South China Sea Coast Research Articles

Characteristics and possible causes of the seasonal sea level anomaly along the South China Sea coast

Based on sea level, air temperature, sea surface temperature (SST), air pressure and wind data during 1980–2014, this paper uses Morlet wavelet transform, Estuarine Coastal Ocean Model (ECOM) and so on to investigate the characteristics and possible causes of seasonal sea level anomalies along the South China Sea (SCS) coast. The research results show that: (1) Seasonal sea level anomalies often occur from January to February and from June to October. The frequency of sea level anomalies is the most in August, showing a growing trend in recent years. In addition, the occurring frequency of negative sea level anomaly accounts for 50% of the total abnormal number. (2) The seasonal sea level anomalies are closely related to ENSO events. The negative anomalies always occurred during the El Nino events, while the positive anomalies occurred during the La Nina (late El Nino) events. In addition, the seasonal sea level oscillation periods of 4–7 a associated with ENSO are the strongest in winter, with the amplitude over 2 cm. (3) Abnormal wind is an important factor to affect the seasonal sea level anomalies in the coastal region of the SCS. Wind-driven sea level height (SSH) is basically consistent with the seasonal sea level anomalies. Moreover, the influence of the tropical cyclone in the coastal region of the SCS is concentrated in summer and autumn, contributing to the seasonal sea level anomalies. (4) Seasonal variations of sea level, SST and air temperature are basically consistent along the coast of the SCS, but the seasonal sea level anomalies have no much correlation with the SST and air temperature.

Field Investigation into Wave Attenuation in the Mangrove Environment of the South China Sea Coast

ABSTRACT Cao, H.; Chen, Y.; Tian, Y., and Feng, W., 2016. Field investigation into wave attenuation in the mangrove environment of the South China Sea coast. Coastal mangroves form the land-sea interface and face an increasingly aggressive threat from ocean waves as a result of sea-level rise. This study investigates the buffering effect of mangroves on the coast of Leizhou Bay in the South China Sea under two different climates (normal windy weather and storm). By doing this, we aim to establish the exact wave damping rate due to the presence of mangroves and to study the wave and spectral characteristics of wave energy in the vegetated area. Wave gauges are mounted along a cross-shore transect to monitor the wave conditions during particular time periods. From the data analysis, we found that the recorded maximum significant wave height is 22.3 cm at the outermost station and remarkable wave damping was experienced within the mangrove troops of 100 meters. To evaluate the wave dissipation on the mudflat...

Shoreline change of the Mekong River delta along the southern part of the South China Sea coast using satellite image analysis (1973-2014)

The Mekong River delta is the world’s third largest delta, consequence of a favourable morphosedimentary setting, high sediment supply and rapid growth during the Holocene. Analysis of Landsat satellite images from 1973 to 2014 shows that nearly 70 % of the 160 km - long South China Sea shoreline of the delta has strongly eroded. This trend represents a reversal of the massive, long-term Holocene progradation that characterized this part of the delta. Erosion and land loss along the South China Sea coast are not related to lobe switching, but more likely to decreasing river sediment supply and variations in patterns of sediment storage in the delta that appear to be due to human-induced modifications. These include fluvial sediment trapping by dams, enhanced subsidence due to massive groundwater abstraction, and riverbed aggregate extractions. Shoreline erosion is further exacerbated by the replacement of protective mangroves by shrimp farms. This erosion constitutes an additional hazard to the future integrity of a mega-delta already considered particularly vulnerable to subsidence, and to future large-capacity dams.

Impacts of decaying eastern and central Pacific El Niños on tropical cyclone activities over the western North Pacific in summer

