Zhoushan Archipelago Research Articles

Spatiotemporal Changes and Utilization Intensity of the Zhoushan Archipelago Coastline over Four Decades

Coastal changes in China, notably in the Zhoushan Islands, have primarily been driven by coastal reclamation since the establishment of New China. This study conducted a comprehensive analysis of the Zhoushan Archipelago shoreline spanning four decades, employing remote sensing, aerial photographs, and shoreline data since 1984, along with GIS (Geographic Information System) technology. We assessed shoreline changes using the shoreline change index and shoreline artificialization index, as well as examined the influence of the Yangtze River’s suspended sediment and impoldering activities on Zhoushan’s shoreline. Furthermore, the correlation between local economic development and shoreline development was explored. The results revealed the following key findings: (1) From 1984 to 2018, the Zhoushan Archipelago shoreline decreased by 7.05 km. Temporally, the shoreline change index was −0.08%, with the most significant reduction occurring between 2008 and 2018. Spatially, differences among island groups were not pronounced. (2) The shoreline diversity index consistently increased, indicating greater diversity and complexity in shoreline use over the four decades. (3) The shoreline artificiality index steadily rose, particularly after 2000. It was highest in the south, followed by the center, and lowest in the north. (4) The intensity index of coastal land use continuously increased, with the southern island group having a higher index compared to the Zhoushan Islands. (5) The Yangtze River contributed significantly to sand inflow, influencing shoreline changes and beach shaping in Zhejiang. However, reclamation projects were identified as the primary and direct factor. (6) A positive correlation existed between Zhoushan City’s economic development and the intensity of coastal land use. This study emphasized the need for improving the control over reclamation projects and the better management of coastal protection and use. These measures could optimize resource allocation and establish a more scientific and rational coastal zone pattern.

Emergency Capability Evaluation of Port-Adjacent Oil Storage and Transportation Bases: An Improved Analytic Hierarchy Process Approach

The large-scale storage and stable supply of oil products are essential for national energy security and economic development. As the economy expands and energy demands rise, centralized storage and supply systems become increasingly vital for ensuring the efficiency and reliability of oil product distribution. However, large oil storage depots present substantial safety risks. In the event of fires, explosions, or other accidents, emergency response efforts face stringent demands and challenges. To enhance the emergency response capabilities of oil storage and transportation bases (OSTBs), this paper proposes an innovative approach that integrates the improved analytic hierarchy process (IAHP) with the Entropy Weight Method (EMW) to determine the combined weights of various indices. This approach reduces the subjective bias associated with the traditional analytic hierarchy process (AHP). The emergency response capabilities of OSTBs are subsequently evaluated through fuzzy comprehensive analysis. An empirical study conducted on an OSTB in the Zhoushan archipelago quantitatively assesses its emergency preparedness. The results show that the base excels in pre-incident prevention, demonstrates robust preparedness and response capabilities, and exhibits moderate recovery abilities after incidents. These findings provide a theoretical foundation for reducing the likelihood of accidents, enhancing emergency response efficiency, and mitigating the severity of consequences. Practical recommendations are also offered based on the results.

Impact on Local Economy from Zhoushan National New Area

To empirically study the policy impact of a National New Area on the local economy, this paper evaluates the effect of the Zhoushan Archipelago New Area on local GDP growth rate and economic efficiency. Firstly, the economic efficiency of 20 prefectural-level cities in Jiangsu, Zhejiang and Anhui provinces is estimated by data envelopment analysis with input and output data from 1995 to 2015. In selecting some cities except Zhoushan as a control group, we construct some counterfactuals of Zhoushan by a panel data approach. The difference between the actual and counterfactual values for the GDP growth rate and economic efficiency of Zhoushan is calculated and compared to conclude the treatment effect of the National New Area. The research shows that in the first four years, the policy of the National New Area promoted Zhoushan's economic quality by raising its efficiency, but relatively reduced its economic quantity by negatively affecting the local GDP growth rate. Then the policy influence on Zhoushan’s GDP growth rate and economic efficiency gradually disappeared after four years. Combining some other research on our study, we find that the policy effect on the GDP growth rate is related to the level of economic growth in these areas. The policy of the National New Area has less influence on GDP growth if approved in the developed region rather than in the undeveloped region. We think that it is better to set up a National New Area in a relatively undeveloped area.

