Sanmen Bay Research Articles

Response of hydrodynamic environment to land reclamation in Sanmen Bay, China over the last half-century

Sanmen Bay (SMB) is one of the important harbors in Zhejiang Province. It is a semi-enclosed shallow bay that has undergone large-scale land reclamation activities. Long-term reclamation has changed the hydrodynamic conditions of SMB, such as tide, residual current, tidal prism, water exchange capacity, and tidal asymmetry. In this study, three typical periods of numerical models, based on historical charts and remote sensing, were established to investigate the influence of reclamation activities on the hydrodynamic conditions of SMB from 1971 to 2020. These model results reveal that the amplitude and phase of M2, the main tidal components in SMB, decreased by ~0.1–0.3 m and ~ 5°–15°, respectively, over the last half-century. Additionally, under the influence of ~200 km2 reclamation, many hydrodynamic conditions in SMB also changed. This includes the reduction of a residual current and tidal prism, an increase in residence time, and a change in tidal asymmetry characteristics. The residence time in nearby Xiayangtu exhibited a downward trend from 2003 to 2020, because land reclamation squeezed, and thus, enhanced the residual current eddy. The water-exchange capacity of the bay became weaker with the reduction of tidal prism to one-third and an increase in residence time. The tidal asymmetry characteristic of SMB changed from half of flood dominant to fully flood dominant by the influence of shoreline and bathymetry, which raised the flood risk. Research on the response of the hydrodynamic environment to reclamation activities in SMB reminds the local government to reassess the impact of land reclamation on the hydrodynamic environment.

Monitoring Dissolved Oxygen Concentrations in the Coastal Waters of Zhejiang Using Landsat-8/9 Imagery

The Zhejiang coastal waters (ZCW), which exhibit various turbidity levels, including low, medium, and high turbidity levels, are vital for regional ecological balance and sustainable marine resource utilization. Dissolved oxygen (DO) significantly affects marine organism survival and ecosystem health, yet there is limited research on remote sensing monitoring of DO in the ZCW, and the underlying mechanisms are unclear. This study addresses this gap by utilizing high-resolution Landsat 8/9 imagery and sea surface temperature (SST) data to develop a multiple linear regression (MLR) model for DO estimation. Compared to previous studies that utilize remote sensing band reflectance data as inputs, the results show that the red and blue bands are more suitable for establishing DO inversion models for such water bodies. The model was applied to analyze variations in the DO concentrations in the ZCW from 2013 to 2023, with a focus on Hangzhou Bay (HZB), Xiangshan Bay (XSB), Sanmen Bay (SMB), and Yueqing Bay (YQB). The temporal and spatial distributions of DO concentrations and their relationships with environmental factors, such as chlorophyll-a (Chl-a) concentrations, total suspended matter (TSM) concentrations, and thermal effluents, are analyzed. The results reveal significant seasonal fluctuations in DO concentrations, which peak in winter (e.g., 9.02 mg/L in HZB) and decrease in summer (e.g., 6.83 mg/L in HZB). Changes in the aquatic environment, particularly in the thermal effluents from the Sanmen Nuclear Power Plant (SNPP), significantly decrease coastal dissolved oxygen (DO) concentrations near drainage outlets. Chl-a and TSM directly or indirectly affect DO concentrations, with notable correlations observed in XSB. This study offers a novel approach for monitoring and managing water quality in the ZCW, facilitating the early detection of potential hypoxia issues in critical zones, such as nuclear power plant heat discharge outlets.

