Xiamen Bay Research Articles

Nature-Based Solution for Climate Change Adaptation: Coastal Habitats Restoration in Xiamen Bay, China

Nature-based solutions (NbSs) of biodiversity conservation and ecosystem restoration have been paid increasing attention as an essential approach to slow down climate change. However, to what degree an NbS approach will contribute to the combined effects of human intervention and climate change has not been well studied. From a habitat quality perspective, we set four NbS scenarios to analyze whether the NbS—mangrove restoration in particular—will be enough for climate change in Xiamen Bay of Fujian Province, China. The habitat quality module of the InVEST model (InVEST-HQ) and the Sea Level Affecting Marshes Model (SLAMM) were used to simulate the spatial-temporal changes in habitat types and habitat quality. Results show that (1) rising sea levels will cause coastal squeeze effects, impacting habitat quality due to erosion and inundation in the study area; (2) mangrove restoration is an effective way to mitigate climate change effects and to increase habitat quality; and (3) further analysis of the effectiveness of mangrove restoration shows that the consideration of mangrove fragmentation effects and sea-use impacts are necessary. The findings in this study will enrich the international discussion of NbSs to climate change in coastal areas.

Ecological vulnerability assessment and spatial-temporal variations analysis in typical ecologically vulnerable areas of China

Ecological vulnerability assessment is crucial for environment protection, ecological restoration and resource utilization. However, many former studies have limitations in the indicator system of the assessment, which were not comparable for different types of ecologically vulnerable areas. It is difficult to apply directly to the ecological vulnerability assessment of different types and in various regions. Aiming to solve these problems, the study proposed a well-established and comprehensive indicator system for ecological vulnerability assessment and conducted ecological vulnerability assessment application of five types of typical ecologically vulnerable areas of China based on remote sensing, meteorological, geographic and other data. The results show that the average EVIs value of Zhangbei County ranging from 0.525 to 0.559 are the highest among the five research areas during the four periods, followed by Zoige region and Xiamen bay. However, the region with the lowest average EVI value varies. In 2005 and 2015, it was Taihe County, while in 2010 and 2020, it was the Sanjiangyuan region. The variation of average EVIs in the five typical areas presents slight fluctuation and remains generally stable from 2005 to 2020. It indicates that the environmental protection measures and projects undertaken by the Chinese government in recent years have had a striking effect, curbing the trend of ecological environment deterioration.

Drought reduces nitrogen supply and N2O emission in coastal bays

Severe droughts are increasingly prevalent under global climate change, disrupting watershed hydrology and coastal nitrogen cycling. However, the specific effects of drought on nitrogen transport from land to sea and subsequent nitrogen dynamics remain inadequately understood. In this study, we evaluated the consequences of the 2020–2022 drought on nitrogen supply and N2O emissions in Xiamen Bay, Southeast China. The results showed that drought significantly reduced annual NH4N, NO2N, and NO3N concentrations in Xiamen Bay by 49.4 %, 32.1 %, and 40.3 %, respectively, compared with the pre-drought year of 2019. The decline in NH4N concentration was mainly attributed to reduced surface runoff across all seasons. NO3N and NO2N concentrations declined only during spring and summer, primarily due to increased potential evapotranspiration (PET) hindering nitrogen supply via groundwater and concurrently enhancing land denitrification. Annual N2O emission from Xiamen Bay decreased by 40.0∼72.7 % during the drought, highly correlated with the decline in the concentrations of NO3N, DIN, and DTN (p < 0.001). Comparative analysis revealed that NO3N concentration exhibited consistent negative linear regressions with PET and declined as evaporative demand drought conditions worsened across Xiamen Bay, Sansha Bay, and Chesapeake Bay throughout 2010–2022. NH4N concentration showed a positive regression with river discharge in Xiamen Bay, but negative regressions in the other two bays. Our results indicates that drought reduces N2O emission primarily driven by nitrate substrate reduction in the bay. This study provides new insights for predicting coastal nitrogen dynamics and greenhouse gas emissions under global environmental change.

