A VERTICAL DISTRIBUTION MODEL OF NUTRIENTS AND DISSOLVED OXYGEN IN THE SOUTHERN TAIWAN STRAIT

Sinoe vertical transport of nutrients and dissolved oxygen are quite important in the water col-umn and have drawn serious attention these recent years, a one-dmension numerical model is tried to simulate the vertical distribution of nutrients and dissolved oxygen in June at two research sites in the southemTaiwan Strait. Physical transport parameters are calibrated by temperature simulation, and thenare used to simulate the profiles of NO_3, PO_4 and dissolved oxygen. The simulation was generally success-ful for both stations. The importance of various factors, such as upwelling tidal current andbiogeochemical activities, which influence the vertical distribution of nutrients and dissolved oxygen, is revealed by analysis of the modeling results. Some important rates, fluxes and ratios are also estimated anddiscussed on the basis of simulation.     

The effects of estuarine processes on the fluxes of inorganic and organic carbon in the Yellow River estuary

Riverine carbon flux is an important component of the global carbon cycle. The spatial and temporal variations of organic and inorganic carbon were examined during both dry and wet seasons in the Yellow River estuary. Concentrations of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in the Yellow River during dry seasons were higher than those during wet seasons. The effective concentrations of DOC (C_DOC*) were higher than the observed DOC at zero salinity. This input of DOC in the Yellow River estuary was due to sediment desorption processes in low salinity regions. In contrast to DOC, the effective concentrations of DIC were 10% lower than the DIC measured at freshwater end, and the loss of DIC was caused by CaCO₃ precipitation in low salinity region. Particulate organic carbon (POC) and particulate inorganic carbon (PIC) contents of the particles stabilized to constant values (0.5%±0.05% and 1.8%±0.2%, respectively) within the turbidity maximum zone (TMZ) and showed no noticeable seasonal variations. A rapid drop of PIC and rise of POC occurred simultaneously outside the TMZ due to an intense dilution of riverine inorganic-rich particles being transported into a pool of aquatic organic-poor particles outside the TMZ. Annually, the Yellow River transported 6.95×10⁵ t of DIC, 0.64×10⁵ t of DOC, 78.58×10⁵ t of PIC and 2.29×10⁵ t of POC to the sea.     

DISTRIBUTIONS OF CHEMICAL ELEMENTS WITH RELATION TO MAJOR WATER CIRCULATIONS IN THE CENTRAL AND NORTHERN PARTS OF THE TAIWAN STRAIT

Data obtained from a comprehensive multidisciplinary oceanographic survey in the central and northern parts of the Taiwan Strait, 24°20′-26°00′N, 118°45°-121°00′E by the Fujian Institute of Oceanology during the period May, 1983 through May, 1984, showed that the distributions of dissolved oxygen (DO), nitrate, dissolved inorganic phosphate and silicate concentrations here had obvious areal and seasonal characteristics that were mainly influenced by the seasonal circulation ofthree major water systems in the Taiwan Strait-- the Taiwan Strait Warm Water (TSWW), theZhejiang-Fujian Coastal Water (ZFCW), and the Northeastern Strait Warm Water (NESWW).     

Nutrient structure of the Taiwan Warm Current and estimation of vertical nutrient fluxes in upwelling areas in the East China Sea in summer

Based on field data for nutrients collected on the continental shelf of the East China Sea (ECS) during summer 2006, the structure and variations of nutrients in every water mass related to the Taiwan Warm Current (TWC) were analyzed. The supplementary effect of nutrient of upwelling on harmful algal blooms (HABs) in the ECS was also estimated, based on upwelling data. Then the maintenance contribution of nutrient of upwelling to HABs was assessed. The results showed that N/P ratio is fairly low in both surface and deep layers of the TWC, which possibly controls nutrient structure of the HABs-frequently-occuring areas. In upwelling areas, the rate of phosphate (PO₄-P) uptake exceeds that of nitrate (NO₃-N) of the TWC. The TWC may relieve PO₄-P limitation during the process of HABs. Furthermore, upwelling plays an important role in providing nutrients to HABs. After estimating nutrient fluxes (NO₃-N, PO₄-P, SiO₃-Si) in the upwelling areas along a typical section (S07), the results showed that the nutrient uptake rate is the greatest at 10–20 m below euphotic zone, sustaining the ongoing presence of HABs. The uptake rate of PO₄-P is the highest among dissolved inorganic nutrients. Therefore, upwelling is most likely the main source of PO₄-P supply to HABs.     

