degradation rate of dimethyl phthalate. The experimental results showed that the optimum conditions were obtained at pH 3 for the UV/H 2 O 2 /Fe 2+ system, with original H 2 O 2 and Fe 2+ concentrations of 5.00×10 −4 and 1.67×10 −4 M, respectively. The photo-degradation percentage of dimethyl phthalate within 120 min was as high as 81% under the optimum conditions. Therefore, the process of photo-Fenton was an effective treatment process under acidic condition and produced a higher photo-degradation percentage of dimethyl phthalate during a very short radiation time.

Merging Satellite Infrared and Microwave SSTs: Methodology and Evaluation of the New SST

Abstract: The Global Ocean Data Assimilation Experiment (GODAE) requires the availability of a global analyzed SST field with high-resolution in space (at least 10 km) and time (at least 24 hours). The new generation SST products would be based on the merging of SSTs from various satellites data and in situ measurements. The merging of satellite infrared and microwave SST data is investigated in this paper. After pre-processing of the individual satellite data, objective analysis was applied to merge the SST data from NOAA AVHRR (National Oceanic and Atmospheric Administration, Advanced Very High Resolution Radiometer), GMS S-VISSR (Geostationary Meteorological Satellite, Stretched-Visible Infrared Spin Scan Radiometer), TRMM MI (Tropical Rainfall Measuring Mission, Microwave Imager: TMI) and VIRS (Visible and Infrared Scanner). The 0.05° daily cloud-free SST products were generated in three regions, viz., the Kuroshio region, the Asia-Pacific Region and the Pacific, during one-year period of October 1999 to September 2000. Comparisons of the merged SSTs with Japan Meteorological Agency (JMA) buoy SSTs show that, with considerable error sources from individual satellite data and merging procedure, an accuracy of 0.95 K is achieved. The results demonstrate the practicality and advantages of merging SST measurements from various satellite sensors.

Promotive effects of alginate-derived oligosaccharide on maize seed germination

Abstract: The influence of alginate-derived oligosaccharide (molecular weight 1445 Da) was tested on the maize seed germination at different concentrations. Assays of α-and β-amylase and protease activities showed the highest response at 0.75‰.Compared with the control, root growth on days 3 and 7 showed increases of 34% and18%, respectively; and shoot growth on day 7 an increase of 46%. In the case of protease activity, treatments with both 0.75‰ and 1.50‰ alginate-derived oligosaccharide gave higher activities than the control. These results indicate that the rate of seed germination was enhanced by increasing the activities of several enzymes beneficial for germination.

Eddy Shedding from the Kuroshio Bend at Luzon Strait

Abstract: TOPEX/POSEDIENT-ERS satellite altimeter data along with the mean state from the Parallel Ocean Climate Model result have been used to investigate the variation of Kuroshio intrusion and eddy shedding at Luzon Strait during 1992–2001. The Kuroshio penetrates into the South China Sea and forms a bend. The Kuroshio bend varies with time, periodically shedding anticyclonic eddies. Criteria of eddy shedding are identified: 1) When the shedding event occurs, there are usually two centers of high Sea Surface Height (SSH) together with negative geostrophic vorticity in the Kuroshio Bend (KB) area. 2) Between the two centers of high SSH there usually exists positive geostrophic vorticity. These criteria have been used to determine the eddy shedding times and locations. The most frequent eddy shedding intervals are 70, 80 and 90 days. In both the winter and summer monsoon period, the most frequent locations are 119.5°E and 120°E, which means that the seasonal variation of eddy shedding location is unclear.

Wind Energy Input to the Ekman Layer

Abstract: Wind stress energy input through the surface ageostrophic currents is studied. The surface ageostrophic velocity is calculated using the classical formula of the Ekman spiral, with the Ekman depth determined from an empirical formula. The total amount of energy input over the global oceans for subinertial frequency is estimated as 2.4 TW averaged over a period from 1997 to 2002, or 2.3 TW averaged over a period from 1948 to 2002, based on daily wind stress data from NCEP‐NCAR. Thus, in addition to the energy input to the near inertial waves of 0.5‐0.7 TW reported by Alford and by Watanabe and Hibiya, the total energy input to the Ekman layer is estimated as 3 TW. This input is concentrated primarily over the Southern Ocean and the storm track in both the North Pacific and North Atlantic Oceans.

Phosphorus cycling in sediments of the Bohai and Yellow Seas

Abstract: Using a box-sampler, surface and core sediment samples were collected from the Bohai and Yellow Seas in 1998–1999. The sediments were sequentially extracted to determine six phosphorus fractions, and non-sequentially extracted for total P (TP) and inorganic P (IP), where the difference between TP and IP was assumed to be organic P (OP). It was found that more than 70% of the total P is inorganic P. The concentrations of phosphorus were high near the river mouth, reflecting the influence from the Huanghe and Changjiang sediment loads. The phosphorus levels in the Bohai Sea are higher than those in the Yellow Sea, which is related to the sediment sources and distribution of chlorophyll a in these areas. Concentrations of TP in the Bohai and Yellow Seas are comparable to the other worldwide coastal areas. Among the six forms of phosphorus, phosphorus distribution ranges were 0.8–2% for loosely sorbed P, 3–10% for iron-bound inorganic P, 4–19% for leachable organic P, 3–15% for authigenic apatite, 35–66% for detrital apatite and 14–36% for refractory organic P. Potentially bioavailable phosphorus accounts for a small amount of TP, while phosphorus load associated with eroded soil may be larger than the anthropogenic load. The regeneration of dissolved P from sediments is a slow process, which could play a role in maintaining low phosphate levels in the seas. Most of the phosphorus was regenerated in a water column, and almost all of the remaining phosphorus was buried in the sediments after its accumulation. The high values of P burial efficiencies in the study areas were related to low benthic phosphate flux, which is due to the high percent of detrital apatite that is not bioavailable and the high sediment accumulation rate.

