Sanya Bay Research Articles

Nutrient Distribution in Coral Reef Degraded Areas within Sanya Bay, South China Sea

ABSTRACT Guo, J.; Yu, K.; Wang, Y.; Xu, D.; Huang, X.; Zhao, M.; Yang, H., and Zhang, R., 2017. Nutrient distribution in Coral Reef degraded areas within Sanya Bay, South China Sea. An investigation was conducted in August 2014 to explore the spatial distribution of dissolved inorganic nitrogen (DIN) and phosphate ( ) in overlying water, pore water, and surface sediment from Sanya Bay and living coral cover on Luhuitou fringing reef. Generally, nutrient contents gradually decreased from the estuary to the central bay, which confirmed that terrigenous inputs from Sanya River and Sanya Harbor were the primary nutrient sources. The results of K-means cluster analysis suggested the Luhuitou fringing reef is in danger of being affected by the pollution source. The results of nutrient diffusive fluxes at the sediment-seawater interface indicated diffusion from pore water to overlying water. Compared with other coral reef areas around the world, nutrient levels in Luhuitou fringing reef were at the medium level....

Cool water brought by upwelling in the Sanya Bay benefits corals in the background of global warming

It has been reported that global warming has negative effects on coral ecosystems in the past 50 years and the effects vary in different ocean environment. In order to make clear the coral reef status in the background of global warming along the south coast of Hainan Island of China, satellite and in situ data are used to retrieve the information of the coral reef status and surrounding environmental factors. The results show that cool water induced by upwelling along the south coast of Hainan Island is found in the area every summer month, especially in the relatively strong El Nino years (2002–2003 and 2005). From the NOAA satellite data, degree heating week (DHW) index does not exceed 3 in Sanya Bay even in the relatively strong El Nino years. By comparison of a coral reef growth rate in the Sanya Bay with respect to El Nino events from 1957 to 2000, coral’s growth rate is relatively greater during 1972, 1991–1994 and 1998 El Nino event. By analyzing the environmental factors, it is found that the cool water induced by upwelling may be the main reason for protecting corals from global warming effects.

Comparison of metals levels in two mangrove species (Rhizophora stylosa and Sonneratia hainanensis) from Hainan Island, South China

Trace metals in mangrove tissues (leaf, branch and root) of two species (Rhizophora stylosa and Sonneratia hainanensis) from Dongzhai Harbor and Sanya Bay of Hainan Island were studied. The total average concentrations of Cu, Pb, Zn, Cd, Cr, Hg and As in the two mamgrove species were 2.4±1.3, 1.1±0.7, 7.8±8.0, 0.03±0.05, 1.4±1.6, 0.03±0.01 and 0.2±0.2 µg g-1 dw, respectively. Metals concentrations among different tissues of mangroves showed different pattern. In general, Zn, Cd and Hg were slightly enriched in leaf, Cu, Pb and As was enriched in root, and Cr were enriched in branch. Metals levels in R. stylosa and S. hainanensis from both Dongzhai Harbor and Sanya Bay were compared, which suggested that different mangrove species have their unique mechanism to bioaccumulate metals and TOC in the mangrove sediment could be one of the important factors for regulating metals in mangrove tissues. The biota-sediment accumulation factors (BSAF) of metals in mangrove tissues were calculated. The distribution of metals concentrations in mangrove tissues against metals levels in sediment demonstrated that mangrove leaves could be employed as a bio-indicator for some metals (Cu, Zn, Cd and Hg) with temporal monitoring.

SNP detection by parallel targeted sequencing from degraded DNA samples in Haliotis diversicolor

The small abalone, Haliotis diversicolor, is an economically important shellfish species in East Asia. The wild stocks have been highly threatened due to overfishing in the past several decades. Taking into account conservation and recovery of wild resources, long preserved samples were used to analyze population structure. However, extreme fragmentation of DNA limited the use of these degraded DNA samples. In this study, a total of 96 novel single nucleotide polymorphisms (SNPs) were identified based on transcriptomes of H. diversicolor. The parallel target sequencing was then used to examine one wild population collected in 2003 from Sanya Bay, Hainan Province with degraded DNA. Nineteen loci appeared in more than 80% of individuals and were polymorphic. This study provides a valuable method for using degraded DNA and molecular markers for genetic diversity analysis of H. diversicolor.

