Search

Selenium (Se) is an essential element for humans, playing a critical role in the functioning of the immune system. The global prevalence of dietary Se deficiency is a significant public health concern, largely attributed to the low levels of Se present in crops. The sufficient Se in plants and humans is determined by the presence of stable Se sources in the soil. The Leizhou Peninsula is an important agricultural region in China, but the concentration and spatial distribution of Se in its soils remain unclear. To address this issue, we analyzed Se concentration data from 3333 soil samples collected at the depth of 0–20 cm from the Leizhou Peninsula, covering an area of 13,225 km2. The results indicate that the mean soil Se concentration was 0.50 mg kg−1, with Se-enriched soils being widely distributed. This provides prospects for the development of Se-enriched crops. Using random forest (RF) modeling and correlation analysis, the clay minerals (Fe–Al oxides), chemical index of alteration (CIA), and soil organic carbon (SOC) have been identified as the principal determinants of Se distribution in soil. During the weathering processes of the basalts, Fe–Al oxides serve as a crucial factor in Se accumulation in the red soils. Furthermore, the tropical climate further contributes to increasing the degree of weathering and the proportion of clay minerals and SOC in the soil. Atmospheric deposition derived from marine and precipitation is another important factor that promotes Se flux into soils. In conclusion, the distribution pattern of Se is jointly determined by the weathering process of basalt and climatic conditions. The results of the geographically weighted regression (GWR) analysis revealed that SOC, Al2O3, TFe2O3 and CIA change spatially and exhibit a spatial non-stationarity relationship with Se. This study offers a theoretical foundation and practical guidance for the sustainable development of Se-enriched agriculture and similar climate settings worldwide. [ABSTRACT FROM AUTHOR]

Grasping the genetic structure ofmarine fish populations is vital for comprehending species connectivity patterns and determining the appropriate spatiotemporal scales for conservation management strategies. Here, we analyzed the population genetics of the Orangefin Ponyfish (Photopectoralis bindus Valenciennes, 1835) by examining a portion of the gene coding for the mitochondrial cytochrome c oxidase subunit I. The aim was to evaluate the haplotype pattern, genetic structure, demographic history, as well as the influence of ecological connectivity through the Qiongzhou Strait on the distribution patterns of this species in the northern South China Sea and the Beibu Gulf. In total, 257 specimens yielded only 13 haplotypes, with the predominant haplotype present at all sampling locations. The analysis revealed a "star-like" haplotype pattern, indicating low levels of both haplotype and nucleotide diversity. Additionally, a small but significant genetic structure was observed between the coastal regions flanking the Leizhou Peninsula. These patterns in the haplotype network and genetic structure may be significantly influenced by contemporary currents, particularly through the connectivity of the Qiongzhou Strait. Tajima's D and Fu's Fs demonstrated pronouncedly negative values, along with a unimodal mismatch distribution, suggested a recent demographic expansion of Photopectoralis bindus during the late Pleistocene, likely influenced by fluctuations in sea levels. [ABSTRACT FROM AUTHOR]

The distribution characteristics of size-fractionated Chlorophyll a (Chl-a) and the environmental factors were studied in the coastal area of the Leizhou Peninsula in January 2022. The result showed that Chl-a ranged from 0.39 to 4.78 mg/m³ (averaging 1.21 mg/m³ ) at the surface and 0.43 to 2.78 mg/m³ (averaging 1.04 mg/m³) at the bottom layer, respectively. The spatial distribution of Chl-a concentration was associated with salinity. High Chl-a concentration was observed in the eastern part of the Leizhou Peninsula characterized by lower salinity, and low Chl-a concentration in Qiongzhou Strait with higher salinity. Nanophytoplankton (2-20 µm) was the dominant contributor, accounting for 61.3% and 63.7% of the total Chl-a at the surface and bottom layer, respectively. Both microphytoplankton (>20 µm) and nanophytoplankton displayed increased Chl-a with the increase in total Chl-a. Salinity, nutrients and temperature appear to influence the phytoplankton size structure in the coastal area of the Leizhou Peninsula. Additionally, the regulation of nutrient varied among phytoplankton of different sizes. This study contributed to our understanding of coastal ecosystem processes and has potential implications for coastal management and monitoring efforts. [ABSTRACT FROM AUTHOR]

Mineral carbonation, which precipitates dissolved carbon dioxide (CO2) as carbonate minerals in basaltic groundwater environments, is a potential technique for negative emissions. The Leizhou Peninsula in southwest Guangdong province has extensive basalt, indicating a promising potential for CO2 storage through rapid mineralization. However, understanding of the basic geological setting, potential, and mechanisms of CO2 mineralization in the basalts of the Leizhou Peninsula is still limited. The mineralization processes associated with CO2 storage at two candidate sites in the area are investigated in this paper: Yongshi Farm and Tianyang Basin (of the dried maar lake). Petrography, rock geochemistry, basalt petrophysical properties, and groundwater hydrochemistry analyses are included in the study. Numerical simulation is used to examine the reaction process and its effects. The results show that basalts in the study areas mainly comprise plagioclase, pyroxene, and Fe–Ti oxides, revealing a total volume fraction exceeding 85%. Additionally, small amounts of quartz and fayalite are available, with volume fractions of 5.1% and 1.0%, respectively. The basalts are rich in divalent metal cations, which can form carbonate minerals, with an average of approximately 6.2 moles of metal cations per 1 kg of rock. The groundwater samples have a pH of 7.5–8.2 and are dominated by the Mg–Ca–HCO3 type. The basalts demonstrate a porosity range of 10.9% to 28.8%, with over 70% of interconnected pores. A 20-year geochemical simulation revealed that CO2 injection dissolves primary minerals, including anorthite, albite, and diopside, while CO2 mineralization dissolves precipitation secondary minerals, such as calcite, siderite, and dolomite. Furthermore, a substantial rise in pH from 7.6 to 10.6 is observed in the vicinity of the injected well, accompanied by a slight reduction in porosity from 20% to 19.8%. Additionally, 36.8% of the injected CO2 underwent complete mineralization within five years, revealing an increasing percentage of 66.1% if the experimental period is extended to 20 years. The presence of abundant divalent metal cations in basalts and water-bearing permeable rocks in the Leizhou Peninsula supports the potential for mineral carbonation in basalts, as indicated by the geochemical simulation results. Additional research is necessary to identify the factors that influence the CO2 mineralization, storage, and sensitivity analysis of basalt in the Leizhou Peninsula. [ABSTRACT FROM AUTHOR]

Although the water environment has certain self-purification capability, the natural balance is disrupted, leading to water quality deterioration when the discharge load of wastewater exceeds a certain threshold. This problem implies the urgency of evaluating marine environmental capacity as a necessary parameter for marine sustainable development of marine ecosystems. Through principal component analysis (PCA), clustering, and other methods, we analyzed the average concentration and fluxes of land-sourced pollutants and determined the pollution level around the Leizhou Peninsula. Combined with the Delft3D hydrodynamic numerical model, tidal hydrodynamic forces and pollutants migration and diffusion were calculated. Based on in-situ measured data, the model was validated. The sharing rate method was used to calculate the marine environmental capacity in Zhanjiang Bay and analyzed their impact on seawater eutrophication. The results showed that: (1) The average concentrations of chemical oxygen demand (COD), ammonia nitrogen (NH4+), total nitrogen (TN), and total phosphorus (TP) around Leizhou Peninsula were 22.56 mg/L, 0.69 mg/L, 6.69 mg/L, and 0.69 mg/L, respectively. (2) Six areas (Area A-F) can be divided into, based on the discharge of land-sourced pollutants into the sea area. According to the results of PCA, clustering, and other methods, the average concentration and fluxes of land-sourced pollutants in Area B (i.e. Zhanjiang Bay) were very high. (3) The environmental capacity of Zhanjiang Bay was calculated through Delft3D numerical simulation, and it was found that the COD and TN environmental capacity of 6 sewage outlets exceeded the standard, while the TP environmental capacity of 3 sewage outlets exceeded the standard. (4) According to the statistical research result, most of the Zhanjiang Bay waters has been restricted by nitrogen for over a decade. Therefore, we speculate that although TN environmental capacity exceeds the standard, its impact on eutrophication in Zhanjiang Bay is still limited to a certain extent.

