Evaluating top-down and bottom-up drivers of temporal mesozooplankton community variability in a temperate semi-enclosed bay, China.

In our comprehensive study spanning 2003 to 2011 in Jiaozhou Bay (JZB), we evaluated the top-down and bottom-up drivers that regulate the temporal fluctuations of the mesozooplankton community. Throughout the study period, the zooplankton community exhibited a distinct seasonal pattern, with abundances reaching their peak during the spring-summer months following a winter minimum, closely associated with environmental factors such as precipitation, water temperature, and chlorophyll a concentration. Strikingly, the community also underwent significant interannual variations, with the lowest abundance maxima occurring in 2009 and 2011, and the highest in 2005 and 2008. These profound shifts coincided with population surges of Aurelia coerulea and extreme rainfall events, suggesting a complex interplay between top-down and bottom-up forces. In JZB, the predominant top-down impact of moon jellyfish during their bloom periods appears to override the bottom-up influence of rainfall, which could have substantial impacts on the food web dynamics within the ecosystem.

System efficiency of methylmercury production, an important indicator for evaluating the long-term risk of mercury: From a case study in the Jiaozhou Bay to global coastal seas.

With the implementation of the Minamata Convention, total Hg (THg) in coastal seas are expected to be reduced. However, methylmercury (MeHg) levels in aquatic environments depend not only on THg, but also the system efficiency of MeHg production (represented by MeHg/THg ratio in seawater) whose variations with time remain unclear. By choosing the Jiaozhou Bay (JZB) as a typical coastal system, combined with the published data from the global coastal systems, system efficiency of MeHg production in coastal seas were investigated. The mass budget of MeHg showed that the in situ production and degradation are the major source and sink of MeHg in the JZB. The relationships of MeHg in the seawater and fish with MeHg/THg in seawater indicate that system efficiency of MeHg production may control the risk of MeHg in coastal systems. The sulfate and nitrate in seawater, organic matter in sediment, biotic methylation, and transport of inorganic Hg from the seawater to sediment were identified to be critical parameters and processes for the MeHg/THg in global coastal seas. The findings of this study highlight the importance of monitoring the system efficiency of MeHg production and its controlling processes and parameters for evaluating the long-term risk of Hg.

Assessment of coastal eco-environmental sustainable development under multiple pressures: A case study of Jiaozhou Bay, China.

The increasing demand for economic development in the coastal zone is exerting greater pressure on the eco-environment in this region. Therefore, it is imperative to conduct comprehensive research on the sustainable development of the eco-environment in coastal areas. Grounded in sustainable development theory and Integrated Coastal Zone Management (ICZM), this study assessed sustainable development of Jiaozhou Bay (JZB), China over the period from 2015 to 2019 under multiple pressures applying the Driver-Pressure-State-Impact-Response (DPSIR) framework. Subsequently, a SWOT (Strengths, Weaknesses, Opportunities and Threats) analysis was employed to propose specific countermeasures and recommendations. In terms of weight within the criterion layer, Response (R) and Pressure (P) were assigned higher weights. The comprehensive assessment value Z in the target layer indicated a slight decrease in 2016 followed by a gradual increase that eventually led to stabilization. The comprehensive assessment values of the indicators varied depending on different conditions, implying that higher values would contribute to sustainable development of the eco-environment. Based on a SWOT analysis, strategies for Qingdao were derived from a combination of research findings and future development policy. These strategies include preventing and controlling land and sea pollution, governing reclamation activities, optimizing industrial structure, and strengthening public opinion guidance. This study highlights the application of quantitative and qualitative analysis methods in ICZM, providing specific recommendations based on policy analysis for achieving sustainable development in JZB's eco-environment under multiple pressures.

Evaluation of the coordinated development level in the coastal eco-environmental complex system: A case study of Jiaozhou Bay, China.