Seasonal changes of dissolved and particulate organic carbon in Donghu Lake, China

Concentrations of dissolved and particulate organic carbon (DOC and POC) were documented in 1996–1997 at 4 different trophic state stations in Donghu Lake, a typical shallow eutrophic lake along the Changjiang River's middle reaches. The mean concentrations of DOC were 15.11±3.26, 15.19±4.24, 14.27±3.43, and 13.31±3.30 mg/L in Station I, II, III, and IV, respectively. The DOC concentrations of the studied area were very similar to that in other lakes along the Changjiang River's middle reaches. The POC mean of the whole lake was 5.01 mg/L due to the large amount of organic detritus of both allochthonous and autochthonous origin. Significant linear relationship was found between POC and chlorophyll a at all 4 stations, which presumably reflect that phytoplankton, its exudates and its metabolic products were the main contributors to the POC pool in the water column. The slope of such linear relationship at Station IV was significantly steeper than that at Station I, II and III. In addition, the DOC/POC ratios (mean value: 4.40) indicated that the organic detritus was the most important component of the particulate organic matter; in other works, next to organic detritus, phytoplankton dominated the particulate organic matter in Donghu Lake. Project 39770146, 39430101 supported by NSFC and the State Key Laboratory of Freshwater Ecology and Biotechnology, affiliated to the Institute of Hydrobiology, Chinese Academy of Sciences.     

Simulating dry deposition fluxes of PM10 and particulate inorganic nitrogen over the eastern China seas during a severe Asian dust event using WRF-Chem model

A WRF-Chem model including a comprehensive gas-phase nitrogen chemistry module was used to simulate a severe dust event appearing in the eastern China on 19-25 March, 2002. The modeling result well reproduced PM10 concentrations in various distances from the dust sources and the transport pathway of the dust strom. The results showed that both the concentrations and the dry deposition fluxes of PM10 increased over the China seas during the dust event following the passage of a cold front system. The maximum fluxes of PM10 in the Yellow Sea and the East China Sea during the dust event were 5.5 and 8.4 times of those before the event, respectively. However, the temporal variations of the dry deposition fluxes of particulate inorganic nitrogen differed over the Yellow Sea from those over the East China Sea. Nitrate and ammonium in the whole northern China rapidly decreased because of the intrusion of dust-loaded air on 19 March. The dust plume arrived in the Yellow Sea on 20 March, decreasing the particulate inorganic nitrogen in mass concentration accordingly. The minimum dry deposition fluxes of nitrate and ammonium in the Yellow Sea were about 3/5 and 1/6 of those before the dust arrival, respectively. In contrast, when the dust plume crossed over the Yangtze Delta area, it became abundant in nitrate and ammonium and increased the concentrations and dry deposition fluxes of particulate inorganic nitrogen over the East China Sea, where the maximum dry deposition fluxes of nitrate and ammonium increased approximately by 4.1 and 2.6 times of those prior to the dust arrival.     

Simple ecosystem model of the central part of the East China Sea in spring

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The distribution and concentration of particulate biogenic silica in surface waters of Prydz Bay, Antarctica, during the austral summer of 2011

The concentrations and distributions of particulate biogenic silica （PBSi） in the upper surface waters of Prydz Bay, Antarctica, were investigated during the 27th Chinese National Antarctic Research Expedition cruises of January 2011. We aimed to characterize the correlations between PBSi and plankton, nutrients and particulate organic carbon. The results showed that the concentrations of biogenic silica ranged from 0.76--19.72 ktmol-dm3 and the average concentration of biogenic silica was 6.06 mol.dm3. The distribution of surface PBSi had significant regional characteristics： The concentrations were higher south of 67S than to the north. The distribution of PBSi, chlorophyll a and particulate organic carbon showed similar patterns, and PBSi distribution had a negative correlation with that of silicate. In the vertical direction, the mole ratio of PBSi and POC （Si/Co） decreased with increasing depth. This trend indicated a higher rate of PBSi dissolution, or a lower rate of organic matter reminer- alization rate, in the upper 200 m.     

