Ao Island Research Articles

Quantifying and spatializing the island landsenses ecological condition using a two-dimensional model

Achieving the harmonious development of the “social-ecological” system is a crucial aspect of the global sustainable development goals. Landsenses ecology is an emerging concept that emphasizes sustainable land use planning and comprehensive management. Islands serve as ideal study areas setting for studying the landsenses ecology due to their vulnerability as ecosystems exposed to significant human activities. To assess the condition and spatial distribution of landsenses ecology, we established a quantitative evaluation framework that encompassed eight factors across two perceptions - physical and psychological. Our study focused on two islands situated in southeast China, which, despite their proximity, demonstrate remarkable differences in terms of natural and economic characteristics. The results revealed a significant spatial heterogeneity in the landsenses ecological condition on both islands. Nan'ao island (NAI) exhibited higher values for physical (0.5) and psychological (0.243) perceptions compared to Dongshan island (DSI), which was primarily attributed to varying natural environments and topographic factors. Notably, elevation and slope demonstrated strong correlations with landsenses ecological condition, acting as critical determinants of island development. Finally, using beaches as an example, we examined the impact of landsenses ecological conditions about the tourist resources of the islands. This study contributes to the development of scientifically informed urban and tourism planning processes by providing decision-makers with valuable insights.

Forward numerical investigation of potential tsunami deposits in the South China sea: A case study of Nan'ao Island

The South China Sea (SCS) coastlines are particularly vulnerable to tsunamis due to rapid urbanization and dense infrastructures. However, whether the SCS has experienced ocean-wide tsunamis is still under debate. Some geological records from the offshore islands inside the SCS imply a regional tsunami event may have occurred approximately 1000-yr-ago. We address these questions for the first time using forward numerical simulations in the SCS: what source could be responsible for such deposits, how the deposits were formed and at what conditions do the deposits could be preserved? Here, we assume the validity of the tsunami deposit hypothesis and use the forward model COMCOT-SED to investigate if these tsunami deposits can be linked to potential seismogenic tsunami sources inside the SCS, including megathrust earthquakes (Mw8.8–9.2) from the Manila subduction zone (MSZ) and the 1918 Mw7.5 Nan'ao earthquake from the Littoral Fault Zone (LFZ) in the northern continental shelf of the SCS. We also utilize a reported tsunami deposit from Qing'ao Embayment, Nan'ao Island, China, to exemplify the deposit formation process in a typical barrier-low coastal plain system. Quantitative analysis suggests large earthquakes from the MSZ may account for the reported geological deposits. The full-rupture earthquake scenario could best explain the depositions if such extreme case is geophysically and geologically plausible. If not, earthquakes (∼ Mw 9.0) covering the northern (16–23.5°N) or southern portion (14–19°N) of the MSZ could also be suitable candidates. Such great earthquakes can generate large tsunami waves (>7 m) that inundate the Qing'ao Embayment, transporting sediments and leaving tsunami deposits in low-lying areas. Conversely, tsunamis triggered by nearshore earthquakes in the LFZ cannot cause deposition in Qing'ao Embayment. The barrier-low coastal plain system is well-suited for preserving tsunami deposits, which remain unaltered by subsequent tsunami waves. Our findings offer a quantitative reference for paleo-tsunami research in the SCS and enhance global understanding of the tsunami deposition process in barrier-low coastal plain systems.

Fault structure, seismicity, and magmatism of the Littoral Fault zone, northern South China sea: Insights from high-resolution seismic reflection data