The effects of four transplantation methods on five coral species at the Sanya Bay

Coral transplantation is considered as one of the major tools to increase coral abundance for degraded coral reefs. To investigate the effects of various methods and coral species in transplantation, coral fragments (n=902) of five coral species were transplanted by four methods at Luhuitou, the Sanya Bay, Hainan Province, China, where the reef has been over-exploited and is still threatened by human activities and natural disasters. Ten months after the transplant, the average survivorship of the transplanted corals was 45.5%. Methodologies had different effects on the transplanted corals, but none of them was efficacious for all coral species. Methodology could not change the decreasing trend for Montipora foliosa and Acropora hyacinthus, although it did slow down their decline. All transplants of A. hyacinthus and M. foliosa had high mortalities and significant decrease on survival area, while Porites andrewsi and Galaxea fascicularis had lower mortalities and partial mortalities. Only one method had significant effect on increasing survival area of G. fascicularis, same as P. andrewsi. Out of the five transplanted coral species, Pocillopora damicornis was the only species that had living tissue area increase in all applied methods, while the others had decreased live tissue area in one or more methods. The results of this study suggested that performing coral transplantation in a highly threatened area was not efficient unless the threats were diminished or erased. Moreover, proper species selection for coral transplantation is crucial, especially in a disturbed environment. Methodology, although having limited effects on improving results of coral transplantation, cannot compensate the maladjustment of vulnerable species to the stresses on the Luhuitou Reef. Coral transplantation on Luhuitou Reef should not be performed unless the stresses are under controlled, and corals with good tolerance to the environment should be considered first.

Seasonal variation of dissolved oxygen in Sanya Bay

Dissolved oxygen concentration is central in determining the water quality level for an aquatic ecosystem. In this article, we analyzed in situ dissolved oxygen and other related parameters from a dataset observed during 2004–2010 in Sanya Bay to find out its status in recent years and what controlled its seasonal variation. Different to worldwide coastal and estuarine ecosystems, dissolved oxygen concentrations in the Bay reached minimum values in autumn rather than summer during most of the seven years, while maximum values were seen in winter. Results showed that the seasonal trend of dissolved oxygen was mainly controlled by physical instead of biochemical processes. While many harmful factors normally act to lower dissolved oxygen concentration during summer, such as high surface water temperature, strong stratification, and large loads of nutrients from the river basin, upwelling driven by summer monsoons cooled down the bottom water. This increased dissolved oxygen saturation and hindered biochemical oxygen demand. On the contrary, the bottom water was warmed up abruptly during autumn, when upwelling was reduced due to the cessation of summer monsoon. This decreased bottom water dissolved oxygen saturation and enhanced some biochemical processes. Overall, dissolved oxygen values were greater than 6.0 mg l−1 during most years, indicating a healthy water quality environment in the Bay. Nevertheless, low dissolved oxygen bottom water conditions (<6.0 mg l−1) still existed in the whole Bay during some seasons—like the summer of 2009—which indicates there is some concern for the current stage of water quality in the Bay.

Characterization and Complete Genome Sequences of Three N4-Like Roseobacter Phages Isolated from the South China Sea.

Three bacteriophages (RD-1410W1-01, RD-1410Ws-07, and DS-1410Ws-06) were isolated from the surface water of Sanya Bay, northern South China Sea, on two marine bacteria type strains of the Roseobacter lineage. These phages have an isometric head and a short tail, morphologically belonging to the Podoviridae family. Two of these phages can infect four of seven marine roseobacter strains tested and the other one can infect three of them, showing relatively broader host ranges compared to known N4-like roseophages. One-step growth curves showed that these phages have similar short latent periods (1-2h) but highly variable burst sizes (27-341pfucell(-1)). Their complete genomes show high level of similarities to known N4-like roseophages in terms of genome size, G+C content, gene content, and arrangement. The morphological and genomic features of these phages indicate that they belong to the N4likevirus genus. Moreover, comparative genomic analysis based on 43 N4-like phages (10 roseobacter phages and 33 phages infecting other lineages of bacteria) revealed a core genome of 18 genes shared by all the 43 phages and 38 genes shared by all the ten roseophages. The 38 core genes of N4-like roseophages nearly make up 70% of each genome in length. Phylogenetic analysis based on the concatenated core gene products showed that our phage isolates represent two new phyletic branches, suggesting the broad genetic diversity of marine N4-like roseophages remains.

