Coral reefs over the Nansha Islands have characteristic geomorphological patterns; they exist in the form of atolls. The Niu’e (also known as Mckennan) and Ximen (Whitsum) reefs of the Jiuzhang Giant Atoll are two secondary atolls with newly-formed debris deposits, which may represent an important stage of landform evolution from a submerged atoll towards a reef island. Grain-size analysis of the surficial sediment samples collected from the two reefs shows that gravel-sized coral debris is the main component of the deposit. Medium grain sizes of the samples (measured by the long axis) range from 14 to 45 mm. Sorting coefficients range from 4.5 (being poorly sorted) to 31 with a sphericity value of 0.52 to 0.68 (far from a sphere shape). Medium grain sizes show a trend of increasing away from the shoreline. Medium grain sizes of the sediment samples are positively correlated with sorting coefficients, whereas they are more or less negatively correlated with sphericity values. Based on an analysis of historical records and satellite images, these beach ridge- or sand bar-like deposits represent modern accumulation landforms; their formations are related to storm waves and to some extent to the winter monsoon waves. The sand bar on the Niu’e reef had been extending towards the southeast and at the same time moving towards the north. The sand bar on the Ximen reef had an overall migration towards the southeast, with recurved sand spits on both sides. The mechanisms for the formulation of these features, in terms of changes in coral material supply and storm wave pattern, need further investigations.

Marine planktonic ostracods are small crustaceans with a wide distribution, playing an important role in ocean carbon cycle. The ostracods in smaller size are usually underestimated when marine zooplankton samples were collected with 505 μm mesh. Based on the zooplankton samples collected with 505 and 160 μm meshes in the northern South China Sea from July to August 2006 (summer) and from December 2006 to January 2007 (winter), the capture efficiency for the ostracods using two planktonic mesh sizes was compared, and the community structure and the influence of environmental factors on their distributions were analyzed. We found that the abundance of ostracods obtained by the 160 μm mesh net was six times that by the 505 μm net in summer. The community structure of planktonic ostracods collected by the 160 μm mesh was analyzed with the following findings. 1) The species richness of planktonic ostracods of a total of 32 species was identified to increase from nearshore to offshore, and the difference between the areas with water depth shallower and deeper than 100 m was extremely significant (p<0.01). 2) The abundance of planktonic ostracods was higher in summer, when the high abundance area appeared mainly in the coastal waters of the Leizhou Peninsula and northeast Hainan Island higher than that in offshore significantly (p<0.05), and lower in winter, when the distribution of ostracods abundance was homogeneous. 3) Euconchoecia aculeata, dominant species, contributed the most to high abundance in the nearshore. 4) The species richness of ostracods was positively correlated with temperature and water depth; and the abundance was negatively correlated with temperature and salinity, and positively correlated with chlorophyll α concentration. Qiongdong coastal upwelling and Yuexi Coastal Current boosted the abundance of planktonic ostracods up to 1252 ind·m ^-3 in the coastal waters of the Leizhou Peninsula and northeast Hainan Island. Results suggest that smaller mesh net should be used for the overall assessment of community characteristics of planktonic ostracods.

Marine ecosystem dynamics model is an important means to study marine ecological environment. As the model complexity increases, the number and uncertainty of biological parameters increase, which has a great impact on model results; therefore, optimization of model parameters is particularly important. In this paper, a one-dimensional physical-biological model is applied to the northern South China Sea, and the key biological parameters obtained through sensitivity analysis are optimized by using genetic algorithm. The results show that the sensitive parameters in the model are related to phytoplankton growth, zooplankton growth, feeding and death, and detritus sinking. Based on the genetic algorithm optimization of the above-mentioned parameters, we find that the surface and vertical simulation errors of the model are reduced by 27.80% and 21.40%, respectively, by using only surface satellite data; the surface and vertical simulation errors are reduced by 14.90% and 32.70%, respectively, by adding observed profile data. The success of applying genetic algorithm in the one-dimensional model provides the basis for its further application in three-dimensional marine ecosystem models.