Given the exponential population growth and remarkable socio-economic advancements, coastal areas face increasingly complex challenges in eco-environmental management due to anthropogenic pressures. With the current emphasis on high-quality economic development, there is an urgent need to establish and evaluate a comprehensive indicator system to ensure the sustainable development of the coastal eco-environment and to meet evolving management demands. Research on the coordinated development level of coastal eco-environmental complex system, based on the concept of land-sea coordination, plays a pivotal role in promoting the resolution of eco-environmental issues in coastal areas, achieving sustainable socio-economic development in these regions. In this study, we construct an indicator system for the eco-environmental complex system in Jiaozhou Bay (JZB) coastal zone, China, comprising six sub-systems and thirty indicators. The comprehensive development level and coupling coordination degree model (CCDM) are employed in this study to analyze the indicator system in 1980-2020, aiming to elucidate the processes involved in the improvements in this complex system. The findings indicate: (i) the system's comprehensive development level evaluation and coupling coordination degree (CCD) exhibit a two-stage pattern: a declining trend in 1980-2005, followed by a rising trend in 2005-2020. (ii) despite improvements, the comprehensive development level and the CCD of the system in 2020 still hold potential for further enhancement compared to 1980; and (iii) policymaking and changes in anthropogenic pressures in coastal areas are the primary factors influencing the performance of the system. In the future, policymaking can reduce anthropogenic pressures on the coastal eco-environment, improve the comprehensive development level and CCD of the complex system, and encourage a commitment to sustainable development.

Organic carbon in wet deposition of an urbanized coastal bay, North China: Flux, sources and biogeochemical implications.

The process of atmospheric organic carbon (OC) entering the ocean through wet deposition plays a crucial role in the global carbon cycle. To gain insights into the biogeochemical dynamics of OC at the land-sea margin, we conducted an extensive four-year investigation on precipitation OC in Jiaozhou Bay (JZB). The results showed that the volume-weighted mean concentration of particulate OC (POC) and dissolved OC (DOC) in precipitation were 0.38 and 2.06 mg C L-1 with an average wet deposition flux of OC for 2666.5 mg C m-2 yr-1. The source of POC in precipitation is predominantly by the C3 plant emission and burning and fossil fuel combustion. Wet deposition contributed 986.6 t yr-1 of OC of which 506.3 t yr-1 of bioavailable DOC, which could have significant implications for carbon cycle in the JZB. This study could enhance the understanding of the marine atmospheric OC in coastal areas.

Rich diversity and active spatial-temporal dynamics of Thalassiosira species revealed by time-series metabarcoding analysis.

Thalassiosira is a species-rich genus in Bacillariophyta that not only contributes positively as primary producer, but also poses negative impacts on ecosystems by causing harmful algal blooms. Although taxonomical studies have identified a large number of Thalassiosira species, however, the composition of Thalassiosira species and their geographical distribution in marine ecosystems were not well understood due primarily to the lack of resolution of morphology-based approaches used previously in ecological expeditions. In this study, we systematically analyzed the composition and spatial-temporal dynamic distributions of Thalassiosira in the model marine ecosystem Jiaozhou Bay by applying metabarcoding analysis. Through analyzing samples collected monthly from 12 sampling sites, 14 Thalassiosira species were identified, including five species that were not previously reported in Jiaozhou Bay, demonstrating the resolution and effectiveness of metabarcoding analysis in ecological research. Many Thalassiosira species showed prominent temporal preferences in Jiaozhou Bay, with some displaying spring-winter preference represented by Thalassiosira tenera, while others displaying summer-autumn preference represented by Thalassiosira lundiana and Thalassiosira minuscula, indicating that the temperature is an important driving factor in the temporal dynamics. The application of metabarcoding analysis, equipped with appropriate molecular markers with high resolution and high specificity and databases of reference molecular marker sequences for potential all Thalassiosira species, will revolutionize ecological research of Thalassiosira species in Jiaozhou Bay and other marine ecosystems.

Spatial and temporal variations in the pollution status and sources of mercury in the Jiaozhou bay.