Spatial and temporal variability of copepod assemblages in Sanya Bay, northern South China Sea

Sanya Bay, a tropical open coral-reef bay in the northern South China Sea, is undergoing great changes in environmental conditions due to the rapid increase in human activities. This study assessed spatial and temporal variation in copepod species composition, abundance, and distribution in relation to environmental variables in Sanya Bay. A total of 63 copepod species were identified. The annual average abundance of copepods was 4707.1± 2763.8 ind m–3, with the highest densities observed in winter and the lowest densities observed in summer. The number of copepod species increased from nearshore to offshore waters of the bay, whereas their abundance decreased seaward, with highest values being recorded in nearshore waters. Approximately 90% of copepod recorded in this study belonged to 11 dominant species.Parvocalanus crassirostriswas the most common and abundant species in Sanya Bay. Abundances of total copepods and P. crassirostris were negatively correlated with temperature and positively correlated with chlorophyll a concentration, but no significant correlation between them was found in spring, summer or fall. High abundances of copepods were mainly concentrated near the mouth of the Sanya River. The seasonal and regional patterns of copepod variation in Sanya Bay were characterized by low diversity and high abundance in winter, and by highest abundance in the nearshore waters during the four sampling periods. Copepod abundance distribution in winter was enhanced by low temperature and high chlorophyll aconcentration, and was driven by the dominant species P. crassirostris.

海南三亚湾海岸地貌与沉积环境研究进展

三亚湾现代海岸绝大部份位于宽平的海岸大沙坝上，是激浪活跃的砂质堆积海岸：湾的两端是海蚀的基岩岸，且不同程度地分布着珊瑚礁。在整体上，三亚湾为一大型的较开阔的港湾海岸，波浪作用为主，但在某些岸段潮流作用与生物活动亦为活跃的因素。所以，三亚湾海岸地貌类型丰富。本文拟对三亚湾海岸作简单剖析，对沉积动力与海岸地貌的形成进行初步讨论。 The modern Sanya Bay coast is most located in the wide Dashaba coast, and is Sandy accumulation coast by Active wave: both ends of the bay are the bedrock coastal because marine-abrasion. And the coral reefs are distributed in different degrees. As a whole, as the wave action, Sanya Bay is a large open embayed coast. But the tidal current and biological activities are also active in some coastal areas. Therefore, Sanya Bay coastal landform types are abundant. This paper intends to make a simple analysis of the coastal Sanya Bay, and preliminary discussion on the formation of sedimentary dynamics and coastal geomorphology.

Mapping the bathymetry of shallow coastal water using single-frame fine-resolution optical remote sensing imagery

This paper presents a bathymetry inversion method using single-frame fine-resolution optical remote sensing imagery based on ocean-wave refraction and shallow-water wave theory. First, the relationship among water depth, wavelength and wave radian frequency in shallow water was deduced based on shallow-water wave theory. Considering the complex wave distribution in the optical remote sensing imagery, Fast Fourier Transform (FFT) and spatial profile measurements were applied for measuring the wavelengths. Then, the wave radian frequency was calculated by analyzing the long-distance fluctuation in the wavelength, which solved a key problem in obtaining the wave radian frequency in a single-frame image. A case study was conducted for Sanya Bay of Hainan Island, China. Single-frame fine-resolution optical remote sensing imagery from QuickBird satellite was used to invert the bathymetry without external input parameters. The result of the digital elevation model (DEM) was evaluated against a sea chart with a scale of 1:25 000. The root-mean-square error of the inverted bathymetry was 1.07 m, and the relative error was 16.2%. Therefore, the proposed method has the advantages including no requirement for true depths and environmental parameters, and is feasible for mapping the bathymetry of shallow coastal water.

Black coral as a new environmental recorder: The lead profiles in coral skeletons over the past century

Lead (Pb) is a typical heavy metal pollutant in the environment, and most Pb contamination comes from human activities. In the present work, the Pb contents of two black coral specimens (Cirrhipathes spp.) collected from the northern South China Sea were measured by synchrotron radiation micro X-ray fluorescence (SR μ-XRF) analysis with 2.5μm resolution. The results showed that sample SY-1 from the Sanya Bay (near the continent) exhibited higher Pb levels and greater fluctuations than sample XS-1 from the Xisha Islands (off the continent), reflecting the influence of terrestrial input and atmospheric deposition in coastal surface seawater. The present work also demonstrated that the Pb profile in black coral nearshore was highly influenced by human activities, mainly by war and economic development. Thus, black coral may serve as a new potential environmental Pb recorder with SR μ-XRF analytical technology.

