Environmental pollution is serious in the Pearl River Estuary due to human activities and an increasing attention has been paid to the pollution in this region. This paper mainly reviews the eutrophication characteristics and the pollution patterns of persistent toxic substances (PTS, including heavy metals and persistent organic pollutants—POPs) in the water. Results in-dicate that the excessive input of nitrogen and phosphate has led to the high eutrophication in the water. Eutrophication plays an important role in triggering red tides. The coupling effect of the water stratification and eutrophication leads to the seasonal hypoxia in certain areas of the estuary. PTS mainly accumulate in sediment and organisms. The records of pollutants in sedi-ment cores reflect that pollutant accumulation in sediments is closely related to the rapid economical development of the Pearl River Delta in the past three decades. Finally, the critical issues of research are put forward on the environmental pollution of this area in the future, which include biotransformation of pollutants in tissues and bioaccumlation in food chain, the combined pollution of various pollutants in eutrophic water, mechanisms of microbial biodegradation of pollutants, pollution control strategy, among others.

The traditional mangrove land-based enclosure aquaculture model originated in the Pearl River Delta is a good example showing how mangroves can be used sustainably. This paper introduces three examples of mangrove land-based enclosure aquaculture at the mouth of the Pearl River Estuary. The first example is about the only operating traditional mangrove land-based enclosure for shrimp farming located in Mai Po Marshes Nature Reserve of Hong Kong and managed by WWF Hong Kong; its history goes back to the mid-1940s and its focus for management strategy has evolved from being commercial culture ponds to performance of multi-ecological functions including feeding habitat for piscivorous water birds, bird-watching, environmental education, as well as shrimp farming. The second example is the mangrove land-based enclosure for traditionally extensive aquaculture trial in the Dawei Bay on the Qi’ao Island of Zhuhai City, regarding measurement and analyses of relationship between the environmental condition change of water level and salinity and the mangrove community dynamics inside land-based enclosure. The third example is the mangrove planting-aquaculture system trial in the Shenzhen Waterlands Resort on the east coast of the Lingdingyang Estuary, including research on water purification function by mangroves. For mangrove protection and management and for marine pollution prevention in the Pearl River Estuary waters, the following suggestions are given: 1) Preventing resolutely the development model of clearing mangrove for aquaculture ponds, and disseminating and applying the eco-development model of land-based enclosure aquaculture or mangrove-friendly aquaculture; 2) Building new land-based enclosure aquaculture demonstration site in major mangrove regions, and exploring mangrove-friendly restoration model in aquaculture pond areas built by clearing mangroves; 3) strengthening relevant scientific research for maximizing comprehensive efficiency of mangrove land-based enclosure aquaculture.

Dredged sediment is the main accumulative site of terrigenous pollutants going into the sea and main potential source of marine pollution. During the course of dredging and marine dumping, these pollutants in the dredged sediment can be released into the sea again, which can harm the marine environment. Therefore, treatment to turn the contaminated dredged sediment into harmless material has significant importance to the scientific management of marine dumping and the effective protection of the sea. The aim of this study is to review six main dredged sediment decontamination and treatment technologies, such as chemical and biosurfactant leaching, thermal treatment, electrodialytic method, ultrasound method, flotation method and bioremediation. The authors discuss the mechanisms of these technologies, effective factors, advantages and deficiencies. Combining several of treatment techniques such as physical, chemical and biological processes is a potentially effective way to treat the polluted dredged sediment in the near future.

The RCA water quality model was incorporated with the sediment module and the light shading effect due to the high turbidity in the Pearl River Estuary (PRE). The modified RCA water quality model was then applied to the PRE. Results show that the modified RCA model can reproduce the distribution of nutrients, phytoplankton and dissolved oxygen (DO) in the PRE successfully, which means the modified model can capture the main processes of water quality in the PRE. In the wet season, huge amount of fresh water enters the PRE and results in a river plume. Particulate organic matter (POM) deposits intensely in specific areas of western and central shoal of the Lingdingyang Estuary and outside Modaomen as a result of the plumes. Furthermore, high deposition rate of POM in specific areas leads to high sediment oxygen demand (SOD), which coincides with the areas with strong stratification. High SOD and strong stratification lead to hypoxia. On the shelf areas, primary production increases as the suspended sediment concentration decreases, but the increasing primary production does not result in hypoxia as the marine particulate organic carbon (POC) spreads all over the shelf and the stratification is weak.