An improved drift model of dropped containers under wind and current effects

In the face of the increasing risk of Maritime accidents caused by global climate change, it is necessary to improve the accuracy of drift model of the dropped containers at seas for Maritime Search and Rescue (SAR). Sensitivity test on the classic drift model illustrates that immersion ratio (Ir) of container plays a dominate role in the drift trajectory of container compared to the drag coefficients. Inspired from it, a new scheme of variable Ir is proposed to improve the model by considering the water entering process of container in the study. Based on the stability analysis of four floating attitudes of intact empty container under strong wind condition, the variable Ir is estimated according to the orifice inflow theory and the Archimedes' principle of buoyancy. The new scheme is compared with the fixed Ir scheme from the simulation of the drift trajectory of the dropped container at Xiamen Bay of China. The result shows that error arisen from the fixed Ir would be accumulated as the time integral, but the new scheme of variable Ir can obviously improve the model accuracy for the long-time prediction of SAR. In addition, the drag coefficients of wind and water in the drift model of the dropped container are suggested to be 0.8 and 1.2, respectively.

Continuous Flow-Double Purge and Trap Method for Preconcentrating Mercury in Large Volumes of Seawater for Stable Isotope Analysis.

Mercury (Hg) isotopes provide a useful tool to understand Hg sources and processes in the environment. The Hg isotopic composition of seawater remains poorly constrained due to the lack of an efficient method to process large volumes of low-Hg-concentration seawater samples. Here, we develop a continuous flow-double purge and trap device for the in situ preconcentration of Hg in seawater. This method yielded a good Hg recovery of 91.7 ± 3.3% (n = 4, 1SD) for spiked seawater samples and gave reasonably similar Hg isotope ratios of NIST 8610, indicating a limited matrix effect and limited Hg isotope fractionation during processing of seawater. NIST 8610 δ202Hg (-0.55 ± 0.09‰, n = 4, 1SD) and Δ199Hg (0.07 ± 0.02‰, n = 4, 1SD) were similar to previously published data. The method was successfully applied to seawater collected from the Xiamen Bay and the South China Sea. The seawater samples showed a Hg recovery of 91.6 ± 5.4% (n = 12, 1SD). Seawater Δ199Hg (-0.04 ± 0.05‰, n = 7, 1SD) in the Xiamen Bay was different from seawater Δ199Hg (0.05 ± 0.07‰, n = 5, 1SD) in the South China Sea, which implies distinct Hg sources to coastal and open ocean areas and highlights the robustness of our method in understanding the Hg isotopic composition of seawater.

A study on transboundary governance of marine plastic debris-the case of an adjacent waters between China and Taiwan.

This study aimed to construct a transboundary marine governance mechanism in the Kinmen-Xiamen waters through literature review, field survey, in-depth interview, and expert opinion survey. The study finds that monsoons, ocean currents, and tides are the main factors affecting the drift of marine debris in the Xiamen Sea area to the beaches of Kinmen. The marine debris mainly included marine plastic debris (MPD), bamboo, and wood in Kinmen and was documented impacting a variety of species, including the horseshoe crab to marine mammals the IndoPacific dolphin. In addition, the problem of marine micro-plastic pollution is becoming increasingly worrisome and hazardous to rare creatures in the Xiamen Sea area. The pollution sources of MPD in Xiamen Bay included coastal tourism activities, micro-plastic discharged from sewage treatment plants, plastic waste produced by lost and discarded marine aquaculture, and plastic drifting terrestrial waste transported from the Jiulong River Basin. Our results show that microplastic pollution in the Kinmen-Xiamen waters may have a greater impact on marine ecology and the surrounding environment. The relevant transboundary marine governance mechanisms are discussed in this study.

Microplastic Contamination in Sediments of Xiamen Bay: Investigating Ecological Consequences

Microplastic contamination in aquatic ecosystems poses a global environmental challenge, with local variations requiring focused investigations. This study examines the prevalence, characteristics, and ecological implications of microplastics in Xiamen Bay sediments, providing insights into the potential risks for both the environment and human health. The analysis encompasses spatial and temporal distribution patterns, ecological impacts on sediment biota, and pathways of human exposure. Key considerations for human health risk assessment are identified, considering particle characteristics, exposure levels, and vulnerable populations. The study concludes by emphasizing the importance of interdisciplinary collaboration in addressing these challenges and proposes strategies for mitigating the impact of microplastic contamination in Xiamen Bay.