Multianalysis Between Chlorophyll-a and Environmental Factors in Sanmen Bay

Multianalysis Between Chlorophyll-a and Environmental Factors in Sanmen Bay

Fresh and saline groundwater nutrient inputs and their impacts on the nutrient budgets in a human-effected bay

Submarine groundwater discharge (SGD) can be highly enriched in nutrients, especially in bays with strong human activity, but has often been overlooked in coastal nutrient budgets. This study investigated the impact of both fresh and saline SGD on nutrient budgets in Sanmen Bay, China, a region heavily influenced by human activities. Based on the 224Ra mass balance model, the total SGD flux was estimated to be (1.1 ± 0.1) × 108 m3 d−1 (13.9 ± 0.5 cm d−1). Additionally, a water-salt mass balance model revealed that fresh SGD flux accounted for ~9.0 % of the total SGD flux. The results highlight the significance of fresh SGD as a freshwater source, contributing to 35.9 % of the total dissolved inorganic phosphorus (DIP) flux via SGD. Considering all nutrient sources and sinks in the Sanmen Bay, SGD was identified as the primary source of nutrients in Sanmen Bay, contributing 53.9 % and 11.9 % of the total dissolved inorganic nitrogen (DIN) and DIP input, respectively. Furthermore, the discharge of industrial/domestic sewage and mariculture wastewater also posed a potential threat to nutrient levels in the bay. Thus, initiatives such as reasonable control of culture species and scale, strengthening wastewater discharge and SGD management are crucial for maintaining the ecological environment of the Sanmen Bay.

The first record of Egglestonichthys bombylios (Gobiiformes: Gobiidae) from China with its first fresh colouration information.

During bottom trawl surveys carried out between 20132021, 52 specimens (33.854.0 mm SL) of Egglestones bumblebee goby Egglestonichthys bombylios were collected at a depth of 1.515 m from Dongshan Bay, Sanmen Bay, and Niushan Island, China. They represent the first records of this species from China. A full description, including fresh colouration of the species is provided as it is poorly known. The individuals collected in China agree with most morphological features of the holotype, except for the pelvic fin fraenum that was not observed or appears to be absent in most specimens. A strong relationship between E. bombylios, Larsonella pumilus, and the genus Priolepis is herein demonstrated by the mitochondrial genome sequences of E. bombylios and twenty closely related species. This study enriches the existing genetic data of the so-called Priolepis lineage and provides useful insights into the phylogenetic relationships across species of the genera Egglestonichthys, Priolepis, and Larsonella.

Mechanism and genesis of Sanmen Bay as a sink of Holocene Yangtze River sediment, Zhejiang Province, China

Introduction: The Holocene mud deposits that extend from the Yangtze River mouth to the Taiwan Strait along the Zhejiang–Fujian coast, East China Sea (ECS), have attracted considerable research attention. However, there is a lack of consensus regarding the redistribution flux of Yangtze River sediment after it enters the sea. There are many bays along the Zhejiang and Fujian coasts, but their role in the source–sink process of Yangtze River sediment is not well-documented owing to limited data.Methods: In this study, data from shallow seismic profiles, core samples, and surface sediment samples were analysed to assess the role of Sanmen Bay, the second largest bay in Zhejiang Province, in the source–sink process of Yangtze River sediments.Results: The results showed that Sanmen Bay is an important sink for Yangtze River sediments. The characteristics of the clay minerals indicate that the fine-grained sediments in Sanmen Bay are mainly derived from Yangtze River sediments. The thickness of Holocene deposits in Sanmen Bay ranges from 8.2 to 32.0 m, with an average of 23.4 m and a total sediment volume of 5.06 × 104 Mt, accounting for 1% of Yangtze River sediment in this time period. The Bayesian age-depth model based on borehole accelerator mass spectrometry (AMS) 14C dating shows that a high sedimentation rate occurred in the early and late Holocene but decreased significantly in the mid-Holocene, which is similar to that of the inner shelf of the East China Sea (ECS).Conclusion: The variation in the Holocene sedimentation rate in Sanmen Bay is related to the southward transport process and mechanism of Yangtze River sediments. The results of this study provide a basis for understanding the source–sink process of sediment in large rivers.