Tracking dynamics characteristics of tidal flats using landsat time series and Google Earth Engine cloud platform

Tidal flats serve as vital spatial resources within coastal wetlands and play crucial roles in biological habitat preservation, environmental conservation, and human development. However, accurately delineating their extent from instantaneous remote sensing images poses challenges, owing to the dynamic interplay between seawater and land. Therefore, this study utilized the consistency of remote sensing satellites and developed a multi-feature decision approach based on the long-term remote sensing datasets and the Google Earth Engine (GEE) cloud platform for determining the spatial extent, classifying types, and mapping the spatial-temporal distribution of the tidal flats. Initially, a multi-temporal image stack was compiled from the filtered remote sensing images. Subsequently, the modified normalized difference water index (MNDWI) and automated water extraction index (AWEI) were calculated to establish the maximum and minimum water surfaces using the extreme value composite algorithm (EVCA). The Otsu algorithm and spatial overlay analysis method were then utilized to accurately delineate the spatial extent of the tidal flats. Additionally, the Normalized Difference Vegetation Index (NDVI) was utilized to accurately identify tidal flat types. Post-processing involves elevation data and mathematical morphological methods to mitigate the impact of permanent water bodies. Finally, the accuracy of the extracted spatial extent and types of tidal flats was evaluated. The efficacy and practicality of the proposed method were validated using the Zhoushan Archipelago and Landsat time series in China. The results revealed the following: (1) the acquired tidal flat information exhibited evident boundaries and accurate types, achieving an overall accuracy (OA) of 94.80 % and a Kappa coefficient of 0.89; (2) the area of tidal flats in the Zhoushan Archipelago increased from 2,182.19 ha in 1985 to 3,761.21 ha in 2020, with an average annual increase of 45.12 ha and an average annual increase rate of 1.57 %; and (3) over 35 periods, the area transformed from other land types to tidal flats amounted to 2,895.74 ha, while the area converted from tidal flats to other land types totaled 1,651.90 ha. The three islands with the most rapid growth in tidal flat area were Liuheng Island, Dachangtu Island, and Daishan Island, with changes of 675.68 ha, 380.47 ha, and 362.63 ha, respectively. This method can offer an automated, swift, and accurate approach for tidal flat extraction, demonstrating high precision and practical effectiveness, thereby providing robust technical support for coastal resource surveys.

EDNA Metabarcoding Reveals the Species-Area Relationship of Amphibians on the Zhoushan Archipelago.

The species-area relationship is important for understanding species diversity patterns at spatial scales, but few studies have examined the relationship using environmental DNA (eDNA) techniques. We investigated amphibian diversity on 21 islands of the Zhoushan Archipelago and nearby mainland areas in China using the combination of eDNA metabarcoding and the traditional line transect method (TLTM) and identified the species-area relationship for amphibians on the islands. The mean detection probability of eDNA is 0.54, while the mean detection probability of TLTM is 0.24. The eDNA metabarcoding detected eight amphibian species on the islands and nine species in the mainland areas, compared with seven species on the islands and nine species in the mainland areas that were identified by TLTM. Amphibian richness on the islands increased with island area and habitat diversity. The species-area relationship for amphibians in the archipelago was formulated as the power function (S = 0.47A0.21) or exponential function (S = 2.59 + 2.41 (logA)). Our results suggested that eDNA metabarcoding is more sensitive for the detection of amphibian species. The combined use of eDNA metabarcoding and the traditional line transect method may optimize the survey results for amphibians.