We investigate the influences of the decaying eastern Pacific El Nino (EP-El Nino) and central Pacific El Nino (CP-El Nino) on tropical cyclone (TC) activities in the western North Pacific (WNP) during July, August, and September (JAS). During this period, TC geneses and tracks are reduced in the central and eastern WNP. However, TC tracks reaching the Philippines increase, and more TC geneses appear west of 145°E during EP-El Nino. During CP-El Nino, tracks reaching the South China Sea (SCS) and southeast coast of China increase, and positive anomalies of TC genesis are found in the southern part of the central WNP and southern SCS. It is possible that the different variations of the anomalous anticyclone over east of the Philippines in the WNP induced by El Ninos are instrumental to the different TC variations in the two types of decaying El Ninos during JAS. Compared with EP-El Nino, strengthening and northward expansion of the anomalous anticyclone during CP-El Nino cause a westward shift of the western Pacific subtropical high in summer, which is responsible for more westward TC tracks over the SCS and southeast coast of China. This northward expansion can cause the center of suppressed TC geneses in the central WNP to migrate further north during CP-El Nino. A decreased magnitude of vertical shear dominates the southern part of the central WNP and southern SCS, which enhances TC formation in these regions during CP-El Nino.

Unusually low TEX86 values in the transitional zone between Pearl River estuary and coastal South China Sea: Impact of changing archaeal community composition

TEX86, calculated based on the distribution of isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs), is used worldwide for paleotemperature reconstruction in marine and lacustrine environments. Recently, however, increasing evidence showed that TEX86 could be affected by multiple environmental variables. In this study, TEX86 was calculated for core and polar GDGTs obtained from water column and surface sediments in the lower Pearl River and its estuary. Together with previously published core GDGT data from the coastal and open South China Sea (SCS), a comparison was made between TEX86-derived and satellite-based surface water temperature, which showed a TEX86-temperature minimum that is considerably lower than winter satellite temperature in the transitional zone between the Pearl River estuary and the coastal SCS. TEX86 showed significantly positive correlation with GDGT-2 and GDGT-3 in this transitional zone, indicating that they are the primary compounds for the TEX86 bias toward cooler temperature. Lipid and molecular DNA data both indicate that the variation in archaeal community composition rather than water depth or seasonality is likely the crucial factor causing the deviation of TEX86 in the transitional area. Our study has implications for studies in ancient continental margins where unusually low TEX86 temperatures may be observed in the geological record.

A New Coumarin Produced by Mixed Fermentation of Two Marine Fungi

A new coumarin, 7-(γ,γ-dimethylallyloxy)-6-hydroxy-4-methylcoumarin (1), was isolated from the mixed fermentation broth of two mangrove fungi (strain No. K38 and E33) isolated from the South China Sea coast. The structure of 1 was determined by comprehensive spectroscopic methods, especially 2D NMR techniques. Primary bioassays showed that compound 1 at 0.25 mM has no inhibitory activity against Fusarium graminearum, Gloeosporium musae, Rhizoctonia solani, and Phytophthora sojae.

Salinity-dominated change in community structure and ecological function of Archaea from the lower Pearl River to coastal South China Sea.

Archaea have multiple roles in global biogeochemical cycles. However, we still have limited knowledge about how environmental factors affect the diversity and function of different archaeal lineages. The goal of this study was to examine the change in the abundance and community structure of Archaea in the sediments collected from the lower Pearl River (mainly North River tributary), its estuary, and coastal South China Sea (SCS) in order to evaluate how archaeal ecological function might change along the salinity gradient. Pyrosequencing of the 16S rDNA gene of Archaea was performed on sediment samples from Feilaixia Dam on the North River tributary to Wanshan islands, which have a salinity range of 0.1 to 31.2‰. Consistent with the salt tolerance of cultivated representatives, methanogens in the genera Methanoregula, Methanosaeta, and Methanosarcina and Nitrososphaera within Thaumarchaeota of the ammonia-oxidizing Archaea (AOA) were abundant in freshwater sediments of the North River tributary, whereas the marine-associated genera Methanococcoides and Nitrosopumilus were the most abundant methanogens and AOA, respectively, in the estuary and coastal SCS. However, the percentages of total methanogens decreased and Thaumarchaeota increased with salinity, respectively. The phylum Crenarchaeota was largely represented by class-level lineages with no cultivated representatives, which collectively were more abundant in the estuary and coastal SCS in comparison to freshwater sites. This study indicates that salinity is the dominating factor affecting archaeal community structure and ecological function from the North River tributary of the Pearl River, its estuary, and coastal SCS, which is consistent with salinity control on microbial diversity in other regions of the world.