The Chinese probably first had the name of the South China Sea (pronounced as “Nanhai” in Chinese, where “Nan” means “south”, “hai” means “sea”) in writing at the time of Wuwang Period (1046 BC-1043 BC) during the Zhou Dynasty. “Nanhai (place name)”, was named for its closeness to the South China Sea (Nanhai), which clearly suggests that the term “Nanhai (place name)” was used later than the term “Nanhai (sea name)”. During Chengwang Period (1042 BC-1021 BC) of the Zhou Dynasty, the famous tribute of black millet (Indian millet), known as the story of “Millet of Nanhai”, was from the “Nanhai (place name)”. In Xuanwang Period (827 BC -782 BC) of the Zhou Dynasty, the name “Nanhai” used in the poem Jiang Han includes both the “Nanhai (sea name)” and “Nanhai (place name)”, which was the first time the name was used in writing. “Nanhai” was then used in Yu Gong of Shang Shu in late Zhanguo Period (475 BC -221 BC), but whether it meant the “Nanhai (sea name)” or not has yet to be confirmed. “Nanhai” was later used in Hai Nei Dong Jing of Shan Hai Jing during the Qin (221 BC -207 BC) and Han (206 BC- AD 220) Dynasties; it was also used in Nan Yue Lie Zhuan of Shi Ji and in an ancient map of early Western Han Dynasty (206 BC- AD 8), where it was definitely referring to the “Nanhai (sea name)”, just like its present meaning. From the Eastern Han Dynasty (AD 8-220) to the Tang (AD 618-907) and Song (AD 960-1279) Dynasties, the “Nanhai” was referred as the “Zhanghai”. Over the Ming (AD 1368-1644) and Qing (AD 1644-1911) Dynasties, the “Nanhai” was called the “Daminghai” and “Daqinghai” by foreigners. Then the “Nanhai” was translated as the “South China Sea” by foreigners and the name “South China Sea” has been widely used all over the world. Unfortunately, some Chinese translate the English name “South China Sea” directly into Chinese as the “Nanzhongguohai”, which is then used by some books, magazines and media. The “Nanhai” was first found and named by Chinese around 3 000 years ago, which has been well recognized all over the world. The “Nanhai” is the only name used in official publications and maps by the most recent governments of China. The “Nanhai” is also the only name used in the related administrative departments, armed forces and institutions. Therefore, the “Nanhai” should not be called the “Nanzhongguohai”. People using the name “Nanzhongguohai” can be considered ignorant to Chinese history, which may mislead people to think that the “Nanhai” (South China Sea) was first found and named by foreigners, and further confuse the Chinese sovereignty on the Nanhai.

Over the last two years, Chinese scientists from the both sides of the Taiwan Strait and from overseas, met several times to discuss the direction of deep-sea research in China. All agreed that the South China Sea should be the first priority, and a preliminary sketch of research program of the “The South China Sea Deep” was drafted. The overarching goal of the proposed program is to unveil “the life of a marginal sea”, from three major perspectives: (1) evolution of the oceanic crust in the deep basin, which will be revealed by validating the magnetic anomalies in the South China Sea using new techniques, implementing deep-water drilling of the oceanic crust, and systematically investigating the volcanic mountain chains in the basin; (2) deep-sea sedimentation, including observation of the modern deep-water currents and benthic sedimentation, and reconstruction of sediment response to the evolution of the marginal basin; and (3) biogeochemical processes to be approached by exploring the dynamics and consequences of subsurface fluid circulation, and by evaluating the microbial contribution to the deep-sea carbon cycling. Research breakthroughs are expected in the South China Sea on the basis of nation-wide cooperation with a combined effort by the scientific and engineering communities.

Using ADCP （Acoustic Doppler Current Profiler） and CTD (Conductivity/Temperature/Depth profiler) data acquired in August 2007 and the Gregg model, the authors estimate the internal-wave-scale mixing in the intermediate and deep layers of the South China Sea. They also use the Thorpe scale to study the vertical overturns in these layers and the corresponding diapycnal diffusivity. The results by the two methods are consistent, showing that the dissipation rate and diapycnal diffusivity in the upper 400m near the Luzon Strait are larger than those at 18°N, while there is no obvious distinction in the mediate and deep layers. These results, therefore, suggest that there may be active internal waves resulting in intensive internal wave mixing and vertical overturning in the upper 400m near the Luzon Strait. The dissipation rate and diapycnal diffusivity estimated by the Gregg model are at the level of 10–9 W?kg–1 and 10–6 m2?s–1, respectively. At most of the CTD stations surveyed, there always exists vertical overturning in the intermediate and deep layers and the diapycnal diffusivity estimated by the Thorpe scale does not decrease with depth. The characteristics of the fine-scale mixing reported here will facilitate the understanding of the intermediate and deep layers of the South China Sea.