Biogeographic effects shape soil bacterial communities across intertidal zones on island beaches through regulating soil properties

Island coastal zones are often mistakenly perceived as “ecological desert”. Actually, they harbour unique communities of organisms. The biodiversity on islands is primarily influenced by the effects of area and isolation (distance from the mainland), which mainly focused on plants and animals, encompassing studies of entire islands. However, the application of area and isolation effects to soil microorganisms on island beaches across the intertidal zones remains largely unexplored. We hypothesized that island area and isolation shape soil bacterial communities by regulating soil properties on island beaches, due to the fact that local soil properties might be strongly influenced by land-use, which may vary among islands of different sizes and isolations. To test this hypothesis, we conducted a study on 108 plots spanning 4 intertidal zones on 9 representative island beaches within Zhoushan Archipelago, eastern China. We employed one-way ANOVA and Tukey's honestly significant difference (HSD) test to assess the differences in diversity, composition of soil bacterial communities and soil properties among intertidal zones. Redundancy analysis and structural equation modelling (SEM) were used to examine the direct and indirect impacts of beach area and isolation on soil bacterial communities. Our findings revealed that the area and isolation did not significantly influence soil bacterial diversity and the relative abundance of dominant soil bacterial phyla. However, soil nitrogen (soil N), phosphorus (soil P), organic carbon (SOC), available potassium content (soil AK), and electrical conductivity (soil EC) showed significant increases with the area and isolation. As the tidal gradient increased on beaches, soil bacterial OTU richness, Chao 1, and relative abundance of Planctomycetota and Crenarchaeota decreased, while relative abundance of other soil bacterial phyla increased. We found that influences of island area and isolation shape soil bacterial communities on beaches by regulating soil properties, particularly soil moisture, salinity, and nutrients, all of which are also influenced by area and isolation. Island with larger areas and in lower intertidal zones, characterized by higher soil water content (SWC), soil EC, and soil AK, exhibited greater soil bacterial diversity and fewer dominant soil bacterial phyla. Conversely, in the higher intertidal zones with vegetation containing higher soil N and SOC, lower soil bacterial diversity and more dominant soil bacterial phyla were observed. These findings have the potential to enhance our new understanding of how island biogeography in interpreting island biome patterns.

Mapping the distribution and dynamics of coastal aquaculture ponds using Landsat time series data based on U2-Net deep learning model

ABSTRACT The extraction of coastal aquaculture ponds from remote sensing images is affected by the effect of ‘same object with different spectrums’ and ‘different objects with same spectrums’. The U2-Net deep learning network is able to capture more contextual information from different scales to solve this problem and is suitable for salient object detection. This study proposed a remote sensing information extraction model of coastal ponds based on U2-Net deep learning network, completed the remote sensing information extraction of coastal aquaculture ponds in Zhoushan Archipelago from 1984 to 2022, analyzed the spatiotemporal evolution of coastal aquaculture ponds in Zhoushan Archipelago. The results showed that the developed model was more accurate with a precision rate of 96.12%, a recall rate of 95.43%, and an F1-measure of 0.96. During the study period, the area of the aquaculture ponds in the Zhoushan Archipelago demonstrated an increasing trend, expanding from 471.21 hm2 in 1984–3668.55 hm2 in 2022. In addition, over half of the aquaculture ponds had been active for more than 10 years. The method developed in this study is capable of rapidly and accurately mapping coastal aquaculture ponds, and thus is significant for the management of marine resources and promoting sustainable development.

City-scale methane emissions from the midstream oil and gas industry: A satellite survey of the Zhoushan archipelago

As the second most abundant greenhouse gas after carbon dioxide, methane (CH4) leakage and emissions pose potential climate threats and environmental problems in the midstream oil and gas storage and transportation (OGST) industry. In this study, the Tropospheric Monitoring Instrument on the Sentinel-5P satellite was adopted to investigate the coverage of atmospheric CH4 concentrations over the Zhoushan archipelago, which is China's largest OGST base. Specifically, the distribution of atmospheric CH4 and nitrogen dioxide (NO2) concentrations over Zhoushan in August 2022 and August 2023 were evaluated, where changes in concentrations around the OGST companies were monitored. Using surface temperature inversion and average temperature statistics, we analyzed the heat island effect in Zhoushan. The results showed that: (1) although there is limited valid data (>200 pixel/day) for Zhoushan, the amount of valid data increased from 3.2% in January 2020 to 32.3% in August 2023; (2) around the region of the OGST companies, the atmospheric CH4 concentration shown significant variation at both the spatial and temporal scales, which may be due to the storage, loading, and unloading of petroleum products; (3) under geographic isolation conditions, NO2 can be used as a tracer gas to track the CH4 emissions from OGST companies; and (4) Surface temperature analysis underscores OGST companies' contribution to Zhoushan's urban heat island effect, with local average temperature increases outstripping broader national trends, highlighting the intricate interplay of human and natural factors in the city-scale climate dynamics.