Source and spatial distributions of particulate organic carbon and its isotope in surface waters of Prydz Bay,Antarctica, during summer

In this study, we investigated the distributions of sea-surface suspended particulate organic carbon （POC） and its stable isotope （δ13C POC） in Prydz Bay, Antarctica, and examined the factors influencing their distribution, sources, and transport. We used measurements collected from 61 stations in Prydz Bay during the 29th Chinese National Antarctic Research Expedition, in combination with remote sensing data on sea surface temperature （SST）, chlorophyll a concentration, and sea ice coverage. The POC concentration in the surface waters of Prydz Bay was 0.28-0.84 mg.L-1, with an average concentration of 0.48 mg.L-1. The δ13C POC value ranged from -29.68‰ to -26.30‰, with an average of-28.01‰. The concentration of suspended POC was highest in near-shore areas and in western Prydz Bay. The POC concentration was correlated with chlorophyll a concentration and sea ice coverage, suggesting that POC was associated with phytoplankton production in local water columns, while the growth of phytoplankton was obviously affected by sea ice coverage. The δ13C poc value in suspended particles decreased gradually towards the outer waters of Prydz Bay, while in eastern Prydz Bay the δ13Cpoc value become gradually more negative from nearshore to deep-water areas, suggesting that δ13C poc was mainly influenced by CO2 fixation by phytoplankton. The δ13C POC value in suspended particles near Zhongshan Station was significantly negative, possibly as a result of the input of terrigenous organic matter and changes in the phytoplankton species composition in the nearshore area.     

Seasonal variations of riverine organic carbon contents in Makou and Hekou gauge stations of the Zhujiang River, China

Water samples were collected and analyzed in high water season (July 1997) and in middle water season (October, 1997) from two main lower reach gauge stations of the Zhujiang (Pearl) River, namely Hekou and Makou, respectively. Content of particulate organic carbon is always higher than that of dissolved organic carbon in both seasons, which is obviously different from the global average pattern, i.e. dissolved organic carbon is the dominant component of the transported riverine organic carbon. The content of dissolved and particulate organic carbon changes with the water levels in a direct ratio. The percentage of organic carbon in total suspended substance changes with the content of total suspended substance in an inverse ratio. The more intense is the soil erosion in the drainage, the more concentrated is the riverine organic carbon in the river. The contribution of autochthonous organic carbon is large in high water season than in middle water season. Fundation item: This project was supported financially by the National Natural Science Foundation of China (No. 49901002), the key funds of resources and eco-environmental research of the CAS (No. KZ952-J1-402), a funds of the state key laboratory of organic geochemistry, and Guangdong Province Science Funds (No. 984131). Biography: Gao Quan-zhou (1965 —), male, a native of Anhui Province, associate professor. His research interests are geomorphology and Quaternary geochemistry.     

Variations of the suspended matter and the particulate organic carbon in the entry of the Gironde Estuary,France

The effects of using different types of glass fiber filters (GF/F, GF/C) and of sample treatments were evaluated. Studies on the variation of suspended matter (SM) and particulate organic carbon (POC) showed that: 1) the transversal and day to night variations are important and must be taken into account in order to get a correct river flux; 2) no regular seasonal variations of SM and POC were observed, as they are controlled essentially by the climatological, hydrologic, physiochemical, biological, and geological conditions of the drainage area. Contribution No 2246 from the Institute of Oceanology, Chinese Academy of Sciences.     

A field study on the conversion ratio of phytoplankton biomass carbon to chlorophyll-<Emphasis Type="Italic">a</Emphasis> in Jiaozhou Bay,China

A one-year field study was conducted to determine the conversion ratio of phytoplankton biomass carbon (Phyto-C) to chlorophyll-a (Chl-a) in Jiaozhou Bay, China. We measured suspended particulate organic carbon (POC) and phytoplankton Chl-a samples collected in surface water monthly from March 2005 to February 2006. The temporal and spatial variations of Chl-a and POC concentrations were observed in the bay. Based on the field measurements, a linear regression model II was used to generate the conversion ratio of Phyto-C to Chl-a. In most cases, a good linear correlation was found between the observed POC and Chl-a concentrations, and the calculated conversion ratios ranged from 26 to 250 with a mean value of 56 μg μg⁻¹. The conversion ratio in the fall was higher than that in the winter and spring months, and had the lowest values in the summer. The ratios also exhibited spatial variations, generally with low values in the near shore regions and relatively high values in offshore waters. Our study suggests that temperature was likely to be the main factor influencing the observed seasonal variations of conversion ratios while nutrient supply and light penetration played important roles in controlling the spatial variations.     

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.     