Dynamics and geochemical responses of dissolved metals (Mn and Cu) in a subtropical estuary, China.

Theresearch delved into the occurrence and dynamics of dissolved metals, specifically manganese (Mn) and copper (Cu), withinthe Jiulong River Estuary, South China,a medium-sized subtropical estuary. Our findingsunveiled a nuancedseasonal and spatial variability of dissolved metals throughout the entire estuarine system.Notably,dissolved Mnconcentrations peaked (~ 3.5μM) in the upper estuary, diminishingsharply along the salinity gradient, with a modest risein the middle estuary and outer Xiamen Bay. In the upper estuary, heightenedconcentrations of dissolved Mn occurred in spring due to augmented terrestrial particle inputs, followed by suboxically reductive releases; conversely, concentrations were low in summer, attributed to dilution fromincreased freshwater discharges and particle scavenging. In contrast, dissolved Cu exhibited differently, with elevated concentrations (29.2-37.5nM) in the upper and middle estuaries, driven byreductive dissolution of Mn particles and chloride-induced ion exchanges, respectively. Concurrently, heightenedinputs of nutrients and metalscorrelated with elevated phytoplankton productivity (indicated by chlorophyll a) in the upper andouter estuaryregions. Our analysis underscored the sensitivity ofdissolved metals to environmental parameters, including temperature, pH, and dissolved oxygen. The integration of compiled historical dataunderscored the dynamic nature of dissolved metals, particularly Cu, in response to geochemical processes.The elevated ion levels indicated intensified ion releasesfrom particles and sediments, attributable to increased anthropogenic perturbation and climatic changes(e. g. oceanwarming).

A new dinoflagellate Gonyaulax pospelovana with resting cysts resembling Spiniferites delicatus and its biogeography and ecology revealed by DNA metabarcoding

ABSTRACT Extant species of the dinoflagellate genus Gonyaulax are capable of producing resting cysts morphologically similar to different cyst-based genera, and their cyst-theca relationships are far from resolved. Here we have carried out germination experiments on several living cysts that resemble Spiniferites delicatus from the subtropical regions of China and Mexico. Both cyst and theca morphology were examined by light and scanning electron microscopy. A new species, Gonyaulax pospelovana, is described, characterized by a cingulum displacement and an overhang of twice its width, and two short antapical spines. The cysts of G. pospelovana had a granular surface and gonal processes with petaloid tips. Maximum likelihood and Bayesian inference analyses based on LSU and SSU rRNA gene sequences revealed that strains identified as G. pospelovana were monophyletic, forming a sister clade to Gonyaulax ellegaardiae and several presumable strains of Gonyaulax spinifera. One Chinese strain and two Mexican strains of G. pospelovana were examined for yessotoxin production using LC-MS/MS, but were not found to produce a detectable amount of toxins. Metabarcoding targeting the 18S V4 rRNA gene was performed on monthly collected samples in Xiamen Bay, China. A ZOTU (zero-radius operational taxonomic units) was detected that was consistent with G. pospelovana. Its maximum abundance was recorded in summer. Additionally, an OTU was identified as G. pospelovana from the Tara Oceans metabarcoding data, which occurred in the Indian and Pacific oceans at temperatures ranging from 28°C to 31°C, suggesting that it is a warm water species.

Assessing the effects of different management activities on the conservation of endangered Indo-Pacific humpback dolphin

Predictions of population viability can provide valid information for guiding the management and conservation of species. However, such studies are rarely conducted on cetaceans due to limited basic data. In this study, a detailed assessment of the population dynamics of Indo-Pacific humpback dolphins (Sousa chinensis) in Xiamen Bay, China was carried out using a Vortex model that was based on model parameters that were derived from monitoring data and published sources. Then, sensitivity analyses were conducted to test the relative importance of the uncertainty of the model parameters. Moreover, potential management models were evaluated to determine their effectiveness in assisting with species recovery. The baseline model projected a decline in the population abundance with a growth rate (r) of -0.031, and the probability of extinction was 58.7% over the next 100 years. The sensitivity analyses revealed that juvenile mortality and fertility were the most pivotal factors for the viability of this population. All the conservation measures, including habitat improvement, catastrophe control, and individual supplementation, contributed to population increases when compared with the baseline model. In particular, decreasing calf and juvenile mortality through habitat improvement, at high levels, was the only way to generate positive growth rates. The findings suggest that these practical management activities can reduce the risk of extinction for this species.