Taxonomic, phylogenetic, and functional nestedness of mammal assemblages in the Zhoushan Archipelago, China

Abstract Nestedness is an important part of the theoretical framework of island biogeography and community ecology. However, most previous studies focused on taxonomic dimension and overlooked functional and phylogenetic nestedness. Here, we simultaneously investigated taxonomic, functional, and phylogenetic nestedness of terrestrial mammals on 39 land-bridge islands in the Zhoushan Archipelago, China. As mammals’ response to the environment may depend on their body size, we performed analyses for three mammal assemblages separately: overall species, large and medium-sized species, and small species. The taxonomic nestedness was quantified by organizing the species incidence matrix, while the functional and phylogenetic nestedness were estimated by combining the similarity of their ecological traits and phylogeny. Island characteristics (island area, three isolation indices, land use intensity, and habitat diversity) and species traits (body size, litter size, habitat specificity, geographic range size, and minimum area requirement) were used as predictors of nestedness. Overall and small species were significantly nested in 3 facets of nestedness, and results supported the selective extinction, selective colonization, and habitat nestedness hypotheses. Large and medium-sized species were functionally and phylogenetically nested when matrices were ordered by increasing distance to mainland, supporting the selective colonization hypothesis. Overall, differences in nestedness and its underlying mechanisms were detected not only in 3 facets of nestedness but also in the 3 mammal assemblages. Therefore, frameworks that incorporate taxonomic, phylogenetic, and functional nestedness can contribute to a more comprehensive understanding of nestedness processes. Additionally, it also improves our ability to understand the divergent responses of mammal assemblages to the insular environment.

Examining the Social Costs of Carbon Emissions and the Ecosystem Service Value in Island Ecosystems: An Analysis of the Zhoushan Archipelago

Assessments of the ecosystem service value (ESV) and the social cost of carbon (SCC) inform national and government management decisions in the areas of human well-being and climate change mitigation and adaptation, respectively. Studying the correlation between the two provides a theoretical basis for low-carbon and high-quality regional development, achieving economic decarbonization, and improving human well-being. In this study, we take Zhoushan Archipelago as a case study, consider the ESV and SCC in Zhoushan Archipelago during the period 2010–2020, analyze their spatial development characteristics, and analyze the correlation between the two in time and space. The findings indicate that, with only a 1.5% change, the overall ESV in the Zhoushan Archipelago fell between 2010 and 2020. Conversely, there was a 1604.01 × 104 t increase in net carbon emissions and a quick 2452% increase in SCC. During the study period, a substantial positive association was found between ESV and SCC in the Zhoushan Archipelago, according to the global spatial correlation analysis of the two variables. It passed the test for p-value. This study presents a new potential way to solve the environmental and economic difficulties caused by climate change by providing a mechanism for quantitatively assessing the environment from the perspective of monetary worth. In order to improve the ecological security pattern and ease the burden of regional carbon emissions, it is vital to make use of regional advantages, maintain forests, and develop blue-carbon resources such as mudflats. It is a good idea to cooperate regionally with nearby metropolitan agglomerations. The study’s findings are crucial for advancing sustainable development planning in the Zhoushan Archipelago, both theoretically and practically.

