Qinzhou Bay Research Articles

Phaeocystis globosa Bloom Monitoring: Based on P. globosa Induced Seawater Viscosity Modification Adjacent to a Nuclear Power Plant in Qinzhou Bay, China

The mucus produced by the outbreak of Phaeocystis globosa in the adjacent waters of the Fangchenggang Nuclear Power Plant (FCGNPP) in China has blocked the entrance of the cooling water filtration system of the FCGNPP, and posed a threat to the safe operation of the FCGNPP. At present, there is no related research on whether the changes in seawater viscosity could be used as a new method for monitoring and providing early warning of P. globosa tide. During a complete red tide cycle, the temporal and spatial changes in the hydrological conditions (temperature, salinity, dissolved oxygen), chlorophyll-a (Chl-a), composition and abundance of phytoplankton, number and size of P. globose colonies, concentration of transparent exopolymer particles (TEP) and the seawater viscosity were measured in this study. The results indicate that there was an extremely significant negative correlation between the physical seawater viscosity ηT,S and temperature, and the correlation coefficient reached −0.998. The biological seawater viscosity ηBio was positively correlated with the number of P. globosa colonies, and the correlation coefficients is 0.747. Because the increase in phytoplankton abundance, especially during the outbreak of P. globosa and a large amount of mucus produced by the colonies could significantly increase seawater viscosity, we suggest that biological factors were the main reasons for the increase in seawater viscosity. The ηBio was completely consistent with the occurrence process of P. globosa bloom and could be used as a valuable index for P. globosa bloom monitoring.

Occurrence and transfer of heavy metals in sediments and plants of Aegiceras corniculatum community in the Qinzhou Bay, southwestern China

Mangrove wetlands can reduce heavy metal pollution by trapping heavy metals. In this study, the concentration, transport and bioaccumulation of Cr, Cd, Cu, Zn and Pb in the sediments and different parts of Aegiceras corniculatum at four different sites in the Qinzhou Bay in southwestern China were investigated. The results showed that although the potential ecological risk of all five heavy metals was slight, the concentration of Cr was at a moderate pollution level due to the emissions of industries and aquaculture waste water. Core sediment records indicated that the concentrations of heavy metals at the depth of 0–20 cm were relatively high, showing an increasing trend of heavy metals over the past 20–30 years. Cr, Cu, Pb and Cd accumulated mainly in the roots of A. corniculatum, while Zn accumulated mainly in the stems. Aegiceras corniculatum showed the strongest transport capacity for Zn and Cu and the strongest bioaccumulation ability for Cd. Compared with other mangrove communities, A. corniculatum can be chosen as a restoration species in tropical and subtropical coastal zones polluted by Zn, Cu and Cd.

Numerical modeling of COD transportation in Guangxi coastal bays: A short communication

A three-dimensional numerical model of Guangxi coastal hydro-dynamical environment was constructed based on ECOMSED to study the COD transport with fine grid based on latest coastline and bathymetry data. The experiment results showed that the trace of COD was mainly affected by the flood and ebb tide in coastal regions; The area in Qinzhou Bay with COD concentration exceeding 1mg/L, 3mg/L and 6mg/L on the 31th day was 60.5km2, 14.8km2 and 3.7km2 respectively. The corresponding results at Nanliu river estuary was 64.7km2, 23.1km2 and 0 km2 respectively. The COD-polluted water at the Nanliu river esturay spread more widely but no concentration larger than 6mg/L was found, which could be explained by the different topographic conditions in these two places. The vertical distribution of COD transport was approximately the same as in surface, except that the area exceeding 1mg/L decreased slightly in the middle and bottom layer.