Wind Energy Input to the Surface Waves

Abstract: Wind energy input into the ocean is primarily produced through surface waves. The total rate of this energy source, integrated over the World Ocean, is estimated at 60 TW, based on empirical formulas and results from a numerical model of surface waves. Thus, surface wave energy input is about 50 times the energy input to the surface geostrophic current and 20 times the total tidal dissipation rate. Most of the energy input is concentrated within the Antarctic Circumpolar Current.

Anti-oxidation of agar oligosaccharides produced by agarase from a marine bacterium

Abstract: In order to prepare the active agar oligosaccharide, agarase extracted from a strain of unidentified marine bacterium from the South China Sea coast was selected for the agar depolymerization. The optimum decomposing conditions were determined to be pH 7.0, 35 °C and halophilic properties 2%. Three main degraded products, AOS-1, AOS-2 and AOS-3, were separated by ethanol fractionation and anion exchange chromatography. The molecular mass was analyzed by MALDI-TOF-MS. The agar oligosaccharides exhibited antioxidative activities in scavenging hydroxyl free radical, scavenging superoxide anion radical and inhibiting lipid peroxidation. The fragment with the sulfate group showed stronger antioxidative activities than that without the sulfate group. Higher antioxidative activities were found when the molecular mass was increased. The results indicated that the antioxidative activities were closely related to the molecular mass of the agar oligosaccharides and the substitute groups binding the carbohydrate ring.

Effects of temperature on non-specific immune parameters in two scallop species: Argopecten irradians (Lamarck 1819) and Chlamys farreri (Jones & Preston 1904)

Abstract: The effect of chronic (2 weeks) temperature (19, 22, 25, 28 and 31°C) on certain non-specific immune parameters of two species of scallops, Argopecten irradians (Lamarck 1819) and Chlamys farreri (Jones & Preston 1904) were studied. The survival ratio of the two species of scallops at 31°C was the lowest. Haemocyte concentration of C. farreri in the 19 and 22°C treatment groups was significantly lower than that of the 25 and 28°C treatment groups but significantly higher than that of the 31°C treatment group. With elevation of seawater temperature, the alkaline phosphatase (ALP) and acid phosphatase (ACP) activities in sera of two scallop species increased and reached the peak at 25°C and then decreased. However, the specific activity of ALP and ACP of the 31°C treatment group was the highest. The results demonstrated that temperature of seawater significantly affected immunity of scallops. The concept that the stress of high environmental temperature on C. farreri may be partially responsible for the mass mortality of the organism is also introduced.

Thermobaric structure of a traverse across western Dabieshan: implications for collision tectonics between the Sino‐Korean and Yangtze cratons

Abstract: As the best preserved high- and ultrahigh-pressure (HP and UHP) metamorphic terrane in the Qinling-Dabieshan-Sulu orogen, western Dabieshan is divided into six lithotectonic units along a traverse across the orogen, i.e. from north to south, the Nanwan, Balifan, Huwan, Xinxian, Hong'an and Mulanshan units. In this terrane five eclogite-bearing zones (I–V) are developed. The garnet and clinopyroxene in eclogites from these zones exhibit chemical zoning, suggesting that the rims record general peak temperature and pressure. Thermobarometric study indicates that the peak P–T conditions of eclogite are 550–570°C and 21 kbar for Zone I, 470–500°C and 14–17 kbar for Zone II, 620–670°C and 26–29 kbar for Zone III, 530–560°C and 20–22 kbar for Zone IV, and 490–510°C and 19–20 kbar for Zone V. The symmetrical thermobaric pattern, in conjunction with structural and geochronological data, demonstrates that the Huwan and Hong'an units belong to the same HP slice overlying the UHP slice. This pattern, together with the Mulanshan LT/HP blueschist–greenschist belt in the south, roughly constitutes a ‘normal’ metamorphic zonation. However, clear metamorphic gaps occur between different slices. It is inferred that the LT/HP, HP and UHP slices were broken up from the downgoing slab during subduction and reached different depths along different geothermal gradients. The successive subduction of underlying slices leads to a nearly concomitant uplift of overlying slices, whereas exhumation of the deepest UHP slice was effected by underthrusting of the lower crust of the Yangtze craton.

Synthesis of Polyaniline Nanobelts

Abstract: Polyaniline nanobelts have been synthesized by a self-assembly process using the chemical oxidative polymerization of aniline in a surfactant gel The morphologies of polyaniline nanostructures were characterized by field-emission scanning electron microscopy and transmission electron microscopy The effects of the concentrations of cetyltrimethylammonium bromide on the morphologies of polyaniline nanostructures have also been investigated