Diversity and Antibacterial Activity of Fungus–Bacterium Symbionts from Marine Sediments in the Beibu Gulf

Long-lived radionuclides in marine sediments from the Beibu Gulf, South China Sea: Spatial distribution, controlling factors, and proxy for transport pathway

Potential toxic elements (PTEs) in the surface sediments of the Beibu Gulf, South China Sea: Spatiotemporal variation, geochemical fractionation and ecological risk assessment.

Ocean current modulation of the spatial distribution of microplastics in the surface sediments of the Beibu Gulf, China.

The impact of national energy structure on the concentrations, environmental behavior, and sources of polycyclic aromatic hydrocarbons in riverine and coastal sediments of the Beibu Gulf, China

Xia, Z.; Waniek, J.J., and Leipe, T., 2013. Anthropogenic fingerprint in Beibu Gulf (South China Sea) sediments. In: Harff, J., Leipe, T., Waniek, J.J., and Zhou, D. (eds.), Depositional Environments and Multiple Forcing Factors at the South China Sea's Northern Shelf, Journal of Coastal Research, Special Issue, No. 66, pp. 72–90. Coconut Creek (Florida), ISSN 0749-0208.Surface sediments and five cores were chosen to determine grain size, geochemical elements, heavy metals concentrations and age using 14C dating to study sedimentary environment and anthropogenic impact in the Beibu Gulf (South China Sea). The grain size analysis shows differences in the depositional environment amongst the subareas of the gulf. In the north of the gulf, the depositional environment is strong and unstable with complicated hydrodynamics because of the combined influence of rivers, tide, littoral current and the monsoon. In the central part, the depositional environment is weaker and stable, whereas in the south of the gulf (at the entrance), the deposition is higher and influenced mainly by tide. The deposition rate is around 0.3 mm/yr based on 14C dating. The geochemical element analysis indicates different sediment sources in different subareas of the gulf and possible influence of a biogenic source. The terrigenous elements (Al, Fe, Li, Ti, K and Zr) have high positive correlation coefficients, and originate from the northern coast and Hainan Island. The trace elements are mostly enriched within the fine sediments. The enrichment factors (EF) and cultural enrichment factors (CEF) based on aluminum and titanium show that total organic carbon (TOC), As and Hg have high concentrations in the surficial sediments in the north (9.92 mg/kg and 34 μg/kg) and the south (15.5 mg/kg and 22 μg/kg) of the gulf, and are enriched below the surface. Despite the regional differences in heavy metal concentrations in surface sediments, no anthropogenic impact was observed in the center of the gulf according to the results of EF and CEF using the core data. Measured concentrations of the anthropogenic elements were below the evaluation criterion values of the National Standards of GB18668-2002, P. R. China indicating low anthropogenic impact in the entire gulf.

The opening of the Qiongzhou Strait during the Holocene was a significant geological event in the Beibu Gulf, profoundly influencing sediment provenance and ocean circulation systems. Due to the scarcity of geological records documenting this event, the understanding of regional Holocene sedimentary evolution has been constrained. To investigate the impact of this event on sediment provenance and ocean currents in the Beibu Gulf, geochemical analyses were conducted on sediment core SO-31 retrieved from the South China Sea. The sediments in core SO-31 were stratigraphically divided into three units based on vertical geochemical profiles, reflecting changes in sea level and shifts in sediment provenance within the study area. The Th/Cr vs. Th/Sc scatter plot for core SO-31 indicate that sedimentary materials primarily originated from the Red River during 11,400–7700 a BP, and a significant change in provenance occurred in the study region around 7700 a BP, characterized by increased contributions from the Qiongzhou Strait and decreased contributions from the Red River. This suggests that the opening of the Qiongzhou Strait significantly influenced the sediment supply to the central Beibu Gulf around 7700 a BP. These findings provide critical geochemical evidence for studying the Qiongzhou Strait opening event and enhance our understanding of Holocene sedimentary evolution and “source–sink” transitions in the Beibu Gulf.

Sedimentary bacterial communities in subtropical Beibu Gulf: Assembly process and functional profile

As emerging pollutants, organophosphate esters (OPEs) have been reported in coastal environments worldwide. Nevertheless, information on the occurrence and ecological risks of OPEs, especially the related transformation products, in mangrove wetlands is scarce. For the first time, the coexistence and distribution of OP triesters and their transformation products in three mangrove wetlands in the Beibu Gulf were investigated using ultrasonication and solid-phase extraction, followed by UHPLC-MS/MS detection. The studied OPEs widely existed in all the sampling sites, with the total concentrations ranging from 6.43 ng/g dry weight (dw) to 39.96 ng/g dw and from 3.33 ng/g dw to 22.50 ng/g dw for the OP triesters and transformation products, respectively. Mangrove wetlands tend to retain more OPEs than the surrounding coastal environment. Pearson correlation analysis revealed that the TOC was not the sole factor in determining the OPEs’ distribution, and degradation was not the main source of the transformation products in mangrove sediments in the Beibu Gulf. The ecological risks of selected OPEs for different organisms were also assessed, revealing a medium to high risk posed by OP diesters to organisms. The levels or coexistence of OPEs and their metabolites in mangroves need constant monitoring, and more toxicity data should be further studied to assess the effect on normal aquatic organisms.

