2008 Vol. 27, No. 5

Display Method:
Thermal fronts and cross-frontal heat flux in the southern Huanghai Sea and the East China Sea
PARK Sunghyea, CHU Peter C
2008, (5): 1-20.
Synoptic features in/around thermal fronts and cross-frontal heat fluxes in the southern Huanghai/Yellow Sea and East China Sea (HES) were examined using the data collected from four airborne expendable bathythermograph surveys with horizontal approxmately 35 km and vertical 1 m(from the surface to 400 m deep) spacings. Since the fronts are strongly affected by HES current system, the synoptic thermal features in/around them represent the interaction of currents with surrounding water masses. These features can not be obtained from climatological data. The identified thermal features are listed as follows:(1) multiple boundaries of cold water, asymmetric thermocline intrusion, locally-split front by homogeneous water of approxmately 18℃, and mergence of the front by the Taiwan Warm Current in/around summertime southern Cheju-Changjiang/Yangtze front and Tsushima front; (2) springtime frontal eddy-like feature around Tsushima front; (3) year-round cyclonic meandering and summertime temperature-inversion at the bottom of the surface mixed layer in Cheju-Tsushima front; and (4) multistructure of Kuroshio front. In the Kuroshio front the mean variance of vertical temperature gradient is an order of degree smaller than that in other HES fronts. The southern Cheju-Changjiang front and Cheju-Tsushima front are connected with each other in the summer with comparable cross-frontal temperature gradient. However, cross-frontal heat flux and lateral eddy diffusivity are stronger in the southern Cheju-Changjiang front. The cross-frontal heat exchange is the largest in the mixing zone between the modified Huanghai Sea bottom cold water and the Tsushima Warm Current, which is attributable to enhanced thermocline intrusions.
A preliminary study on the response of marine primary production to monsoon variations in the South China Sea Basic characteristics
WANG Hui, JIN Qihua, GAO Shan
2008, (5): 21-35.
Seasonal, interannual and interdecadal variations of monsoon over the South China Sea (SCS) directly influence the ocean circulation and the mass transport process, etc., especially the changes of horizontal circulation pattern and upwelling area. These changes directly influence the nutrient transport and the photosynthesis of phytoplankton, which induce the change of the marine ecosystem in the SCS, including the change of marine primary production in this sea area. On the basis of climatic data for long-time series and primary production estimated by remote sensing, the multi-time scale variations of monsoon, seasonal and interannual variations of primary production, and the response of primary production to monsoon variations were analyzed. Furthermore, the spatio-temporal variations of primary production in different sea areas of the SCS and their relations to the monsoon variations were given. The results showed that the strong southwesterly prevailed over the SCS in summer whereas the vigorous northeasterly in winter. The seasonal primary production in the entire sea area of the SCS also produced a strong peak in winter and a subpeak in summer. And the seasonal primary production distributions displayed different characteristics in every typical sea area. The variations of the annual and summer averaged primary production in the entire sea area of the SCS showed almost the same rising trend as the intensity of the summer monsoon. Especially for 1998, the summer monsoon reached almost the minimum in the past 54 a when the primary production was also found much lower than any other year (1999-2005). The responses of annual primary production to monsoon variation were displayed to different extent in different sea areas of the SCS; especially it was better in the deep sea basin. Such research activities could be very important for revealing the response of marine ecosystem to the monsoon variations in the SCS.
A study of SAR remote sensing of internal solitary waves in the north of the South China Sea: Ⅱ. Simulation of SAR signatures of internal solitary waves
FAN Zhisong, ZHANG Yuanling, SONG Mei
2008, (5): 36-48.
A new model developed from the full-spectrum model of Lyzenga and Bennett (1988) is built up by us preliminarily through considering the impact of the ocean surface mixed layer turbulence on SAR remote sensing of internal solitary waves. In the partial differential equation of the action spectral density of the surface gravity-capillary waves the source function representing the contribution of the turbulence is added besides the usual source function representing the contribution of the wind. The source function is determined by applying the k-ε model and adopting the Nasmyth spectrum of oceanic turbulence (Nasmyth, 1970; Oakey, 1982; Fan, 2002) on the basis of the previous simulation results of internal tide transformation obtained in the companion paper (Fan et al.,2008). Either under relatively high wind speed, or under low wind speed, our model predicts significant large modulations of radar backscatter at all three bands (L, C and X bands) for both VV and HH polarization. These results prove that considering the impact of ocean surface mixed layer turbulence on SAR remote sensing of internal solitary waves is reasonable and appropriate for settlement of the well-known problem of contemporary radar imaging models.
Improving the wind and wave estimation of dual-frequency altimeter JASON1 in Typhoon Shanshan and considering the rain effects
YANG Le, LIN Mingsen, ZOU Juhong, LI Zhenghua, PAN Delu
2008, (5): 49-62.