Understanding the effects of land use on soil structure and nutrients is important for soil and water conservation in an ecologically fragile zone. This study was carried out to examine the variability of physicochemical properties in three different land use types: abandoned land (AL), eucalyptus plantation (EP), and road lawn (RL) sites at soil depths of 0–10 and 10–20 cm in the Leizhou Peninsula, a tropical coastal ecologically fragile zone of South China. Soil physicochemical property patterns exhibited extremely significant differences among the three land uses (p < 0.001) at both soil depths. Soil nutrients, natural water content, and total porosity, from high to low, in the different land use types were RL, AL, and EP, while the bulk density, from high to low, was EP, AL, and RL. Soil total nitrogen, total phosphorus, total potassium, available potassium, exchangeable calcium, exchangeable magnesium, and natural water content exhibited significant differences (p < 0.05) among the three land use types at soil depths of 0–10 and 10–20 cm, while no significant changes were detected regarding soil organic carbon, available phosphorus, and total porosity. The correlation between physical and chemical properties at the 10–20 cm depth (R = 0.97, p < 0.001) was closer and more significant than that at the 0–10 cm depth (R = 0.95, p < 0.01). Overuse of land (EP) without a rest in the ecologically fragile zone leads to soil erosion and compaction. Compared with natural restoration (abandoned land), artificial restoration (road lawn) can improve soil nutrient and water status more quickly, but cannot modify the soil organic carbon and porosity in the short term. [ABSTRACT FROM AUTHOR]

Understanding past long-term vegetation responses to regional or even global climate change and forcing mechanisms is essential to future climate change projections. However, due to the lack of long-term terrestrial sedimentary records, there are few studies focusing on vegetation changes in tropical southern China since the last glacial period, especially from the perspective of peat n -alkane records. Here, we have presented a peat core record from the Xialu peatland in the northern Leizhou Peninsula, and n -alkanes were investigated in conjunction with multiple proxy indicators. Our results showed that the organic matter sources were mainly a mixture of aquatic and terrestrial vegetation, with terrestrial vegetation accounting for most of the bulk organic matter composition. From ∼44.1 to 29 cal kyr BP, the organic matter source was mainly dominated by terrestrial vegetation, which corresponds to warm and humid conditions. From 29 to 14 cal kyr BP, the input of the terrestrial vegetation was reduced, the aquatic vegetation input increased, implying cool and dry conditions. From 14 to 9.3 cal kyr BP, the climate gradually became warmer and wetter, and terrestrial vegetation dominated in this area. Overall, the climatic conditions from the Xialu peatland were generally consistent with other records from adjacent areas. Our results suggest that, during the Last Glacial Maximum (LGM), a substantial drop in regional and global sea levels may have been the main cause of drought in tropical southern China on orbital timescales. Meanwhile, several climatic fluctuations on millennial timescales could have been influenced by the variability of the North Atlantic Meridional Overturning Circulation (AMOC) and migration of the Intertropical Convergence Zone (ITCZ). [Display omitted] • n -alkanes were investigated together with multiple proxy indicators. • Terrestrial vegetation accounted for most of the bulk organic matter. • Vegetation changes are mainly regulated by sea level change on orbital timescales. • AMOC and ITCZ affect vegetation and environmental changes on millennial timescales. [ABSTRACT FROM AUTHOR]

Colorful dissolved organic matter (CDOM) is an optically important active substance in marine habitats that feature significant biochemical conservatism. Additionally, CDOM is an important tracer and indicator of pollution status in marine water masses. In this study, we use sampling data collected in September 2020 and May 2021 from the marine areas around the Leizhou Peninsula. This information is combined with the Delft 3D numerical simulation analysis to carry out a study on the relationship between the ag (355) in the marine areas and to determine the regional marine pollution levels. The results show that (1) the nearshore areas of the Leizhou Peninsula in spring and autumn are mainly lightly polluted. Compared with the same period in history, the pollution level has significantly decreased, and the ag (355), DIN, and DIP concentrations show a trend of high near the shore and low far from shore. The peak concentrations are mainly in the Zhanjiang Bay, Qiongzhou Strait, Wailuo Port, Liusha Port and Guangxi Tieshan Port. (2) ag (355) can be used as an indicator to characterize the degree of water pollution in the nearshore waters of the Leizhou Peninsula. In spring, the ag (355) interval of [0.115, 0.200] m−1, [0.201, 0.245] m−1 and [0.246, 0.484] m−1 can be considered clean, lightly polluted, and moderately polluted water, respectively. In autumn, the ag (355) interval of [0.180, 0.275] m−1, [0.276, 0.478] m−1, [0.479, 0.642] m−1, [0.643, 0.921] m−1 can be considered clean, lightly polluted, moderately polluted and heavily polluted water, respectively. (3) The response models between the ag (355) and pollutant dispersion trends were constructed in the Zhanjiang Bay and Tieshan Port. The RMSEs of the ag (355) validation points in the models were lower than 0.12 mg/L, and the MAPEs were lower than 30 %, the pollution traceability of CDOM is verified.

Mudflats play a vital role in maintaining the dynamic balance between sea and land. To understand the characteristics, sources, and pollution risks of six heavy metals (As, Cd, Cr, Cu, Hg, and Pb) in the coastal mudflats on the Leizhou Peninsula, 257 surface sediment samples were studied using mathematical statistics, correlation analysis, and factor analysis. The results show that the overall concentrations of these heavy metals are low although there are several high abnormal points in the local areas. The strong correlation between these heavy metals indicates that the sources of some of the metals are similar, yet their elemental combinations in different cities (counties) varied. According to the calculated enrichment factor (EF), anthropogenic activity-induced heavy metals were determined in order of decreasing influence: As, Cd, Pb, Cr, Cu, and Hg. The low EF values of Hg indicate that it does not present as a contaminant in the study area, while low values of Cr and Cu from the Lianjiang City suggest that these two metals were also attributed to natural sources. The presence of As, Cd, Cr, Cu, and Pb from the remaining cities (counties) should be influenced by anthropogenic activities. The overall potential ecological risk index indicates that the ecological risks posed by the six analyzed heavy metals to the Leizhou Peninsula mudflats, in order of decreasing risk, are Cd, As, Hg, Pb, Cu, and Cr. It is noteworthy that only Cd in Lianjiang City demonstrated substantial ecological risk. Other examined heavy metals in other cities of the study area showed slight ecological risk. [ABSTRACT FROM AUTHOR]