Four destructive M7+ earthquakes and 18 M6+ earthquakes demonstrate that the Littoral Fault Zone (LFZ) is one of the most seismically active regions in the offshore area of South China. However, the location, geometry, and structural characteristics of the LFZ, which spans over 1000 km, have not been properly examined. In this study, we investigate the precise position of the LFZ offshore East Guangdong (EGD) and map the fault structure using recently acquired high-resolution multi-channel seismic (MCS) reflection data. The LFZ consists of an array of normal faults that collectively form a terraced sidewall fault zone linked to the continental rifting of the South China Sea (SCS). This fault zone is approximately 35–75 km wide and runs parallel to the shoreline. The primary faults of the LFZ EGD segment correlate to a high-gravity gradient zone and serve as the northern boundary of the Zhu-I Depression. During the syn-rift phase, the LFZ experienced significant intra-plate deformation, resulting in fault throws of up to 1000 m. This deformation was locally influenced by pre-existing structures, giving rise to a listric geometry at depth. In the post-rift period, the LFZ exhibited inherited activity along its rift-related faults. The presence of growth fault structures suggests that the LFZ remained active throughout the Cenozoic, with numerous active faults extending practically to the seafloor. The negative flower structure confirms the strike-slip character of the LFZ, which is influenced by the modern tectonic stress field. Intense multi-phase Cenozoic magmatism, including igneous intrusion, volcanism, and lava flows, has been detected in the offshore area of Nan'ao Island. The frequent earthquakes in the study area are primarily attributed to far-field stress release resulting from the subduction of the Philippine Sea Plate beneath the Eurasian Plate. Additionally, the intense magmatism weakens crustal structures, further facilitating stress release and the frequent occurrence of earthquakes.

Diversity, composition and ecological networks of bacterial communities in response to a full cultivation cycle of the seaweed, Gracilariopsis lemaneiformis

Cultivation of the seaweed, Gracilariopsis lemaneiformis, supports environmental bioremediation and the aquaculture economy in coastal ecosystems, and microorganisms play important roles during the cultivation process. In this study, we aimed to understand the response of bacterial communities through a full cultivation cycle of G. lemaneiformis. We analyzed the bacterial communities using 16S rRNA gene amplicon sequencing and defined the environmental factors of 144 water samples from the Nan'ao Island, South China Sea. Community diversity, keystone species and ecological networks of bacterial communities shifted markedly in the cultivation zone largely due to changes in the environmental factors, seaweed biomass and cultivation stages. The bacterial communities at the seaweed zone have lower species richness, more seaweed-associated taxa and simpler but more stable co-occurrence networks compared to the control zone. Persistent microbial groups such as Aquimarina, Formosa, Glaciecola and Marinobacter exhibited a strong association with seaweed during the growth and maturity stages. We describe a conceptual model to summarize the changes in the bacterial community composition, its diversity and the ecological networks in seaweed cultivation zone. Overall, this study provides new perspectives on the dynamic interaction of seaweed cultivation, bacterial communities and environment factors and their potential ecosystem services as observed in the example of the G. lemaneiformis cultivation ecosystem.

Geochronology and geochemistry of Early Cretaceous high-silica granites in the Nan’ao Island, South China: Petrogenesis and implications for lithospheric extension

Geochronology and geochemistry of Early Cretaceous high-silica granites in the Nan’ao Island, South China: Petrogenesis and implications for lithospheric extension

Migratory movements and foraging grounds of endangered green sea turtles in South China Sea based on satellite telemetry during fishing moratorium

The insights gained from individual tracking can improve the conservation of released young green sea turtles by providing detailed data on migration route, feeding place and habitat distribution. During the fishing moratorium from May 1 to August 16 in 2021, we used satellites to track 6 juvenile green sea turtles released from China’s Huidong Sea Turtle Nature Reserve, and located and reconstructed their migration routes and foraging sea areas. The tracking data shows that the longest tracking time is 91 days, the shortest time is 10 days, and the total tracking time is 213 days, of which three (50%) obtained tracking data for more than one month, and the total movement distances (statistics LC3-LCB) ranges from 124 to 4627 km, while the accurate movement distances (counted by dot pitch above LC0) ranged from 39.5-2331 km. The average daily movement distances ranges from 3.95 to 51.4 km, and the average speed varies between 0.16 to 2.14 km/h. The green turtles released from the China Turtle Bay migrate along the northern coastline of the South China Sea or go straight to the South China Sea. After a month or so, they migrate from Huidong Turtle Bay to Hainan Lingao, Beibu Gulf and Xisha Islands. The northern coast of the South China Sea is one of the migration routes of green sea turtles. Beibu Bay, Zhanjiang Port, Daya Bay, Red Bay, Nan’ao Island, Zhelin Bay and Xisha Islands are important foraging places for green sea turtles. The protection of migration routes and important foraging grounds is one of the key measures to protect sea turtles.