Coastal habitat quality assessment and mapping in the terrestrial-marine continuum: Simulating effects of coastal management decisions

Assessment and mapping of coastal habitat quality are critical for integrated coastal zone management. However, in the coastal zone, characterized as a terrestrial-marine continuum, few studies have incorporated land-sea connections while mapping and predicting the quality of habitats. In this study, we propose a novel framework that integrates an ecosystem service assessment model and global ecosystem classification, and within this framework, the cross-system threats from both ocean- and land-based human activities were considered. On this basis, by linking the threat sources of habitat quality with management policy scenarios, the prediction of habitat quality across land and sea was realized. Xiamen Bay, a typical intensively developed bay in Southeast China, was used as a case study. Thirteen habitat types and 12 threats were identified in the upland/supratidal, intertidal, and subtidal zones of Xiamen Bay. Each threat affected habitats in at least two coastal zone subdivisions. The results showed that by 2030, 26.9% of the total habitat area is expected to decline in quality, while 16.9% will improve. Intertidal habitats are especially vulnerable to multiple threats. Our study revealed a strong negative correlation between threat intensity and habitat quality changes. Eight of the 12 threats will be changed by the five coastal management policies, and six types of habitats are potential beneficiaries. Overall, local coastal zone management strategies will contribute to enhance the quality of intertidal and subtidal habitats, whereas upland/supratidal zone are anticipated to experience a decline. The tourism development policy may have negative impacts on all 13 habitats and cover the largest area, while the aquaculture regulation policy is expected to yield the greatest benefits. We revealed that cross-system threats are prevalent in coastal zone habitats, making it possible for coastal zone management policies to have cross-system impacts. The tool developed herein can support integrated coastal zone management in the terrestrial-marine continuum and facilitate effective decision-making.

The Species Diversity of the Genus Echinogorgia in Xiamen Bay and Its New Record in China

The rapid reduction in coral reefs worldwide has led to increasing attention toward protecting and restoring coral reef ecosystems. Coral reefs not only have a rich diversity of coral species, but they can also provide important products and services for human beings. One type of coral, Echinogorgia, has important scientific research value and application prospects. To understand the diversity of coral species, diving surveys were conducted in Xiamen Bay in 2017 and 2021, and a total of 928 samples were collected. Taxonomic research was conducted using methods such as morphological identification through electron microscopy. Specific phylogenetic trees of the COI gene, mtMuts gene, and ITS1 gene were analyzed. There were 47 specimens of Echinogorgia coral included among 928 samples. Fifteen species of Echinogorgia were identified, including Echinogorgia ramosa, Echinogorgia flexilis, Echinogorgia russelli, Echinogorgia ramulosa, and Echinogorgia gracilima (which represent the newly recorded species in the waters of China). This study increases the species diversity records in China and contributes to new geographical distribution information of Echinogorgia worldwide. The primary data also serve as the baseline data for long-term biomonitoring programs to estimate the status of octocorals in Xiamen Bay.

Simultaneous Measurement of Trace Levels of Hg, As, Sb, and Bi in Coastal Seawater with a Multichannel Chemical Vapor Generation Atomic Fluorescence Spectrometer.