Spatial variations of bacterial community and its relationship with water chemistry in Sanya Bay, South China Sea as determined by DGGE fingerprinting and multivariate analysis.

Bacteria play important roles in the structure and function of marine food webs by utilizing nutrients and degrading the pollutants, and their distribution are determined by surrounding water chemistry to a certain extent. It is vital to investigate the bacterial community's structure and identifying the significant factors by controlling the bacterial distribution in the paper. Flow cytometry showed that the total bacterial abundance ranged from 5.27 × 10(5) to 3.77 × 10(6) cells/mL. Molecular fingerprinting technique, denaturing gradient gel electrophoresis (DGGE) followed by DNA sequencing has been employed to investigate the bacterial community composition. The results were then interpreted through multivariate statistical analysis and tended to explain its relationship to the environmental factors. A total of 270 bands at 83 different positions were detected in DGGE profiles and 29 distinct DGGE bands were sequenced. The predominant bacteria were related to Phyla Protebacteria species (31 %, nine sequences), Cyanobacteria (37.9 %, eleven sequences) and Actinobacteria (17.2 %, five sequences). Other phylogenetic groups identified including Firmicutes (6.9 %, two sequences), Bacteroidetes (3.5 %, one sequences) and Verrucomicrobia (3.5 %, one sequences). Conical correspondence analysis was used to elucidate the relationships between the bacterial community compositions and environmental factors. The results showed that the spatial variations in the bacterial community composition was significantly related to phosphate (P = 0.002, P < 0.01), dissolved organic carbon (P = 0.004, P < 0.01), chemical oxygen demand (P = 0.010, P < 0.05) and nitrite (P = 0.016, P < 0.05). This study revealed the spatial variations of bacterial community and significant environmental factors driving the bacterial composition shift. These results may be valuable for further investigation on the functional microbial structure and expression quantitatively under the polluted environments in the world.

Isolation and screening of microsatellite markers from the pearl oyster, Pinctada fucata using FIASCO method.

Pearl oyster, Pinctada fucata is an important commercial species that is cultured for pearl in China (Meng et al. 1996). Pearls produced by this species are well-known worldwide and called ‘South China Sea Pearl’. In China, artificial reproduction of this species was successful in 1965. Since then, hundreds of hatcheries have been established (Meng et al. 1996), and currently the industry of pearl production relies mainly on hatchery produced spats. Each year, the hatcheries use cultured stocks as the brood stocks to produce the next generation for culture. This operation has been continued for more than 40 years which lead to some degeneration of growth traits, such as miniaturization of body size, reduction of resistance to pathogens and adverse environments, and decrease of cultured pearl quality. Thus, it is desirable to investigate the genetic variability of this species to provide background information for its genetic improvement. Microsatellite DNA is one of the most popular molecular markers, because of its high level of polymorphism and codominant nature it is increasingly being used for identity test, population genetics and gene mapping (Evans et al. 2006; Herbinger et al. 2006). Here, we report nine polymorphic microsatellite loci that would be useful in genetic studies in the pearl oyster. In a total of 32 individuals, samples for construction of enriched library were collected from Sanya Bay, Hainan Province, and samples for screening and characterization of polymorphic microsatellite loci were collected from Beibu Bay, Guangxi Province. Genomic DNA was extracted from the adductor muscle by proteinase K digestion, phenol– chloroform protocol. The enriched genomic library was constructed following the protocol of the fast isolation by AFLP of sequences containing repeats (FIASCO) as described by Zane et al. (2002). DNA was simultaneously digested with MseI and ligated to MseI-adaptor. The digestion ligation mixture was diluted (1:10) and directly amplified with

Molecular analysis of in situ diets of coral reef copepods: evidence of terrestrial plant detritus as a food source in Sanya Bay, China

Knowledge of copepod in situ diet is critical for accurate assessment of trophic linkages and transfer efficiencies of the marine food web but is limited due to technical challenges. Here we report, using a recently developed eukaryote-universal copepod-excluding ectobiotic ciliate-blocking protocol, to investigate the natural diets of the copepods Temora turbinata, Subeucalanus subcrassus and Canthocalanus pauper in coastal waters in Sanya Bay, China. Analysis of the resultant 18S rDNA clone libraries revealed diverse diet composition for all the three copepod species, with 11 prey species for C. pauper, 9 for T. turbinata and 9 for S. subcrassus. The ingested materials included land plants, green algae, Metazoa, Euglenozoa and Rhizaria, although species numbers from each of these lineages differed. Broussonetia sp. (land plant), which might have been ingested in the form of pollen or fresh detritus were common among all three copepods, and accounted for a significant proportion (>55%) of the clones sequenced. These results suggest that copepods in Sanya coastal waters might use terrigenous detritus as supplementary food sources when phytoplankton production is limited. However, the significance of the plant detritus as a nutrition source of these copepods remains to be determined by analyzing carbon-based proportion and digestion/assimilation rate of the ingested plant materials.