Marketing Strategy of Island Tourism Development under Coronavirus Epidemic Marketing Strategy of Island Tourism Development under Coronavirus Epidemic case study of Nan'ao Island in China

Affected by the new coronavirus pneumonia from the year 2019 to 2022, the economic development of the tourism industry was bleak. According to data released by the Ministry of Culture and Tourism, domestic tourism revenue in 2019 was 5.73 trillion yuan. In 2020, under the impact of the epidemic, the domestic tourism market has entered a low stage, with annual domestic tourism revenue of 2.23 trillion yuan, down 61.07 % year-on-year. Judging from the situation of people's travel in recent years, the development of tourism is growing. Under the epidemic, the tourism industry was pressed the pause button and the expected recovery is full of uncertainty. The epidemic has brought great challenges to the tourism industry, but it is not impossible to break through. This will be a good time for transformation and upgrading. If the tourism industry wants to make more stable and better pace of development, more intelligent information construction services need to be created into it in order to achieve breakthrough and develop characteristic products. In the era of marine economy in the 21st century, island tourism is an important part of the marine industry group. It is favored because it gives tourists a psychological feeling of staying away from the hustle and bustle of the city and returning to nature completely. The island has become a popular attraction in the world. In view of this, it is of great significance to summarize the research on island tourism. Taking Nan'ao Island in Guangdong as an example, this paper analyzes the existing problems of island tourism and formulates corresponding marketing strategies, aiming at improving its competitiveness in the travel industry and forming differentiated competitive advantages.

Two new species of genus Tripyloides (Nematoda, Enoplida, Tripyloididae) from the Chinese sea area

Abstract Two new free-living marine nematode species of genus Tripyloides were discovered in intertidal sediments along Rudong coast of the Yellow Sea and on Qi′ao Island of the South China Sea, respectively. They are described here as Tripyloides conicus sp. nov. and Tripyloides boucheri sp. nov. T. conicus sp. nov. is characterized by outer labial setae two-segments, amphideal fovea circular, buccal cavity with four chambers and with a distinct tooth at the bottom, spicules slender and straight, gubernaculum kidney-like with two lateral denticles at distal end, tail sexual dimorphism (elongated conical in males, conico-cylindrical in females). T. boucheri sp. nov. is characterized by body size small, outer labial setae stout, two-segments, amphidial fovea small, circular, narrow conical buccal cavity without distinct tooth, male with papilliform precloacal supplements, spicules slender, gubernaculum with two lateral denticles at distal end, tail conico-cylindrical and not swollen terminally. An updated dichotomous key for fifteen species of the genus is also given.

Holistic Impact Evaluation of Human Activities on the Coastal Fish Biodiversity in the Chinese Coastal Environment.

Ecological qualities and resources in coasts are threatened by various human activities, such as pollution and fishery. Impact evaluation of environmental stressors over a wide coastal stretch has been limited due to lack of efficient and standardizable biodiversity monitoring and assessment tools. Integrating environmental DNA (eDNA) and ecological traits, a holistic approach was developed to assess the impact of pollution and aquaculture on fish biodiversity in Chinese coastal areas. Taking the Yalujiang Estuary (YLJK) from the Yellow Sea and the Nan'ao Island Area (NAO) from the South China Sea as cases, the performance of the eDNA biomonitoring workflow was validated. First, the eDNA results of 22 sampling sites reached more than 85% of the asymptotes of species or ASVs in each area. A total of 115 fish species in both areas were detected and NAO was 1.8 times richer than YLJK using eDNA and the fish eDNA composition was consistent with the historical data. eDNA recovered distinct variations of fish sequence, taxonomic and functional diversity, and the corresponding trends following the offshore distance between the two areas. Fish sequence diversity was decreased primarily by estuarine pollution factors (chemical oxygen demand and zinc) in the YLJK. Compared with no breeding areas, lower fish sequence diversity was in breeding areas in the NAO. By integrating ecological traits, the eDNA approach offers promising opportunities for future fish biodiversity monitoring and assessment in national and global coastal environments.

