Hainan Island Research Articles

Field Detection of Uranyl in Coastal Water of China Using a Portable Device via DNA Photocleavage.

The urgent need for field detection of uranium in seawater is 2-fold: to provide prompt guidance for uranium extraction and to prevent human exposure to nuclear radiation. However, current methods for this purpose are largely hindered by bulky instrumentation, high costs of developed materials, and severe matrix interferences, which limit their further application in the field. Herein, we demonstrated a portable and label-free strategy for the field detection of uranyl in seawater based on the efficient photocleavage of DNA. Further experiments confirmed the generation of ultraviolet (UV) light-induced reactive oxygen species (ROS), such as O2•- and •OH, which fragmented oligomeric DNA in the presence of uranyl and UV light. Detailed studies showed that DNA significantly enhances uranyl absorption in the UV-visible region, leading to the generation of more ROS. A fluorescence system for the selective detection of uranyl in seawater was established by immobilizing two complementary oligonucleotides with the fluorescent dye SYBR Green I. The strategy of UV-induced photocleavage offers high selectivity, excellent interference immunity, and high sensitivity for uranyl, with a detection limit of 6.8 nM. Additionally, the fluorescence can be visually detected using a 3D-printed miniaturized device integrated with a smartphone. This method has been successfully applied to the on-site detection of uranyl in seawater in 18 Chinese coastal cities and along the coast of Hainan Island within 3 min for a single sample. The sample testing and field analysis results indicate that this strategy has promising potential for real-time monitoring of trace uranyl in China's coastal waters. It is expected to be utilized for the rapid assessment of nuclear contamination and nuclear engineering construction.

Quantitative assessment of population risk to tropical cyclones using hybrid modeling combining GAM and XGBoost: A case study of Hainan Province

Global climate change is expected to increase the proportion of intense tropical cyclones (TCs) in the Northwest Pacific. This study focused on how factors, especially extreme events, may affect disaster losses. To address this issue, an event-based multivariate TC risk assessment model, which employs copulas, a generalized additive model, and undersampling extreme gradient boosting decision tree techniques, is developed to enhance the accuracy of disaster loss prediction. The results suggest that on Hainan Island, the rate of the affected population is positively correlated with the maximum wind speed and maximum daily rainfall while negatively correlated with the gross domestic product and elevation. The study also shows that the TC risk in the cities of Hainan Island increases as the return period expands, and each return period scenario shows a unique geospatial distribution of TC risk on Hainan Island, with higher risks in the coastal and eastern regions. These results highlight the importance of implementing effective disaster management strategies to mitigate the impact of severe TCs in the region.

Effects of rubber intercropping with native trees on litterfall and litter main nutrient return in Hainan Island, China

Understanding the process of litterfall production is crucial for sustainable development of plantations. However, the underlying dynamics of litterfall and its nutrient return in plantation agroforestry systems remain unclear. In this study, we investigated litterfall, including leaves, branches, flowers, and fruits, in three patterns: Hevea monoculture system (RM), Hevea–Michelia intercropping system (RAS1), and Hevea–Mytilaria intercropping system (RAS2) in Hainan Island, China. Our findings indicate that total litterfall was significantly higher in RAS1 (27,309 kg ha−1) and RAS2 (34,477 kg ha−1) than in RM (22,364 kg ha−1) and was predominantly composed of leaf litterfall in all three patterns, followed by branches, flowers, and fruits. The seasonal dynamics litterfall production of RM, RAS1, and RAS2 showed characteristic patterns. Litterfall nutrients exhibited peak and sub-peak monthly dynamics, peaking from February to March, during the dry season. Total nitrogen (TN), total phosphorus (TP), and total potassium (TK) content of annual litterfall in RAS1 significantly increased by 120 kg ha−1, 30 kg ha−1, and 139 kg ha−1, respectively, compared to those in RM, with percentage increases of 67.88%, 122.79% and 96.27%, respectively. Similarly, TN, TP, and TK content of annual litterfall in RAS2 significantly increased by 185 kg ha−1, 35 kg ha−1, and 170 kg ha−1, respectively, with percentage increases of 103.70%, 159.15% and 139.46%, respectively, for the abovementioned in RM. Litterfall showed a strong correlation with monthly average temperature, monthly minimum temperature, and monthly average wind speed, contributing 80.5%, 75.5%, 69.8%, and 69.6% to the total litterfall and its components, respectively. Further analysis indicated that monthly average temperature, monthly minimum temperature, and monthly average wind speed contributed 73.9%, 43.0%, and 66.6%, respectively, to TN, TP, and TK content of the annual litterfall, highlighting the significant influence of temperature and wind speed. These findings enhance our understanding of carbon and nutrient cycling and contribute to the sustainable management of tropical plantation ecosystems.