Preliminary study on particulate organic carbon export fluxes in the Bering Sea

During the Second Chinese National Arctic Expedition (CHINARE) from July to September 2003, depth profiles of dissolved and particulate 234Th in upper water columns were collected at two stations of BR03 and BR24 in the Bering Sea. 234Th was sampled by using a traditional Fe(OH)3 co-precipitation technique, which is a reliable approach to 234Th measurement. We observed 234Th excess at station BR03 below the euphotic zone, which was possibly due to the intensive remineralization of particulate matter. Particulate organic carbon (POC) export fluxes were estimated from a one-dimensional irreversible steady state model of 234Th fluxes together with measurements of the POC/234Th ratio on the suspended particles. The POC export fluxes from the euphotic zone were 11.66 and 11.69 mmol C m-2 d-1 at BR03 and BR24 stations,respectively. The ratios of POC fluxes to primary production at the two stations were about 0.5 and 0.59, respectively, probably due to the presence of large phytoplankton (in particular diatoms).     

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.     

Spatial and temporal variations of Synechococcus and picoeukaryotes in the Taiwan Strait,China

The size-fractionated phytoplankton biomass, and the spatial and temporal variations in abundance of Synechococcus (SYN) and picoeukaryotes (PEUK) were measured in the Taiwan Strait during three cruises (August 1997, February-March 1998, and August 1998). The results show that picophytoplankton and nanophytoplankton dominate the phytoplankton biomass, in average of 38% and 40%, respectively. SYN and PEUK varied over time in abundance and carbon biomass, greater in summer than in winter, in range of (7.70–20...     

Chemical hydrography of coastal upwelling in the East China Sea

Based on the field data obtained during cruises on the shelf of the East China Sea from 1997 to 1999, seasonal variations of coastal upwelling on the inner shelf are discussed by using cross-shelf transect profiles and horizontal distributions of chemical and hydrographic variables. Results show that the coastal upwelling was year-round, but the areas and intensities of the upwelling were quite different in season. The coastal upwelling occurred in all of the coastal areas of the region in spring and summer, but in autumn only in the area off Zhejiang Province, and in winter in the area off Fujian Prov- ince. It was the strongest in summer and the weakest in winter. Geographically, it was the strongest in the area off Zhejiang Province and the weakest in the southmost or northmost parts of the East China Sea. The estimated nutrient fluxes upward into euphotic zone through coastal upwelling were quite large, es- pecially for phosphate, which contributed significantly to primary production and improved the nutrient structure of the coastal ecosystem in the East China Sea.     

MOLAR RATIOS OF C, N, P OF PARTICULATE MATTER AND THEIR VERTICAL FLUXES IN THE YELLOW SEA

The vertical fluxes and molar ratios of carbon, nitrogen and phosphorus of suspended particulate matter in the Yellow Sea were studied based on the analysis of suspended particulate matter,sediments and sinking particles obtained by use of moored sediment traps. The POC ： PON ratios indicate that most of the particulate organic matter in the Yellow Sea water column comes from marine life rather than the continent. The vertical fluxes of SPM, POC, PON and POP in the Yellow Sea are much higher than those in other seas over the world, and present a typical pattern in shallow epicontinental seas. The estimated residence time of the bioactive elements showed that the speed of the biogeochemical process of materials in the Yellow Sea is much shorter than that in the open ocean as there was high primary productivity in this region.     

Temporal and spatial variability of dissolved organic carbon concentration in the Xijiang River, South China

A whole year analysis of riverine dissolved organic carbon (DOC) concentrations in the Xijiang River (XJR), South China, showed that the mean riverine DOC concentration (1.24 mg L-1) in the XJR was notably lower than the averaged value (5.75 mg L-1) of the global riverine DOC concentration in several major rivers. There is an inconspicuous monthly fluctuation of the DOC signal in the XJR, but on a semi-yearly time scale, however, the riverine DOC concentration had significant difference between hydrological...     

Empirical ocean color algorithm for estimating particulate organic carbon in the South China Sea

We examined regional empirical equations for estimating the surface concentration of particulate organic carbon(POC) in the South China Sea. These algorithms are based on the direct relationships between POC and the blue-to-green band ratios of spectral remotely sensed reflectance,R rs( λ B)/ R rs(555). The best error statistics among the considered formulas were produced using the power function POC(mg/m 3)=262.173 [ R rs(443)/ R rs(555)]- 0.940. This formula resulted in a small mean bias of approximately-2.52%,a normalized root mean square error of 31.1%,and a determination coefficient of 0.91. This regional empirical equation is different to the results of similar studies in other oceanic regions. Our validation results suggest that our regional empirical formula performs better than the global algorithm,in the South China Sea. The feasibility of this band ratio algorithm is primarily due to the relationship between POC and the green-toblue ratio of the particle absorption coefficient. Colored dissolved organic matter can be an important source of noise in the band ratio formula. Finally,we applied the empirical algorithm to investigate POC changes in the southwest of Luzon Strait.