Trace levels of Hg, As, Sb, and Bi in coastal seawater have been simultaneously detected by a laboratory-built multichannel chemical vapor generation coupled to an atomic fluorescence spectrometer. The system was configured with a built-in electrochemical H2 generator as the fuel supplier to replace chemical H2 produced by the oxidation of potassium borohydride under acidic conditions in traditional instruments. The electrochemical H2 generator not only isolated the atomization process from the chemical vapor injection process but also improved the stability of atomization, excitation, and fluorescence emission in the hydrogen flame, making it easier to optimize conditions for CVG while introducing evaporating multielement vapors. Calibrations were obtained using a mixed standard solution of Hg(II), As(III), Sb(III), and Bi(III). The addition of KBr to a 3% (v/v) HCl solution was selected as the preservative to ensure the stability of 0.10 μg/L Hg(II) in a multielement standard solution for at least 15 days while also preserving μg/L levels of As(III), Sb(III), and Bi(III) stable. The method detection limits (LOD, 3σ) were 0.001, 0.015, 0.010, and 0.005 μg/L for Hg, As, Sb, and Bi, respectively. The relative standard deviations (RSD, n = 7) of the standard spiked seawater samples were 3.2% (0.020 μg/L Hg), 1.2% (0.50 μg/L As), 1.0% (0.50 μg/L Sb), and 3.5% (0.050 μg/L Bi), respectively. The recoveries of seawater samples spiked with different salinities were in the range of 84.5%(Sb)-114%(Hg). The system has been successfully applied to the simultaneous analysis of the four elements in the seawater samples collected from Xiamen Bay, Southeast China.

Per- and polyfluoroalkyl substances (PFASs) in water and sediment from a temperate watershed in China: Occurrence, sources, and ecological risks

Per- and polyfluoroalkyl substances (PFASs) are a class of synthetic organic fluorides that have been widely used in various industrial and consumer applications. However, their potential ecological risks have raised concerns. In this study, PFASs were investigated in different environmental media in the Jiulong River and Xiamen Bay regions of China, revealing widespread contamination of PFASs in the watershed. PFBA, PFPeA, PFOA, and PFOS were detected in all 56 sites, with short-chain PFASs dominating (72 % of the total). Novel PFAS alternatives, including F53B, HFPO-DA, and NaDONA, were detected in >90 % of the water samples. Seasonal and spatial variations in PFAS concentrations were observed in the Jiulong River estuary, while Xiamen Bay was not significantly affected by seasonal changes. In sediment, PFSAs were dominant with long-chains while PFCAs with short-chains, and the occurrence was influenced by water depth and salinity. PFSAs were more inclined to be adsorbed in sediments than PFCAs, and log Kd of PFCAs increased with the numbers of -CF2-. Paper packaging, machinery manufacturing, WWTP discharge, airport and dock activities were the dominant sources of PFASs. Risk quotient showed that PFOS or PFOA may pose high toxicity to Danio rerio and Chironomus riparius. Although the overall ecological risk in the catchment is still low, the hazard of bio-concentration under long-term exposure and multi-pollutant synergistic toxicity cannot be ignored.

Forecasting land-cover change effects on waterbirds in Xiamen Bay, China: Determining prospective species winners and losers

Waterbirds are vital to coastal wetland ecosystem, and play significant roles in global biodiversity maintenance, cultural and educational services, etc. Waterbirds are particularly vulnerable to environmental change, particularly land-cover change, which has severely degraded their ecological niches. Accordingly, this study developed a waterbird-habitat preference index to quantify waterbird dependence on Xiamen Bay's habitats and a subsidiary waterbird-specific habitat suitability index to predict potential effects of future land-cover change on waterbirds. Results showed that the waterbird-habitat preference index ranged from −9.8 to 18.71, indicating that habitat selection varied greatly among different waterbird species, where tidal flats were the most popular waterbird habitat. Additionally, most waterbird species showed a preference for more than one habitat, which could be indicative of their diverse ecological demands. Effects on waterbirds varied greatly among the three different land-cover scenarios, where positive benefits were predicted under the ecological protection scenario (EPS), while the greatest negative effects were observed under the development and utilization scenario (DUS). Effects also varied among different waterbirds species. Those under the current trend scenario (CTS) (e.g., Tringa brevipes and Calidris ruficollis) could be at risk for species abundance loss (i.e., losers) while others (i.e., Egretta garzetta and Saundersilarus saundersi) could benefit from increased abundance (i.e., winners). Generally, migratory and traveling birds were much more vulnerable than resident birds. Spatially, conservation priority should be given to the Dadeng Waters and those waters adjacent to it (i.e., Tongan Bay and Anhai Bay) because of the highest waterbird loss risk in these areas under a conflict between an urgent need to protect waterbird biodiversity and intense present and future land-cover development. The intent of this study is to provide a useful tool to explore land-cover effects on waterbirds in similar coastal regions, which can provide important information on protection and restoration strategies.