Particle composition-specific approach to estimate the particulate organic carbon concentration off the coastal areas of Guangdong and eastern Hainan Island.

High optical complexity caused by the variability of marine particles poses a major challenge to the development of bio-optical algorithms for particulate organic carbon (POC) concentration retrievals from optical measurements in coastal waters. Here, we developed a particle composition-specific approach to estimate POC off the coastal areas of Guangdong and eastern Hainan Island, China. The ratio of phytoplankton absorption to detritus absorption coefficient aph(443)/ad(443) was used to optically discriminate water types. The samples with aph(443)/ad(443) ≤ 4.9 showed a significant correlation between POC and absorption line height at 676 nm aLH(676) (R2 = 0.75, n = 70, p < 0.01). In contrast, aph-dominant samples with aph(443)/ad(443) > 4.9 had a high covariance between POC and particle scattering coefficient at 675 nm bp(675) (R2 = 0.85, n = 37, p < 0.01). Validation with an independent dataset yielded a small positive bias (R2 = 0.81, APD = 23.10%, RMSE = 29.01 mg m-3, RPD = 16.31%). The approach provided a better estimation of POC concentration in coastal waters compared with univariate algorithms. A depth-resolved index aLH(676)/bbp(442) was defined as the ratio of absorption line height to particle backscattering coefficient. Using the depth-resolved index instead of aph(443)/ad(443) for optical water type classification can be utilized to represent the vertical variations of POC in 1 m bins, and can complement remote sensing observations to accurately characterize the three-dimensional structure of POC distribution in the oceans.

Third birth intention of the working women with two existing children in Hainan Island, China: The impact of fertility costs and utility

This study evaluates the impact of fertility costs and utility on the third birth intentions among working women with two children in Hainan, China. A cross-sectional survey was conducted in Hainan Island, China in 2021 using an offline survey. Among 1067 working women with two children, only 8.06 % of participants reported having a third-birth intention. After adjustment for potential confounding factors, higher economic cost (odds ratio = 1.89) and lower succession utility (odds ratio = 5.08) were significantly associated with the lack of intention to have a third child. The analysis further demonstrates that family values significantly modulate these economic and utility considerations, highlighting a strong cultural influence on fertility decisions. This finding underscores the necessity for policies that not only mitigate financial burdens but also promote family values supportive of higher fertility. Such measures are essential for creating a cultural and economic environment conducive to higher birth rates.

China's Ground‐Based Space Environment Monitoring Network—Chinese Meridian Project (CMP)

AbstractMonitoring and investigation of the solar‐terrestrial space environment is a huge challenge for humans in space age. To this end, China has established the Ground‐based Space Environment Monitoring Network, namely Chinese Meridian Project (CMP). The project comprises three major systems: the Space Environment Monitoring System, Data and Communication System, and Scientific Application System. The Space Environment Monitoring System adopts a well‐designed monitoring architecture, known as “One Chain, Three Networks, and Four Focuses,” to achieve stereoscopic and comprehensive monitoring of the entire solar‐terrestrial space. The “One‐Chain” component utilizes optical, radio, interplanetary scintillation, cosmic ray instruments to cover the causal chain of space weather disturbances from the solar surface to near‐Earth space. For the ionosphere, middle and upper atmosphere, and magnetic field, instruments are deployed along longitudes of 120° and 100°E, and latitudes of 30° and 40°N, forming the “Three Networks.” Furthermore, more powerful monitoring facilities or large‐scale instruments have been deployed in four key regions: the high‐latitude polar region, mid‐latitude region in northern China, low‐latitude region at Hainan Island, and the Tibet region. These four regions are crucial for disturbances propagation and evolution, or possess unique geographical and topographical characteristics. The Data and Communication System and Scientific Application System are designed for data collecting, processing, storage, mining, and providing user service based on data acquired by the Space Environment Monitoring System. The data obtained by CMP will be shared with the global scientific community, facilitating enhanced collaboration on space weather and space physics research.