A New Polysubstituted Benzaldehyde from the co-culture broth of Two Marine Fungi (Strains Nos. E33 and K38)

A new polysubstituted benzaldehyde derivative, ethyl 5-ethoxy-2-formyl-3-hydroxy-4-methylbenzoate (1), was isolated from the co-culture broth of two mangrove fungi (strains Nos. K38 and E33) isolated from the South China Sea coast. The structure of 1 was determined by comprehensive spectroscopic methods, especially 2D NMR techniques. Primary bioassays showed that compound 1 at 0.25 mM inhibited Fusarium graminearum, Gloeosporium musae, Rhizoctonia solani Kuhn, and Phytophthora sojae (Kaufmann & Gerdemann) in 12.06, 11.57, 10.21, and 8.50 mm diameters, respectively.

Enhancement of uranium(VI) biosorption by chemically modified marine-derived mangrove endophytic fungus Fusarium sp. #ZZF51

Fusarium sp. #ZZF51, mangrove endophytic fungus originated from South China Sea coast, was chemically modified by formaldehyde, methanol and acetic acid to enhance its affinity of uranium(VI) from waste water. The influencing factors about uranium(VI) adsorption such as contact time, solution pH, the ratio of solid/liquid (S/L) and initial uranium(VI) concentration were investigated, and the suitable adsorption isotherm and kinetic models were determined. In addition, the biosorption mechanism was also discussed by FTIR analysis. Experimental results show that the maximum biosorption capacity of formaldehyde-treated biomass for uranium(VI) at the optimized condition of pH 6.0, S/L 0.6 and equilibrium time 90 min is 318.04 mg g−1, and those of methanol-treated and HAc-treated biomass are 311.95 and 351.67 mg g−1 at the same pH and S/L values but different equilibrium time of 60 and 90 min, respectively. Thus the maximum biosorption capacity of the three kind of modified biomass have greatly surpassed that of the raw biomass (21.42 mg g−1). The study of kinetic exhibits a high level of compliance with the Lagergren’s pseudo-second-order kinetic models. Langumir and Freundlich models have proved to be well able to explain the sorption equilibrium with the satisfactory correlation coefficients higher than 0.96. FTIR analysis reveals that the carboxyl, amino and hydroxyl groups on the cell wall of Fusarium sp. #ZZF51 play an important role in uranium(VI) biosorption process.

Structure revision and cytotoxic activity of marinamide and its methyl ester, novel alkaloids produced by co-cultures of two marine-derived mangrove endophytic fungi

Marinamide (1) and its methyl ester (2) have been previously reported as pyrrolyl 1-isoquinolone alkaloids, which were produced by co-cultures of two marine-derived mangrove endophytic fungi from the South China Sea coast. Recrystallisation of methyl marinamide (2) from pyridine forms the known pesticide, quinolactacide (3). Treatment of 3 with methyl iodide to afford N-methyl quinolactacide (4) was identified by X-ray crystallography. Thus, the structures of 1 and 2 were revised from the previously reported pyrrolyl 1-isoquinolone structures to pyrrolyl 4-quinolone analogues. In the MTT assays, both 1 and 2 exhibited potent cytotoxic activity against HepG2, 95-D, MGC832 and HeLa tumour cell lines.

A new isobenzofuranone from the mangrove endophytic fungus Penicillium sp. (ZH58)

A new isobenzofuranone, 4-(methoxymethyl)-7-methoxy-6-methyl-1(3H)-isobenzofuranone (1), together with seven known compounds, dilation (2), lumichrome (3), curvulari (4), 5,5′-oxy-dimethylene-bis(2-furaldehyde) (5), chromone (6), harman(1-methyl-β-carboline) (7), N9-methyl-1methyl-β-carboline (8), was isolated from the mangrove endophytic fungus, Penicillium sp. ZH58 obtained from the South China Sea coast. Their structures were determined by analysis of spectroscopic data. Compound 1 exhibited cytotoxicity against KB and KBV200 cells with IC50 values of 6 and 10 μg/mL, respectively.