Perceptions about mangrove restoration and ecosystem services to inform ecosystem-based restoration in Large Xiamen Bay, China

Mangroves provide a multitude of ecosystem services that are threatened due to extensive mangrove degradation globally. Restoration actions have been receiving growing attention for reinstating some of these critically important ecosystem services. Understanding societal perceptions about ecosystem restoration and the services that can be enhanced via them, is critical for designing and implementing effective and equitable landscape and seascape restoration actions. Here, we elicit societal perceptions toward mangrove restoration, and the perceived importance of the ecosystem services it can provide, through 1600 surveys with coastal residents in the Large Xiamen Bay (China). We focus on four districts with different environmental and socioeconomic characteristics, and elicit the perceived importance of mangrove ecosystem services through the Analytical Hierarchy Process. Subsequently we identify the factors affecting these perceptions through regression analysis and redundancy analysis. Overall, the analysis suggests that coastal residents in the four districts have diverse perceptions about the importance of mangrove ecosystem services, with provisioning services receiving higher weights in most cases. Conversely respondents supporting and willing to pay for mangrove restoration tend to assign greater importance to regulating services such as climate regulation and coastal protection. Notably, some of the characteristics of the respondents and their districts significantly influence some of these perceptions. This evidence-based understanding of what affects the perceptions about mangrove restoration (and the ecosystem services it provides) can inform the development of landscape-scale restoration actions that are fit for purpose and can contribute to achieving the restoration goals of the UN Decade of Ecosystem Restoration and the Post-2020 Global Biodiversity Framework.

Real-time underway measurement of ammonium in coastal and estuarine waters using an automated flow analyzer with hollow fiber membrane contactor

Ammonium (NH4+) is an important parameter for aquatic ecosystems. To date, continuous and underway acquisition of NH4+ in coastal and estuarine waters has been challenged by the strongly varying salinity and complex matrices in these waters. To address these issues, a hollow fiber membrane contactor (HFMC) was constructed and incorporated in flow injection analysis (FIA) to achieve online separation/preconcentration of NH4+ in water. In the FIA-HFMC system, NH4+ in the water sample was converted into NH3 under alkaline conditions in the donor channel. The generated NH3 diffused across the membrane and was absorbed in an acid solution in the acceptor channel. The resultant NH4+ in the acceptor was then quantified based on a modified indophenol blue (IPB) method. Parameters affecting the performance of the FIA-HFMC-IPB system were evaluated and optimized. Under the optimized conditions, the proposed system exhibited a limit of detection of 0.11 μmol L−1, with relative standard deviations of 1.0–1.9 % (n = 7), and a good linear response (R2 = 0.9989) for the calibration in the field with NH4+ standards in the range of 0.40–80 μmol L−1. The proposed system was applied to a shipboard underway measurement of NH4+ in a two-day cruise in the Jiulong River Estuary–Xiamen Bay, China. A good agreement was observed between measurements from the proposed system and those from manual sampling and laboratory analysis. Both laboratory and field results demonstrated that the system was free of salinity effect and interference from organic nitrogen compounds. The system also showed excellent stability and reliability during a 16-day observation. This work suggests that the proposed FIA-HFMC-IPB system is applicable for the underway measurement of NH4+ in water, especially for estuarine and coastal waters with varying salinity and complex matrices.