Late Holocene mangrove development and response to sea level change in the northwestern South China Sea

Mangroves, widely distributed along the coasts of tropical China, are influenced by Asia monsoon, relative sea level change and enhanced human activity. To predict the impacts of future climate change on mangrove ecosystems, it can be understood by reconstructing past mangrove dynamics using proxies preserved in coastal sediments. In this study, we quantitatively partitioned buried organic matter (OM) sources, collected from a vulnerable mangrove swamp in the Qinzhou Bay of northwestern South China Sea, using a ternary end-member mixing model of δ13C and C:N values. Mangrove-derived OM (MOM) contribution was used as a tracer for mangrove development since 2.34 cal ka BP. This information, together with paleoclimate records (i.e., speleothem δ18O values, sea level change, grain size parameters) and human activity, was used to divide mangrove development into three stages during the late Holocene: relative flourish (2.34–1.13 cal ka BP), relative degradation (1.13–0.15 cal ka BP) and further degradation (0.15–0 cal ka BP). Before 1.13 cal ka BP, mangroves flourished with a high MOM contribution ((88.9±10.6)%), corresponding to stable and high sea level under a warm and humid climate. After 1.13 cal ka BP, rapid fall in relative sea level coupled with the strengthening of the Asian winter monsoon, resulted in mangrove degradation and MOM reduction ((62.4±18.9)%). Compared with air temperature and precipitation, the relative sea level fall was the main controlling factor in mangrove development before entering the Anthropocene (the time of the Industrial Revolution). After ∼150 cal a BP, reclamation of mangrove swamps to shrimp ponds is the main factor causing mangrove degradation and MOM reduction.

Tidal and tidal current characteristics in the Guangxi Gulf of Tonkin, South China Sea

The Guangxi Gulf of Tonkin (GXGT) is rich in mineral, oceanic energy, and biological resources; however, it has not attracted much attention. Based on ECOMSED, a high-resolution three-dimensional numerical model is constructed in this study, and the accuracy is validated using long-term observational data. The results showed that the GXGT is dominated by regular diurnal tide and mixed mainly diurnal tidal currents and some regions to the northwest and south of Weizhou Island are dominant by mixed mainly semi-diurnal tidal currents. Furthermore, the rotation direction of O1 is found to be counter-clockwise and clockwise in the western and eastern domains, respectively, whereas the rotation directions of the other three tidal constituents are clockwise and counter-clockwise in the open sea and coastal bays, respectively. Similarly, the propagation direction of the tidal energy flux of O1 (northwestward) is different from them of the other three tidal constituents (northeastward) in the western GXGT. On the other hand, the propagation directions of the four tidal constituents are all northeastward in the eastern GXGT. A comparison of the reference run with the summed-up effect of six runs, where each of the tidal constituents has been considered separately, revealed that the nonlinear effect due to the interaction of the six tidal constituents cannot be neglected in the GXGT, especially in the western GXGT. Interestingly, energy input from wind to O1 is larger than that to M2 whereas the tidal dissipation of O1 is less than that of M2 at BBL. Additionally, tidally induced residual currents mostly flow westward in the GXGT, with clockwise eddies present outside the Qinzhou Bay and Tieshan Port. Driven by the monsoon wind, the current structure and strength in the GXGT have obvious seasonal variation. And sensitive experiments show that the residual currents in the GXGT are deeply influenced by the monsoon wind and bottom topography.

Bacterial and Archaeal Assemblages from Two Size Fractions in Submarine Groundwater Near an Industrial Zone

Nutrients and organic pollutants transported by submarine groundwater discharge (SGD) play a significant role in controlling water quality, and can lead to the concerned deleterious effects on marine ecosystems. Subterranean estuaries are complicated habitats of diverse microbial communities that mediate different biogeochemical processes. However, there is less information on how microorganisms mediate biogeochemical cycles in the submarine groundwater system. In this study, we investigated the changes in bacterial and archaeal assemblages from two size fractions (0.2–0.45 μm and >0.45 μm) in the submarine groundwater of Qinzhou Bay, China. Phylogenetic analysis showed that Bathyarchaeota was dominant in archaeal communities in the >0.45 μm size fraction, but was seldom in the 0.2–0.45 μm fraction. The co-occurrence of sequences belonging to Bathyarchaeota and Methanosaeta was found in the >0.45 μm size fraction. Since a gene encoding acetate kinase of Bathyarchaeota is involved in acetate production, and acetate is also a necessary growth factor for Methanosaeta, the acetate produced by Bathyarchaeota can provide food or energy sources for Methanosaeta in this very >0.45 μm size fraction. The most abundant bacterial sequences in the >0.45 μm size fraction was closely related to biomineral iron-oxidizing Gallionella spp., whereas the dominant bacterial sequences in the 0.2–0.45 μm fraction were affiliated with Limnohabitans spp., which can utilize dissolved organic matter as an important source of growth substrates. Notably, approximately 10% of the bacterial sequences in both of the two size fractions belonged to Novosphingobium spp., which plays an important role in the degradation of pollutants, especially aromatic compounds. Furthermore, the predictive functional profiling also revealed that the pathways involved in the degradation of aromatic compounds by both bacteria and archaea were identified. The presence of nutrients or pollutants in our study site provides different substrates for the growth of the specific microbial groups; in turn, these microbes may help to deplete pollutants to the ocean through submarine groundwater. We suggest that these specific microbial groups could be potential candidates for effective in situ bioremediation of groundwater ecosystems.