The authors analyze the internal wave spectra of the ADCP（Acoustic Doppler Current Profiler） data from the South China Sea Monsoon EXperiment (SCSMEX) in 1998. The results suggest that the level of nonlinear interactions amongst internal waves affects the characteristics of internal wave spectra in the north South China Sea. In the seasonal thermocline (depths of 22 m and 58 m), the falloff rate of the spectra with frequency σ trends to fall between σ–1 and σ–2 for internal-wave band due to strong nonlinear interactions; furthermore, tidal harmonic frequency peaks with high energy show an amplitude decrease of σ–3 with frequency. Below the seasonal thermocline (depth 130 m), the nonlinear interactions are weakened with increasing depth so that the internal wave spectrum is similar to canonical Garrett-Munk spectrum, both showing a falloff rate of σ–2.

In order to obtain a forecasting equation of sound velocity for seafloor sediments, the authors first apply the technology of principal component analysis and analyze existing empirical equation and its calculation errors. A principle component model is then built up using the measurement data of sediments from the continental slope and shelf in southern South China Sea. The authors also studied in theory how to exclude correlated parameters from a number of parameters that can affect the sound velocity and how to optimize a few parameters that are obviously related to sound velocity without cross-correlation. Using the optimal physical parameters, such as porosity n, median grain size Md and plastic limit Wp, a three-parameter forecasting equation of sound velocity is established for the continental shelf and slope in southern South China Sea. The equation is Cp =1774–5.0944 +12.499 Md +0.9985Wp. The relative forecasting error ranges only from –4.48% to 3.77%.

The authors analyzed oxygen and carbon isotope of planktonic foraminifera from surface sediments and plankton tow samples collected from southern South China Sea (SCS) in spring 2002, and discussed their relationship with marine environmental parameters and depositional process. Their results show that Globigerinoides ruber and G. sacculifer have almost the same average δ18O values in the spring tow samples, which are obviously lighter than those in the surface sediments. In the surface sediments, however, the average δ18O value of G. ruber is apparently lighter than that of G. sacculifer, which may be related to gametogenesis calcification of G. sacculifer and seasonal difference of the two species. The average δ18O value of Pulleniatina obliquiloculata is apparently heavier than that of G. ruber and G. sacculifer in both the surface sediments and the upper water, suggesting a large intra-species δ18O gap between the three species. The average δ18O value of P. obliquiloculata in the upper water in spring is about 0.7‰ lighter than that in the surface sediments, possibly due to the winter flourish of P. obliquiloculata that prefers the low temperature of winter water. The average δ13C values of the three species show a similar trend in both the sediments and the upper water, namely, the heaviest for G. sacculifer, the lightest for P. obliquiloculata, and G. rubber in the middle. The difference of δ13C values between the three species may be mainly caused by vital effect. The regional variations of δ18O values of G. ruber and G. sacculifer in the surface sediments show a similar trend, with heavy values in the northwest and gradually lightening to the southeast of the studied area, all accords with the trend of yearly-averaged sea-surface temperature of gradually increasing from northwest to southeast. Both the δ18O and δ13C of P. obliquiloculata show heavier values in the upwelling stations of the studied area. The relationship of δ13C of P. obliquiloculata with nutrient level of the upper-water mass in southern SCS is contrary to that in northern SCS, which needs to be confirmed by future studies.

 Curie point isotherm is the temperature isotherm where ferromagnetic minerals in the rocks change from ferromagnetism into paramagnetism because the temperature increases to the Curie point. Below this isotherm, the rocks are thought to be almost non-magnetism because their temperature is higher than the Curie point. Sino-US two-ship expanding spread profiles eastern transect (ESPE) in 1985 and Sino-Japan Ocean Bottom Seismography profile in 1993 (OBS93) crossed the major structural belts and basins in the northeastern South China Sea. Integral gravity, magnetic, heatflow and seismic data were acquired along these profiles. Magnetic Curie point isotherm was obtained by inversion of the magnetic anomalies, and thermal Curie point isotherm (the 575℃ isotherm) was obtained according to the geothermal temperature field calculated from the heatflow survey data. The results showed that the two Curie point isotherms derived respectively from the prior two methods were inconsistent with significant differences in many regions. After analyzing their calculation principle, the authors believed that the reason for these differences was that the prerequisite calculating the stable-state geothermal temperature filed was untenable in some areas with possible unknown underground heat events, then the thermal Curie point isotherm derived from this method would not show the actual Curie point isotherm in such areas. In order to explain these differences more clearly, the authors introduced the concept of thermal equilibrium, which showed that the two types of Curie point isotherm were consistent in thermal equilibrium region and inconsistent in thermal disequilibrium region. As a result, they could achieve the magnetic and thermal Curie point isotherm first in some areas and distinguish the unknown underground heat events from their differences, which has important instructional significance and reference value for the study on regional tectonics, oil and gas geological conditions and resource predictions.