In the past few decades, mercury (Hg) discharged into the coastal bays of China has significantly increased; however, long-term trends regarding the pollution status and sources of Hg in these bays have yet to be clear. Focusing on this issue, surface sediments and core sediments were collected in the Jiaozhou Bay (JZB), a typical bay highly affected by human activities in China, to analyze the concentrations and stable isotopic composition of Hg. Total mercury (THg) concentrations in surface sediment varied from 7 to 163 ng/g, with higher levels located in the eastern JZB, possibly attributed to intensive industrial and population density. THg in sediment cores 14 and 20 displayed fluctuating increasing trends from 1936 to 2019, reflecting the deterioration of Hg pollution. In contrast, THg in sediment core 28 near the river mouth exhibited a declining trend, possibly due to the river dam construction. Using a stable isotope mixing model, contributions of various sources (atmospheric, riverine, and industrial emissions) to Hg in the JZB were estimated. The results showed that industrial emissions were the main source (over 50%) of mercury in the JZB in 2019. Sediment cores recorded an increase in industrial Hg due to early industrialization and Reform and Opening-up before 2000. In addition, sediment core 20 demonstrated a rise in the percentage of riverine Hg due to land reclamation at the bay's mouth during 2000-2007.

Sources and high burial efficiency of fossil organic carbon in small bays and implication for coastal carbon cycle.

Coastal seas receive and store large amounts of organic carbon (OC) from land and ocean, thereby playing a crucial role in the global carbon cycle. Understanding factors that influencing OC sources and burial efficiencies in coastal areas have been challenging. We selected the Jiaozhou Bay (JZB) and its surrounding rivers heavily affected by human activities as a case study small bay. We presented bulk parameters of grain size, sediment surface area (SSA), TOC content and carbon isotopes (δ13Corg and Δ14Corg), terrestrial biomarkers (∑C27 + C29 + C31n-alkanes) and marine biomarkers (brassicasterol and dinosterol) in surface sediments and suspended particulates. Our results showed low TOC and biomarker contents in the Dagu River Estuary from the west of the JZB associated with coarse sediments and lower SSA. To estimate the OC proportions, we applied a three-end member mixing model based on TOC δ13Corg and biomarker ratios and obtained the OC contribution from phytoplankton (average 52 %), soil (average 34 %) and wetlands (average 14 %). A transect from east to west of the JZB was selected to further assess the OC age composition based on radiocarbon isotopic (14C) measurements for a new perspective. The lower Δ14Corg values in the east revealed fossil OC contributions from human activities, such as petroleum pollutant inputs from sewage outlets. Based on a dual­carbon isotope (δ13Corg and Δ14Corg) mass balance mixing model, the OC contributions were 40 %, 34 %, 14 %, 12 % from fossil carbon, phytoplankton, wetlands and soil, respectively. The very high burial efficiency of fossil OC in JZB (111 ± 19 %) indicated that small bays such as the JZB could be an important sedimentary carbon sink.

High throughput amplicon analysis reveals potential novel ammonia oxidizing prokaryotes in the eutrophic Jiaozhou Bay.

Ammonia-oxidizing prokaryotes (AOPs) are the major contributors of ammonia oxidization with widely distribution. Here we investigated the phylogenetic diversity, community composition, and regulating factors of AOPs in Jiaozhou Bay (JZB) with high-throughput sequencing of amoA gene. Phylogenetic analysis showed most of the OTUs could not be clustered with any known AOPs, indicating there might exist putative novel AOPs. With new developed protocols for AOP community analysis, we confirmed that only 3 OTUs of ammonia-oxidizing archaea (AOA) could be affiliated to known Nitrosopumilaceae and Nitrososphaera, and the other OTUs were identified as novel AOA based on the threshold. All abstained OTUs of ammonia-oxidizing bacteria (AOB) were identified as novel clusters based on the threshold. Further analysis showed the novel AOPs had different distribution characteristics related to environmental factors. The high abundance and widespread distribution of these novel AOPs indicated that they played an important role in ammonia conversion in eutrophic JZB.