Halide-specific enhancement of photodegradation for sulfadiazine in estuarine waters: Roles of halogen radicals and main water constituents

Although photochemical transformation is a major degradation pathway for antibiotics in surface freshwaters, the photodegradation of antibiotics from freshwaters downstream into seawater is largely unknown. Herein, sulfadiazine was adopted as a representative antibiotic to probe the alteration of photolytic kinetics along freshwater to seawater sampled from Qinzhou Bay, China. The results showed that the photodegradation rate constants of sulfadiazine significantly increased in estuarine waters along freshwaters to seawaters. Experiments in synthetic water samples with isolated local dissolved organic matter (IL-DOM) indicated that the increased photodegradation of sulfadiazine is attributed to the integrative effect of both IL-DOM and halide ions. Radical quenching experiments with tert-butanol (quenching of ·OH) and isopropanol (quenching of both ·OH and reactive halogen species, RHS) demonstrated that RHS are largely responsible for the halide-specific enhancement in the photodegradation of sulfadiazine, rather than other reactive species, such as triplet-excited IL-DOM and ·OH. However, triplet-excited IL-DOM was involved in the production of RHS by the oxidation of halide ions by the triplet-excited states. Experiments conducted with DOM analogues verified DOM-sensitized RHS formation, and the degradation induced by RHS is positively correlated with the triplet-excited reduction potentials of DOM analogues. These findings are helpful in deeply understanding the transformation of antibiotics, and demonstrate the importance of RHS-induced degradation in antibiotics fate models in estuarine water systems.

Genesis of the Panjia Wu‐Cu‐Mo deposit: Evidence from the geochemistry and geochronology of the Datongkeng pluton, northeast South China Block

The Panjia polymetallic deposit, located in the northwestern region of Zhejiang Province, is a newly discovered medium‐ to large‐sized W–Mo–Cu ore deposit belonging to the northern part of the Qinzhou Bay–Hangzhou Bay metallogenic belt. Through investigation in the field and under the microscope, the hydrothermal activity of this deposit can be divided into four stages: pre‐ore stage, silicate oxidation stage, quartz sulfide stage, and post‐ore stage. The Datongkeng pluton, outcroping in Panjia deposit, is one S‐type intrusive rock and characterised by concentrations of SiO2, K2O and Na2O ranging from 67.03 to 71.09%, 3.03 to 4.89%, and 0.24 to 3.37%, respectively. The major elements display peraluminous, high‐K, calc‐alkaline features. Their A/CNK(A/CNK = n (Al2O3)/ [n (CaO) + n (Na2O) + n(K2O)]) ratios, δEu values, and δCe values vary from 0.93 to 1.98, 0.45 to 0.91, and 0.93 to 1.07, respectively. These rocks are enriched in light rare earth elements (all record values of (La/Yb)N <10, except for one) whereas are depleted in Sr, Ba, Nb, P, Eu, and Ti. The end‐member study of the Pb and S isotopes shows that the mantle material plays an important role in the ore‐forming. Zircon U–Pb dating indicates that the second part of the multiperiod magmatism (154–150 Ma) of Datongkeng pluton is the relevant crystallisation age, and the study of metallogenic stage manifests that the molybdenite is formed at the third stage of the mineralisation sequence considered as the main period of mineralisation, subsequent to the mineralogenetic epoch of scheelite. The petrogenesis is related to the materials in the crust and a small amount of materials in the mantle. While the low degree of mantle source and the Proterozoic basement contribute to the Mo, Cu ore‐forming materials. Finally, two types of metallogenic assemblage are formed, including the W‐Mo polymetallic deposit in the Datongkeng pluton and the W‐Cu‐Pb‐Zn‐Ag polymetallic deposit in the veins in the Lantian Formation.