Impact of sea level rise on tidal energy budget in a macro-tidal coastal bay with archipelago

With sea level rise (SLR), tidal nuisance flooding has become a growing threat, especially around estuaries with large tidal amplitudes. This study investigated how sea level change affects tides in Hangzhou Bay, a macro-tidal estuary with high SLR rate. By downscaling climate projections to a regional hydrodynamic model, the amplitude of primary tidal constituent (M2) was predicted to increase by 0.25 m in the upper bay, where the amplitude of major diurnal tide (K1) was also predicted to increase by 15%. In addition, the sensitivity of tidal amplitude to mean sea level was examined by a set of numerical simulations with different SLR. It was found that the increase of tidal amplitude is nonlinear to SLR, and the tidal amplitudes almost cease to increase when SLR is over 1.5 m. Although predictions show less amplitude changes in the lower bay, Zhoushan Archipelago around the bay mouth strongly modulates the incoming tidal energy, thus affecting the tidal amplitude in the upper bay. Energy budget analysis revealed that the complex topography, such as narrow channels, in the archipelago area leads to strong horizontal shear, which dissipates approximately 25% of total tidal energy in the bay. On the other hand, around 60% of the energy is dissipated in the bottom boundary layer. However, the bottom dissipation decreases by 4% due to reduced friction, while horizontal dissipation increases by 10% due to enhanced horizontal shear with SLR. This suggests that the strong horizontal shear in the Zhoushan archipelago region can play a more important role in the tidal energy budget in the future.

Exploring the Relationships between Tradeoffs and Synergies among Island Ecosystem Service Bundles: A Study on Zhoushan Archipelago Located on the Southeast Coast of China

Due to the rapid rise of China’s coastal economic zone, the urbanization of the surrounding islands has accelerated. Intensive disturbance caused by human activities and frequent changes in land types have resulted in the continuous erosion of ecological sources and the degradation of ecosystem services on the islands year by year. It is particularly important to explore sustainable development strategies for the islands to achieve a balance between conservation and development, which is particularly important for the islands in the process of urbanization. Taking Zhoushan Archipelago as an example, this paper uses multi-source spatial data and employs InVEST models and USLE to quantify island ecosystem services. Furthermore, using principal component analysis and cluster analysis, the study aims to identify clusters of island ecosystem services and investigate their tradeoffs, synergistic mechanisms, and regional heterogeneity using spatial analysis. In addition to providing island urban planners with effective zoning governance recommendations and assistance in spatial planning to promote coordinated and sustainable development, the findings of this study can assist in the development of appropriate management plans for each ecological functional service cluster on islands.

Tidal current energy resources assessment in Zhoushan Archipelago, China

ABSTRACT Zhoushan Archipelago, the largest archipelago in China, harbors a significant tidal stream resource due to robust tidal currents coursing through numerous channels between its islands. Nevertheless, the tidal energy resource in the Zhoushan Archipelago has not been systematically characterized considering both topography and energy flow density. This study presents a modeling study aimed at characterizing the tidal energy resource in the whole Zhejiang coast, including Zhoushan Archipelago, employing a high-resolution tidal hydrodynamic model, i.e. MIKE 21. Through a comparison of the model output with observed data from two tidal stations and three current stations, the accuracy of the numerical model was confirmed. The study identified areas with robust currents and suitable water depths, both essential factors for the advancement of tidal current energy. The findings showed that many channels in Zhoushan Archipelago and Wenzhou Bay in Zhejiang experience the highest tidal power density, reaching nearly 5500 W/m2. Furthermore, the study estimated the theoretical tidal current energy production for the whole area, highlighting Loutou channel, Cezi channel, Taohuagang, and the channel between Xiushan island and Daishan island as regions with high potential.

Tracing magmatic differentiation of peralkaline granites by using K stable isotopes