The contribution and impact of shallow water platform as a potential source area on siliceous submarine fans

AbstractThe shelf‐margin deltas are the primary ‘sources’ of interest in siliceous submarine fan source‐to‐sink systems. However, less has yet to be discovered about the roles and effects of the shallow water platform situated on continental slopes. Using the Miocene sediments of the Ledong‐Lingshui Sag in the western part of the Qiongdongnan Basin (QDNB), this paper studies the YC35 coarse‐grained submarine fan that developed in the Meishan Formation (Fm.). The material sources, depositional characteristics, and developmental mechanisms of this fan were investigated. The restored palaeogeomorphology, based on high‐resolution 3D seismic data, shows that a shallow water platform exists. According to geochemical palaeoenvironmental data, the shallow water platform was ideal for forming carbonate deposits in the Meishan Fm., owing to the warm and humid palaeoclimate and the shifting trend in palaeowater depth. Based on the combined source tracing of heavy minerals, coherence slices, and seismic profiles, the shallow water platform and the Ningyuan River source on Hainan Island contributed to the YC35 coarse‐grained submarine fan. Compared to submarine fans formed during different periods, coarse‐grained fan stands out due to its distinct sedimentary structure, rock composition, and microlithological characteristics. Aside from not following the usual Bowmar sequence, there is an excess of gravel and no clear bedding or lamination. A large number of rock fragments, mostly granite and sedimentary rock (carbonatite), make up the rock composition. According to these results, the shallow water platform significantly affects submarine fan material composition. In addition, the attribute slice based on the root mean square reveals that shallow water platforms moderate peripheral deposition. We attribute the development and proximal supply of the shallow water platform to diapirism and forced regression. Our research provides novel insights and comprehension into the investigation of submarine fan sedimentary systems.

Soil phosphorus fraction and availability dynamics along a 2-million-year soil chronosequence in northern Hainan Island, China

The low phosphorus (P) content and availability in highly weathered tropical soils may limit ecosystem service and function. However, information on P fraction dynamics and availability during tropical soil development is scarce. Understanding P transformations and their impacts on P availability at various stages of tropical soil evolution is crucial for effective nutrient management strategies. In this study, a soil chronosequence (ranging from 0.09to 2.30 million years) was combined with the sequential P extraction to assess temporal changes in P fractions with soil age in northern Hainan Island, China. Results showed that total P (TP) content increased initially (<0.146-million-year), declined at the 0.64- million-year site, and then rebounded (>1.12-million-year) as soil age increased. Sequential P extraction revealed that the stable P pools, including concentrated HCl extracted P and residual-P, were the dominant P fractions, mirroring the temporal trend of TP. The labile NaHCO3-Pi concentration, which reflects soil P availability, ranged from 2.29 to 5.63 mg kg−1. Despite the low labile P content, it is sufficient to meet plant P requirements, even in the oldest soil. Structural equation modeling indicated that moderately labile NaOH-Pi and the stable P pools significantly influenced soil P availability, together explained 51.0 % of the variation in labile P. This study elucidates the pattern of P transformation during tropical pedogenesis over a 2.30-million-year timescale, highlighting the substantial contribution of stable P pools to P supply in tropical soils with low labile P content.