Numerical models are the basis for quantitative modeling of the tectono-thermal evolution of sedimentary basins. Due to the importance of rift basins in scientific research and petroleum exploration, extensive studies have been devoted to building numerical models for rift basins. This paper summarizes the models that have great influence or play an important role in the study of the passive continental margin of the South China Sea, including the most fundamental model of McKenzie, and the models of finite-rate stretching, simple shear stretching, flexural cantilever stretching, depth-dependent stretching, and multiphase stretching. Special emphasis was placed on their basic assumptions, application conditions, and numerical formulations for the geothermal field and basin subsidence. The similarities, differences, and correlations of these models were expounded. Finally, the applications of the models in studying the rift basins in the northern South China Sea were briefed, which may help to advance our understanding of the methods and applications of the numerical models.

From the 6th March to the 9th April in 2008, serial bottom-current observations were carried out at the sand-wave zone of the continental shelf and slope in the northern South China Sea (SCS). The measurements show that the tidal current and ocean current are weak at the observation sites, but bottom currents as strong as 30-77 cm.s-1 occur frequently. The directions of the strong bottom currents are related to the northwestward propagation of the internal waves in the region. Most of the strong currents are nearly northwestward or nearly southeastward, and the southeastward currents are stronger than the northwestward ones, which corresponds to the feature of downslope flows stronger than upslope ones when internal waves propagating onshore. Rotary power spectral analysis is carried out for the time series of current velocity. The results show that most of the rotary components higher than the frequency of M2 tide have the characteristics of internal-wave flows, further demonstrating that the frequent, strong bottom currents are induced by internal waves. The measurements are used to calculate the motion speed of sand waves. The results also show that the strong currents can initiate the sea bottom sediments, and due to downslope flows stronger than upslope ones, the sand waves move southeastwards at a low speed less than 1.6 m.yr-1. In addition, the authors model the coupled tide-storm bottom current fields in the northern SCS. From the modeling, the bottom currents, driven by strong typhoon and tide, can move the sand waves, but only move them a very short distance during each typhoon process. The direction of the movement is subject to the typhoon route, which is not always southeastward. Therefore, the coupled tide-storm currents are not the major factor to move the sand waves.

Based on comprehensive consideration of topography, geological structure，seismological features and historical records, the authors analyze the hazardous tsunamigenic zones in the South China Sea and discuss the possibility of potential tsunami hazards in the region. A tsunami induced by a hypothetical earthquake in the Manila Trench is simulated using a nested 3-layer grid system with high resolution. Each grid area in the grid system can be configured with its own type of coordinate system depending on its coverage, simulation parameters as well as the governing equations in terms of the characteristics at different stages of tsunami propagation. This flexible, nested grid setup allows for a balance between computational accuracy and efficiency. The simulation results，such as the calculated travel time map, maximum surface elevation and water height series at four virtual gauges, indicate that the tsunami hazards could happen on the coasts off South China. Further research is necessary to determine the need for a monitoring system of tsunami in the region.

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Based on the monthly averaged sea surface temperature (SST) derived from the optimum interpolation sea surface temperature (OISST) from January 1982 to December 2006, the authors analyze the spatial and temporal variability of SST anomalies (SSTA) in southern South China Sea using the Empirical Orthogonal Function (EOF) method. The results show the existence of three major SSTA spatial patterns, which include the basin-scale single gyre pattern with the center in the northern area, the west-eastward antiphase dipole pattern, and the north-southward antiphase dipole pattern. The three modes all have interannual variations, which reflect the relationship between the SSTA of southern South China Sea and ENSO phenomena. The semi-annual and the intraseasonal variations are also found in Mode 3, which results from wind forcing and heat budget.