Effective vegetation restoration plays an important role in maintaining and improving soil nutrients and can promote the fixation of soil organic carbon (SOC) and its fractions in degraded soil areas. To understand the influence of Eucalyptus plantation on SOC and its fractions in severely degraded soil in Leizhou Peninsula, China, vegetation restoration with Eucalyptus (RE: Eucalyptus–shrub ES, Eucalyptus–grass EG, and Eucalyptus–Dicranopteris ED) was chosen as the research object, and natural vegetation restoration without Eucalyptus (RNE: shrub S, grass G, and Dicranopteris D) nearby was used as the control group. SOC and its fractions in different vegetation types were compared and analyzed after sample plot surveys and sample determination, and the driving forces of SOC and its fractions were discussed. SOC, dissolved organic carbon (DOC), microbial biomass carbon (MBC), easily oxidized organic carbon (EOC), and particulate organic carbon (POC) in RE were significantly different from those in RNE, increasing by 194.4%, 36.3%, 111.0%, 141.6%, and 289.9%, respectively. The order of SOC, EOC, DOC, MBC, and POC content in RE was ES > EG > ED. SOC and its fractions were positively correlated with leaf litter cover and biomass, and soil organic matter. SOC, total nitrogen, available nitrogen, total phosphorus, available phosphorus, and enzyme activities were negatively correlated with microbial diversity but were not significantly correlated with soil bulk density and microbial richness. Structural equation modeling analysis results showed that soil enzyme activity was a direct driving force of SOC and its fractions. The input of carbon sources from leaf litter and soil properties were indirect factors that affected SOC and its fractions by affecting microbial characteristics and enzyme activities. Thus, planting Eucalyptus in harsh environments, where natural restoration is difficult, can be an effective measure for early vegetation restoration. [ABSTRACT FROM AUTHOR]

Abstract As the second common type of volcanic vent on Earth, maar-diatreme volcanoes and their post-eruptive lacustrine sediments are a main focus of volcanology, palaeolimnology, palaeoclimatology and palaeontology. A number of maar-type volcanoes have been found in Leizhou Peninsula, South China, but little is known about their eruption processes and detailed stratigraphy of the post-eruptive sediments. We present a combined geophysical and geological analysis to study the eruptive history and post-eruptive sediment stratigraphy of a large maar, the elliptical (1.8 × 3.0 km2) Jiudouyang (JDY) maar. The lacustrine stratigraphy revealed by drilling cores shows that the JDY maar lake has three major stages of evolution: (i) deep-lake sedimentary environment characterized by high autochthonous diatom productivity; (ii) shallow lake to swamp with very low water levels, characterized by a high total organic carbon (TOC) and abundant wood fragments; and, (iii) intermittent shallow lake and alluvial deposits composed of clay minerals and sand. The electrical resistivity tomography (ERT) values and lithological features are highly consistent, which clearly reveal the presence of ca. 50 m thick lacustrine sediments, directly underlain by a ca. 70 m thick basaltic lava rather than diatreme breccia in the crater. This infill sequence implies an alternation of eruption style from phreatomagmatic to Strombolian and/or lava flow, due to high magma flux and ascent rate of the Hainan Plume during the middle Pleistocene. The ERT data also reveal the initial phreatomagmatic crater floor at ca. 120 m depth. The initial crater had a large diameter/depth ratio (ca. 17), with an elongated shape (major axis to minor axis = 0.6), implying possible lateral vent migration during the eruption. A significant erosion under tropical weathering condition during the last few hundred thousand years, accounted for the large size of the maar crater. The study provides insights into the eruptive history and post-eruptive evolution of a large maar, as well as the spatial distribution of the lacustrine sediments.

Amphioctopus aegina is an important fishery resource in the coastal waters of China. In the present study, the genetic diversity and population genetic structure among four populations of A. aegina throughout its distributional range in China were assessed using the mitochondrial cytochrome oxidase 1 (COI) sequences. The results revealed a generally low genetic diversity (Hd: 0.2842-0.6670; Pi: 0.0007-0.0015) in A. aegina populations. The neighbor-joining (NJ) phylogenetic tree and the haplotype networks, as well as the results of the molecular variance (AMOVA) analyses, indicated a shallow phylogeographic structure among the four populations. However, pairwise FST statistics and genetic distance analyses revealed significant (p<0.01) genetic differentiation among Qinzhou and the rest three populations of Zhanjiang, Huizhou, and Dongshan. The demographic history analyses indicated a population expansion in A. aegina, and the role of Leizhou peninsula isolation in shaping the population differentiation. These results would largely enhance our understanding of the genetic structure and hence promote the scientific management of A. aegina fishery resources in coastal waters of China. [ABSTRACT FROM AUTHOR]

This paper explores the adaptive design of historic villages and dwellings in response to the typhoon climate of the Leizhou Peninsula. A field investigation involving 917 historic villages was conducted. The physical features of the villages were superimposed with the visualized spatial trajectories of the cyclones. Case studies were also adopted to reveal their windproofing mechanisms. The results show that villages are safeguarded through systematic approaches. First, planting windbreaks with appropriate densities and locations was a first line of defence. Second, dwellings were arranged to form a dense-alley pattern, through which the windward faces were reduced and rapid drainage was achieved. Third, the courtyard layout, strengthened exterior walls, and a set of roof protection technologies were applied to increase the stability and integrity of the building. Traditional wisdom was identified in that villages and dwellings were built with the philosophy of reducing the possibility of a disaster in an ordinary windstorm situation through appropriate rather than excessive windproof construction to achieve a balance between survival and development under resource constraints. This knowledge complements the traditional technologies of wind protection developed in other regions of the world and has modern significance for building climate-adaptive and environmentally friendly settlements and buildings. [ABSTRACT FROM AUTHOR]

Total organic carbon (TOC), total nitrogen (TN) and multi-biomarker indexes were analyzed for two sediment cores from the eastern coastal area of the Beibu Gulf (core 45, AMS 14C dated) and Qiongzhou Strait (core 29), South China Sea. The results showed that the TOC and TN content of the samples studied were 0.32–0.62% and 0.02–0.07%, respectively. The hydrocarbons in offshore sediments of Leizhou Peninsula were consisted of biogenic hydrocarbons and petrogenic hydrocarbons. The Core 29 sediments contain more terrigenous organic matter than that of sediments in core 45 due to the difference in hydrodynamic conditions. The composition and distribution of various lipid biomarkers indicate the presence of petrogenic hydrocarbons in the sediments of the whole profile of two sediment cores. There are multiple natural sources of hydrocarbons that could potentially contribute to the petroleum background through oil seeps and erosion of carbon-rich rock outcrops or bitumen deposits. Deep sourced hydrocarbon inputs from the submarine hydrocarbon seepage cannot be excluded. Further study is needed to resolve the specific sources for the petrogenic hydrocarbons and may be significant to petroleum exploration in the study area.