Based on topographic summary of estuaries and taken into account of many factors including river discharge, tide, channel topography and mixing type between saline water and fresh water, a fast prediction model for daily maximum chlorinity and maximum distance of saline water intrusion was set up and used to simulate and predict the saline water intrusion in the West River Delta. The results show that the model can be used to simulate daily maximum chlorinity and maximum distance of saline water intrusion in the channels in the West River Delta. In addition, the model can predict the degree of effects of topographic variation and other environmental factors such as river discharge and tide on the saline water intrusion. More actual data or parameterizations are needed to further quantify other factors to amend the model, hence to improve the accuracy and prediction of the model.

Available water volume for phytoplankton photosynthesis, effect of zooplankton grazing on the regeneration of phosphorus and bio-utilization of phosphorus in the waters of the Pearl River Estuary were studied by both field and laboratory experiments. Analysis of the data between 2002 and 2003 indicated that the available water volume for phytoplankton photo-synthesis changed seasonally, with about 9.7×104m3 in dry season and 6.6×104m3 in wet season. The same trend was also found in primary productivity, with approximate 36kg.d-1 in dry season and 31kg.d-1 in wet season, respectively. Phosphorus regen-eration could be accelerated by zooplankton grazing and could meet 1.5%-15.6% of phosphorus required by phytoplankton growth seasonally. Amount of phosphorus that directly released from zooplankton grazing was much higher than that from zooplankton biological turnover.

Trifluoroacetic acid (TFA) levels in surface waters of the Pearl River Estuary and neighboring eastern offshore sea area were determined by Gas Chromatography-Mass Spectrometry after derivatization process. TFA levels in surface water ranged from 113 to 170ng.L–1 in the Pearl River Estuary and from 202 to 336ng.L–1 in neighboring Daya Bay and Honghai Bay. The average TFA concentration in coastal waters of the Honghai Bay was 279ng.L–1, which was much higher than that in the water samples from the open sea (210ng.L–1), suggesting possible source input within or around the Honghai Bay. The average TFA level in surface waters of open sea was 69.1ng.L–1 higher than that in surface waters of the Pearl River Estuary, indicating unknown anthropogenic or natural sources leading to accumulation in the ocean as final sink of this strongly hydrophilic and fully persistent chemical.

To understand the characteristics of atmospheric nutrient deposition into the Pearl River Estuary, measurements of dry and wet depositions of nitrogen and phosphorus were made at Hengmen in Zhongshan from December 2006 to November 2007. Results showed that, on an annual basis, volume-weighted concentrations in wet deposition for ammonium nitrogen (NH4+-N), nitrate nitrogen (NO3--N), total nitrogen (TN), total phosphorus (TP) were 0.82, 0.52, 2.14, 0.039mg.L-1, respectively; their corresponding annual deposition fluxes (dry + wet) were 1.584, 1.142, 4.295 and 0.055g.m-2.a-1, respectively. The budget of wet deposition corresponded with that of dry deposition for NH4+-N, NO3--N and TN, and wet deposition was the major source for TP. Seasonal change of total deposition fluxes for TN showed no significant difference among spring, summer and autumn, while that for TP was highest in summer, lower in autumn, and lowest in winter.

Blooms of Cochlodinium polykrikoides occur frequently around the world. During October to November, 2006, an unusual bloom of Cochlodinium geminatum occurred in the coastal eutrophicated waters in Zhuhai, Guangdong. The water temperature and salinity in the bloom zone ranged between 23.41-27.54℃ and 15.49-17.92 psu, respectively. The density of C. geminatum increased significantly with water temperature and salinity and reached to the highest density of 1.6×106 ind.L-1. During the latter period of bloom, the decrease of water temperature and the increase of density of Mesodinium rubrum might be responsible for the dissipation of the C. geminatum bloom.