Altimetry data have been widely used in various fields of oceanography, including the extreme weather events such as tropical cyclones, typhoons, and hurricanes. The performance of JASON1 in Typhoon Shanshan is assessed by examining the sensor geophysical data record and illustrates how the measured return waveform, significant wave height, and backscatter are all affected by various factors associated with the typhoon, with details by the rain are illustrated. The correction method to maintain accurate wave height and wind speed measurements in Typhoon Shanshan and the results are presented. Furthermore, the additional results of rain rate and typhoon eye diameter can be retrieved. Because of the lack of in-situ measurements of wind, wave, and rain rate at Typhoon Shanshan, results are compared with the forecasted typhoon data and a good agreement is found.
Mean water level setup/setdown in the inlet-lagoon system induced by tidal action-a case study of Xincun Inlet, Hainan Island in China
GONG Wenping, SHEN Jian, WANG Daoru
2008, (5): 63-80.
With the tides propagating from the open sea to the lagoon, the mean water level (MWL) in the inlet and lagoon becomes different from that at the open sea, and a setup/setdown is generated. The change of MWL (setup/setdown) in the system imposes a great impact on regulating the development of tidal marshes, on determining the long-term water level for harbor maintenance, on the planning for the water front development with the flood control for the possible inundation, and on the interpretation of the historical sea level change when using tidal marsh peat deposits in the lagoon as the indicator for open sea's sea level. In this case study on the mechanisms which control the setup/setdown in Xincun Inlet, Hainan in China, the 2-D barotropic mode of Eulerian-Lagrangian CIRCulation (ELCIRC) model was utilized. After model calibration and verification, a series of numerical experiments were conducted to examine the effects of bottom friction and advection terms, wetting and drying of intertidal areas, bathymetry and boundary conditions on the setup/setdown in the system. The modeling results show that setup occurs over the inlet and lagoon areas with an order of one tenth of the tide range at the entrance. The larger the bottom friction is, a larger setup is generated. Without the advection term, the setup is reduced due to a decrease of water level gradient to compensate for the disappearance of the advection term. Even without overtides, a setup can still be developed in the system. Sea level rise and dredging in the inlet and tidal channel can cause a decrease of setup in the system, whereas shoaling of the system can increase the setup. The uniqueness of the Xincun Inlet with respect to MWL change is that there is no evident setdown in the inlet, which can be attributed to the complex geometry and bathymetry associated with the inlet system.
Historic changes in flux of matter and nutrient budgets in the Bohai Sea
LIU Sumei, ZHANG Jing, GAO Huiwang, LIU Zhe
2008, (5): 81-97.
Over the past four periods (1959-1960, 1982-1983, 1992-1993, and 1998-1999), the ecosystem of the Bohai Sea changed due to both a significant decrease of river water discharge from the Huanghe River and a reduction of precipitation. The shifts in nutrient chemistry could result in changes in the phytoplankton composition with an increased potential for non-diatom algal blooms. Simple box model was used to estimate the water-mass balance and nutrient budgets for the Bohai Sea. Water budgets indicate that the residual flow changed from out of the Bohai Sea before 1993, but became inflow to the Bohai Sea after then. The nutrient budgets developed indicate that the Bohai Sea was a sink for nutrients except for phosphate in 1959-1960 and 1982-1983 and for silicate in 1982-1983. Net water flow transports nutrients out of the Bohai Sea in 1959-1960, 1982-1983 and 1992-1993, but into the sea in 1998-1999 due to climate changes, such as precipitation and subsequent freshwater discharge. The residual fluxes of nutrients are minor relative to atmospheric deposition and riverine inputs. Conversions of phosphate values to carbon by stoichiometric ratios were used to predict that the system was net heterotrophic before 1982-1983 and net autotrophic after then. Nutrient budgets can explain the change of nutrient concentrations in the Bohai Sea except nitrates, which should include the surface runoff.
A nitrogen and phosphorus dynamic model of mesocosm pelagic ecosystem in the Jiaozhou Bay in China
LI Keqiang, WANG Xiulin, LIANG Shengkang, SHI Xiaoyong, ZHU Chenjian, CHEN Hu
2008, (5): 98-110.
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.
Nutrient composition and distributions in coastal waters impacted by the Changjiang plume
WANG Xiulin, WANG Baodong, ZHANG Chuansong, SHI Xiaoyong, ZHU Chenjian, XIE Linping, HAN Xiurong, XIN Yu, WANG Jiangtao
2008, (5): 111-125.