As the second common type of volcanic vent on Earth, maar-diatreme volcanoes and their post-eruptive lacustrine sediments are a main focus of volcanology, palaeolimnology, palaeoclimatology and palaeontology. A number of maar-type volcanoes have been found in Leizhou Peninsula, South China, but little is known about their eruption processes and detailed stratigraphy of the post-eruptive sediments. We present a combined geophysical and geological analysis to study the eruptive history and post-eruptive sediment stratigraphy of a large maar, the elliptical (1.8 × 3.0 km2) Jiudouyang (JDY) maar. The lacustrine stratigraphy revealed by drilling cores shows that the JDY maar lake has three major stages of evolution: (i) deep-lake sedimentary environment characterized by high autochthonous diatom productivity; (ii) shallow lake to swamp with very low water levels, characterized by a high total organic carbon (TOC) and abundant wood fragments; and, (iii) intermittent shallow lake and alluvial deposits composed of clay minerals and sand. The electrical resistivity tomography (ERT) values and lithological features are highly consistent, which clearly reveal the presence of ca. 50 m thick lacustrine sediments, directly underlain by a ca. 70 m thick basaltic lava rather than diatreme breccia in the crater. This infill sequence implies an alternation of eruption style from phreatomagmatic to Strombolian and/or lava flow, due to high magma flux and ascent rate of the Hainan Plume during the middle Pleistocene. The ERT data also reveal the initial phreatomagmatic crater floor at ca. 120 m depth. The initial crater had a large diameter/depth ratio (ca. 17), with an elongated shape (major axis to minor axis = 0.6), implying possible lateral vent migration during the eruption. A significant erosion under tropical weathering condition during the last few hundred thousand years, accounted for the large size of the maar crater. The study provides insights into the eruptive history and post-eruptive evolution of a large maar, as well as the spatial distribution of the lacustrine sediments. [ABSTRACT FROM AUTHOR]

Widely distributed wetlands in China play an important role in the global carbon cycle. However, the long-term response of wetland evolution and carbon storage in tropical southern China to climate change remains unclear. Here, we present a sediment core record from the Tiaoshu Wetland in the northern Leizhou Peninsula and multiple proxy indicators are investigated, with the aim of better understanding past vegetation and environmental changes. The following conclusions were drawn: (i) The organic matter deposited in the Tiaoshu Wetland was mainly derived from terrestrial C3 plants and aquatic plants growing in and/or around the catchment. The temporal variability in the relative proportions of organic matter contributed by various sources revealed paleoenvironmental changes in the study area, generally consistent with regional and global climate records. (ii) The peat formation pattern in the Tiaoshu Wetland is in contrast to some individual sites reported in subtropical China, suggesting that there may be different peat formation patterns in the tropical and subtropical regions of China, which may be closely related to specific hydrothermal conditions in different regions. In addition, by comparison with atmospheric CH 4 concentrations, our results suggest potential relationships between the evolution of wetlands in tropical China and global atmospheric CH 4 cycles. • Alternation between terrestrial and aquatic plants dominated the organic matter sources in the Tiaoshu Wetland. • Variations in organic matter sources reveal vegetation succession and a response to climate changes. • Peat formation patterns may differ between tropical and subtropical regions of China. [ABSTRACT FROM AUTHOR]

Microplastic is an emerging pollutant and a technical fossil in Anthropocene sediments. Typhoon frequency and intensity have increased due to climate change, which has a major effect on the distribution patterns of microplastics. It is still unknown, though, how the topography of the peninsula affects the reconstruction of the distribution of microplastic in typhoons. Due to frequent typhoons, the Leizhou Peninsula (LZP) in the north part of the South China Sea is an ideal place to study the impact of topographic variations on microplastic distribution during typhoon events. This study investigated microplastics ranging in size from 50 μm to 5 mm in sediment. Microscopic inspection and μ-FTIR tests were used to identify microplastic characteristics from offshore surface sediments before and after typhoons. The average microplastic abundance in offshore sediments decreased from 18 ± 17 items/kg to 15 ± 15 items/kg after typhoons. Results show that typhoons only increase the microplastic abundance in topographically protected areas along the northeast coast of LZP, with no significant difference observed in other regions. The influence of typhoon on the morphological characteristics of microplastics in sediments is more pronounced and widespread, as evidenced by a shift in the predominant shape of microplastics from fibers to fragments and a decrease in size accompanied by an increased abundance within the 100 μm–1 mm fraction. The color of microplastics remained similar before and after typhoons, and the polymer composition of microplastics became more uniform. The alteration of microplastic morphology may be attributed to the enhancement of wave intensity induced by typhoons. This study enhances the comprehension of typhoon-induced impacts on pollutant redistribution, specifically microplastics, thereby providing essential empirical evidence and theoretical foundations for pollution regulation. [Display omitted] • Typhoon increased microplastic (MP) abundance in topographically protected areas. • Impact of typhoon on MP morphology is more significant than other MP characteristics. • Typhoon changed the predominant MP shape from fibers to fragments. • Typhoon made MP smaller and more concentrated in 100 μm–1 mm fraction. • Redistribution of MP shapes may be primarily due to typhoon-induced wave enhancement. [ABSTRACT FROM AUTHOR]

Nitrogen, as the main bioactive element, plays an important role in biological productivity, ecosystem function, and biogeochemical processes in marine environment. In this study, seawater samples collected from China's Leizhou Peninsula coastal water (LZPCW) during dry, normal, and wet seasons in 2018 were explored to reveal the spatiotemporal variation, composition, and transport flux of dissolved inorganic nitrogen (DIN) linked to hydrographic condition. DIN concentration and speciation showed significantly seasonal variation (P < 0.01), and the concentration of DIN species was significantly higher in dry season than other seasons. The annual mean DIN concentration was 8.01 ± 5.79 μmol L−1. In addition, the N–NO 2 −, N–NO 3 − and N–NH 4 + were significantly different in the DIN bulk in different seasons. The largest fraction of DIN was N–NO 3 −, followed by N–NH 4 +, the lowest was N–NO 2 −, comprising up to 67.92 ± 23.20%, 23.90 ± 23.19% and 8.18 ± 8.19%, respectively. Besides, the Beibu Gulf was subjected to 7.28 × 1010 mol DIN annual flux through the Qiongzhou Strait. The annual transport fluxes of N–NO 2 −, N–NO 3 −, and N–NH 4 + accounted for 6.43%, 77.20% and 16.36%, respectively. The DIN concentration and coastal water flow led to the largest DIN flux transport in dry season. This study revealed that the coastal ocean currents, river plumes and human activities jointly drove the dynamic variations of N species in LZPCW. It provides a baseline data for studying the spatiotemporal effects of hydrographic condition on nitrogen distribution and transport flux in the LZPCW, which is implications for understanding nutrients dynamics and coastal water quality management in future. • Significant DIN variations were observed in spatiotemporal scale. • Beibu gulf was subjected to huge DIN flux by Qiongzhou Strait transport. • N–NH 4 +, N–NO 2 -, and N–NO 3 - accounted for 16.36%, 6.43%, 77.20% in annual DIN flux. • DIN concentration and coastal water flow lead to the largest DIN flux in dry season. • Coastal current and riverine input strongly impacted on the DIN variation. [ABSTRACT FROM AUTHOR]