The authors analyzed species composition, distribution of species richness and phytoplankton density based on the data collected from two cruises carried out during saline water intrusion period from the end of 2007 to the beginning of 2008 at both spring and neap tides in the Pearl River Estuary. In addition, influence of environmental factors on phytoplankton community was discussed. Seventy-six species in total were identified, including 38 diatoms, 18 green algae, 14 dinoflagel-lates, 4 cyanobacteria and 2 euglenas. In general, the distribution of species richness decreased from inner section to outer section of the Pearl River Estuary. The species richness of phytoplankton was higher at neap tide than at spring tide, and it distributed unevenly among different water layers. The dominant species were mainly freshwater diatoms, such as Melosira granulate, Melosira granulata v. angustissima, Cyclotella sp. and Thalassiosira sp. The dominant species were very out-standing in the inner section of the Pearl River Estuary with the characteristics of uneven density distribution and low even-ness index value. The mean phytoplankton densities at spring and neap tides were 53.80×104 and 62.21×104ind.L-1, and the ranges of cell density were from 1.48×104 to 290.41×104 and from 1.52×104 to 283.62×104ind.L-1, respectively. Phyto-plankton density decreased from the inner to outer sections of the Pearl River Estuary, and the density of diatom was the highest among different groups during both spring and neap tides. The community of phytoplankton presented clear tidal pe-riodicity. Environmental factors such as salinity and nutrients played an important role in the composition and distribution of phytoplankton during saline water intrusion period in the Pearl River Estuary.

Two cruises were carried out to investigate the water quality and ecological status in the Pearl River Estuary in July 2006 and March 2007. Water comprehensive pollution index and biodiversity index (including phytoplankton, zooplankton and benthos) were used to assess the pollution status. In addition, rationality of the assessment by using the biodiversity index was also discussed. The results indicated that the pollution degrees of the Pearl River Estuary were between moderate to severe. Water comprehensive pollution index showed that it was at a severely polluted status both in wet and dry seasons. Biodiversity index led to different results, which varied from lightly-moderate pollution to severe pollution. Among the three biodiversity indices, we considered that zooplankton diversity index was more congruent than the other two indices in pollution status assessment. However, the evaluation criteria should be verified and modified in future study. It was concluded that assessment for the environment quality and ecological status by using different biodiversity indices may come to a varied result, and a simple conclusion could not be hastily educed but should be associated with physicochemical factors.

The Nanao Island is the main island of the Nanao County, Guangdong province, and the sea area around the island is important for local social and economic development. A survey of heavy metal content, distribution, enrichment and pollution state in sediments was conducted in May and July 2004. A total of eleven sediment samples were collected from mariculture base: Houjiang Bay, Baisha Bay and A tourist resort: Qingao Bay along the coast of the Nanao Island. The results showed that the contents of heavy metals were Cd: 0.19mg.kg-1, Cr: 26.86mg.kg-1, Cu: 20.71mg.kg-1, Ni: 22.78mg.kg-1, Pb: 35.67 mg.kg-1, Zn: 79.48mg.kg-1, much higher than those in similar bays of economically developed coastal areas and lower than those of offshore areas without anthropogenic impact. Average heavy metals in sediment tended to be lower in inner bays than at the mouth of the bay, and higher at aquaculture sites than non-aquaculture ones. However, there was no significant difference among studied bays, suggesting that river input maybe the main source of heavy metals in sea areas around the Nanao Island, which resulted in the enrichment of Cu (Cf = 2.75) and Pb (Cf = 2.27) that are representative elements of sewage. Based on the marine sediment quality standard, sediment quality criteria and baseline values for the United States Pacific Coast, the heavy metal pollution near the Nanao Island generally presented a slightly higher level. However, more attentions should be paid to the potential pollution effects.

Based on the field data of Shenzhen coastal surface sediments from 2000–2007, methods of geo-accumulation index and potential ecological risk index are employed to evaluate heavy-metal pollution status in the area. Results show that Shenzhen coastal sediments have been polluted by heavy metals. The quality degree of most coastal sediments are Class II except for the Gushu Coast. The severity of heavy-metal pollution is: the Gushu Coast, the middle of the Shenzhen Bay, the mouth of the Shenzhen Bay, followed by the mouth of the Shatoujiao Bay that is least polluted. Among heavy metals found in the sediments, Cu and Zn are the two most seriously-polluting elements. The average contents of Cu and Zn in Gushu coastal sediments are 128.96mg·kg−1 and 199.40mg·kg−1, belonging to Class III; other coastal areas of Shenzhen belong to Class II. The results also reveal that there are no potential ecological risks for Shenzhen coastal sediments. The order of potential ecological risks is, Hg＞Cd＞Cu＞As＞Pb＞Cr＞Zn.