An Improved Empirical Model for Retrieving Bottom Reflectance in Optically Shallow Water

Satellite remote sensing has become an essential observing system to obtain comprehensive information on the status of coastal habitats. However, a significant challenge in remote sensing of optically shallow water is to correct the effects of the water column. This challenge becomes particularly difficult due to the spatial and temporal variability of water optical properties. In order to model the light distribution for optically shallow water and retrieve the bottom reflectance, a parameterized model was proposed by introducing an important adjusted factor g. The synthetic data sets generated by HYDROLIGHT were utilized to train a neural network (NN) and then to derive the adjustable parameter values. The parameter g was found to vary with water depth, water optical properties, and bottom reflectance. Specifically, it revealed two obvious patterns among the different benthic habitat types. In coral reef, seagrass, and macrophyte habitats, g exhibited a remarkable peak at about 550 nm. The peak has a value of about 2.47-2.49. In white sand or hardpan habitats, g spectra are relatively flat. The semi-empirical model was applied to calculate the bottom reflectance from the new weighting factor, the downward diffuse attenuation coefficient, and the irradiance reflectance just below the sea surface collected in Sanya Bay in 2008 and 2009. Good agreement between the predicted and measured values demonstrated that the weighting factor g is an effective tool to modify the model for interpreting and predicting bottom reflectance without the need for any localized input (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> > 0.79).

Inventory change (1990s–2010s) in the marine flora of Sanya Bay (Hainan Island, China)

Sanya Bay lies at the southern part of Hainan Island, 18°15′N 109°28′E. The seawater in the bay has been catastrophically polluted during the past two decades with urban sewage from the rapidly developing Sanya City. The marine flora research in Sanya Bay was started at the beginning of the 1930s and the most detailed studies were performed by two German-Chinese expeditions in 1990 (October–December) and in 1992 (March–April). In April, October, November and December 2008–2010 the marine flora of Sanya Bay was studied by the authors at three localities: Luhuitou Peninsula, Xiaodong Hai and Dadong Hai. Marine algae were sampled in the intertidal and upper subtidal zones (to 4–5 m depth). The list of species (including varieties and forms) of the marine algae for Sanya Bay sampled during the period from 2008 to 2010 is compared with those collected at the same localities in 1990/1992. Comparative analysis of the floristic composition of the marine red, brown and green algae (found during different time periods) revealed that considerable changes have taken place between 1990/1992 and 2008–2010 at Sanya Bay. There was an increase in filamentous, tubular and fine blade-like green and red algae (mainly epiphytes with a high surface to volume ratio) and a displacement of upright-growing fleshy, foliose and other large green, brown and red algae with a low surface to volume ratio. It is assumed that the changes reflect mainly increased pollution by urban sewage and mariculture pond wastes and probably by coral bleaching events of 1998.

Coastal acidification induced by tidal-driven submarine groundwater discharge in a coastal coral reef system.

We identified a barely noticed contributor, submarine groundwater discharge (SGD), to acidification of a coastal fringing reef system in Sanya Bay in the South China Sea based on time-series observations of Ra isotopes and carbonate system parameters. This coastal system was characterized by strong diel changes throughout the spring to neap tidal cycle of dissolved inorganic carbon (DIC), total alkalinity, partial pressure of CO2 (pCO2) and pH, in the ranges of 1851-2131 μmol kg(-1), 2182-2271 μmol kg(-1), 290-888 μatm and 7.72-8.15, respectively. Interestingly, the diurnal amplitudes of these parameters decreased from spring to neap tides, governed by both tidal pumping and biological activities. In ebb stages during the spring tide, we observed the lowest salinities along with the highest DIC, pCO2 and Ra isotopes, and the lowest pH and aragonite saturation state. These observations were consistent with a concurrent SGD rate up to 25 and 44 cm d(-1), quantified using Darcy's law and (226)Ra, during the spring tide ebb, but negligible at flood tides. Such tidal-driven SGD of low pH waters is another significant contributor to coastal acidification, posing additional stress on coastal coral systems, which would be even more susceptible in future scenarios under higher atmospheric CO2.