Mangrove actinomycetia are considered one of the promising sources for discovering novel biologically active compounds. Traditional bioactivity- and/or taxonomy-based methods are inefficient and usually result in the re-discovery of known metabolites. Thus, improving selection efficiency among strain candidates is of interest especially in the early stage of the antibiotic discovery program. In this study, an integrated strategy of combining phylogenetic data and bioactivity tests with a metabolomics-based dereplication approach was applied to fast track the selection process. A total of 521 actinomycetial strains affiliated to 40 genera in 23 families were isolated from 13 different mangrove soil samples by the culture-dependent method. A total of 179 strains affiliated to 40 different genera with a unique colony morphology were selected to evaluate antibacterial activity against 12 indicator bacteria. Of the 179 tested isolates, 47 showed activities against at least one of the tested pathogens. Analysis of 23 out of 47 active isolates using UPLC-HRMS-PCA revealed six outliers. Further analysis using the OPLS-DA model identified five compounds from two outliers contributing to the bioactivity against drug-sensitive A. baumannii. Molecular networking was used to determine the relationship of significant metabolites in six outliers and to find their potentially new congeners. Finally, two Streptomyces strains (M22, H37) producing potentially new compounds were rapidly prioritized on the basis of their distinct chemistry profiles, dereplication results, and antibacterial activities, as well as taxonomical information. Two new trioxacarcins with keto-reduced trioxacarcinose B, gutingimycin B (16) and trioxacarcin G (20), together with known gutingimycin (12), were isolated from the scale-up fermentation broth of Streptomyces sp. M22. Our study demonstrated that metabolomics tools could greatly assist classic antibiotic discovery methods in strain prioritization to improve efficiency in discovering novel antibiotics from those highly productive and rich diversity ecosystems.

We developed a numerical model, RFLUX, which uses the heat tracer method for vertical groundwater flux estimation, and applied it to the Leizhou Peninsula, South China, to provide information to inform local groundwater resource utilization and management. The temperature–depth (TD) profiles of 24 boreholes, along with the observed ground surface temperature (GST) and surface air temperature (SAT) series in recent decades, were collected in this area. Underground TD data demonstrated the capacity to identify groundwater flow patterns, and local GST and SAT data demonstrated a strong correlation with each other over monthly, seasonal, and annual scales. In the RFLUX model, the average GST and SAT series were applied as an upper boundary condition, and a nonlinear initial condition was set using an analytical solution from the literature. The model results of selected TD profiles demonstrated that the annual vertical groundwater flux was about 0.15 m a−1, which tended to be overestimated if a linear initial condition was used. This model can be easily applied with minor modifications, considering its clear purpose and simplicity. [ABSTRACT FROM AUTHOR]

To elucidate the spatial patterns of understory species in fragmented forests adjacent to human settlements, we examined the spatial distribution and intraspecific correlations of three dominant species Mallotus philippensis , Dasymashalon trichophorum , and Psychotria rubra by employing point pattern analysis, which were the top three in terms of importance value in the shrub layer of Fengshui forest in Leizhou Peninsula, Guangdong. The results showed that all the three species were mainly aggregated at the scale of 0-25 m, especially for young trees. The degree of aggregation gradually diminished with increasing age class. The spatial distribution patterns of three species were predominantly influenced by habitat heterogeneity, negative density dependence, and dispersal limitation. They showed positive association among different age classes, especially between young trees and middle age trees and between young trees and adult trees. Therefore, in the ecological restoration process of Leizhou Peninsula, M. philippensis , D. trichophorum , and P. rubra should be planted in clusters at a small scale within the range of 0-25 m, with the degree of clusters depending on plant morphology. For larger scales, a dispersed cultivation approach was advocated.

Zhong, Z.; Yang S., and Duan, Y., 2018. Sustainable development of typhoon prone coastal areas based on SD model. In: Liu, Z.L. and Mi, C. (eds.), Advances in Sustainable Port and Ocean Engineering. Journal of Coastal Research, Special Issue No. 83, pp. 754–769. Coconut Creek (Florida), ISSN 0749-0208. Sustainable development systems are a dynamic and complicated large systems, that can both be modestly destroyed and restrained by typhoon disasters. System dynamics can be used to study the problems of sustainable development. In this study, based on the theory of sustainable development and targeting typhoon disaster events in Leizhou Peninsula of China, we selected four subsystems (economy, population, environment, and water resource) using the background of typhoon disasters to empirically analyze the effectiveness and practicability of simulation models. Based on this, the restricting factors for sustainable development of the Leizhou Peninsula were assessed via scenario analysis. It was found that typhoon disasters introduced both benefits and harms to the economic development. The existing environmental protection investment did not meet the demands for social development, and the supply-demand contradiction of water resources remained severe. To promote sustainable development of the Leizhou Peninsula, the government has to adjust industrial structure, increase environmental investment, preserve water resources, and improve water quality. [ABSTRACT FROM AUTHOR]

The LeiZhou Peninsula is situated at the southern tip of mainland China with frequent tropical cyclone activity. Its special feature of large-scaled westward concaved coastline results in complex storm-induced hydrodynamic processes in a variety of spatial scales. Statistics show that the surge distributions in the east LeiZhou Peninsula are sensitive to the landfall location and moving direction of the storm tracks. This paper provides a detailed assessment to investigate the nearshore and coastal responses to different tropical cyclone behaviours in this region. A high-resolution integrally-coupled wave and circulation model (FVCOM-SWAVE) on a large-domain unstructured mesh containing the northern South China Sea is applied in this study. The model is validated by observed water level records during three typical typhoon events of Krovanh (2003), Kai-tak (2012) and Mujigae (2015). Induced by the right-handed cyclone wind rotation at the northern hemisphere, surges at ZhanJiang and NanDu perform as set-up processes when the storm lands to the south of the ZhanJiang Bay and as mixtures of slight set-up and medium set-down when the storm lands to the north of the ZhanJiang Bay. For set-up cases, the storm tracks with moving direction of WNW ( α  = 10° ∼ 30°) are more likely to cause heavy surges. Complex coastal morphology has great impacts on the surge distributions. For outer-bay coastlines, the area at the distance of 1 ×  RMW  ∼ 1.5 ×  RMW right to the cyclone track is most dangerous prone to high surge. For inner-bay areas, three high-risk regions—the NanSan Channel, the HuGuang branch of the ZhanJiang Bay and west coast of the LeiZhou Bay—are more likely to generate violent surges because of their westward narrowing-down configurations. Protected by a narrow entrance oriented to ESE, surge variations in the ZhanJiang Bay are less sensitive to the variations of landfall location and moving direction than that in the LeiZhou Bay. [ABSTRACT FROM AUTHOR]

With the emergence of the neologism ‘intangible cultural heritage’ in 2003 and the adoption of the Intangible Cultural Heritage Law of the People’sRepublic of China in 2011 various popular religious practices in China which used to be considered as feudal superstitions started to be recognized as examples of cultural heritage worthy of protection. If we examine the concept of religious diversity at a local level in contemporary China, the process of a ‘patrimonialization’ of popular religious practices that reflect the dynamic relationships which can be detected across diverse discourses, multiple stakeholders and cultural policies in different arenas could offer us a new perspective on religious practices to explore. In this article I offer an analysis, based on fieldwork conducted between 2013 and 2016 on the Leizhou Peninsula in southern China’s Guangdong Province, of the varying degrees of acceptance, accommodation and resistance prompted by the actualization of popular religious practices in this era of patrimonialization.