Implications of policy changes for coastal landscape patterns and sustainability in Eastern China

ContextThe capacity of a landscape to maintain multifunctionality through ongoing pressures relates to its sustainability and is affected by land use policy and environmental changes. In coastal zones, limited empirical evidence exists regarding the impact of macro-level policy changes on local landscapes and their resulting temporal and spatial responses.ObjectivesThis paper investigates the impact of national and provincial policies on local landscape patterns in China’s Zhejiang coastal zone, encompassing human expansion and ecological restoration in terms of landscape sustainability.MethodsA cluster-based landscape pattern mining is conducted from 1990 to 2020 using Google Earth Engine, which is coupled with a historical policy classification analysis.ResultsCoastal zone policies evolved in three stages: development-oriented (1990–2010), conservation turning (2010–2017), and land-sea coordination (2017-present). Consequently, significant temporal and spatial differences in local landscape changes are observed. Artificial surface expansion aligned with these stages, especially in Hangzhou Bay, Xiangshan Bay, and Sanmen Bay. Expansion responded more swiftly to development-stimulating policies, exhibiting longer-lasting effects. Conservation policies faced delays due to conflicting interests, varied implementation entities, unsynchronized cycles, and a lack of coordinated conservation priorities across terrestrial and marine domains.ConclusionsThis study provides insights into the processes and patterns of human expansion and ecological restoration in coastal zones, offering implications for coastal policies and landscape sustainability. It facilitates an evaluation of the effectiveness of coastal zone policy implementation and suggests differentiated sustainable transformation plans. Moreover, it underscores the need to strengthen coordination between sea and land development for effective coastal zone management and sustainability.

Characteristics of arsenic speciation in mainly cultured shellfish from Sanmen Bay, Zhejiang Province, China

Sanmen Bay plays a crucial role in economic shellfish aquaculture in China, yet few studies exist on the arsenic speciation of shellfish from this area. In this study, arsenic speciation of 11 cultured shellfish species from Sanmen Bay were analyzed by HPLC/ICP-MS. The results showed that organic arsenic particularly AsB, was the dominant arsenic species, constituting 21 %–71 % of the total arsenic. Conversely, the levels of inorganic arsenic were relatively low, ranging from 0.007 to 0.093 mg/kg, only accounted for 0.2 %–5.7 % of the total arsenic. There was no significant level correlation between inorganic arsenic and total arsenic in Sanmen Bay shellfish, so the concentration of inorganic arsenic did not increase with the total arsenic. Overall, the present study firstly revealed the arsenic speciation of shellfish from Sanmen Bay and also suggested that the proportion of inorganic arsenic should be considered in the revision of arsenic limit values.

Wave–Tide Interaction by Typhoon Ampil on Wave and Storm Surge in the Changjiang River Estuary and Its Adjacent Coastal Areas

The study used the SCHISM ocean model combined with the WWM III wind wave model to quantify the interaction between wind waves and tides in the coastal zone of the Changjiang River Estuary and its adjacent areas. The wave and storm surge during Typhoon Ampil, which made landfall in July 2018 in Shanghai, were simulated by using the Climate Forecast System Version 2 (CFSv2) and Medium-Range Weather Forecasts (ECMWF) latest reanalysis (ERA5) wind dataset from 1 July to 31 July. Model results with CFSv2 forcing show better performance in terms of significant wave height and storm surge than those with ERA5 forcing. To investigate the interactions between waves, water levels, currents, and their combined effects on significant wave and surge variations, six numerical sensitivity experiments were designed according to the different coupling methods between SCHISM and WWMIII. The research shows that in coastal areas with water depths of less than 10 m, waves are affected by water levels and currents. The differences in the effect on significant wave height between wave-tide coupling and one-way coupling with water levels and currents are negligible. Wave setup is an important physical term which cannot be ignored during the variations of storm surge caused by Typhoon Ampil. The contributions of wave set up were concentrated in coastal areas with water depths less than 10 m. The peak wave setup occurred in the Changjiang River Estuary, reaching 0.15 m. In Xiangshan Bay and Sanmen Bay, wave radiation stress makes the proportion of wave setup to the total surge reached more than 30%. The consideration of wave-tide interaction can effectively improve the accuracy of numerical wave and storm surge simulations, which can provide more accurate hindcasts of wave and storm surge variations in the Changjiang River Estuary and its adjacent coastal areas.