Seasonal home range utilization of Hainan gibbons (Nomascus hainanus) in a secondary tropical forest of Hainan Island, South China

The home range utilization of primates reflects their behavioral and ecological strategies to adapt to their environment. However, little is known about the home range behavior of endemic gibbons (Nomascus hainanus) found in a secondary tropical forest of Hainan Island, China. Knowledge of their ranging patterns could contribute to scientific evaluations of the survival risk of this species under habitat conversion. In this study, we analyzed the home range utilization patterns and the seasonal variation of a group of Hainan gibbons in secondary tropical forests in the Bawangling area of National Park of Hainan Tropical Rainforest, using infrared cameras and direct observations. The results show that the annual home area of the gibbon group was 137.4 ha, with no significant difference between the wet and dry seasons. The feeding hotspots of Hainan gibbons are more scattered in the rainy season and more concentrated in the dry season, but not for sleeping hotspots. The relatively small home range suggests that secondary forests may not represent low-quality habitats and thus have a supporting role for the Hainan gibbon population. The widely distributed range of feeding hotspots in the rainy season may be related to the abundance of fruit resources in this season, while gibbons reduce their travel distance and energy expenditure when food is scarce in the dry season. Overall, our findings provide insights into the ecological flexibility of gibbons to seasonal variations in food resources and highlight the conservation value of secondary forests for gibbon populations.

Distribution of the mysterious Chevron Crickets Melanabropsis Wang &amp; Liu, 2020, with a remarkable new species from Hainan, China (Orthoptera: Anostostomatidae: Anabropsini)

Melanabropsis is a rare genus of Chevron Crickets from East Asia. In this study, Melanabropsis nightfury sp. nov. is described from Hainan Island in China. The new species is the first macropterous species belonging to the genus Melanabropsis, distinctly different from other species of the genus, which are all micropterous. Based on the data of the new species and records on iNaturalist, a suitability distribution map of the genus is generated using the Maxent model. The results indicate that this genus is primarily distributed in islands and mountains with small temperature differences and high precipitation. Taiwan Island in China shows high potential for distribution. Type specimens are deposited in the Museum of Biology, East China Normal University.

Early Palaeozoic affinity of Hainan Island to Gondwana: New clues from metamorphic monazite and titanite of the Baoban Complex

The Early Palaeozoic metamorphic records play a crucial role in determining the geological connection between Hainan Island and the Gondwana supercontinent. Nevertheless, the geochronological data for the Early Palaeozoic period is still sparse in Hainan Island. In this study, we conducted an integrated UPb geochronological and geochemical analysis of crystals from six monazite and three titanite samples obtained from the Mesoproterozoic Baoban Complex in the western region of Hainan Island. The mineral morphology and elemental compositions suggest that the examined monazite and titanite crystals exhibit characteristics typical of a metamorphic origin. Monazite and titanite UPb dating show two distinct metamorphic age populations: ca. 453–464 Ma and ca. 430–437 Ma. Our new data, combined with a comprehensive synthesis of metamorphic-magmatic ages from previous studies and other geological observations, offers crucial constraints on the palaeogeographic position and potential timing for the amalgamation of the micro-continents along the fringe of the Gondwana supercontinent. We suggest that Hainan Island was geologically connected to the Gondwana supercontinent during the Early Palaeozoic, a relationship that may have persisted until ca. 430 Ma. By this time, Hainan Island was probably closely linked to the South China and Indochina blocks.

Second-home Tourism in Tropical China: residents’ perception of socio-economic impacts

ABSTRACT Despite the significant growth of second-home tourism research, its geographical focus remains limited to a few countries. China has become a global economic powerhouse, with a rapidly growing middle class with disposable income. A combination of the latter with a range of favourable socialist housing policies and unique cultural forces have encouraged, and in some cases demanded, multiple-home ownership among Chinese families. At the forefront of this phenomenon are vast numbers of senior snowbirds who have chosen the tropical island of Hainan as the location of their second home. While there has been some investigation around this topic in select locations in China, the academic understanding of this phenomenon remains in its infancy. This paper investigates residents’ perceptions of Haikou, the capital of Hainan Province, regarding the socio-economic impact of second-home ownership on their lives, communities and the city. The results of this study will inform policy recommendations for local government while shedding new light on global narratives on second-home tourism phenomena.