A triply-nested two-dimensional (2D) ocean circulation model along with observed sea level records are used to study tide-surge interaction along the east coast of the Leizhou Peninsula (LP) which is characterized by extensive mudflats, large tidal ranges and a complex coastline. The dependency of surge maxima on the water level and the phase of tide are respectively investigated using two statistical approaches. Results show that tide-surge interaction along the east coast of the LP is significant, where surges peak 3–6 h before or after the nearest high water. The triply-nested 2D ocean circulation model is used to quantify tide-surge interaction in this region and to investigate its physical cause. The largest amplitudes of tide-surge interaction are found in the shallow water region of the Leizhou Bay, with values up to 1 m during typhoon events. Numerical experiments reveal that nonlinear bottom friction is the main contributor to tide-surge interaction, while the contribution of the nonlinear advective effect can be neglected. The shallow water effect enhances the role of nonlinear bottom friction in determining tide-surge modulation, leaving the surge peaks usually occur on the rising or falling tide. It is also found that the relative contribution of local wind and remote wind is different depending on the storm track and storm intensity, which would finally affect the temporal and spatial distribution of tide-surge interaction during typhoon events. These findings confirm the importance of coupling storm surges and tides for the prediction of storm surge events in regions which are characterized by shallow water depths and large tidal ranges. [ABSTRACT FROM AUTHOR]

Here, we present a well-dated terrestrial charcoal chronology covering the interval ~ 41,000–7050 cal BP and identifying the millennial-scale variability in biomass burning for the tropical Leizhou Peninsula, south China. Our results show that changes in biomass burning closely followed regional temperature and precipitation variations on orbital timescales, i.e., more biomass burning occurred during the warm/wet Marine Isotope Stage (MIS) 3, and less biomass burning occurred during the cold/dry MIS 2. Superimposed on this general trend, our charcoal record shows millennial-scale variability in biomass burning corresponding to the rapid climate changes associated with Dansgaard–Oeschger (D–O) cycles, i.e., biomass burning increased during D–O warming events, whereas biomass burning decreased during intervals of rapid cooling terminated by Heinrich events. During the cooler/drier periods, low biomass burning can be explained by the decline of vegetation productivity, whereas the warmer/wetter periods are characterized by higher biomass burning related to increasing fuel availability. Therefore, climate control can be considered as the major forcing factor of biomass burning from 41,000–7050 cal BP on both orbital and millennial timescales in the northern Leizhou Peninsula. [ABSTRACT FROM AUTHOR]

A well-dated palynological record spanning the interval ~ 40,500–7060 cal yr BP, retrieved from a peatland on the Leizhou Peninsula in south China, clearly shows regional vegetation and climate changes during the last glacial period. Pollen data showed that the study region was mainly covered by subtropical evergreen trees during Marine Isotope Stage 3 (MIS 3), indicating a subtropical climate with relatively high temperature and precipitation. During MIS 2, subtropical evergreen-deciduous forest with large areas of grassland occurred, implying cooler and drier conditions. Some tropical forest elements increased during the early Holocene, indicating a warm and wet trend. Several millennial-scale oscillations of the pollen records appeared to correlate with the cold anomalies in the North Atlantic region. Our records agree well with many records from other regions, but they are a bit different than that inferred from the neighboring Huguang Maar Lake. Furthermore, our results suggest that the vegetation surrounding Xialu peatland was strongly influenced by the migration of the intertropical convergence zone (ITCZ) and variability in the East Asian summer monsoon (EASM). Changes of atmospheric CO 2 concentration ( p CO 2 ) levels may have also affected the long-term vegetation changes in the study region. [ABSTRACT FROM AUTHOR]

Mangroves play an important role in sequestering carbon and trapping sediments. However, the effectiveness of such functions is unclear due to the restriction of knowledge on the sedimentation process across the vegetation boundaries. To detect the effects of mangrove forests on sediment transportation and organic carbon sequestration, the granulometric and organic carbon characteristics of mangrove sediments were investigated from three vegetation zones of four typical mangrove habitats on the Leizhou Peninsula coast. Based on our results, sediment transport was often 'environmentally sensitive' to the vegetation friction. A transition of the sediment transport mode from the mudflat zone to the interior/fringe zone was often detected from the cumulative frequency curve. The vegetation cover also assists the trapping of material, resulting in a significantly higher concentration of organic carbon in the interior surface sediments. However, the graphic parameters of core sediments reflected a highly temporal variability due to the sedimentation process at different locations. The sediment texture ranges widely from sand to mud, although the sedimentary environments are restricted within the same energy level along the fluvial-marine transition zone. Based on the PCA results, the large variation was mainly attributed to either the mean grain size features or the organic carbon features. A high correlation between the depth and δC value also indicated an increasing storage of mangrove-derived organic carbon with time. [ABSTRACT FROM AUTHOR]

Highlights: [•] AVS and SEM concentration in coastal surface sediments were first obtained throughout the Leizhou Peninsula. [•] The high AVS-concentration and high SEM-concentration zones were located in the aquaculture areas or ports. [•] Most of the coastal surface sediments had no adverse biological effects based on ([SEM]–[AVS])/f OC. [•] ([SEM]–[AVS])/f OC indicated adverse biological effects may be expected in 2 stations. [ABSTRACT FROM AUTHOR]

The Leizhou Peninsula is an important base for tropical and subtropical cash crops in China, but still lacks systematic research on regional eco-geochemical characteristics. Here the elemental results show that risk-free soils accounted for 9168 km 2 and were mainly concentrated in the northern Leizhou Peninsula, while risk-controllable soils occupied 3318 km 2 and were mostly distributed in the southern part. The contributor of the heavy metals in soils was mainly natural rocks, while the road traffic dust and coal combustion were also responsible for the origin of anomalous elements Cd, Cr, and Ni (0.004-1.8, 0.76-590, and 0.14-372 mg/kg, respectively). 90.15 % of the Leizhou Peninsula plants were not obviously contaminated, yet the comparison between the data collected in 1997 and 2018 allows us to speculate that Ni in the studied soils will reach the risk screening value in 7 years, followed by Cr and Cu in 39 and 92 years, respectively., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Abstract: Organic carbon stable isotopes (δ 13Corg) have been widely used to estimate past C3 and C4 vegetation changes. As the relative abundance of C3 and C4 plants can normally be affected by multiple factors including atmospheric CO2 concentrations (ACC) and climatic conditions (e.g., temperature, aridity), the relative importance of these factors is still debated and may differ greatly in different regions. By using the δ 13Corg records from a peat sequence in the tropical Leizhou Peninsula, South China, we estimate the past C3 and C4 plant abundances (CCPA) from 41,000cal BP to 10,000cal BP. The results indicate that lower δ 13Corg values and thus more C3 plants generally occurred during Marine Isotope Stage 3 (MIS-3), whereas higher δ 13Corg values and thus more C4 plants generally occurred during MIS-2. Moreover, several short positive excursions of δ 13Corg records, indicating expansions of C4 plants also occurred, corresponding with the known YD and H1–H4 events in high latitudes. We conclude that the CCPA in northern Leizhou Peninsula is mainly controlled by precipitation, which in turn is associated with the East Asian summer monsoon (EASM) intensity, both on orbital time scales and suborbital time scales. The ACC may have slightly affected the long-term variation trend of CCPA on orbital time scales. It is likely that the temperature threshold, which is normally an important factor in high latitudes, may have less important influence on the CCPA in tropical south China. Our results provide the quantitative estimations of CCPA from the tropical Leizhou Peninsula, and more studies are necessary in low latitudes to examine possible connections between past vegetation changes and potential controlling factors on shorter timescales. [Copyright &y& Elsevier]