The environmental adaptability and reproductive properties of invasive green alga Codium fragile from the Nan’ao Island, South China Sea

The environmental adaptability and reproductive properties of invasive green alga Codium fragile from the Nan’ao Island, South China Sea

Selection of the Most Scenic Viewpoints on an Island Based on Space-Time Perception: The Case of Nan'ao Island, China.

Selecting the most scenic viewpoints in an island forest park can provide a scientific basis for island ecotourism planning. In this paper, considering the influence of climatic conditions on sightseeing, landscape factors, accessibility factors, and seasonal change factors are selected from the perspective of time and space to analyze the landscape spatiotemporal characteristics, and the construction of a landscape spatiotemporal perception evaluation model and the analysis of influencing factors are carried out. The results show that the evaluation model for landscape spatiotemporal perception factors can quantitatively describe tourists’ comprehensive perception of a landscape in different regions and time periods in ecotourism areas, and can identify the spatiotemporal characteristics of landscape perception. Case studies preliminarily prove the feasibility of the model and calculation process. This method provides a strong reference for the development and planning of island tourism, especially providing new ideas and methods for the design of sightseeing routes in the development and planning of small-scale scenic viewpoints, which can enrich island tourism planning.

Dietary exposure assessment of paralytic shellfish toxins through shellfish consumption in Shenzhen population, China.

Paralytic shellfish toxins (PSTs) produced by certain marine dinoflagellates accumulate in filter-feeding marine bivalves. We used LC-MS/MS to detect and quantify 13 PSTs in 188 shellfish samples of 14 species collected from Shenzhen city's Buji seafood wholesale market from March 2019 to February 2020. Twenty-six of 188 shellfish samples (13.8%) were PSTs detectable. Within 14 species, 10 out of 34 noble clam Chlamys nobilis samples contain detectable PSTs with the highest detection rate 29.4%. Seven out of 17 samples from Nan'ao island contained detectable PSTs with the highest detection rate 41.2% among 11 origins. Samples containing PSTs were concentrated in spring and winter, with the highest levels in March>December>January. Among PSTs detected, C1 was dominant. Acute dietary exposure assessment for Shenzhen residents were based on mean adult body weight, 99th percentile daily shellfish consumption of Shenzhen food consumption survey 2008 and maximum PSTs concentration for each shellfish species. The outcome for Chlamys nobilis was 2.4~3.7-fold higher than recommended ARfDs. Mean PSTs concentration, P99, and mean shellfish consumption were used to assess chronic dietary exposure. The results were lower than recommended ARfDs. In conclusion, residents in Shenzhen are at risk for acute PSTs poisoning, while relatively safe from chronic PSTs exposure.

Impacts of coastal aquaculture on sedimentary phosphorus speciation and fate: Evidence from a seaweed cultivation area off Nan'ao Island, South China

How aquaculture impacts the coastal phosphorus (P) cycle remains poorly understood. Here we compared different P species from two sedimentary records off Nan'ao Island, South China, with core S1 collected in a large seaweed cultivation area and core S2 in a non-mariculture area. The results showed that the concentration of total P (TP) in sediment cores varied from 143.67 to 400.92 μg/g, and organic P (OP) was the dominant P species. The TOC/OP ratios in the two sediment cores were higher than the Redfield ratio in 26 samples (52%) from core S1 and 39 samples (78%) from core S2, suggesting that terrestrial organic matter was an important carbon source to Shen'ao Bay. The lack of change in Ex-P (exchangeable or loosely sorbed P) and OP in the area around core S1 since the 2000s may be due to the large-scale seaweed cultivation.