Seasonal dynamics and habitat preferences of juvenile fish assemblages in the Wanquan Estuary, South China: Implications for conservation and management

Tropical estuaries encompass diverse habitats, which are crucial for supporting juvenile fish by providing nurseries, refuges, and migration routes. In the present study, we investigated the seasonal and spatial dynamics of juvenile fish assemblages in the Wanquan Estuary, Hainan Island, China, examining variations during the wet and dry seasons across four types of habitats. Our research aimed to test the hypotheses: (1) the wet season supports a greater abundance and species richness of juvenile fish compared to the dry season, and (2) juvenile fish showed varying habitat preferences across seasons. We recorded a total of 3617 individuals belonging to 33 families, 50 genera, and 78 taxa. Our findings revealed significant seasonal fluctuations in the assemblage structure, with peak abundance during the wet season in August, primarily consisting of diadromous species. A notable shift towards marine species was observed in March. Spatially, juvenile fish exhibited significant habitat preferences, with a strong preference for sand substrates for most species. Contrary to common expectations, mangrove fringe habitats were not identified as the primary nursery grounds for juvenile fish. Instead, our study highlights the importance of habitat diversity and connectivity in enhancing nursery functions. Water temperature and salinity were the key drivers influencing the seasonal and temporal patterns of juvenile fish assemblages in the Wanquan River estuary The pronounced temporal dynamics of these assemblages, driven by seasonal environmental alterations affecting water variations and habitat connectivity, were more significant than spatial differences. The findings emphasize the need for focused connectivity of various habitats to support the conservation of diverse fish communities in tropical estuarine ecosystems.

Species composition and distribution of common Crassostrea and Saccostrea oysters along the coast of Hainan Island

Species composition and distribution of common Crassostrea and Saccostrea oysters along the coast of Hainan Island

Species diversity of fish at the Wuzhizhou Island, South China Sea, based on environmental DNA.

Wuzhizhou Island (WZZ) is located in Haitang Bay in the northern region of Sanya, Hainan Island. The sea area surrounding WZZ represents a typical tropical marine ecosystem, characterised by diverse and complex habitats. Therefore, there is a rich variety of marine fish species at WZZ. The marine ecosystem of WZZ was seriously destroyed initially in the 1970s-1980s and recovered in the 1990s, then constructed as the first national tropical marine ranch demonstration area of China in 2019. As fish is an important high trophic vertebrate in the marine ecosystem, understanding the composition and distribution of fish species could help us to recognise the status of the ecosystem of WZZ and supply scientific data for construction of the national marine ranch demonstration area. This study used eDNA technology to investigate the composition of fish community surrounding WZZ and provided a scientific basis for realising and protecting the marine ecosystem of the South China Sea. The WZZ is an offshore island in the South China Sea, harbouring abundant marine fish resources. Although previous research investigated fish species of WZZ, the data were, however, still incomplete due to limitation of sampling methods and survey seasons. In this study, we intended to take advantage of eDNA and supplement data of fish species at WZZ as much as possible. Based on eDNA, this study provided the data on 188 fish species (including nine undetermined species denoted by genus sp.) belonging to 17 orders, 63 families and 124 genera and they were the more comprehensive records of fish species surrounding WZZ. In addition, the information on Molecular Operational Taxonomic Units (MOTUs) for taxon identification was also provided, aiming to contribute to the establishment of a specific eDNA taxon database for fish of the South China Sea. This study included two datasets, which were occurrences of fish taxa at WZZ, as well as MOTUs sequences and geographical coordinate information of sampling sites. The "fish taxon occurrences" dataset presented records on taxonomic, distribution and habitat conditions of 188 fish species detected using eDNA, as well as the latitude and longitude information of the sampling sites, the "MOTUs information" dataset provided the MOTUs sequences, source of sequences, abundance of sequences for 188 fish species, also included the species matched in NCBI and the best NCBI BLAST sequence similarity.