Spatiotemporal distributions, source apportionment and potential risks of 15 pharmaceuticals and personal care products (PPCPs) in Qinzhou Bay, South China

In the present study, we investigated the spatiotemporal distributions and risks of 15 non-antibiotic pharmaceuticals and personal care products (PPCPs) in surface water collected from Qinzhou Bay, China during the summer and winter of 2017. Our results showed that 14 out of the 15 target PPCPs were detected, and they had higher concentrations in the winter than the summer, except for N, N-diethyl-m-toluamide and indomethacin. Furthermore, N, N-diethyl-m-toluamide and caffeine respectively were the dominant contaminants in the summer and winter, with their highest concentrations up to 33.7 ng/L and 26.8 ng/L. Generally, concentrations of PPCPs were higher in the inner bay than outer bays, with untreated sewage and effluents of sewage treatment plants (STPs) as main pollution sources. The results of the risk assessment indicate that diclofenac may pose risks to aquatic organisms. Overall, our results provided occurrence and important insights into the risk management of PPCPs in Qinzhou Bay.

Sensitivity of the half-life time of water exchange in coastal waters

A three-dimensional model was established to investigate water exchange in coastal waters, and applied to Qinzhou Bay (QZB) in the South China Sea. Given the strong tidal current in QZB, a half-life time was calculated for water exchange by filtering the tidal signal from the concentrations of a conservative substance. In a control run driven by the tide, without external inputs and an open boundary concentration of zero, it was estimated that the average half-life time in QZB was 54.8 d. Numerical experiments showed that wind accounted for an 11.9% reduction in the half-life time to 48.3 d. When rivers were included in the model, the half-life time decreased by 74.6% to 13.9 d. Sensitivity experiments showed that the half-life time for water exchange was greatly affected by the concentration of the conservative substance which was used at the open boundary. In response to 10, 20, 30, and 40% increases in the boundary concentration, the half-life time increased to 91.5, 168.3, 186.2, and 229.1 d, respectively. Results also suggested that for coastal bays with large intertidal areas such as QZB, consideration of the wet and dry processes produced more accurate simulations of the hydrodynamics and the half-life times. Simulations, which did not incorporate wet and dry processes, were more than likely to have overestimated or underestimated the half-life times for water exchange.

钦州湾春、夏季浮游植物群落特征及其与环境因子的关系

钦州湾春、夏季浮游植物群落特征及其与环境因子的关系

Characterization, source, and retention of microplastic in sandy beaches and mangrove wetlands of the Qinzhou Bay, China

Severe microplastic pollution from anthropogenic activities in coastal zones presents an imminent risk to marine ecosystems. In this study, abundant microplastics (15–12,852 items kg−1) with sizes ranging between 0.16 and 5.0 mm were extracted from 17 sediment samples collected in sandy beaches and mangrove wetlands of the Qinzhou Bay, Guangxi Province, Southwest China. Three types of microplastics (i.e. polystyrene, polypropylene, and polyethylene) were identified with Fourier transform infrared (FTIR) spectroscopy analysis. These detected microplastics were characterized by different colors (white, transparent, yellow, green, red, and blue) and shapes (fragment, fiber, and sphere). Microplastics were concentrated on supratidal beaches and wetlands outside of mangrove, and less abundant on intertidal beaches and inside of mangrove wetlands. Meanwhile, high microplastic concentrations were observed near mollusk farms. The spatial distribution and chemical speciation indicated that microplastics were derived from disintegration of large plastic debris (e.g., Styrofoam buoys used to support mollusk rafts) abandoned by aquaculture industry. Further, coastal vegetation (e.g. mangrove) could trap microplastic particles.