In order to study accumulation effects of marine culture on sediments, the contents and profile distribution characteristics of total nitrogen (TN), total phosphorus (TP) and total organic carbon (TOC) in core sediments from marine culture areas of Dapeng Cove in the Daya Bay were investigated. The pollution status of nitrogen and phosphorus of marine culture area were discussed. The results show that the contents of TN in cage culture, shellfish culture and control areas are in the range of 638.2-3 803.9mg.kg-1, 740.9-2 152.1mg.kg-1 and 343.2-471.9mg.kg-1, respectively; the contents of TP are in the range of 344.7-3 233.9mg.kg-1, 297.9-497.5mg.kg-1 and 650.2-1 327.2mg.kg-1, respectively; the contents of TOC are in the range of 0.96%-2.22%, 0.87%-1.13% and 0.69%–0.95%, respectively. The vertical distributions of the TN, TP and TOC contents increased from the bottom to surface layers in the study areas and the variation range in upper layers was greater than that in lower layers. The profile distributions of the contents increased most drastically in the cage culture area, followed by those in the shellfish culture area and least in the control area. The contents of TN in core sediment samples all exceeded the assessment standard, while the most serious one was in the cage cul-ture area, followed by the shellfish area and least in the control area. The contents of TP only exceeded the standard in the cage cul-ture area in the surface layer, while the contents of TP in the shellfish culture area and control area did not exceed the assessment standard.

The authors study the characteristics and sources of organic carbon, nitrogen and the hydrolysable amino acids (THAA), total carbohydrates (TCHO), total lipid and acid-insoluble organic compounds (AIOC) in the surface sediments of the Pearl River Estuary (PRE) and its adjacent shelves. The results show that the organic matter in the PRE was mainly derived from mixed sources of terrestrial and aquatic origins, whereas the organic matter in the adjacent shelves was predominantly algal-derived. Terrestrial higher plants were rich in more lignin and cellulose, which were exported to the PRE. As a result, the content of TCHO in the sediment of the estuary was higher than that in the adjacent shelves, while the content of aquatic organic matter in the estuary was close to that in the adjacent shelves. The proportions of THAA and TCHO were 56%, 48% and 19% in plankton, suspended particulate and surface sediment, respectively; suggesting that the organic matter had undergone degradation during the sedimentation to the water-sediment interface.

The geological environments in the Pearl River Estuary are comparatively complicated and pregnant with hazardous geology factors. High-resolution seismic data, satellite remote sensing, borehole data and systematic survey have been used to examine marine hazardous geologic types and their distributions in the Pearl River Estuary; hazardous geologic maps of the estuary have been completed. The geological hazards are classified into neotectonic, erosive-deposit, fluid-plastic and heterogeneous hazardous geology types, including active fault, earthquake, coastal erosion, coastal accumulation, sand wave, tidal sand ridge, buried paleochannel, shallow gas, erosion gutter, shallow bedrock, among others. The scale of distribution of hazardous geologic types is large; the types of hazardous geology are complex and distributed in almost the whole area. Geologic environmental evolution including neotectonic movement and sea-level change since late Pleistocene decides the formation and regularity of geologic hazards. More attentions should be given to severe hazardous geologic phenomena that can greatly threaten regional economic development and engineering construction.

By comparing and analyzing the maps of 1965, 1984, 1999, and 2005, the authors discuss accretion/erosion of the south shoal, groove and the outer at the Yangpu Bay. The results show that: 1) the south shoal was basically depositing during 1965-1984, with the largest distance of 640 m in the southwest part, and suffered erosion during 1984-1999, because of the wave and alongshore currents in the bay. The south shoal was deposited near the mouth of the bay, due to the hydrodynamic force at the mouth. The whole shoal was stable during the period. 2) The Yangpu groove showed unlikeness degree of change: accretion on the western border slope, erosion on the eastern border slope, narrowing and shoaling the groove line. Of particular concern is the 5 profile. 3) The upper reach of the mouth bars showed different changes during recent years, but they are mainly accretion. The siltation depth of the outer-mouth bar was about 1 m during 1965-2005, but the magnitude of siltation will decrease in future due to sand reduction.