55-PUB: Prevalence and Patterns of Multimorbidity among Elderly Aged 65 and above in the Hainan Island

55-PUB: Prevalence and Patterns of Multimorbidity among Elderly Aged 65 and above in the Hainan Island

Rubber Plantation Age Affects Soil Aggregate Stability, Organic Carbon, and Nitrogen Distribution in Hainan Island, China

Rubber Plantation Age Affects Soil Aggregate Stability, Organic Carbon, and Nitrogen Distribution in Hainan Island, China

Characteristics of precipitation changes during tropical cyclone processes in China from 1980 to 2019

Tropical cyclones (TCs) and their associated intense rainfall are among the most significant natural disasters. Exploring the characteristics of tropical cyclone precipitation (TCP) has always been a challenging issue in TC research. This study utilized the TC track data from the International Best Track Archive for Climate Stewardship and precipitation data from the multi-source weighted-ensemble precipitation covering the years 1980–2019, to examine shifts in precipitation rates and peak precipitation levels before and after TC landfall. The results highlight several key findings: (1) Precipitation during the TC landfall process is relatively stable beforehand but tends to decrease slightly after landfall. Generally, the maximum precipitation occurs during the landfall. (2) From 1980 to 2019, the rate of precipitation changes before landfall has significantly increased. Conversely, after the year 2000, the rate of precipitation changes after landfall has significantly decreased. (3) Over the past 40 years, while peak precipitation levels of landfalling TCs have remained relatively constant, the total precipitation has shown an increasing trend, particularly in regions like the main island of Hainan, southern Zhejiang, and Shanghai, which are characterized by high peak precipitation. The results help clarify the TC processes and provide reference points for parameter selection in regional TCP modeling.

Land-Use/Cover Change and Driving Forces in the Pan-Pearl River Basin during the Period 1985–2020

Land use/cover change (LUCC) is a vital aspect representing global change and humans’ impact on Earth’s surface. This study utilized the ESRI Land Cover 2020 and China Land Cover Dataset (CLCD), along with historical imagery from Google Earth, to develop a method for the assessment of land use data quality. Based on the assessment, the CLCD was updated to generate an improved Re-CLCD for the Pan-Pearl River Basin (PPRB) from 1985 to 2020, and to analyze LUCC in the PPRB over the past 35 years. The results indicate the following: (1) Among the seven land uses, built-up land experienced the most dramatic change, followed by cropland, forestland, grassland, shrubland, waterbody, and bare land, with notable increases in built-up land and forestland, and rapid decreases in cropland, grassland, and shrubland. (2) The magnitude of land use changed very widely, with the highest change in the Pearl River Delta, followed by small coastal river basins in southern Guangdong and western Guangxi, the Dongjiang River Basin, the Hanjiang River Basin, the Xijiang River Basin, the Beijiang River Basin, and lastly, Hainan Island. (3) The largest increase happened in built-up land, with a total increase of 12,184 km2, mainly due to the occupation of cropland and forestland, corresponding to the highest decrease in cropland, with a net loss of 10,435 km2, which was primarily converted to forestland and built-up land. The study results are valuable in providing a scientific basis for policy overhaul regarding land resources and management to safeguard ecological balance and promote sustainable development in the Pan-Pearl River Basin.

Geographic Location Affects the Bacterial Community Composition and Diversity More than Species Identity for Tropical Tree Species.

Microorganisms associated with plants play a crucial role in their growth, development, and overall health. However, much remains unclear regarding the relative significance of tree species identity and spatial variation in shaping the distribution of plant bacterial communities across large tropical regions, as well as how these communities respond to environmental changes. In this study, we aimed to elucidate the characteristics of bacterial community composition in association with two rare and endangered tropical tree species, Dacrydium pectinatum and Vatica mangachapoi, across various geographical locations on Hainan Island. Our findings can be summarized as follows: (1) Significant differences existed in the bacterial composition between D. pectinatum and V. mangachapoi, as observed in the diversity of bacterial populations within the root endosphere. Plant host-related variables, such as nitrogen content, emerged as key drivers influencing leaf bacterial community compositions, underscoring the substantial impact of plant identity on bacterial composition. (2) Environmental factors associated with geographical locations, including temperature and soil pH, predominantly drove changes in both leaf and root-associated bacterial community compositions. These findings underscored the influence of geographical locations on shaping plant-associated bacterial communities. (3) Further analysis revealed that geographical locations exerted a greater influence than tree species identity on bacterial community compositions and diversity. Overall, our study underscores that environmental variables tied to geographical location primarily dictate changes in plant bacterial community composition. These insights contribute to our understanding of microbial biogeography in tropical regions and carry significant implications for the conservation of rare and endangered tropical trees.