Comprehensive assessment of occurrence, temporal-spatial variations, and ecological risks of heavy metals in Jiaozhou Bay, China: A comprehensive study.

Heavy metals play a significant role in marine ecosystems, exerting notable impacts on the environment and human health. In this study, water, sediment, and aquatic organism samples from Jiaozhou Bay were investigated to comprehensively assess the distribution, temporal-spatial variations, and ecological risks of heavy metals. The results indicate that pollution from industrial wastewater discharge contributes to regional differences in the distribution of heavy metals, possibly being a major source of Zn, Cr, Cd, and Hg (r > 0.7, p < 0.05). Biological and physicochemical processes influence the distribution of Zn, Cr, and Pb in the water and sediment. Hg exhibits a polluted state in both the water and sediment, with As and Hg being the two highest-risk heavy metals in water and sediment, respectively. Among the organisms, crustaceans show significantly higher levels of heavy metal content and accumulation compared to mollusks and fish (p < 0.05), and the bioamplification of heavy metals occurs in the sediment-Rapana venosa-Portunus trituberculatus biological pathway. Portunus trituberculatus, Charybdis japonica, Oratosquilla oratoria, and Octopus ocellatus could pose risks to human health, especially for children and vulnerable populations. This study aims to enhance our understanding of the current status of heavy metal pollution in Jiaozhou Bay and to provide a scientific basis and favorable support for the ecological environmental protection and prevention of ecological risks associated with heavy metal pollution in Jiaozhou Bay and other bays in China.

Environmental forcing of phytoplankton carbon-to-diversity ratio and carbon-to-chlorophyll ratio: A case study in Jiaozhou Bay, the Yellow Sea.

The relationships between phytoplankton carbon (C) biomass and diversity (i.e., C-to-H' ratio) and chlorophyll a (i.e., C-to-Chl a ratio) are good indicators of marine ecosystem functioning and stability. Here we conducted four cruises spanning 2 years in Jiaozhou Bay to explore the dynamics of C-to-H' and C-to-Chl a ratios. The results showed that the phytoplankton C biomass and diversity were dominated by diatoms, followed by dinoflagellates. The average C-to-H' ratio ranged from 84.10 to 912.17, with high values occurring in the northern region of the bay. In contrast, the average C-to-Chl a ratio ranged between 15.55 and 89.47, and high values primarily appeared in the northern or northeastern part of the bay. In addition, the redundancy analysis showed that temperature and phosphate (DIP) were significantly correlated with both ratios in most cases, indicating that temperature and DIP may be key factors affecting the dynamics of C-to-H' and C-to-Chl a ratios.

Contrasting effects of river inflow and seawater intrusion on zooplankton community structure in Jiaozhou bay, the Yellow Sea.

Environmental changes associated with river inflow and seawater intrusion are known to affect zooplankton communities in coastal systems, but how zooplankton respond to these environmental changes remains unclear at present. Here we explored the effects of river inflow and seawater intrusion on zooplankton community structure in Jiaozhou Bay. The results showed that the river inflow and seawater intrusion are key in driving zooplankton dynamics, but with contrasting effects. According to the distinct hydrographic conditions, the sampling area could be geographically divided into the river inflow area with low-salinity and high-nutrient conditions (i.e., EIZ) and the seawater intrusion zone with high-salinity and low-nutrient conditions (i.e., SIZ). There were significant differences in zooplankton communities (e.g., abundance and species composition) between the two regions with seasonal changes. For example, the zooplankton abundance was significantly higher in the SIZ than in the EIZ during spring, whereas an opposite pattern was observed for the summer season. In contrast, the species richness was higher in the EIZ than in the SIZ in spring, while an opposite variation trend was observed during summer. These results together suggested that the river inflow and seawater intrusion had contrasting effects on zooplankton community structure in different seasons. According to the canonical correspondence analysis, we observed that the zooplankton community structure was mainly driven by temperature, chlorophyll a (Chl a), and nutrients in the EIZ, but it was largely affected by salinity in the SIZ. The implication is that changes in temperature, Chl a, and nutrients as a result of river inflow and changes in salinity as a consequence of seawater intrusion are key in driving the dynamics of zooplankton communities in Jiaozhou Bay.