Environmental factors shape the epiphytic bacterial communities of Gracilariopsis lemaneiformis

Macroalgae host various symbionts on their surface, which play a critical role in their growth and development processes. However, there is still incomplete understanding of this epiphytic bacteria-host algae interactions. This study comprehensively analysed variation of the epiphytic bacterial communities (EBC) composition of red macroalga Gracilariopsis lemaneiformis at different geographic locations and environmental factors (i.e., nitrogen and phosphorus), which shape the EBC composition of G. lemaneiformis. The composition and structure of EBC were characterized using high throughput sequencing of the V3-V4 hypervariable region of the 16S rRNA gene. The results revealed that epiphytic bacteria varied significantly among three different geographic locations in China, i.e., Nan’ao Island (NA), Lianjiang County (LJ), and Nanri Island (NR). Redundancy analysis (RDA) showed that the relative abundance of Bacteroidetes, Firmicutes, Verrucomicrobia, and Epsilonbacteraeota at NR were strongly positively correlated with total nitrogen (TN), total phosphorus (TP), nitrate nitrogen (NO3-N), and dissolved inorganic nitrogen (DIN), but negatively correlated with nitrite nitrogen (NO2-N). The relative abundance of Cyanobacteria at NA and LJ were strongly positively correlated with NO2-N, but negatively correlated with TN, TP, NO3-N, and DIN. Besides, the Mantel test results indicated that the EBC composition was significantly correlated with these environmental factors, which was also confirmed by Spearman correlation analysis. Thus, environmental factors such as NO3-N and DIN play a key role in the community composition of epiphytic bacteria on G. lemaneiformis. This study provides important baseline knowledge on the community composition of epiphytic bacteria on G. lemaneiformis and shows correlation between different epiphytic bacteria and their surrounding environmental factors.

Effects of tidal zones and seasons on nutritional properties of commercially importance gastropods

Gastropods are important protein sources for coastal communities. This study performed a case study in Nan'ao Island to compare the spatial and temporal variations of lipids, proteins, carotenoids and antioxidant capacity of commercially important gastropods. Seven commercially important gastropods were identified from the rocky shores of Nan'ao Island. All the gastropods analysed had medium to high fat, low protein, and a considerable amount of total carotenoids. From low tide zone to high tide zone, the total antioxidant capacity of gastropods increased dramatically. In terms of fatty acid composition, all analysed gastropods had PUFA/SFA >0.45, but only three species had n-3/n-6 >1.00. In conclusion, some gastropods, especially Lunella coronata coreensis and Monodonta labio, have good nutritional value and potential health effects. This study is the first comprehensive assessment of the nutritional properties of commercially important gastropods in different rocky shore microenvironments and different seasons.

Diatom assemblages from sediment traps in response to large seaweed Gracilaria cultivation off Nan'ao island, South China

Most previous studies on seaweed bioremediation largely focus on laboratory control tests or short-time, in-situ field experiments. Here we present a dataset from 4-year-long field monitoring (2014–2018) in a mariculture area of the Baisha Bay off Nan'ao Island, South China, attempting to examine how the large seaweed Gracilaria lemaneiformis cultivation affects a mariculture ecosystem. The temporal variation in seawater physicochemical properties (TN, TP, Reactive silicate, CODMn, and chlorophyll α) and sediment proxies (TN and TP) suggest that the Baisha Bay maintained a better water quality during the Gracilaria cultivation periods (December–May) than other months. Additionally, sedimentary diatom assemblages during the Gracilaria cultivation periods showed an increase in Shannon-Wiener values, but a decrease in the dominant Thalassionema nitzschioides abundance, total diatom abundances and P/(A + B) ratios [Planktonic/(Attached + Benthic)]. These changes consistently suggest that Gracilaria cultivation may have helped improve seawater quality and phytoplankton diversity, thereby maintain a healthy mariculture ecosystem.

Characteristics of expanded polystyrene microplastics on island beaches in the Pearl River Estuary: abundance, size, surface texture and their metals-carrying capacity.