Four cruises were conducted during 2002-2003 in the Changjiang Estuary and adjacent coastal areas. The data presented show a clear coast to open sea gradient in nutrients related to the river inputs. Maximum values of chlorophyll a were typically observed at intermediate salinities at surface water and coincided with non-conservative decreases in nutrients along the salinity gradient, indicating that removal of nutrients was related to phytoplankton uptake. The seasonal variations of nutrient concentrations were just opposite to those of chlorophyll a, indicating that the seasonal variations of nutrients were mainly controlled by phytoplankton uptake, whereas riverine inputs merely weakened or balanced its extent. During the estuarine mixing, phosphate demonstrated some remobilization during all the four cruises; whereas both conservative and non-conservative behaviors for dissolved inorganic nitrogen and silicate were observed in the study area, indicating that both biotic and abiotic events may affect their behaviors during the estuarine mixing. Under the influence of freshwater inputs with high value of ratio of nitrogen to phosphorus, the estuarine and coastal waters impacted by the Changjiang plume were high (> 30) in ratio of nitrogen to phosphorus, but rates of primary production were apparently not constrained by any kind of nutrient elements. However, the low (< 1) ratio of silicate to nitrogen in most of the study area might be linked with the rapidly increasing frequency of harmful algal bloom(HAB) incidents in recent years in the coastal waters impacted by the Changjiang plume.
Intragenic and intergenic sequences regulating the expression of the 5'-to-5' linked adult αand β-globin genes from large yellow croaker Pseudosciaena crocea
CHU Wuying, YU Lian, QIAN Ronghua, MENG Tao, ZHOU Ruixue, FU Guihong, CHEN Jia, ZHANG Jianshe
2008, (5): 126-133.
One adult α-globin gene and one β-globin gene have been cloned from the large yellow croaker Pseudosciaena crocea. Linkage analysis indicated that the αand β-globin genes were oriented head-to-head relative to each other. To identify the regulatory elements present in the intergenic and intragenic regions of the globin complex, the intergenic region alone or together with the β-globin gene first intron was cloned into the luciferase-reporter vector pGL3-Basic respectively, and the chimeric constructs were transiently transfected into Vero cells and primary fish erythrocytes. The intergenic region cannot support the high-level expression of luciferase. However, the promoter activity of the intergenic region was strongly stimulated by the positive regulatory elements (PRE) located in the β-globin gene intron 1. Thus, it is proposed that the intergenic promoters and intragenic PRE were necessary for the effective expression of the linked αand β-globin genes.
Molecular identification of scallop planktonic larvae using species-specific microsatellites
ZHAN Aibin, HU Xiaoli, BAO Lisui, LU Wei, PENG Wei, WANG Mingling, HU Jingjie
2008, (5): 134-146.
The identification of scallop larvae is essential to understand the population structure and community dynamics and to assess the potential environmental impacts caused by scallop larvae released or escaped. However, the larvae identification by morphological characteristics is notoriously difficult, mainly due to the small size (usually being less than 150 μm) and vague morphological characteristics among different scallop species. A simple and accurate molecular method was developed to identify four economically farmed scallop species, the Zhikong scallop Chlamys farreri, the noble scallop C. nobilis, the bay scallop Argopecten irradians and the Yesso scallop Mizuhopecten yessoensis. The tests used the high degree of species-specific microsatellite markers, which was specified by transferability analyses, assessed by reference individuals and evaluated by BLAST searches. The sensitivity test indicated that the species-specific microsatellites were sensitive enough for the detection of 1%~2% larvae in mixed plankton samples. Larvae collected from scallop hatcheries and their effluents and from the artificially controlled crosses were well identified to the species/hybrid level. The results demonstrated that the one-step PCR-based assay was technically simple, inexpensive and robust in identification analyses, and also less sensitive to initial quality of template DNA extracted from the ethanol-preserved samples for several years.
Grazing impact of microzooplankton on phytoplankton in the Xiamen Bay using pigment-specific dilution technique
HUANG Bangqin, LIU Yuan, XIANG Weiguo, TIAN Haojie, LIU Hongbin, CAO Zhenrui, HONG Huasheng
2008, (5): 147-162.
Phytoplankton group-specific growth and microzooplankton grazing were determined seasonally using the dilution technique with high-performance liquid chromatography (HPLC) in the Xiamen Bay, a subtropical bay in southeast China, between May 2003 and February 2004. The results showed that growth rates of phytoplankton ranged from 0.71 to 2.2 d-1 with the highest value occurred in the inner bay in May. Microzooplankton grazing rates ranged from 0.5 to 3.1 d-1 with the highest value occurred in the inner bay in August. Microzooplankton grazing impact ranged from 39% to 95% on total phytoplankton Chl a biomass, and 65% to 181% on primary production. The growth and grazing rates of each phytoplankton group varied, the highest growth rate (up to 3.3 d-1) was recorded for diatoms in August, while the maximum grazing rate (up to 2.1 d-1) was recorded for chlorophytes in February in the inner bay. Among main phytoplankton groups, grazing pressure of microzooplankton ranged from 10% to 83% on Chl a biomass, and from 14% to 151% on primary production. The highest grazing pressure on biomass was observed for cryptophytes (83%) in August, while the maximum grazing pressure on primary production was observed for cyanobacteria (up to 151%) in December in the inner bay. Net growth rates of larger phytoplanktons (diatoms and dinoflagellates) were higher than those of smaller groups (prasinophytes, chlorophytes and cyanobacteria). Relative preference index showed that microzooplankton grazed preferentially on prasinophytes and avoided to harvest diatoms in cold seasons (December and February).