Cui, Z.; Schulz-Bull, D.E.; Hou, Y.; Xia, Z., and Waniek, J.J., 2016. Geochemical characteristics and provenance of Holocene sediments (core STAT22) in the Beibu Gulf, South China Sea. Geochemical investigations of the core sediments STAT22 from the Beibu Gulf, South China Sea, were carried out to understand the provenance of the Holocene sediments. Geochemical indices of La/Co, La/Sc, and Zr/Ti ratios, combined with distribution patterns of rare earth elements, suggest that the western Hainan Island was the main provenance of the core sediments. The eastern Qiongzhou Strait was also an important source of the sediments at the core location, but its contributions varied spatially and temporally with strait formation and evolution. With the opening of the Qiongzhou Strait, the provenance and hydrodynamic conditions of the Beibu Gulf underwent a significant change. Around 4500 YBP, the materials from the eastern area of the Qiongzhou Strait were transported into the study area and hence became one ...

Clay minerals are the main ingredients of the ocean floor sediments, which completely record a lot of geological information and have important meanings in the studies of source material, sedimentary environment, global climate change, sea-level fluctuation and ocean currents evolution. This paper studies composition and combination distribution characteristics of 312 surface clay mineral samples and makes the mineral mapping in Beibu gulf. The results show that the components of clay minerals in Beibu gulf are mainly mixed layer of illite and montmorillonite, kaolinite, chlorite and illite and each average content are 49.95%, 24.69%, 14.07% and 11.28%, respectively. According to combination and content of the clay minerals, the distribution areas of clay minerals in Beibu gulf can be divided into four divisions of 1, 2, 3 and 4 divisions. The differences of 4 divisions are closely related with the source area parent rocks and circulation.

Polychlorinated biphenyls (PCBs) and organochloride pesticides (OCPs) in sediment from the Beibu Gulf, China: Occurrence, spatial-temporal distribution, source, historical variation and ecological risks.

The Beibu Gulf’s ocean circulation system regulates regional marine ecosystems, sediment transport, and coastal geomorphology while also supporting vital economic activities. This study integrates one-year current observations from four in-situ current observation stations (B1−B4) with simulations using the Regional Ocean Modeling System (ROMS) to characterize circulation dynamics in the gulf. Observations show persistent northward subtidal currents west of Hainan Island year-round, primarily sustained by tidal-induced residual currents. These currents briefly reverse southward during strong northerly wind events, whereas subtidal currents in the northern Beibu Gulf are more wind-dependent, showing pronounced seasonal variations. Numerical results confirm that winter circulation is dominated by a basin-wide cyclonic gyre driven by northeasterly monsoons. In summer, circulation in the northern gulf is cyclonic under southeasterly winds, but turns anticyclonic when southwesterly winds prevail, indicating strong sensitivity to summer monsoon wind direction. By combining multi-station observations and numerical simulations, this study provides a systematic characterization of the seasonal circulation of the oceanic system in the Beibu Gulf, offering new insights into its dynamic mechanisms.

The Beibu Gulf (also named the Gulf of Tonkin), located in the northwest of the South China Sea, is representative of a bay suffering from turbulence and contamination associated with rapid industrialization and urbanization. In this study, we aim to provide the novel baseline levels of heavy metals for the research area. Concentrations of five heavy metals (i.e., Cu, Pb, Zn, Cd and Cr) were determined in surface sediments from 35 sites in the eastern Beibu Gulf. The heavy metal content varied from 6.72 to 25.95 mg/kg for Cu, 16.99 to 57.98 mg/kg for Pb, 73.15 to 112.25 mg/kg for Zn, 0.03 to 0.12 mg/kg for Cd, and 20.69 to 56.47 mg/kg for Cr, respectively. With respect to the Chinese sediment quality criteria, sediments in the eastern Beibu Gulf have not been significantly affected by coastal metal pollutions. The results deduced from the geoaccumulation index (Igeo) showed that the study area has been slightly polluted by Pb, which might be caused by non-point sources. Relatively high concentrations of Cu, Pb and Cd were found around the coastal areas of Guangxi province, the Leizhou Peninsula and the northwest coast of Hainan Island, whereas the highest concentrations of Zn and Cr were found on the northwest coast of Hainan Island. Spatial distribution patterns of the heavy metals showed that bioavailable fractions of Pb were higher than in the residual fractions, while Cu and Cd concentrations in exchangeable and carbonate fractions were relatively higher than those in the bioavailable fractions. Hierarchical clustering analysis suggested that the sampling stations could be separated into three groups with different geographical distributions. Accompanying their similar spatial distribution in the study area, significant correlation coefficients among Cu, Cd and Pb were also found, indicating that these three metals might have had similar sources. Overall, the results indicated that the distribution of these heavy metals in the surface sediments collected from the Beibu Gulf was complex.

Influence of anthropogenic activities on PAHs in sediments in a significant gulf of low-latitude developing regions, the Beibu Gulf, South China Sea: Distribution, sources, inventory and probability risk

Occurrence and distribution of perfluoroalkyl substances in surface riverine and coastal sediments from the Beibu Gulf, south China