The analysis results of constant elements and trace elements in the surface sediments indicate that ome terrigenous materials rich in Si, Al, K, Mg, Fe, Ti are the main components of the sediments in the Pearl River Estuary. The average levels of the main elements of oxides are SiO2 61.16%, Al2O3 14.74%, Fe2O3 5.72%, TiO2 0.88%, MgO 1.84%, K2O 2.63%, CaO 2.70%, and CaCO3 4.79%. Element content and particle size are closely related, with the main elements of Al2O3, MgO, Fe2O3, TiO2, as well as trace elements Cu, Pb, Zn, Cr, V, Co, Ni, Ba, in the northwestern coastal area and central Lingdingyang fine-grained sediment areas, of SiO2, CaO, Zr, Sr in the southwestern and southeastern district coarse sediment enrichment. The main factors that control the geochemical characteristics of sediments in this area are the source material, sedimentary environment, hydrodynamic conditions, sediment particle size, mineral composition and geochemical nature of the elements themselves.

 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.

Distribution, species composition, biomass, habitat of seagrass beds and main threats that seagrass bed habitats suffer are introduced and discussed in this paper based on field surveys in the offshore areas of Guangdong Province. The newly-discovered seagrass beds mainly distribute in the Zhelin Bay, Baisha Lake, Kaozhouyang Lagoon, Daya Bay, Tangjia Bay of Zhuhai, Shangchuan Island, Xiachuan Island, Qishui Bay of Leizhou and so on. There are three species of seagrass, namely Halophila ovalis, Halophila beccarii and Zostera japonica. Percentage coverage, shoot density and biomass of sea-grass are 6.67%-53.33%, 3 428.57-10 542.00shoots.m-2 and 12.86-118.24g.m-2, respectively; while mean density, biomass, diversity and evenness index of benthic organisms on seagrass beds are 16.67-734.67ind.m-2, 15.39-426.88g.m-2, 0.46-1.98 and 0.28-0.89, respectively. However, the seagrass habitats are subjected to some threats resulted from artificial and natural causes, such as culture of oysters and snails, wastewater discharge, fishing by means of electric power, shellfish collection, typhoons and floods.

A spar body was considered and a free-rotated saddle was used in a moored optical buoy. Theoretical results indicated that the buoy’s high initial stability enables it to be stable. Due to the centre of gravity position being lower than the buoyant centre, the rolling angle of the buoy is small, as it would result in strong ability to resist tilting and capsizing. In situ experiment results indicated that 83% of the buoy’s tilt angles are ≤10° and 54% of the buoy’s tilt angles are ≤5° under the conditions of wind speed less than 7 knots and wave height less than 3-4m, therefore the buoy performance satisfies the technical requirement for underwater light measurements. To minimize the shelf–shading effects on the light measurements, two solutions were found: First of all, stroked-out structures were used to avoid shelf-shading of buoy body, and when the solar zenith angle was 0°, the shelf-shading errors of upwelling radiance were lower than 4% and 1% for coastal and open oceans, respectively; Second, fiber spectrometer was used to avoid shelf-shading of sensors. The diameter of designed optical sensors for irradiance and radiance was 0.042m. When the beam attenuation coefficient was 0.12m-1 and the solar zenith angle was 10°, the self-shading error was 1.5% for upwelling radiance.

A stable and low power electric control system was designed for marine optical buoy. A low power PC104 embed-ded computer was used as the core in the electric control system to implement data acquisition and storage automatically. Real-time data and instructions could be transmitted by CDMA and GPRS wireless network. A customized multi-functional board was used to implement data counting, I/O control, A/D conversion and timing. Two-stage “watch-dog” was built up by a single-chip controller in conjunction with calendar clock and power master switch. The electric control system can ensure the marine optical buoy to work independently for a long time under an unmanned situation.

A micro-fiber spectrometer based on non-symmertrical cross-czerny-turner optical structure is developed. In this spectrometer, the light signal collected and transferred by the fiber is dispersed by grating and then measured by a 2048-element line CCD array. The analog signals of CCD can be amplified and converted to digital signals by the data acqui-sition circuit of CCD that is based on the complex programmable logic device and PC104; the digital signals can be translated to the PC104 embedded industrial control block by the PC104 bus. The spectrometer and the data acquisition circuit of CCD have been integrated into a spectrometer module with physical dimensions of 96 mm (wide) ×104 mm (long) ×18 mm (high). Based on the PC104 bus, the spectrometer module and the PC104 embedded industrial control block can be in a cascade con-nection through the “needle” and “hole”. The spectrometer has such features as small volume, low power consumption, quick sample rate and excellent aseismicity among others, which make it suitable for field work under abominable conditions. The micro-fiber spectrometer has been used in an autonomous instrument for trace elements and nutrient measurement in seawater and the testing result is excellent.