A new xanthone derivative from the co-culture broth of two marine fungi (strain No. E33 and K38)

A new xanthone derivative, 8-hydroxy-3-methyl-9-oxo-9H-xanthene-1-carboxylic acid methyl ether (1), was isolated from the co-culture broth of two mangrove fungi (strain No. K38 and E33) isolated from the South China Sea coast. The structure of 1 was determined by comprehensive spectroscopic methods, especially 2D NMR techniques. Primary bioassays showed that compound 1 has inhibitory activity against five microorganisms, including Gloeasporium musae and Peronophthora cichoralearum etc.

Landscape pattern analysis of plankton in northern South China Sea

Based on the data from survey on fishery resources and their habitat environment in the exclusive economic zone and continental shelf of South China Sea conducted during 1997～2002 and sponsored by the state program of special marine survey(HY126-02),we analyzed the landscape pattern of plankton in northern South China Sea(NSCS) by using GIS spatial analysis model and mapping techniques.Results show that high plankton biomass areas patch along coastal waters,and the seasonal variation of their landscape pattern changes with monsoon and coastal monsoon flow.Furthermore,the areas generally enclose in several important upwelling areas and traditional fishing grounds in northern South China Sea coast.

Structure of the female cephalic end and cuticular ornamentations of Paraphilometroides nemipteri (Nematoda: Philometridae), as revealed by SEM

Scanning electron microscopy (SEM) examination of a paratype specimen (gravid female) of the philometrid nematode Paraphilometroides nemipteri Moravec et Shaharom-Harrison, 1989, the type species of Paraphilometroides Moravec et Shaharom-Harrison, 1989, made it possible to recognise the true structure of the cephalic end and the shape of cuticular ornamentations on the body. In contrast to other philometrid genera, the cephalic end is angular in lateral view and rounded in dorsoventral view; large external cephalic papillae are fused together to form a marked dorsal and a ventral ala, each bent into a curve; six minute internal papillae, including a pair of previously not reported lateral papillae, were found; amphids were indistinct. Cuticular ornamentations (inflations) were found to be transversely elongated. These features, especially the unique cephalic structure, clearly distinguish Paraphilometroides from other philometrids and confirm the validity of this genus. Moravec and Shaharom-Harrison (1989) erected the hitherto monotypic philometrid genus Paraphilometroides Moravec et Shaharom-Harrison, 1989 with the type species P. Nemipteri Moravec et Shaharom-Harrison, 1989, described from females found in the fins and operculum of the marine fish (notchedfin threadfin bream) Nemipterusperonii (Valenciennes) from off the South China Sea coast, Malaysia. The male of P. nemipteri remains unknown. The authors distinguished Paraphilometroides from the related genus Philometroides Yamaguti, 1935 mainly by the unusual structure of the female cephalic end, which is unique within the family Philometridae (see Moravec 2006). However, P. nemipteri was studied only by light microscopy (LM), whereas some details of the cephalic structure, especially the cephalic papillae of gravid philometrid females are usually difficult to observe by LM due to a various degree of their reduction and atrophy (Moravec 2004); in the past, some philometrid species were even reported to have no cephalic papillae. Consequently, the only reliable method to study the cephalic structures in philometrids is the use of scanning electron microscopy (SEM). Therefore, one of the ethanol-preserved paratype specimens (gravid female) of P. nemipteri, deposited in the Helminthologi-cal Collection of the Institute of Parasitology, Biology Centre

A new diimide derivative from the co-culture broth of two mangrove fungi (strain no. E33 and K38)

A new diimide derivative, named ( − )-byssochlamic acid bisdiimide (1), was isolated from the mixed broth of two mangrove fungi (strain no. K38 and E33) from the South China sea coast. The structure of 1 was determined by comprehensive spectroscopic methods, including 1D and 2D NMR (COSY, HMQC, and HMBC) and semi-synthesis. Primary bioassays showed that 1 had weak cytotoxic activity against Hep-2 and HepG2 cells.