Novel cytotoxic nine-membered macrocyclic polysulfur cembranoid lactones from the soft coral Sinularia sp.

One novel nine-membered macrocyclic polysulfur cembranoid lactone, sinulariaoid A (1); three new multioxygenated cembranoids, sinulariaoid B (2), sinulariaoid C (3), sinulariaoid D (4); and four known cembranoids, capilloloid (5), dihydrosinularin (6), sinularin (7), and dihydrosinuflexolide (8) were isolated from the soft coral Sinularia sp. collected off of Sanya Bay in the South China Sea. Their stereochemical structures were determined on the basis of extensive spectroscopic methods, including single crystal X-ray diffraction analysis. Sinulariaoid A (1) is the first reported nine-membered macrocyclic polysulfur cembranoid from soft coral. The cytotoxic activities of compounds 1–8 were determined in four human cancer cell lines (HepG2, HepG2/ADM, MCF-7, and MCF-7/ADM). Of these, sinulariaoid A (1) exhibited the most potent anticancer activity in vitro, and its cytotoxicity in HepG2/ADM was more potent than in the other three cell lines. Furthermore, it was found that sinulariaoid A (1) induced apoptosis, and its selective toxicity toward HepG2/ADM cells was not related to P-glycoproteins.

Boron isotopic fractionation and trace element incorporation in various species of modern corals in Sanya Bay, South China Sea

The boron isotope paleo-pH proxy has been extensively studied due to its potential for understanding past climate change, and further calibrations were considered for accurate applications of the proxy because of significant variability related to biocarbonate microstructure. In this work, we studied the boron isotopic fractionation between modern marine corals and their coexisting seawater collected along shallow area in Sanya Bay, South China Sea. The apparent partition coefficient of boron (KD) ranged from 0.83×10−3 to 1.69×10−3, which are in good agreement with previous studies. As the analyzed coral skeleton (∼5 g) spanned the growth time period of 1–2 years, we discussed the boron isotopic fractionation between pristine corals and modern seawater using the annual mean seawater pH of 8.12 in this sea area. Without taking the vital effect into account, (11B/10B)coral values of all living corals spread over the curves of (11B/10B)borate vs. (11B/10B)sw with the α4−3 values ranging from 0.974 to 0.982. After calibrating the biological effect on the calcifying fluid pH, the field-based calcification on calcifying fluid pH (i.e., Δ(pHbiol-pHsw)) for coral species of Acropora, Pavona, Pocillopora, Faviidae, and others including Proites are 0.42, 0.33, 0.36, 0.19, respectively, and it is necessary to be validated by coral culturing experiment in the future. Correlations in B/Ca vs. Sr/Ca and B/Ca vs. pHbiol approve temperature and calcifying fluid pH influence on skeletal B/Ca. Fundamental understanding of the thermodynamic basis of the boron isotopes in marine carbonates and seawater will strengthen the confidence in the use of paleo-pH proxy as a powerful tool to monitor atmospheric CO2 variations in the past.

Spatio-temporal distribution of chlorophyll-a concentration derived from MODIS satellite remote-sensing and in situ observations in Sanya Bay, China

This study examined satellite chlorophyll-a (chl-a) concentration and in situ observations in Sanya Bay (SYB). In situ observation of chl-a was conducted four times per year at 12 sampling stations in SYB from January 2004 to October 2008. Monthly satellite chl-a was derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) during 2000–2012. This study compared satellite chl-a values to in situ measurements in SYB. The two data sets match well in the whole region except for two estuaries. Results show that the average in situ chl-a was 1.49 mg m−3 in SYB. Chl-a was relatively higher (>2 mg m−3) and more variable in coastal areas, with a tendency to decrease offshore (<0.4 mg m−3). The chl-a level in summer displayed obviously vertical stratification, with higher values at the bottom and lower values at the surface. Analysis of monthly mean chl-a showed that the highest level (>2 mg m−3) appeared in December, with the lowest in March (<1 mg m−3). The gradients are ranked winter, autumn, summer and spring. There was higher chl-a in autumn and winter, which may be associated with the stronger wind monsoon then. Annual mean chl-a from 2000 to 2012 varied from 1.17 to 2.05 mg m−3, with the minimum in 2001 and the maximum in 2005. The chl-a level presented a roughly increasing tendency from 2000 to 2012, which may be related to the increasing nutrients associated with the development of tourism and fishery.