The Impact of Coastline and Bathymetry Changes on the Storm Tides in Zhejiang Coasts

Coastal evolutions are expected to have a significant impact on storm tides, disproportionately aggravating coastal flooding. In this study, we utilize a nested storm tide model to provide an integrated investigation of storm tide responses to changes in coastline and bathymetry along the Zhejiang coasts. We selected coastline and bathymetry data from 1980 and 2016, as well as data from three typical typhoon events (i.e., Winnie, Haikui, and Chan-hom) for simulating the storm surge processes. The results indicate that changes in the coastline and bathymetry from 1980 to 2016 have resulted in an increase in storm tides in the northern part and a decrease in the central part of Zhejiang. Specifically, storm tides in Hangzhou Bay have increased significantly, with an average increase of about 0.3 m in the maximum storm tides primarily attributed to coastline changes. On the contrary, in smaller basins like Sanmen Bay, while reclamation itself has reduced peak storm surges, rapid siltation has consequently exacerbated the storm surge. By decomposing storm tides into astronomical tides and storm surges, we discovered that the change in tidal levels was twice as significant as the surge change. Moreover, the nonlinear tide–surge interaction was nearly four times that of the pure surge, significantly contributing to storm surge variation. Alterations in the momentum balance reveal that the water depth-induced bottom friction and wind stress increase contributes to the local enlargement of storm tides at the bay head, while the coastline changes exaggerate nearshore storm tides through an increase in the advection term.

The shared microbiome in mud crab (Scylla paramamosain) of Sanmen Bay, China: core gut microbiome.

The mud crab, Scylla paramamosain, holds great commercial significance as a marine crustacean widely cultivated in the Indo-Pacific region. Understanding the core gut microbiota of aquatic animals is crucial for their overall health and growth, yet the core gut microbiota of mud crab remains poorly characterized. In this study, we gathered gut samples from mud crabs across five locations within Sanmen Bay, China. Through the utilization of high-throughput sequencing, we delved into the composition of the gut microbial community and identified the core gut microbiome of mud crab. Our results demonstrate that the gut microbial diversity of mud crab did not exhibit significant variation among the five sampling sites, although there were some differences in community richness. At the phylum level, we identified 35 representative phyla, with Firmicutes, Proteobacteria, Bacteroidota, and Campilobacterota as the dominant phyla. Among the 815 representative genera, we discovered 19 core genera, which accounted for 65.45% of the total sequences. These core genera were distributed across 6 phyla, and among them, Photobacterium exhibited the highest average relative abundance. Photobacterium has probiotic activity and may play a crucial role in enhancing the immune response of the host and maintaining the diversity of the gut microbiota. Moreover, we observed a positive correlation between the relative abundance of core genera and the stability of the gut microbial community. Furthermore, our findings revealed distinct differences in gut microbial composition and specific taxa between the sexes of mud crab. These differences subsequently influenced the functionality of the gut microbial community. Overall, our investigation sheds light on the core gut microbiota of mud crab, emphasizing the importance of core gut microbial communities in maintaining the health and growth of these commercially significant marine crustaceans.

Evaluation of Hybrid Soft Computing Model’s Performance in Estimating Wave Height

In coastal and port engineering, wind-generated waves have always been a crucial, fundamental, and important topic. As a result, various methods for estimating wave parameters, including field measurement and numerical methods, have been proposed over time. This study evaluates the wave height at Sri-Lanka Hambantota Port using soft computing models such as Artificial Neural Networks (ANNs) and the M5 model tree (M5MT). In order to overcome its nonstationarity, the primary wave height time series were divided into subtime series using the wavelet transform. The collected subtime series were then utilized as input data for ANN and M5MT in order to determine the wave height. For the sake of the model performance, the daily wind and wave data from the Acoustic Wave and Current (AWAC) sensor for Hambantota Port in 2020 and Sanmen Bay in 2017 were used in this study. The training state utilizes 80% of the available data, while the test state uses 20%. The Root Mean Square Error (RMSE) of the ANN, M5, WANN, and Wavelet-M5 models in the Hambantota Port for the test stage are 0.12, 0.11, 0.04, and 0.06, respectively. While in Sanmen Bay, the RMSE of the ANN, M5, WANN, and Wavelet-M5 models for the test stage are 0.14, 0.16, 0.06, and 0.08, respectively. According to the findings of this study, the accuracy of WANN and Wavelet-M5 hybrid models in evaluating wave height is superior to that of classic ANN and M5MT, and it is recommended that WANN and Wavelet-M5 hybrid models be used to estimate wave height.