The genesis of peralkaline granites has fundamental implications for understanding their source characters and tectonic settings, yet it remains highly controversial after decades of research. Two major challenges in studies of peralkaline granites are how the peralkaline magmas evolve and how to trace their magmatic evolution. Here we use K isotopes in granites from Zhoushan archipelago of southeast China to explore these two issues. The Zhoushan archipelago hosts two groups of Cretaceous high-silica granites, which are the peralkaline rocks (PAG) and the calc-alkaline rocks (CAG). The CAG rocks exhibit a small variation (δ41K = −0.54 ± 0.06 ‰ to −0.36 ± 0.06 ‰) in K isotopic compositions, in contrast to the larger variation for the PAG rocks (δ41K = −0.67 ± 0.07 ‰ to −0.27 ± 0.05 ‰). The PAG rocks show strong correlations between δ41K values and various whole-rock major elements (i.e., Al2O3, Na2O, and K2O contents), but these correlations are absent for the CAG rocks. We propose that the separation of Na-rich alkali-feldspar, rather than low-Na alkali-feldspar and/or plagioclase, controlled the K isotope variability in PAG. The alkali-feldspar in PAG is enriched in Na, among which the alkali-feldspar with Or (orthoclase; mol. %) <15 is characterized by high δ41K ranging from −0.34 ‰ to 0.36 ‰. Geochemical modeling demonstrates that 23–33 % fractional crystallization of such Na-rich alkali-feldspar is required to generate the geochemical trends observed in PAG. Those findings suggest that crystallization of Na-rich alkali-feldspars dominates the magma evolution for peralkaline magmatism, supporting strong fractional crystallization in high-silica peralkaline magma. K isotopes show promise to trace detailed magmatic processes and provide constraints on the generation of peralkaline granites.

Mantle-like to low oxygen isotopes in zircon from the mid-Cretaceous high-silica granites reveal unweathered basement recycling along the present coastal area of SE China

Zircon oxygen isotope compositions can provide potential constraints on the origin of granitic magmas. In this work, we report new data of zircon UPb dating, trace elements and HfO isotopes for two types of mid-Cretaceous high-silica granites from Zhoushan archipelago in Zhejiang Province, SE China. The in-situ zircon data are carefully screened for radiation damage and post-magmatic alteration. The analyzed magmatic zircon grains indicate that the Zhoushan calc-alkaline granites (ZCAG; 101–92 Ma) have mantle-like δ18O values of 5.29–5.88 ‰, in contrast to the Zhoushan peralkaline granites (ZPAG; 91–89 Ma) with relatively low δ18O of 4.42–4.6 ‰. The slight decreases in δ18O and εHf(t) from zircon center to periphery of both groups suggest that they may have consistent oxygen isotopic compositions in their parental magma sources and have gone through assimilations to hydrothermally altered wall rocks in the shallow crust. The mantle-like δ18O values in zircon are widespread in the Cretaceous felsic rocks in the present coastal area of SE China, which, in combination Hf isotopes, indicates the possible existence of a buried unweathered Proterozoic basement in the eastern part of the Cathaysia Block. This work highlights the role of deep crustal magma sources, assimilation and post-magmatic radioactive damage on the formation of mantle-like to low δ18O signals in zircons, and has fundamental implications for understanding the formation of widespread mid-Cretaceous felsic rocks along the present coastal area of SE China.

The recovery process of the coastal mud after being sheared by external loads

In muddy coastal regions, wave-seabed interaction highly depends on the mud's rheological properties, which usually exhibit thixotropic behaviors and are closely related to the recovery of the mud. To investigate the recovery process, a series of rheological experiments were conducted on the mud samples collected from the tidal flats of the Zhoushan Archipelago. After being sheared by external loads, the mud storage modulus recovers to an equilibrium value (G∞′), and the normalized equilibrium storage modulus (G∞′/G0′) was utilized to access the structural level of the recovered mud. The effects of the magnitude, frequency, and duration of the shear load on the recovery process of the mud were investigated. Experimental results revealed thatG∞′/G0′ increases with the load magnitude and eventually reaches a constant value, regardless of the density of the mud.G∞′/G0′ is insensitive to load frequencies lower than 4 Hz when the load magnitude is below the fluidic yield stress of the mud. When load magnitude exceeds the fluidic yield stress,G∞′/G0′ decreases monotonically with frequency.G∞′/G0′ is insensitive to shear durations over O(10 s) since the internal structures were destroyed within seconds. Overall, this study offers novel insights into the rheological properties of coastal mud that provide valuable scientific support for understanding wave-mud interaction and fluid mud formation processes.