Characteristics of seismic facies is important for identifing submarine channels. Using 2D and 3D high-resolution seismic data, the authors are able to identify three submarine channels that developed in Pliocene, Miocene and Quaternary on the slope of the Qiongdongnan Basin. The channel that formed in Miocene mainly has such seismic characters as strong amplitude alternating with weak amplitude, reciprocal overlying, and partly developing clutter reflection. The channel that formed in Pliocene mainly has such seismic characters as high amplitude reflections, continuous or semi-continuous transversely, overlying high amplitude reflections vertically. The channel in Quaternary is characterized by classic lower cutting reflections in seismic profile, with low amplitude reflections on the whole but classic High Amplitude Reflections (HARs) at channel axis. These submarine channels should be related with the turbidity current occurring at the Lowstand System Tract (LST).

The authors have summarized a set of rules for choosing and verifying the main acquisition parameters in marine seismic exploration based on previous experiences of long-term practice. Firstly, an analysis is carried out for the selected area to establish a representative seismogeological model using various seismic and geologic information. Considering the current devices’ performances and options，they use a professional simulation software, Nucleus 6.2, to compute source parameters and to compare the response to various combinations of acquisition parameters, in order to choose a combination that is best adaptive to certain task. An actual exploration test is also carried out to verify the parameters’ combination chosen from the simulation test. Finally, the authors select the optimum Parameters’ combination and obtain quality data for production.

The authors report on the mineralogical features and carbon-oxygen isotope composition of the authigenic carbonates build-up of Samples TVG-1 and TVG-11 from Jiulong methane reef in the South China Sea. The results by XRD confirm that the samples are composed of miscellaneous carbonates, including aragonite, Mg-calcite and dolomite, while detrital minerals are less abundant. In Sample TVG-1, aragonite is replaced by calcite and the pseudomorph of the former is observed, suggesting that this sample was formed earlier than the other because phase transformation of aragonite to calcite has occurred. SEM observation reveals that micro-scale acicular aragonite is usually associated with bio-filaments which may be extra-cellular polymeric substances produced by microorganisms. These observations confirm that carbonates precipitation is related to heterotrophic microbial communities fueled by hydrocarbon seepage only having weak activity currently. Stable isotope composition of the carbonates is characterized by strong 13C depletion, with a ?13C value of –46.22‰ and –52.88 ‰ for TVG-1 and TVG-11, respectively, indicating that the carbon source is most probably related to anaerobic oxidation of methane. Another distinct feature of the carbonates is its enrichment of ?18O, +3.19‰ and +4.07‰ for TVG-1 and TVG-11, respectively. 13C depletion and 18O enrichment along with the micro-fabric textural evidence suggest that the Jiulong carbonates build-up might have been precipitated from the fluids originating from gas-hydrate decomposition, which indicates that this area may have gas hydrate resources.