Sources and distribution of sedimentary organic matter in the Beibu Gulf, China: Application of multiple proxies

Geochemical and biomarker methods were combined to investigate the sources of sedimentary organic matter (OM) and their spatial distribution in the Beibu Gulf, a subtropical estuary in southern China. We measured the total organic carbon (TOC) and total nitrogen (TN) content, the glycerol dialkyl glycerol tetraethers (GDGTs) concentration, as well as the isotopic composition of sedimentary OM (δ13Corg and δ15N) in surface sediments collected from the Beibu Gulf. The spatial distribution of the bulk organic parameters (TOC, TN, C/N ratio, δ13Corg, and δ15N) revealed a generally decreasing trend in terrestrial OM from the Maowei Sea to the outer Qinzhou Bay, and from the tributary rivers to the outer bay. The BIT (branched/isoprenoid tetraether) indices also decreased seaward from the Maowei Sea to the Qinzhou Bay, and from rivers to the outer bay, showing that soil OM was mainly delivered to the bay by rivers. The spatial patterns of these bulk parameters suggest that the terrigenous OC is constrained to the coast and adjacent regions. The relatively high GDGT-0/Crenarchaeol ratios and increasing δ15N values along the coast of the Maowei Sea indicate the anthropogenic nitrogen in the Beibu Gulf. Our results show how important a multiproxy approach can be to fully understand and quantify the relative contributions of terrestrial and marine OC components and the biogeochemical processes in the Beibu Gulf, especially in the context of growing anthropogenic activities.

Morphological changes in the Qinzhou Bay, Southwest China

Morphological change in the Qinzhou Bay (QZB), southwest China, has been studied, using bathymetric charts and remote sensing data. Historical admiralty charts were digitized and analyzed in a Geographical Information System (GIS) environment to provide quantitative estimates of underwater topography changes for exploring the accretion-erosion characteristics from 1960s to 2010s. Multi-temporal satellite images have been used to analyze the coastline developments. The results showed that the bathymetry and coastline of QZB changed dramatically in recent decades. The subaqueous area decreased by about 8% in the study area during the last 50 years, mainly due to coastal land reclamation. The average growth rate of the coastlines was 2.07 km/yr. between 1978 and 2013 with natural curvy coastlines being replaced by straighter artificial shorelines. During the period from 1960s to 1990s, the evolution of QZB was mainly governed by natural factors with slight deposition or erosion in the deep troughs. From 1990s to 2010s, intensive large-scale human activities, such as port building, channel dredging and artificial island construction became the main causes affecting morphological changes in the QZB. Approximately half of the underwater terrain had undergone significant changes (greater than ±0.5 m), and the proportion of deposition area accounting for 32.26% of the subaqueous area, about twice more than erosion area. Large scale reclamation projects have made dramatic negative impact on coastal natural ecosystem. Integrated coastal zone management need to be carried out to maintain the balance between economic development and ecological health.

钦州湾秋季和春季浮游动物分布特征及影响因素

钦州湾秋季和春季浮游动物分布特征及影响因素

Analysis of recent coastline evolution due to marine reclamation projects in the Qinzhou Bay