Modeling Suitable Habitats of Indo-Pacific Humpback Dolphins (Sousa chinensis) in a Highly Urbanized Bay

Indo-Pacific humpback dolphins (Sousa chinensis) live in coastal waters that have experienced considerable anthropogenic disturbances. Specifically, along the coasts of highly urbanized regions, available habitats have decreased in both space and scale. This study used Maxent software to simulate the distribution of suitable habitats for S. chinensis during the dry and wet seasons in Xiamen Bay. We also aimed to identify key environmental factors influencing habitat distribution, with the goal of using our results to analyze conservation gaps and propose adjustments. We found that during the dry season, S. chinensis were mainly distributed in the Western Harbor, Jiulong River Estuary, and the mouth of Tongan Bay. During the wet season, they were distributed in the south of Western Harbor, Jiulong River Estuary, and around the Wuyu and Dadeng-Xiaodeng Islands. Nekton density, chlorophyll-a concentration, sea surface temperature, slope, and salinity are the primary factors affecting S. chinensis distribution in Xiamen Bay. To better protect the species, the existing Tongan Bay reserve should be expanded during dry seasons, and suitable habitats in the Jiulong River Estuary should be turned into a seasonal protected region. Similarly, during wet seasons, the original Western Harbor portion of the reserve should increase to include the Jiulong River Estuary, northwest of the Wuyu Islands and south of the Dadeng-Xiaodeng Islands. In addition to this dynamic seasonal management of reserve size, we also recommend developing multiple-use protected areas and establishing a joint protection mechanism between local governments. In conclusion, our model offers important guidance on improving conservation measures of S. chinensis in Xiamen Bay.

Assessment of future flood risk induced by sea level rise and tropical cyclones under global warming in the Xiamen Bay, Fujian, China

Tropical cyclone (TC)-induced coastal flooding can lead to severe hazards in low-lying lands and is expected to be exacerbated by sea level rise and TC climatology changes related to the warming climate. Since the dense population in Xiamen Bay, Fujian, China, it is highly valuable in understanding coastal flooding of it, but little studies involved this topic. In this study, we establish a high-resolution numerical model covering all coastal low-lying land in Xiamen Bay based on FVCOM. This model is then used to assess the flood risk in Xiamen Bay under TCs with 10-, 100-, and 1000-year pressures by applying a multi-tracks blend method. The results show that 126 km2 of low-lying area can be flooded periodically by astronomical tides; and 388, 504, and 598 km2 of low-lying area can be flooded under TCs with 10-, 100-, and 1000-year pressures, accompanied by increased average flood depths of 2.3, 2.8, and 3.4 m, respectively. By 2100 under SSP5-8.5, the well-protected Xiamen Island becomes impacted by TCs with 10-year pressure, and flood areas under TCs with 100-year pressure are estimated to be nearly equivalent to that under TCs with 1000-year pressure at the current climate. The most increased exposure area by climate change are artificial surfaces and agricultural areas, showing the potential higher flood disasters in future.

Quantitative assessment of the response of seawater environmental quality to marine protection policies under regional economic development --A case study of Xiamen Bay, China

Xiamen is the epitome of having steady economic growth and non-negligible environmental stress over decades. Several restoration programs have been applied to address the conflicts between heavy environmental pressures and human activities, but the response of current coastal protection policies to the marine environment remains to be assessed. Therefore, to assess the effectiveness and efficiency of marine conservation policies under regional economic growth in Xiamen, quantitative techniques including elasticity analysis and dummy variable regression models were applied. Here we show the potential relationship between seawater quality (pH, COD, DIN and DRP) and economic growth including Gross Domestic Product (GDP) and Gross Ocean Product (GOP), to evaluate the ongoing related policies by using over 10 years of data (2007–2018). According to our estimates, a GDP growth rate of 8.5% represents a stable economic climate that is favorable for the overall rehabilitation of the local coastal environment. The results of the quantitative research indicate a strong relationship between economic development and seawater quality, with marine protection regulations serving as the direct cause. As GDP growth and pH are significantly positively correlated (coef. = 0.8139, p = 0.012), ocean acidification has decreased over the last decade. With an inversely proportional correlation with GDP (coef. = 0.8456, p = 0.002) and GOP (coef. = 0.8046, p = 0.005), the trend in COD concentrations effectively meets the targets of current pollution control legislation. By using a dummy variable regression model, we found that legislation is the most effective way in seawater recovery in the GOP section, and positive externalities of marine protection frameworks are also estimated. Meanwhile, it is predicted that the negative effects from the non-GOP section will gradually affect the coastal environmental quality gradually. An overall framework for controlling marine pollutant discharges, giving equal attention to maritime and non-maritime anthropogenic activities should be promoted and updated.