During the sporopollen and algae research of the deep-sea sediments at Core 69 in the South China Sea, five sporopollen zones have been distinguished in ascending order as Zone 1 (552.5—470 cm): Quercus (evergreen)-Pinus-Cyathea-Artemisia, Zone 2 (470—350 cm): Pinus-Podocarpus-Quercus-Polypodiaceae, Zone 3 (350—250 cm): Quercus (evergreen)-Castanopsis-Pinus-Polypodiaceae, Zone 4 (250—140cm): Pinus-Podocarpus-Artemisia-Polypodiaceae, and Zone 5 (140—0 cm): Podocarpus-Cyathea-Quercus (evergreen)-Pinus-Polypodiaceae. The sporopollen zones reflect three evolution stages of vegetation, climate and paleoenviornment in the South China Sea since 64 000 yr BP as follows: hot and wet tropical monsoon rainforest, semievergreen monsoon rainforest of northern tropics, and return to hot and wet tropical monsoon rainforest. Stage 1: During this period, the vegetation was characterized by tropical monsoon rainforest，reflecting a hot and wet climate when the sea level rose. There were many evergreen tree species. The tree layer was dominated by Dacrydium, Podocarpus, evergreen Quercus, Pinus, Elaeocarpus, Magnolia, Castanopsis, Palmae, Myrica and Altingia, among others. The herbage layer under canopy included Gramineae, Artemisia，Chenopodiaceae and Cyperaceae. The ferns were dominated by Polypodiaceae, Microlepia, Cyathea, Diplopterygium and Pteris. Mangrove plants grew along the coastal areas. Stage 2: The vegetation was semievergreen monsoon rainforest of northern tropics. This stage was indicated by the palynological Zones 2 to 4. The elements of evergreen Quercus, Castanopsis, Pinus and Magnolia from the southern subtropical zone increased in the vegetation, whereas the elements of Elaeocarpus, Dacrydium and Palmae from the tropical zone decreased. The herbage layer under canopy consisted of Gramineae, Artemisia and Cyperaceae, among others. The ferns were dominated by Polypodiaceae, Pteridium, Cyathea, Diplopterygium and Adiantum. Mangrove plants grew along the coastal areas. The vegetation was characterized by the northern tropical semievergreen monsoon rainforest, reflecting a slightly dry and warm climate when the sea level dropped. Stage 3: The vegetation was again tropical monsoon rainforest. Indicated by palynological Zone 5, the vegetation mainly consisted of Dacrydium, Podocarpus, Altingia, Palmae, Lauraceae, Magnolia, Sapindaceae, evergreen Quercus, Castanopsis and Myrica, among others. The herbage layer under canopy was dominated by Gramineae, Umbelliferae, Chenopodiaceae and Artemisia. The ferns included Polypodiaceae, Cyathea, Dicranopteris, Diplopterygium and Pteris. Mangrove plants grew along the coastal areas. All of these showed a hot and wet environment when the sea level rose. Combined the sporopollen and algae data with oxygen isotope dating, a stratigraphic division was done for the Core 69 in the South China Sea. Palynological Zone 1 corresponds to oxygen isotope period 3, and its stratigraphic time is Q33—2; Palynological Zones 2 to 4 correspond to oxygen isotope period 2, and its stratigraphic time is Q33—3; Palynological Zone 5 corresponds to oxygen isotope period 1, and its stratigraphic time is Q4.

The authors analyze the essential energy loss during sediment acoustic measurement process, describe the principle of differential attenuation measurement that is the research base of parallel-axis and vertical-axis differential distance attenuation measurement methods, and deduce its attenuation coefficient formula. According to sectioning characteristics of the cylinder seafloor sediment samples from the South China Sea, a coaxial differential distance attenuation measurement method (CDDAMM) is put forward with combination of the above two methods, which is reasonable in principle and feasible in practice. Using CDDAMM, they measure the sound propagation signals of the sediments in both room and controlled temperatures, calculate the acoustic attenuation coefficient, and study the effect of temperature on sound propagation energy. The sound attenuation characters of deep-water seafloor sediments from the South China Sea are as follows. The sediments have large acoustic attenuation coefficients with high sand contents. As temperature increases, the attenuation coefficients vary nonlinearly and inhomogenously, with a descending trend on the whole. This research has provided both data and method for acoustic remote measurement and inversion of physical and mechanical properties of seafloor sediments.

In 1994, Sino-Japan cooperative cruise for shipboard three-component magnetic field test was carried out in northern region of the South China Sea, using new Shipboard Three Component Magnetometer (STCM) developed by the Earthquake Institute of Tokyo University. About 2 500 km (6 lines) field survey data were acquired successfully. According to the magnetic boundary strike diagram (MBSD) method proposed by Seama N et al., the author analyzes these data and points out that the MBSD method can be used to express types of magnetic boundary synthetically and visibly. The author then conducts comparative analysis on the calculated result and the verified magnetic lineation of northern South China Sea basin and finds that they agree with each other very well. That study suggests that the MBSD method is useful when dealing with STCM data and studying marine magnetic structure.

Chaoshan Sag has been regarded as a prospective relic Mesozoic sedimentary sag in the South China Sea. Recent drilling confirms the existence of the Mesozoic group. In one field experiment, five sets of ocean-bottom seismometers assembled by Chinese scientists have been deployed successfully to explore the deep geological structure of the basin. The ocean-bottom seismic data show clear phases from inner crust and Moho discontinuity. The data also reveal that the crust over the Chaoshan Sag thins less compared with the neighboring areas in the northern South China Sea, and the seismic velocity of the Mesozoic formation increases considerably, which implies high consolidation of sedimentary rocks, not prone to petroleum accumulation. Such case should be avoided in future exploration of petroleum.