Abstract Intense marine reclamation activities bring obvious benefits, meanwhile, these activities also influence the coastal natural formation, hydrodynamic processes and water environment etc. In order to investigate the exact influence in the Qinzhou Bay brought by marine reclamation behaviors in recent years, based on the remote sensing image data in the Qinzhou Bay in 2006, 2008, 2009, 2012 and 2014, with the help of GIS and RS software, the thesis interprets Qinzhou Bay coastline and artificial reclamation by man-machine interaction and makes quantitative analysis in the Qinzhou Bay coast evolution recently. The results show: (1) Qinzhou Bay coastal morphology change degree was strong in 2006 - 2012 and the coastline changed greatly. Originally part of the natural shore segments which had twists and turns were gradually filled into artificial coast, the coast constantly advanced to the sea, coastline became regular and straight; (2) The change degree of coastline was relatively small in 2006-2008, the average artificial coastline increased 8.86 km/a, the average artificial reclamation area was 20.79 km2 /a; in 2008-2012, the change range of coastline was the greatest, coastline changed most severely, the average artificial coastline increased 16.07 km/a, the average artificial reclamation area was 58.52 km2 /a; however, in 2012-2014, coastline change degree relatively slowed, the average artificial coastline increased 4.04 km per year, the average artificial reclamation area was 3.464 km2 /a. (3) Compared to the studies of predecessors, the innovation of this paper is that it is the first to carry out the detailed research on coastline evolution caused by reclamation engineerings of the Qinzhou Bay, then formed the change results on coastline that caused by intense human activities in the Qinzhou Bay, provided the area of the marine environment protection with full and accurate data.

Crystallization conditions of peraluminous charnockites: constraints from mineral thermometry and thermodynamic modelling

Most igneous charnockites are interpreted to have crystallized at hot and dry conditions, i.e. at >800 °C and <3 wt.% H2O and with an important CO2 component in the system. These charnockites are metaluminous to weakly peraluminous and their formation involves a significant mantle-derived component. This study, in contrast, investigates the crystallization conditions of strongly peraluminous, metasediment-sourced charnockites from the Qinzhou Bay Granitic Complex, South China. To constrain the temperature-melt H2O crystallization paths for the studied peraluminous charnockites, petrographic characterization was combined with fluid inclusion compositional data, mineral thermometry, and thermodynamic modelling. The uncertainties of the thermodynamic modelling in reconstructing the crystallization conditions of the granitic magmas have been evaluated by comparison between modelled and experimental phase relations for a moderately evolved, peraluminous granite (~70 wt.% SiO2). The comparison suggests that the modelling reproduces the experimentally derived phase saturation boundaries with uncertainties of 20–60 °C and 0.5–1 wt.% H2O for systems with ≤1–2 wt.% initial melt H2O at ~0.2 GPa. For the investigated natural systems, the thermometric estimates and modelling indicate that orthopyroxene crystallized at relatively low temperature (750–790 ± 30 °C) and moderately high to high melt H2O content (3.5–5.6 ± 0.5 wt.%). The charnockites finally solidified at relatively “cold” and “wet” conditions. This suggests that thermodynamic modelling affords a possible approach to constrain charnockite crystallization as tested here for peraluminous, moderately low pressure (≤0.3 GPa), and overall H2O-poor systems (≤1–2 wt.% H2O total), but yields results with increasing uncertainty for high-pressure or H2O-rich granitic systems.