Wastewater inputs reduce the CO2 uptake by coastal oceans.

Every year a large quantity of wastewater is generated worldwide, but its influence on the carbon dioxide (CO2) uptake by coastal oceans is not well understood. Here, sea surface CO2 partial pressure (pCO2) and air-sea CO2 flux were examined in the Jiaozhou Bay (JZB), a temperate coastal bay strongly disturbed by wastewater inputs. Monthly surveys from April 2014 through March 2015 showed that surface pCO2 in the JZB substantially varied both temporally and spatially between 163 µatm and 1222 µatm, with an annual average of 573 µatm. During April-December, surface pCO2 was oversaturated with respect to the atmosphere, with high values exceeding 1000 µatm in the northeastern part of the bay, where seawater salinity was low mainly due to the inputs of wastewater with salinity close to zero. During January-March, surface pCO2 was undersaturated, with the lowest value of <200 µatm also mainly in the northeastern part because of low water temperature and strong biological production. Over an annual cycle, apparently sea surface temperature dominated the monthly variation of surface pCO2 in this shallow bay, while wastewater inputs and related biological production/respiration dominated its spatial variability. Overall, the JZB was a net CO2 source to the atmosphere, emitting 9.6 ± 10.8 mmol C m-2 d-1, unlike its adjacent western part of the Yellow Sea and most of the temperate coastal oceans which are a net CO2 sink. This was possibly associated with wastewater inputs that cause high sea surface pCO2 via direct inputs of CO2 and degradation of organic matter. Thus, from this viewpoint reducing wastewater discharge or lowering CO2 levels in discharged wastewater may be important paths to enhancing the CO2 uptake by coastal oceans in the future.

Spatial distribution, source, and ecological risk of polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs) in Jiaozhou Bay, China.

Polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs) are commonly found in the environment as components of brominated flame retardants. Due to their potential impact on human health and wildlife, it is imperative to closely monitor and manage their levels in the environment. This study investigated the spatial distribution, sources, and ecological risks of PBDEs and HBCDs in Jiaozhou Bay (JZB), a large bay situated on the eastern coast of China. The results showed that PBDE concentrations ranged from not detected (ND) to 7.93 ng/L in the water and ND to 65.76 ng/g in the sediment, while HBCD concentrations ranged from ND to 0.31 ng/L in the water and ND to 16.63 ng/g in the sediment. Furthermore, we observed significantly higher concentrations of PBDEs and HBCDs in the inner JZB compared to the outer JZB. Our source apportionment analysis showed that PBDEs primarily originated from the production and debromination of BDE-209, as well as the emission of commercial PeBDEs, whereas HBCDs in sediments mostly stemmed from anthropogenic activities and river input. Finally, our eco-logical risk assessment highlighted the need for continuous monitoring of PBDEs in JZB sediments. Overall, our study aims to provide valuable assistance for the environmental management of the JZB bay area, which is characterized by a complex net-work of rivers and a thriving economy.

Impacts of anthropogenic discharge on distribution, mass budget, and long-term risk of total mercury in coastal region: A case study of the Jiaozhou Bay, China.