While expanded polystyrene (EPS) microplastics have been widely recognized as one of the most important components of plastic litter in the intertidal zones of the global ocean, our understanding of their environmental fate on island beaches is insufficient. In this study, we intended to reveal that the latest EPS microplastic pollution status on 5 island beaches in the Pearl River Estuary, China, by comprehensively assessing the abundance, distribution, size, surface texture and carrying capacity of heavy metals (Cd, As, Cr, Ni, Cu, Pb, Mn, Fe, Al). High level of EPS microplastic abundance ranged from 328 to 82,276 particles m-2 was found, with the highest abundance at Guishan Island and the lowest at Dong'ao Island. Spatial distribution of EPS microplastic abundance was significantly different among different islands. EPS microplastics in the size range of 1-2 mm were the most abundant. The content of heavy metals in EPS microplastics collected on the beaches was greater than that in the new EPS products. The average concentrations of heavy metals in EPS microplastics from 5 islands are Cd (0.27 ± 0.19 μg g-1), As (5.50 ± 3.84 μg g-1), Cr (14.9 ± 8.25 μg g-1), Cu (15.0 ± 7.66 μg g-1), Ni (17.2 ± 17.6 μg g-1), Pb (24.8 ± 7.39 μg g-1), Mn (730 ± 797 μg g-1), Fe (8340 ± 4760 μg g-1), and Al (9624 ± 6187 μg g-1), respectively. The correlation between heavy metals in EPS microplastics and sediments was better than that between heavy metals in EPS microplastics and seawater. The study results indicated that EPS microplastics could act as a carrier for the transport of heavy metals, which might pose a threat to biological and human health.

Maritime trade of Nan'ao Island in Guangdong in the mid-16th century

Maritime trade of Nan'ao Island in Guangdong in the mid-16th century

Gayliella nanaoensis sp. nov. (Ceramiaceae, Rhodophyta) from China

ABSTRACT Because morphological variation in Gayliella species is extensive, a molecular-assisted taxonomic approach is essential for accurate species identification. In China, six Gayliella species have been recorded, but no molecular-assisted identification has been used. In this study, we used detailed morphological analyses combined with rbcL and cox1 sequence analyses to identify Gayliella specimens from Nan’ao Island, Shantou city, China. Morphological analyses revealed that our specimens can be distinguished from other species of Gayliella by a combination of morphological characters: branching at intervals 4(–5) on main axes, 4–6 on lateral axes; five periaxial cells; short basipetal corticating filaments only 1–2 cells long; ovoid gland cells developed from periaxial cells; and tetrasporangia whorled at a node. Molecular sequence analysis also revealed sufficient sequence divergence between our specimens and other Gayliella species to separate them. Therefore, based on combined morphological and molecular analyses, we describe the specimens from Nan’ao Island, Shantou city, China, as Gayliella nanaoensis sp. nov.

Potential causative factors of noble scallop Chlamys nobilis mass mortality in Nan'ao Island, Shantou, China in 2017

Noble scallop Chlamys nobilis is an important marine bivalve that has been extensively cultured in the south coast of China since the 1980s. Unfortunately, since the late 1990s, the farmed scallops often suffered from regional mass mortality, which results in enormous economic losses to farmers and industries. In 2017, another mass mortality event occurred in Nan'ao Island, Shantou, China. In this study, the cause of C. nobilis mass mortality in 2017 was first investigated in the field, and then validated in a laboratory experiment. In the field, three sampling sites were selected according to the scallop mortality rate: Hunter Bay (90% mortality), Baisha Bay (67% mortality) and Longhai (6% mortality). Meanwhile, environmental parameters (temperature, salinity, DO, pH and chlorophyll a) of each site were also measured in situ. Then, water and scallop samples were collected randomly for the analysis of phytoplankton diversity and algal toxin activity using 18S rDNA and PP2A inhibition assay, respectively. In laboratory, healthy scallops were challenged with Karenia mikimotoi (1 × 103 cells/mL) for 30 h. The field results showed that no significant difference in those environmental parameters existed among the three sites, but the relative abundance of K. mikimotoi in seawater and scallops' intestines in Hunter Bay and Baisha Bay was significantly higher than that in Longhai, and sick scallops contained significantly higher algal toxin activity than healthy ones. Laboratory results revealed that challenged scallops with K. mikimotoi showed significantly higher mortality rate and algal toxin activity than healthy ones, and low density of K. mikimotoi (1 × 103 cells/mL) was sufficient to cause >50% scallops' mortality within 26 h. This study provides the first evidence that low K. mikimotoi cell density can cause massive mortality in C. nobilis, and provides useful information as guide to prevent scallop mass mortality in the future.