Abstract: Mangroves are an important affecter of atmospheric CO2 level via sequestrating carbon and trapping sediments. However, their sequestrating effectiveness varies with vegetation development and sedimentation processes under site-specific hydrogeomorphic settings. In order to detect the determinants of organic carbon sequestration, this study investigated four mangrove fringing locations along the coast of the Leizhou Peninsula. Surface and core sediment samples were collected from these sites and analyzed for grain-size distribution, sedimentary organic carbon content (SOCC) and stable isotope signature (δ13Corg). It is found that a significantly higher concentration and density of organic carbon were preserved in the interior surface sediments regardless of location or surface grain size distribution. The sedimentary environments, as indicated by core sediment analysis, are controlled under low-to moderately low-energy conditions. Fluvial action on these sedimentary environments decreases from the river dominated site to the tide dominated site. The more stable energy condition favored both sediment and organic carbon accumulation in the mudflat subzone. However, as revealed by δ13C signature, sedimentary organic carbon of the core samples from the four sites was dominantly derived from suspended particulate matter except the tide-dominated offshore core. Whereby, we conclude that vegetation provided control on the surface sedimentary organic carbon distribution via its influence onmangrove debris input and fluid energy condition over the intertidal surface, while hydrogeomorphology determined the long-term organic carbon burial via its impact on the local sedimentation accretion rate and the proportion of autogenous organic carbon sequestration. [Copyright &y& Elsevier]

Abstract: The situation of the environment contaminated by paralytic shellfish toxin (PST) in Leizhou peninsula, China, has attracted more attention since seafood poisoning occurred occasionally. In this study, we examined the toxicities of shore crab Leptodius exaratus, Thalamita crenata and Metopograpsus latifrons by mouse assay, resistance to PST by lethal test injection with PST, and discussed the toxicity neutralization of their hemolymph. The results showed 12% of shore crabs possessed toxicity of 4.3–4.4 MU/g. The 100% lethal dose of PST for M. latifrons was about 2 times of those for the other two crab species. The hemolymphs of the crabs were all able to neutralize PST and tetrodotoxin (TTX) toxicity in different extent. The above results indicate shore crabs at this area are exposed to an environment potentially contaminated with PST and/or TTX, and the toxicity neutralizing efficacy of their hemolymph directly affects their resistance to the toxins. [Copyright &y& Elsevier]

Leizhou Peninsula, located at southern end of mailand China, has 9 284.3 ha mangrove distributed more than 100 sites along its inlets and open coastlines. This paper presents the surveys on mangrove area in Leizhou Peninsula during 2000 and 2008, especially the survey in the eight major mangrove areas in 2002. The flora recorded in mangrove systems includes 69 large algea species, 13 native true mangrove species, nine native semi-mangrove species, and another seven intoduced true mangrove species with Sonneratia apetala as the quickest growing exotic mangrove species dominatant in the mangrove plantations, and more than 100 land flora species, consisting of 17 main mangrove associations. The plant biodiversity habitats remained mainly small patches and diverse, and were becoming worse under the intensive disturbance of human acitivities and coastal pollutions, which decreased the value of mangrove coasts as the important sites for flying-by migrating birds in Leizhou Peninsula. The effective mangrove conservation measures should be implemented. [ABSTRACT FROM AUTHOR]

Aquifers consisting of unconsolidated sediments in the coastal area near Zhanjiang in southern China are grouped into the shallow, middle-deep and deep aquifer systems. Groundwater exploitation began in the 1950s in this district and has increased from year to year since 1980. Measurements of groundwater levels and monitoring data of groundwater chemistry at some 60 wells since 1981 are examined to analyze the evolution of hydrodynamics and hydrochemistry in the coastal aquifers. The results indicate that groundwater levels in the middle-deep and deep aquifer systems have fallen continuously and the extents of the depression cones in water levels have increased in the past two decades, even though the water levels recovered to some degree during the period of 1997–2001. In 2004, the lowest water levels in the middle-deep and deep aquifer systems were 23.58 and 21.84 m below sea level, respectively. The groundwater has TDS ranging from 40 to 550 mg/L, and is of low pH, commonly varies between 4 and 7. Concentrations of total iron and manganese exceed the concentration limits of the drinking water standards. The hardness is in the range of 10–250 mg/L. Chloride contents of the groundwater range from 10 to 60 mg/L. The chloride and TDS do not show systematically increasing trends. Although the water levels in the exploitation center near the coast are significantly lower than the sea level and the depression cones of water levels in the middle-deep and deep aquifer systems have expanded to the sea, sea water intrusion has not been observed until recently. This phenomenon is quite unique in the coastal area near Zhanjiang. [ABSTRACT FROM AUTHOR]

Detailed in situ LM-ICPMS researches on the composite xenoliths from Yingfengling volcano of Leizhou Peninsula, South China, indicate that most incompatible trace elements of clinopyroxenes in composite xenoliths decrease spatially from pyroxenites to distal Iherzolites, and compatible elements and HREE increase steeply. The increasing and decreasing rate is distinct for different trace elements, which give rise to element chromatographic fractionation within metasomatized Iherzolites. The element chromatographic fractionation result actually from the difference in element diffusive rate in melts or fluids percolating through wall-rock Iherzolites. Based on element variation profiles in composite xenoliths this study indicates that Sr, Nb, La and Ce have the highest diffusive mobility, MREE-HREE are moderate, and Zr, Hf, Ti, Ga and Sc are very low in most cases. Higher diffusive rates of LREE than HREE would enlarge the REE fractionation of metasomatized peridotites, and lower diffusive rate of Zr, Hf and Ti relative to neighbor REEs with similar incompatibility would cause the relative depletion of these elements in metasomatized peridotites. Trace elements commonly have a higher diffusive rate in fluid-rich infiltrating melt, which will weaken element chromatographic fractionation during the metasomatism. The range of mantle metasomatism caused by silicate melt intrusion is very limited, generally within tens of centimeters wide. The width of metasomatized wall-rock peridotites near the pyroxenite or horblendite veins was strictly controlled by both melt volume and chemical characteristics. [ABSTRACT FROM AUTHOR]

Monthly, seasonal and annual water balances of Eucalyptus urophylla plantations on the Leizhou Peninsula, southeastern China were estimated in 40 m×40 m plots at two sites with contrasting soil types. The Jijia site is located on basalt-derived clay rich soils, while the Hetou site is characterised by coarse textured soils formed on Quaternary sediments. Observations of evaporative processes (overstorey canopy interception and transpiration, and soil evaporation), soil moisture dynamics, and climate variables were collected at both sites over 2 years. Canopy interception was measured by throughfall troughs and stemflow collectors, daily transpiration was measured by the heat pulse technique in year 1 and estimated from regressions with potential evapotranspiration and available soil water in year 2, soil evaporation was measured by periodic microlysimetry and used to derive a daily soil surface resistance—matric potential relationship for estimation of daily soil evaporation throughout the study period. Soil moisture storage was measured to 4 m depth and drainage estimated as the residual term in a water balance equation. Total annual evapotranspiration (Et) was similar at 1118 and 1150 mm at Jijia and 969 and 1024 mm at Hetou for years 1 and 2, respectively, despite 20–30% higher rainfall in year 2. These values represent 71 and 66% of annual rainfall in year 1, and 54 and 50% in year 2. Transpiration did not exceed 600 mm in either year and annual soil evaporation was 15–26% of Et, with the higher values from Jijia. The higher rainfall in year 2 was predicted to produce an increase in drainage and runoff rather than tree water use. Dry season water balances showed Et exceeded or approached rainfall, indicating water use from deep soil or ground water storages following soil water depletion, particularly at Hetou. However, storages were replenished by high wet season recharge. The differences in soil properties between the sites resulted in a three-fold greater soil water store at Jijia that provided a supply for Es, and the sandier Hetou soils with poor water holding capacity had greater wet season drainage and higher dry season abstraction from deep storages. The water use of the eucalypts does not appear to be seriously deleterious for water supply in this area. [Copyright &y& Elsevier]