钦州港造纸厂排污口及邻近海域环境监测与评价

于2011~2013年对钦州港造纸厂排污口及其邻近海域水质进行监测，通过分析该水域水体中pH值、无机氮(DIN)、化学需氧量(COD)、悬浮物(SS)、石油类等指标，研究该水域各水质指标的动态变化及趋势，并采用单因子评价法对其结果进行水质分析和评价。结果表明：2011~2013年钦州港造纸厂排污口水质状况整体良好，其中pH值未出现超标现象；DIN和COD含量在2012年3月份异常增大，可能与造纸厂增产导致所排污水含量增加或是造纸厂出现的废水排管管道断裂使得废水直接排海有关；悬浮物和石油类含量在个别时期出现超标，对该海域环境的影响不大。2011~2013年钦州港造纸厂排污口邻近海域水质优于该海洋功能区水质要求，相应监测项目污染指数大体符合排污口>邻近海域的特点，显现出邻近海域污染物含量受陆源污染物排放，以及钦州湾内湾径流、降雨、城区生活污水及生产废水排放量增加等因素影响较大。2011~2013年排污口邻近海域的主要污染物DIN、COD和石油类含量呈增长趋势，在以后的监测过程中，应该着重做好DIN、COD和石油类的监控与治理，严格控制相关废水的排放，降低主要污染物对钦州湾近岸水质影响与破坏，提高生态安全性。 From 2011 to 2013, the water quality of the pulp and paper industry sewage outlet and its adja-cent water in Qinzhou harbor was monitored. The pH, inorganic nitrogen (DIN), chemical oxygen demand (COD), suspended solids (SS) and petroleum were analyzed in order to research the dynamic changes and trends of the water quality. Meanwhile, the single-factor evaluation index method was used to analyze and evaluate the water quality. The results showed that from 2011 to 2013, the water quality of the pulp and paper industry sewage outlet in Qinzhou harbor was generally well, and the pH value did not exceed the standard. DIN and COD contents increased abnormally in March 2012, which could relate to the increase of sewage content or the wastewater pipeline was broken so that the wastewater was directly discharged into the sea. The content of suspended solids and petroleum in the individual period was excessive, which has little effect on the sea environment. The water quality of the pulp and paper industry sewage outlet adjacent water in Qinzhou harbor was better than the water quality requirements of this marine functional area. The pollution index of the corresponding monitoring project was generally conformed to the characteristics of the sewage outlet > adjacent sea area. It showed that the pollutant content of the adjacent sea area was affected by the land source pollutant discharge, as well as the runoff, rainfall, urban sewage and production wastewater emissions increased in the Qinzhou Bay. The contents of DIN, COD and petroleum in the pulp and paper industry sewage outlet adjacent water from 2011 to 2013 are increasing. In the future monitoring, the monitoring and management of DIN, COD and petroleum should be focused on, and the waste water discharge should be strictly controlled and the impact of major pollutants on the coastal waters of Qinzhou Bay should be reduced, so as to improve the ecological security.

Mangrove forest degradation indicated by mangrove-derived organic matter in the Qinzhou Bay, Guangxi, China, and its response to the Asian monsoon during the Holocene climatic optimum

The response of mangrove ecosystems to the Asian monsoon in the future global warming can be understood by reconstructing the development of mangrove forests during the Holocene climatic optimum (HCO), using proxies preserved in coastal sediments. The total organic matter in sediments of a segmented core, with calibrated age ranges between 5.6 and 7.7 cal. ka BP and corresponding to the HCO, from the Qinzhou Bay in Guangxi, China, is quantitatively partitioned into three end-members according to their sources: mangrove-derived, terrigenous, and marine phytoplanktonic, using a three-end-member model depicted by organic carbon isotope (δ 13Corg) and the molar ratio of total organic carbon to total nitrogen (C/N). The percentage of mangrove-derived organic matter (MOM) contribution is used as a proxy for mangrove development. Three visible drops in MOM contribution occurred at ca. 7.3, ca. 6.9, and ca. 6.2 cal. ka BP, respectively, are recognized against a relatively stable and higher MOM contribution level, indicating that three distinct mangrove forest degradations occurred in the Qinzhou Bay during the HCO. The three mangrove forest degradations approximately correspond to the time of the strengthened/weakened Asian winter/summer monsoon. This indicates that even during a period favorable for the mangrove development, such as the HCO, climatic extremes, such as cold and dry events driven by the strengthened/weakened Asian winter/summer monsoon, can trigger the degradation of mangrove forests.

Speciation and risk of heavy metals in sediments and human health implications of heavy metals in edible nekton in Beibu Gulf, China: A case study of Qinzhou Bay

We investigated the total concentrations of heavy metals in surface sediments and nekton, along with sediment metal chemical partitioning in Qinzhou Bay of the Beibu Gulf. Cd was preferentially associated with the acid-soluble fraction and Pb mainly with the reducible fraction, whereas a major portion of Cr, Ni, Cu, and Zn was strongly associated with the residual fractions. A principal component analysis (PCA) in sediment metal speciation revealed three groupings (Cd; Pb; Cr, Ni, Cu, and Zn) that mainly resulted from different distributions of the metals in the various fractions. The Cr concentrations in nekton species were higher than maximum Cr concentrations permitted by the Chinese National Standard (GB 2762-2012). Taking as a whole, surface sediments of Qinzhou Bay had a 21% incidence calculation of adverse biological effects, based on the mean probable-effects-levels quotient. A human health risk assessment indicated no significant adverse health effects from consumption of nekton.