Harmful algal blooms have increased in recent years, and the building of early observing and monitoring system is very difficult. The authors indicated in this paper that, during the experimental time in the Pearl River Estuary, the variations of chlorophyll a and cell density were 0.9-31.1mg•m-3 and 1.28×104-1.76×106cell•L-1, respectively, and diatom was the dominant algal species. The diffuse attenuation coefficient, remotely sensed reflectance and fluorescence obtained by hyperspectral radiometers can be used to retrieve chlorophyll a and cell density, with relative root mean square error (RRMS) of chlorophyll a of 26.1%, 25.2% and 54.6%, and RRMS of cell density of 64.5%, 65.6% and 60.8%, respectively. Since the hyperspectal radiometers can obtain data at 1 hour interval, the moored optical buoy equipment with hyperspectral radiometers can be used for algal bloom observation and monitoring system.

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.

The algal cells were first simplified as two-layer structure consisting of cytoplasm and chloroplast, and based on Aden-Kerker theory, the influence of physical properties of algal cells on their optical properties was then discussed. The results were also compared with the optical properties of homogenous spherical algal cells. They showed that, compared to homogenous spherical cell structure, the cell structures with chloroplast as outer would enhance the backscattering efficiency factor and backscattering ratio, while the cell structure with chloroplast as core would reduce the absorption efficiency due to package efficiency; For the algal cells with chloroplast as outer, the variations of cell size, relative chloroplast volume and the imaginary part of refractive index of chloroplast would have important influence on absorption efficiency of algae; both cell size and the real part of refractive index of chloroplast were the two key factors for backscattering efficiency and backscattering ratio of algae.

Variability of particulate backscattering ratio and its interpretation were examined using in-situ measurements performed during May 2007 in the Daya Bay. The results indicated that the particulate backscattering ratio values range between 0.004 and 0.0245, with a mean value of 0.0082±0.0032. There was some spectral dependence of the particulate backscattering ratio, and less than 15% variability between wavelengths was estimated. A global decreasing of particulate backscattering ratio with increasing chlorophyll concentration was visible, and the low backscattering ratios were observed in water with high chlorophyll concentration. Particle-size distribution slope was the main factor controlling the variability of particles backscattering ratio: The particle backscattering ratio increased with particle-size distribution slope. Average particle refractive index was another influencing factor. With similar particle-size distribution, the amount of non-pigment material relative to phytoplankton that was characterized by the variability of refractive index had a strong effect on particulate backscattering ratio.

The absorption spectra of phytoplankton have gradually become an accessible parameter from hyperspectral ocean color. The retrievals of main pigment concentrations from absorption spectra of phytoplankton by multilayered perceptrons were performed. The input parameters for multilayered perceptions were phytoplankton absorption spectra, and the retrieved parameters were Chlorophyll a, b, c, and photosynthetic and non-photosynthetic carotenoids, respectively. The results indicated that Chlorophyll a and c were the most accurate retrieval pigments with average relative deviation of 19.06% and 15.90%, respectively, for the test data subsets, while the poorest performances were found for photosynthetic and non-photosynthetic carotenoids, with average relative deviation of 37.62% and 36.96%, respectively, for the test subsets. Chlorophyll b was retrieved with average relative deviation of 27.47% for the test subsets. The comparable performances of multilayer perceptrons for the training subset and the test subsets suggest that they could be successfully operated on retrieval of main pigments for the waters around the Dangan Islands in the Pearl River Estuary. The multilayer perceptrons of retrieving main pigment from phytoplankton absorption spectra also provide an important way to detect phytoplankton community from hyperspectral ocean color.

In August 2007, bio-optical measurements were collected over a period of 16 days in the Pearl River Estuary, and an algal bloom was detected. In situ radiometric data were obtained using a marine optical buoy. The variations in absorption properties and ocean color of seawater and their internal relationship were investigated. The results show that the colored detrital matter (CDM), especially the colored dissolved organic matter (CDOM), had large contributions to the total absorption of seawater at blue waveband, while the absorption contribution of phytoplankton tended to increase with the rapid increase of chlorophyll a concentration when the bloom occurred. Linear regression was used to express the spectral correlations between total absorption coefficients at 443nm and at other visible bands, and the blue-to-red ratio of absorption showed a big effect on the spectral distribution of spectral reflectance. An empirical hyperspectral ocean color model for retrieving the absorption coefficient was developed, and the calculated and measured results showed small discrepancy, with relative root mean square error being less than 24% over the visible spectrum.