Resource and environmental situation and countermeasures for high-quality development of Sanmen Bay, China

Sanmen Bay is one of the six major bays in Zhejiang Province, China. Its economic development over the past few decades has been rapid, and the intensity of ocean development has also been increasing. This paper analyzes the main resource and environmental problems in Sanmen Bay, including severe coastline development, significantly increased utilization of its intertidal zones, the threat to island resources from development, undiversified sea area use, and non-confirmation of ownership rights on a large scale. It then proposes countermeasures for high-quality development, including strictly controlling new land reclamation, strengthening coastal wetland protection and restoration, maintaining the natural shoreline retention rate, and preserving near-shore back-up spatial resources.

Sedimentary Records of Phytoplankton Communities in Sanmen Bay in China: The Impacts of ENSO Events over the Past Two Centuries

Phytoplankton communities, showing significant spatiotemporal variation within bay areas, play an important role in the structure and function of nearshore marine ecosystems. However, the absence of long-term high-resolution datasets has hindered our understanding of the effect of ENSO-driven environmental changes on phytoplankton communities in coastal ecosystems. Herein, by performing biomarker inversion analyses on two centuries’ worth of sedimentary organisms in the Sanmen Bay area, we observed a marked El Niño/La Niña-related succession; specifically, that El Niño-induced warming had increased the biomass of phytoplankton by 57.89%, while also increasing the proportion of diatoms by 76.40%. In contrast, La Niña years exhibited a decrease in the biomass of phytoplankton by 54.23%. Further, over three decades of observational data from the Sanmen Bay suggest that La Niña years can promote occasional blooms through monsoonal mixing and land-based inputs. Consequently, the nearshore marine ecosystem of the bay area, being subject to intense anthropogenic activity and land–sea interactions, can be said to be influenced by global-scale ocean–atmosphere processes. Going forward, the connection between short-term extreme events and long-term changes in the nearshore marine ecosystem should receive greater attention.

Total and active benthic foraminiferal community and their response to heavy metals revealed by high throughput DNA and RNA sequencing in the Zhejiang coastal waters, East China Sea.

Benthic foraminifera, large protists abundant in marine environments, have been widely used as bioindicators of environmental conditions. In this study, high-throughput sequencing based on small subunit rDNA and rRNA amplifications was used to investigate total and active benthic foraminifera community composition and diversity from nineteen and twelve superficial marine sediment samples in the Zhejiang coastal waters, respectively. The results showed that the dominant taxa of total foraminifera changed from Buliminellidae (hyaline) to Saccamminidae (agglutinated) from north to south along the coastal waters of Zhejiang Province. According to our survey, heavy metal contamination was moderate in Zhejiang coastal waters, and the potential ecological risks posed by Cd and Hg were higher. The contamination level of heavy metals at Yueqing Bay was the highest, followed by those at Sanmen Bay and Hangzhou Bay. Cd, Cu and grain size may be key factors affecting the distribution and composition of active foraminiferal communities.

Distributions, contamination level and ecological risk of heavy metals in surface sediments from intertidal zone of the Sanmen Bay, East China

The concentrations of heavy metals, total organic carbon and total phosphorus were analyzed to assess the environmental pollution characteristics, ecological risk levels, and possible sources of heavy metals in the surface sediments from the intertidal zone of Sanmen Bay. The mean concentrations of As, Cd, Cr, Cu, Hg, Pb and Zn were 14.3 ± 1.4, 0.112 ± 0.018, 84.8 ± 6.0, 40.7 ± 4.4, 0.067 ± 0.008, 30.5 ± 3.3, and 116 ± 1.6 mg/kg dry weight, respectively. The contamination factors and ecological risk assessment indicated that the intertidal zone of Sanmen Bay is not currently facing ecological risk of studied heavy metals. The results of Pearson's correlation and principal component analysis showed that Cd, Cr, Hg, and Pb may be mainly derived from natural inputs, and hydrodynamic condition and organic matter content have major effects on the distribution of heavy metals. However, As, Cu and Zn could come from both natural and anthropogenic sources.