Early Holocene initiation of the Mekong River delta, Vietnam, and the response to Holocene sea-level changes detected from DT1 core analyses

The Early Holocene initiation of the Mekong River delta, Vietnam, was investigated based on sedimentary facies, microfossil analyses, and radiocarbon dating of DT1 core taken from the upper delta plain. The DT1 core (105°38′51″E, 10°17′02″N, elevation + 2 m) is 51.5 m long and located in fill of a buried incised valley. This incised valley of the Paleo-Mekong River formed during the last glacial maximum, which is 20–30 km wide, has been traced spatially from the Cambodian border to the South China Sea coast by compilation of existing core data. The DT1 core records the history of the estuarine channel and delta systems of the Mekong River during the early to middle Holocene. The sedimentary facies, determined particularly from sedimentary structures, diatom and foraminifera assemblages, grain-size variation, and the accumulation rate, clearly show an upward-deepening succession in the lower part of the core from marsh or intertidal flat to subtidal-inner bay facies and an overlying upward-shallowing succession from prodelta to intertidal flat-floodplain. The boundary between the two successions, indicating the maximum flooding surface, occurred at approximately 8.0 ka, at the time that the Mekong River delta was initiated. The delta initiation and sediment facies succession are closely linked to Holocene sea-level changes, particularly a standstill from 8.0 to 7.5 ka after a rapid rise of sea level from 8.8 to 8.2 ka. During the further sea-level rise from 7.5 to 7.0 ka, sediments aggraded, forming topset sedimentary deposits.

A new xanthone derivative from mangrove endophytic fungus No. ZSU-H16

A new xanthone derivative, 3,5,8-trihydroxy-2,2-dimethyl-3,4,4-trihydro-2H,6H-pyrano[3,2-b]-xanthen-6one (1), together with three known compounds, 5,8-dihydroxy-2,2-dimethyl-2H,6H-pyrano[3,2-b]xanthen6-one (2), cyclo-(N-O-methyl-L-Trp-L-Ile-D-Pip-L-2-amino-8-oxo-decanoyl) (3), and cyclo-(Phe-Tyr) (4), was isolated from the mangrove endophytic fungus No. ZSU-H16 obtained from the South China Sea coast. Their structures were elucidated by spectroscopic methods, mainly 1D and 2D NMR spectroscopic techniques. Compound 1 exhibited cytotoxicity against KB and KBV 200 cells with IC50 values greater than 50 μg/mL, respectively.

ChemInform Abstract: Two Metabolites with DNA‐Binding Affinity from the Mangrove Fungus Xylaria sp. (#2508) from the South China Sea Coast.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Two Metabolites with DNA‐Binding Affinity from the Mangrove Fungus Xylariasp. (#2508) from the South China Sea Coast

AbstractA novel metabolite xylopyridine A (1), together with a known compound pyrocoll (2), was isolated from mangrove endophytic fungus Xylaria sp. (#2508) collected from the South China Sea coast. Their structures were established on the basis of spectroscopic analysis, especially 2D‐NMR. Their affinities toward calf thymus (CT) DNA were studied by fluorescence quenching and spectrophotometric titration experiments. The results indicate that 1 showes strong DNA‐binding affinity presumably via an intercalation mechanism, thus it is exploitable as strong DNA‐binders.

First report of an endophyte (Diaporthe phaseolorum var. sojae) from Kandelia candel

Mangrove endophytic fungus 1893 was isolated from Kandelia candel from an estuarine mangrove on the South China Sea Coast. Two new lactones 1893A and 1893B, together with other known compounds, have been isolated from its fermentation broth. To classify the endophyte correctly for further industrial application, a combination of morphological and molecular techniques was used to approach its identity. The endophyte was compared with similar species having trichogynes or trichogyne-like hyphae which apparently fused with antheridium-like hyphae, and perithecia initials developing from an ascogonial coil surrounded by enveloping hyphae in early developmental stages on pure culture. Further morphological characteristics on host and non-host were used for comparison with similar species when the endophyte was cultivated on leaves of Kandelia candel and Mangifera indica, respectively, which resulted in classifying the endophyte as a Phomopsis species. The ITS sequence of rDNA was used to infer its phylogenetic relationships with Phomopsis species that resembled the strain in morphology or ecology. Finally, the endophyte was identified as Diaporthe phaseolorum var. sojae based on morphological and molecular evidence. Our study is a first report of Diaporthe phaseolorum var. sojae isolated from mangrove Kandelia candel.