Data from three cruises conducted in the northern South China Sea (SCS), the Daya Bay and the Pearl River Estuary, respectively, were examined to access the variations of phytoplankton size structure. A spectral mixing model was established to retrieve phytoplankton size parameter from phytoplankton absorption spectra, with S as a proxy of the size parameter. There were significant similarities in phytoplankton size structure in the estuarine and coastal waters; however, it is very dif-ferent in the open ocean. In the estuarine and coastal waters, the micro-phytoplankton plays a dominant role, while in the open ocean the pico-phytoplankton was the dominant species. Phytoplankton size parameter tended to decrease with increasing micro-phytoplankton, and to increase with increasing pico-phytoplankton. There was an increasing trend for chlorophyll a concentration from the open ocean to the coastal sea. Phytoplankton size parameter showed a power function relation with chlorophyll a concentration and decreased with increasing chlorophyll a concentration. The results showed that there was a relationship between phytoplankton size parameter retrieved from the spectral mixing model and the bio-optical characteristics in different circumstances of the SCS. This spectral mixing model provided a simple tool for extracting ecological information of phytoplankton species from optical measurements, and can be used to analyze the influence of dominant phytoplankton size structure on optical characteristics.

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 authors use the spectrum of Thalassia to analyze the optical properties of seagrass substrates. The results show that in the range of 450?780nm, the derivative spectral reflectance of seaweed can reflect the variability of leaf area index with high accuracy. Red edge calculated by the first order derivative spectrometry is a good indicator for chlorophyll concentration. In the derivative spectra, there are two obvious peaks at 625nm and 675nm, and the difference between the two peak values is large for seagrass. Other dominated peaks appear at 550nm, 700nm, and 750?780nm. Combining with the relationship between seagrass coverage rate and the spectral properties, the properties of peak distribution can be utilized to classify plenty of re-mote sensing data sets in order to monitor large scale spatio-temporal dynamic patterns.

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.

Current profile data of about 80 days were obtained by the submersible buoy measurement at two stations at the mouth of the Beibu Gulf during the spring monsoon transition in 2007. Using cross spectrum analysis, the structure of residual currents and the factors that influence the structure are analyzed, with the addition of QuikSCAT sea-surface wind data ob-tained from NASA Jet Propulsion Laboratory Physical Oceanography Distributed Active Archive Center, and sea-surface temperature data provided by NOAA National Climatic Data Center. The results are as follows. The northward component of the wind had oscillations with a period about 10 days during spring monsoon transition in the Beibu Gulf. The wind could generate the oscillation of the density field, which could lead to the variation of density current. The residual currents at Sta-tion M4 were mainly controlled by wind. Water at Station M4 was transported into the Beibu Gulf. The residual currents at Station M5 were very different between surface and bottom. The whole water column was affected directly by wind, while the surface layer was also affected by the variation of density current controlled by wind. So wind affected residual currents in two ways at Station M5.

Sea spray, an important factor in the air-sea interaction, plays an essential role in the occurrence and evolution of typhoon. In order to examine the impact of different sea spray parameterizations on typhoon simulations, the Fairall and Andreas schemes were included in the WRF atmosphere model to simulate two typhoons. The results show that the latent and sensible heat fluxes increased greatly in the Fairall scheme. Since the heat construction of the typhoons changed and the warm core was obvious, the dynamic construction changed as well. Relative diff-vortex explains the cause of the change in typhoon's track and the diff-divergence, vortex and the vapor flux affect the intensity of typhoon. The Andreas scheme, which considers the change of roughness in momentum, heat, and moisture with wind speed and relative humidity, has lower latent and sensible heat fluxes than the Fairall scheme, so the intensity of the typhoons is strong. The simulation of track is less impacted by different sea spray parameterizations.