The Lei-Qiong Depression Zone, near the Leizhou Peninsula in southern China, consists of unconsolidated sediments of 500–3,000 m thickness. Groundwater occurs in a multi-aquifer system in the Leizhou Peninsula. The aquifers receive recharge from precipitation, canal and reservoir infiltration, and discharge mainly through subterranean drainage into the sea. Artificial pumping for drinking and agricultural purposes is another way of groundwater discharge. Groundwater development along the coast faces the threat of seawater intrusion. A quasi-three-dimensional finite element model, containing 457 nodes and 833 elements, has been used to simulate the spatial and temporal distribution of groundwater levels in the three-aquifer system. Verification of various aquifer parameters and boundary conditions was performed with the simulation model. Linear programming models have been developed for groundwater exploitation within the two confined aquifers. The objective function of the models is to maximize the total groundwater pumpage from the confined aquifers. Control of seawater intrusion is examined by restricting the water levels at points along the coast and the withdrawal rates in coastal management cells. A response matrix approach was used in the optimization models. The response matrix was obtained from the simulation model by forecasting drawdown produced by pumping at a unit impulse discharge. Groundwater development in the Leizhou Peninsula can be primarily optimized by allocating the pumping rates of the management cells. [ABSTRACT FROM AUTHOR]

The exotic Sonneratia apetala in Leizhou Peninsula, has shown outstanding fast-growing ability in restored mangrove forests, at the middle and high tide intertidal zone, with year-round fresh water input from drainage. By setting plot and selecting standard tree, investigation and measurement on height growth, diameter growth, biomass, productivity, and so on, were made in a S. apetala plantation at age of six at Lanbel, Fucheng, Leizhou Peninsula in May 2001. The investigating results showed that the mean annual height growth of plantation was 2.03 m and mean annual growth of diameter at breast height (DBH) was 2.35 cm. There exists a significant correlation between the diameter at ground surface (DGS) and DBH. The average biomass of a single standard tree in dry weight was 95.647 kg/m2. A ratio of above-ground biomass to under-ground biomass was 1.60. The stand biomass of unit area was 22.955 kg/m2, singletree wood volume was 88.23 dm3, and the annual wood volume productivity ( P A) of the same year was 0.407. The forest energy accumulation was 424.851 MJ/m2, with annual solar energy fixing rate of 40.68×10−7%. It is concluded that S. apetala species had characteristics of outstanding high biomass accumulation and could be used as coastal planting tree species in southern China. [ABSTRACT FROM AUTHOR]

Mangrove actinomycetia are considered one of the promising sources for discovering novel biologically active compounds. Traditional bioactivity- and/or taxonomy-based methods are inefficient and usually result in the re-discovery of known metabolites. Thus, improving selection efficiency among strain candidates is of interest especially in the early stage of the antibiotic discovery program. In this study, an integrated strategy of combining phylogenetic data and bioactivity tests with a metabolomics-based dereplication approach was applied to fast track the selection process. A total of 521 actinomycetial strains affiliated to 40 genera in 23 families were isolated from 13 different mangrove soil samples by the culture-dependent method. A total of 179 strains affiliated to 40 different genera with a unique colony morphology were selected to evaluate antibacterial activity against 12 indicator bacteria. Of the 179 tested isolates, 47 showed activities against at least one of the tested pathogens. Analysis of 23 out of 47 active isolates using UPLC-HRMS-PCA revealed six outliers. Further analysis using the OPLS-DA model identified five compounds from two outliers contributing to the bioactivity against drug-sensitive A. baumannii. Molecular networking was used to determine the relationship of significant metabolites in six outliers and to find their potentially new congeners. Finally, two Streptomyces strains (M22, H37) producing potentially new compounds were rapidly prioritized on the basis of their distinct chemistry profiles, dereplication results, and antibacterial activities, as well as taxonomical information. Two new trioxacarcins with keto-reduced trioxacarcinose B, gutingimycin B (16) and trioxacarcin G (20), together with known gutingimycin (12), were isolated from the scale-up fermentation broth of Streptomyces sp. M22. Our study demonstrated that metabolomics tools could greatly assist classic antibiotic discovery methods in strain prioritization to improve efficiency in discovering novel antibiotics from those highly productive and rich diversity ecosystems. [ABSTRACT FROM AUTHOR]

In this paper diatomite samples taken from the Leizhou Peninsula have been studied by chemical analysis, DTA, TG, XRD, IR, SEM and X-ray Energy Spectroscopy. The study shows that the diatomaceous genera and species and their organic contents are variable with buried depth, from Melosira to Stephanodiscus and the to Cyclotella. Various impurities in the samples, such as quartz, kaolinite and montmorillonite indicate different sedimentary environments. When heated, the diatom would change in shape due to the phase transformation in which amorphous silica crystallized from disordered opal to ordered cristobalite. The temperatures of phase transformation are different for various diatoms due to the presence of different impurities and constituents of diatomaceous genera and species. [ABSTRACT FROM AUTHOR]

Tropical cyclones (TCs) often affect the surface sediments of coastal areas, and impact the sediment imprint. Although the sediment magnetism is sensitive to coastal changes, the understanding of the coastal magnetic minerals' redistribution affected by TCs is far from adequate. Here, the magnetic and grain-size records from the seafloor sediments along the Leizhou Peninsula coast in South China before and after two violent TCs (Mangkhut and Barijat) occurred in September 2018 are present. The magnetic minerals mainly consist of magnetite, hematite, and goethite. For most sites, the content of hematite increased compared to magnetite and the magnetic minerals became coarser after the TCs subsided, while the amount of fine clay (<2 μm) decreased and the amount of coarse sand (500–2000 μm) increased. This is due to the preferential deposition of the lamellae hematite from the soils and the enhanced hydrodynamic transportation of suspended sediments. The mangrove forest resists the change to a certain degree, especially in the Leizhou Bay. The magnetic and grain-size properties are sensitive to the TC-induced deposits, and provide convincing tools to aid in detecting the paleo-TC activity in tropical coastal regions. • Tropical cyclones (TCs) led to more content of hematite in coastal sediments compared to magnetite. • After the TCs, magnetic particles in sediments became coarser. • The <2 μm content decreased, and the 500–2000 μm content increased after the TCs. • The mangrove forests resist the redistribution of magnetic particles to a certain degree when the TCs landing. [ABSTRACT FROM AUTHOR]