Spatial Variability of Phytoplankton and Environmental Drivers in the Turbid Sanmen Bay (East China Sea)

Spatial Variability of Phytoplankton and Environmental Drivers in the Turbid Sanmen Bay (East China Sea)

Marine Environmental Capacity in Sanmen Bay, China

Estuarine environmental capacity is the foundation for coastal biological diversity and self-purification capacity. Hence, studies on the marine environmental capacity (MEC) are the foundation for the total discharge control and water quality improvement of land-based pollutants. In the article, A calibrated two-dimensional hydrodynamic model was used to study the environmental characteristics of Sanmen Bay, including the tides, the residual currents, the tidal prism, and water exchange abilities. The model results were used to estimate the environmental capacity of the bay. Taking the pollution problem in Sanmen Bay as an example, the method of response factor, the sub-unit control method, and the phased control method were used to estimate the environmental capacity, pollutant amounts, and the pollutant reduction in the bay. The concentrations of COD, inorganic nitrogen, and acid salt in Sanmen Bay are spatially varied, with higher values occurring in the western part and in the inner bay. The half exchange time of the whole bay is about 23 days, and the exchange time of 95% water body is about 60 days. The evaluation of MEC cannot only provide technical support for the offshore aquaculture industries but also provide a scientific basis for the total control of terrigenous pollutants in coastal cities in Southern Zhejiang Province.

Assessment of Ecological Sustainability for International Bays in the Context of Common Prosperity—A Case Study of Sanmen Bay in Zhejiang Province

In this paper, the spatial distribution maps of Sanmen Bay’s landscape genres between 1995 and 2020 were drawn based on spectra, GPS data, and the genres’ information extracted through remote-sensing imagery, in a way to fundamentally evaluate the region’s coupling and coordinated development. Moreover, to provide a science-based reference point for protecting and utilizing the Bay’s wetlands, changes of landscape genres were examined through a transition matrix, and the drivers of these dynamics were analyzed on a Logistic regression model. In addition, a theoretical and appraisal system compatible with the comprehensive evaluation of a bay’s ecosystem was built upon the analysis of Sanmen Bay’s land and sea areas. This would provide a scientific basis for bay ecosystem preservation by complementing the theoretical architecture of comprehensively evaluating a bay’s environment and keeping the evaluation more timely and complete. Beyond that, we investigated the region’s social development and its spatial improvement over the marine economy from the perspective of a bay’s coupled society-economy-ecology system, which took into account manifest and latent environmental factors that have been absent in conventional bay development planning. Finally, through empirical analysis, to improve the social and economic landscape of Sanmen Bay provides effective policy recommendations, the study also made new efforts to explore and promote the sustainability of China’s Gulf ecosystem.

Numerical Simulation on Environmental Capacity Assessment in Sanmen Bay, China

Estuarine environmental capacity is the foundation for coastal biological diversity and self-purification capacity. Hence, studies on the marine environmental capacity (MEC) are the foundation for the total discharge control and water quality improvement of land-based pollutants. In the article, A calibrated two-dimensional hydrodynamic model was used to study the environmental characteristics of Sanmen Bay. The model results were used to estimate the environmental capacity of the bay. Taking the pollution problem in Sanmen Bay as an example, the method of response factor, the sub-unit control method, and the phased control method were used to estimate the environmental capacity, pollutant amounts, and the pollutant reduction in the bay. The concentrations of COD, inorganic nitrogen, and acid salt in Sanmen Bay are spatially varied, with higher values occurring in the western part and in the inner bay. The half exchange time of the whole bay is about 23 days, and the exchange time of 95% water body is about 60 days. The evaluation of MEC can not only provide technical support for the offshore aquaculture industries but also provide a scientific basis for the total control of terrigenous pollutants in coastal cities in Southern Zhejiang Province.