Measuring the Multi-Scale Landscape Pattern of China’s Largest Archipelago from a Dual-3D Perspective Based on Remote Sensing

Measuring the landscape pattern from a three-dimensional perspective is of great significance for comprehensively revealing the complex spatial characteristics of island ecosystems. However, the archipelago composed of rocky islands has received little attention as its three-dimensional landscape characteristics are difficult to quantify. This study took the largest archipelago in China, the Zhoushan Archipelago, as the study area and constructed an island landscape pattern evaluation model from a dual-three-dimensional (dual-3D) perspective. The model divided the island into upper and lower layers, namely the surface landscape based on topography and the landscape elements above the surface (i.e., vegetation and buildings), and then evaluated their landscape patterns from a three-dimensional perspective, respectively. The landscape pattern model based on a dual-3D perspective and multiple scales achieved excellent results in the archipelago. First, the island landscape pattern was evaluated from three-dimensional perspectives, including human interference, landscape fragmentation, vegetation space, and building space. Second, landscape indices such as the human interference three-dimensional index (HITI), the landscape fragmentation three-dimensional index (LFTI), the vegetation three-dimensional index (VTI), and the building three-dimensional index (BTI) established at multiple spatial scales revealed spatial heterogeneity within and between islands. Environmental factors such as elevation, slope, and island area exhibited significant correlations with them. There were significant differences in landscape pattern indices between the two-dimensional (2D) and the three-dimensional (3D) perspectives, and high values were mainly distributed in areas with significant topographic changes and larger islands. In addition, as the evaluation unit increased, the landscape indices increased, and HITI became more responsive to the transitions from 2D to 3D, while LFTI was the opposite. Therefore, the multiscale landscape pattern measurement of China’s largest archipelago based on high-resolution remote sensing was carried out from three-dimensional perspectives to accurately reveal the spatial heterogeneity.

A modelling study of the tidal stream resource around Zhoushan Archipelago, China

A modelling study of the tidal stream resource around Zhoushan Archipelago, China

Observation and Modelling on the Shipping Noise in Shallow Waters with Complex Islands and Reefs of the East China Sea

The impact of the noise radiated from merchant ships on marine life has become an active area of research. In this paper, a methodology integrating observation at a single location and modelling the whole noise field in shallow waters is presented. Specifically, underwater radiated noise data of opportunistic merchant ships in the waters of Zhoushan Archipelago were collected at least one day in each month from January 2015 to November 2016. The noise data were analyzed and a modified empirical spectral source level (SSL) model of merchant ships was proposed inspired by the RANDI-3 model (Research Ambient Noise Directionality) methodology. Then combining the modified model with the realistic geoacoustic parameters and AIS data of observed merchant ships, the noise mappings in this area were performed with N×2D of Normal Mode calculations, in which the SSL of each ship was estimated using the modified model. The sound propagation at different receiving positions is different due to the shielding effect of islands and bottom topography. The methodology proposed in this paper may provide a reference for modelling shipping noise in shallow waters with islands and reefs.

An approach to assess the potential of wave energy resources based on directional energy flux

Estimating the total available wave energy surrounding islands holds significant importance in accessing the hosting capacity of wave energy. This study proposes a novel method for estimating the total available wave energy resources around islands using directional wave energy flux as a key parameter. By introducing the concept of directional across section, this method incorporates the directionality into the total resource calculation. A case study of the northern Zhoushan Archipelago was conducted to demonstrate the practical application of this method. The wave conditions were computed using the SWAN wave model for a 10-year period and validated against 7 months of buoy observations near Shengshan island. Basic wave energy resource characteristics were analyzed and the spatiotemporal features were analyzed using various indices. Subsequently, the proposed method was applied to calculated the total available wave energy around islands at various extend distances from the coastline. The wave energy potential of the islands in the study area stands at 349 MW, 302 MW, 318 MW, and 387 MW respectively, at extend distances of 5 km, 7.5 km, 10 km, and 12.5 km from the shoreline. These values represent approximately 25.1%–42.2% of the total energy obtained using existing methods.