The authors analyze the causes of abnormal rainfall in Shenzhen in June 2008 based on the NCC/CMA data. The results indicate that the abnormally low sea surface temperature in the equatorial western Pacific during July 2007-Februry 2008 and the more spacious snowy area over the Qinghai-Tibet Plateau in the winter before June 2008 were the climatic background of the abnormal rainfall in Shenzhen. Moreover, the blocking high was much stronger in Northeast China and the Urals long-wave trough was abnormally deepening in June 2008, which promoted the meridional circulation. At the same time, much stronger cold air mass outburst in China frequently in the form of ladder troughs, which provided energy for the Shenzhen rainfall. Finally, the subtropical high was stronger and shifted southward, stronger monsoon transmitted huge water vapor and heat, and cold and warm air masses converged in Shenzhen frequently; these were the causes of the abnormal rainfall in Shenzhen. In summary, all the above conditions worked together and resulted in the abnormal rainfall in Shenzhen.

The Zhujiang River Estuary, the most active region in China's economic development, is experiencing rapid urbanization and industrialization, of which effective sustainable use of the funding sources becomes an ultimate goal to develop and utilize space technology and resources. In this article the authors mined and extracted the farming information with the same spatial scale and precision based on the analysis of data from the three-phase multi-source remote sensing information of the Zhujiang River Estuary and conventional survey with classification system and spatial accuracy consistency, to introduce the model of single land use dynamic index, the landscape fragmentation, and multi-model analysis of spatial information such as changes in the distribution area statistics and the gravity center. Quantified results show that from 1985 to 2005 aquaculture area increased from 125.49km2 to 345.20km2, 2.75 times as large as that in 1985. The average annual growth rate of aquaculture area was 14.30% between 1985 and 1995, and dropped to 1.32% after 1995. In the past 20 years from 1985 to 2005, the fragmentary degree of aquaculture area gradually increased from 0.000015 to 0.002824. The change of aquaculture area presented regional differences for the five cities in the Zhujiang River Estuary. The growth rate in Guangzhou, Dongguan and Zhuhai City kept going up, with quite large difference among them; but for Zhongshan and Shenzhen, the growth rate dropped after a period of increment. Comprehensive analysis leads to the conclusion that the gravity center of the aquaculture area migrated to the northwest in the whole.

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.

Isolation and screening of microsatellite markers from Pinctada fucata were performed using the method of Fast Isolation by AFLP of Sequences Containing Repeats (FIASCO). After restriction of genomic DNA with MseI, the digested fragments were ligated with adaptors and then hybridized with biotinylated (CA)15 probes. The tentative microsatellite DNA was isolated by streptavidin-coated magnetic beads from the hybridized mixture. After purification, the isolated microsatellite DNA was amplified using degenerated primer MseⅠ-N and then cloned into T-vector. After transforming, the microsatellite-enriched library was constructed. The second PCR screening was performed using the primer of (CA)15 probe and T vector’s primers, and 357 positive clones were obtained. Sequencing analysis showed that 297 clones (83.2%) contained microsatellite DNA, including 479 microsatellite domain. Among them, 370 microsatellites (77.3%) were perfect type, 95 (19.8%) imperfect type and 14 (2.9%) compound type. Forty nine pairs of primers were designed and 31 (63%) pairs were effective for PCR amplification. Nine loci showed polymorphism as tested by a population (n=32). PIC values for the nine loci ranged from 0.375 to 0.809 with an average of 0.536. The number of alleles ranged from 2 to 9 with an average of 4.889. The observed heterozygosity ranged from 0.200 to 0.600 with an average of 0.415, and the expected heterozygosity ranged from 0.454 to 0.844 with an average of 0.598. This study demonstrated that FIASCO is a useful technique of microsatellite isolation for Pinctada fucata.

Using PCR-denaturing gradient gel electrophoresis (PCR-DGGE), the polymorphism of 16S-23S rDNA intergenic spacer regions (ISR) from 34 Vibrio parahaemolyticus strains, including type strains and those isolated from environment and aquatic animals, were analyzed. The phylogenic relationships of these strains were also analyzed. The results showed that the ISRs could be separated into 4−10 different bands through PCR-DGGE. Thirty-four V. parahaemolyticus strains shared 15 polymorphic sites. Using MVSP, 34 strains were clustered into four groups, H, I, J, and K. Strains A18 and A25 had farthest genetic distance, with a value of 0.4. The present study suggested that ISR PCR-DGGE provided a new method for genotyping of V. parahaemolyticus.