Based on the monthly mean data of Simple Ocean Data Assimilation (SODA) product, the authors analyze the seasonal salinity budget of surface layer in the southeastern Arabian Sea., The salinity variation in the region cannot be explained by surface freshwater flux. The salinity budgets in two typical regions show that horizontal advection dominates salinity variation, decreasing the salinity in winter and increasing it in summer, except for the coastal region off western India where the surface freshwater flux decreases salinity in summer. During winter, the northeast monsoon current advects fresher water from the Bay of Bengal into the Arabian Sea along the same latitude and then transports the low saline-water northward, resulting in salinity reduction in the surface layer of the southeastern Arabian Sea. During summer, southwest monsoon current advects high-salinity water in the northwestern Arabian Sea southeastward, increasing the salinity in the surface layer of the southeastern Arabian Sea. In the southeastern Arabian Sea, salinity variation of the surface layer is prominently stronger in winter than in summer.

Using monthly products from the International Comprehensive Ocean-Atmosphere Data Set (ICOADS), the International Satellite Cloud Climatology Project (ISCCP), and the Optimum Interpolation Sea Surface Temperature (OISST), the authors investigate the interannual variation of sea-surface temperature (SST) along a meridional transection in the South China Sea (SCS). It is found that the air-sea interaction in the tropical Pacific plays an important role in the SCS SST variation. Taking warming as an example, the SCS SST warms up in the winter of El Nino developing year and again in the following summer. The first SCS warming occurs during the mature phase of El Nino. The decrease in cloudage and increase in net shortwave radiation flux contribute to the SST warming in the winter. The air-sea interaction associated with El Nino has a direct impact on this SCS warming process. The second warming occurs in the summer after the decay of El Nino. The weakening summer monsoon reduces the latent heat flux release and coastal upwelling off the southeastern Vietnam, which could not be attributed to the direct impact of the El Nino.

With 42 in situ measurements of remote sensing reflectance and component absorption coefficients taken in the South China Sea and coastal waters off Fujian (China) in different seasons, the performance of the Quasi-Analytical Algorithm (QAA) and the Garver-Siegel-Maritorena (GSM) algorithm for water’s absorption coefficients are evaluated. It is found that the retrieval performance of the two algorithms is similar as those by other researchers performed in different regions. To waters in this study, QAA performed better in the South China Sea than for waters off Fujian coast. For total absorption coefficient at 443 nm (a443), the root-mean-square-error (RMSE) is 0.046 in the South China Sea, with an averaged percentage error of 7.9%, and averaged error in log scale (δ) close to 0. For coastal waters off Fujian, RMSE, an averaged percentage error and δ are 0.194, 30.6%, and -0.167, respectively. The performance of GSM is similar for the two regions of waters. For a443, RMSE and an averaged percentage error are 0.161 and 27.7% in the South China Sea, respectively; and are 0.149 and 32.1% for waters off Fujian coast. Their δ values, however, are negative (-0.142, indicating underestimation) in the South China Sea, and positive (0.016, indicating slight overestimation) in coastal waters off Fujian. Further analysis indicate that the differences between the empirical parameters employed in the algorithms and actual values of the waters under study are the main reasons causing errors in remote sensing retrievals, and it is necessary to regionally refine those parameters in order to improve the algorithm performances.wei

Phytoplankton size structure is an important biological parameter that governs functioning of pelagic food-webs and consequently affects the rate of carbon cycle. Relationships between spectral phytoplankton absorption (aph(λ)) and phyto-plankton size structure were investigated based on in situ data collected in the northern South China Sea. The spectral slope of phytoplankton absorption in the range of 443 and 510 nm was used as an index (S) for describing phytoplankton size classes, which tended to increase with increasing dominant roles of large-sized phytoplankton. There existed positive correlations be-tween S and phytoplankton absorption coefficient and chlorophyll a concentration, which were then discussed by considering size-fractioned chlorophyll a contribution. Taking 40% as the cutoff, relatively clear division between pico- and mi-cro-phytoplankton dominated waters was found, with chlorophyll a concentration of ~0.70 mg•m-3 and aph(443) of ~0.05 m-1, and accordingly the value of S being around 0.0004 (m•nm)-1. A bio-optical model was developed between S and blue-to-green band ratio of remote sensing reflectance (Rrs(443)/Rrs(555 )), which showed good correlations with R2 being about 0.91. This model pro-vided much insight into the retrieval of phytoplankton size structure from ocean color remote sensing.

Based on the cruise in the northern South China Sea from 18th September to 2nd October, 2004, the authors analyzed the characteristics of phytoplankton distribution and community structure in the surface layer. The results showed that there were 152 species belonging to 53 genera, including Bacillariophyta, Pyrrophyta, Cyanophyta and Chrysophyta. The wide-distributing dominant species were Pseudo-nitzschia delicatissima, Prorocentrum sigmoides, P. mininum, Scrippsiella trochoidea, Trichodesmium erythraeum and etc. Phytoplankton biomass fluctuated, from 0.11×106 to 23.61×106cells•m-3, and decreased from coastal area to far-shore area, with the maximum and minimum appearing at stations E506 and B3, respectively. The highest species numbers was 51 species at E708 close to the Pearl River estuary. The quantities of diatom ranged from 0.02×106 to 8.13×106cells•m-3 and mainly distributed in higher-salinity waters. Cyclotella spp., a kind of dimethylsulfoniopropionate (DMSP) producing species, were found at many stations. Dinoflagellate were mainly found in coastal waters with the maximum of 15.67×106cells•m-3 (at station E506), thereinto, many of them were red-tide species including Scrippsiella trochoidea, Prorocentrum sigmoides, P. mininum, Gyrodinium spp. and etc. Trichodesmium erythraeum, a nitrogen-fixation species, widely distributed in the survey waters, but mainly at the eastern waters, with the maximum biomass of 1.8×107cells•m-3 at station E206. Hydrological data and phytoplankton data in other layers had been analyzed contrastively. The results showed that the distribution of Trichodesmium erythraeum had relationship with the infall of Kuroshio current, and its distribution was affected by water mass and ocean current.

The tidal energy fluxes and dissipation of the principal barotropic tidal constituents M2, S2, K1 and O1 over the South China Sea (SCS) are examined in detail using the simulated tidal results of the Estuarine, Coastal and Ocean Model(ECOM). The results show that the M2, S2, K1 and O1 tidal energy fluxes across the Luzon Strait from the west Pacific are 38.93, 5.77, 29.73 and 28.97 GW into the SCS respectively, and the corresponding fluxes across the Karimata Strait into the Java Sea are 2.42, 0.36, 8.67 and 7.86 GW, respectively. There are also M2 tidal energy fluxes of 25.28 GW into the Taiwan Strait from the East China Sea and northwest of the Luzon Strait. The semi-diurnal tidal energy fluxes into the Beibu Gulf of and the Gulf of Thailand (6.52 GW in all) are much weaker than the diurnal tides (24.74GW). There is 12.28GW of diurnal tidal energy flux into the Sulu Sea from the SCS, while 1.92 GW of semi-diurnal tidal energy flux in a contrary direction. The net tidal energy fluxes and bottom boundary layer dissipation, which should be equal to each other in steady state, are not balanced in each area of the SCS. The most convenient management to this is to modulate the bottom friction coefficients, which are calculated to be 0.0023, 0.0024, 0.0023, and 0.0021 for the Taiwan Strait, the Beibu Gulf, the Gulf of Thailand and deep sea areas in the SCS, respectively.

Using modified DNA extraction and purification method, high-quailty environmental DNA was obtainedfrom deep-sea sediments of the Bashi Channel in the northern South China Sea. Diversity of eubacteria was studied by PCR, ARDRA and sequence analysis of 16S rDNA and compared with the published sequences in the GenBank. Based on the ARDRA profile generated, 118 clones from the 16S rDNA library were divided into 23 operational taxonomic units (OTUs). Phylogenetic analysis showed that the representative clones of the 23 OUT fell into nine groups: Actinobacteria (26%), Proteobacteria (22%), Planctomycetes (18%), Verrucomicrobia (4.5%), Sphingobacteria (4.5%), Nitrospira (4.5%), Chloroflexi (5%), Firmicutes (4.5%), and Acidobacteria (4.5%), repspectively. Among the 23 clones, there was no clone being identical to the known 16S rDNA sequences in the Ribosomal Database Project small subunit RNA database. In this clone library, 11 clones had less than 95% similarity to rDNA sequences retrieved from the DNA databases. The results suggested that bacterial population in the Bashi Channel of the northern South China Sea is very diverse in phylogeny and there are the massive unknown microorganism deserve further studying and exploration as valuable resources.