Mercury (Hg) as a toxic pollutant in marine systems have been paid more attention. The Jiaozhou Bay (JZB) is located at the western coast of the Yellow Sea surrounded by Qingdao city, a developed city in China. >10 rivers and several sewage treatment plants carry lots of Hg input it, increasing the environmental risks JZB facing. However, there is still a lack of knowledge on its cycling in the JZB, limiting sound understanding of Hg fate in coastal regions. To address these needs, four cruises were conducted in different seasons, to investigate distribution, influencing factors, and mass budget of total Hg (THg) in the JZB. Higher THg concentrations were determined in seawater (22.8 ± 13.9 ng L-1) and sediment (148 ± 107 ng g-1), indicating serious Hg pollution in the JZB. Temperature, salinity in water and enrich factor (EF) in sediment were identified to be possible environmental factors influencing THg distribution in the JZB. Mass budget of THg showed that anthropogenic discharge (river, wastewater input, and atmospheric deposition) was dominant source of THg in the JZB. The results of statistical analyses and mass budget of THg also indicated that anthropogenic discharge plays important roles in long-term risk of THg in the JZB. These results suggested that anthropogenic discharge comprehensively affects distribution, mass budget, and long-term risk of THg in coastal systems. The outcomes highlighted that regular investigations of Hg cycling should be conducted to assess Hg pollution in coastal ecosystems. Our study also shed new light on control of long-term risk posed by Hg in marine systems according to investigations of Hg cycling and link between Hg contamination and other pollutant (e.g., nutrient).

Land-derived wastewater facilitates antibiotic resistance contamination in marine sediment of semi-closed bay: A case study in Jiaozhou Bay, China.

The emergence of antibiotic resistance is a severe threat to public health. There are few studies on the effects of sewage discharge on antibiotics and antibiotic resistance genes (ARGs) contamination in Jiaozhou Bay sediment. Herein, a total of 281 ARG subtypes, 10 mobile genetic elements (MGEs), 10 antibiotics and bacterial communities in marine sediments from Jiaozhou Bay were characterized. Similar bacterial community structures and ARG profiles were identified between the various sampling sites inside the bay, which were both dominated by multidrug and (fluoro)quinolone resistance genes and harbored lower relative abundances of ARGs than those in the sampling sites near the bay exit. Compared with antibiotics and MGEs, bacterial community composition was a more important driver of ARG diversity and geographic distribution. The abundance of pathogens carrying genetic information increased dramatically in southern Jiaozhou Bay is affected by sewage discharge, which indicating that wastewater discharge facilitated ARG contamination of marine sediments. This study highlights the risk of disseminating antibiotic resistance-influencing factors from treated wastewater discharge into marine environment there is an urgent need to optimize or improve wastewater treatment processes to enhance the removal of antibiotics and ARGs. This study has necessary implications for filling the gap in information on antibiotic resistance in Jiaozhou Bay and developing future pollution regulation and control measures.

Occurrence, transport and environmental risk assessment of pharmaceuticals and personal care products (PPCPs) at the mouth of Jiaozhou Bay, China based on stir bar sorptive extraction.

In recent years, research on pharmaceuticals and personal care products (PPCPs) in the marine environment has attracted increasing attention worldwide. However, more work is needed to improve PPCPs detection methods, specifically for seawater environments. An analytical method based on stir bar sorptive extraction (SBSE) had been developed and fully optimized for the pretreatment and detection of ten widely used PPCPs that are commonly found in seawater samples. By optimizing several variables including the material of the stir bars, extraction temperature, extraction time, ionic strength, desorption solvent, and desorption time, the optimized method has achieved excellent results in the detection and quantification of target PPCPs with detection limits ranging from 0.03 to 1 ng/L. The distribution of target PPCPs at the mouth of Jiaozhou Bay was successfully determined by this method, and the concentrations and detection frequencies of PPCPs varied greatly from N.D. to 449.36 ng/L and from 9.1 % to 100 %, respectively. Moreover, the distributions of PPCPs were explained by the Lagrangian particle-tracking model, and the results showed that the Tuandao sewage treatment plant had the most significant impact on the study area. The environmental risk assessment results showed that several target PPCPs might pose risks to aquatic organisms. In particular, triclocarban should receive more attention and the risk quotients of the mixtures (MRQ) should not be ignored.

Evolution of polycyclic aromatic hydrocarbons in the surface sediment of southern Jiaozhou Bay in northern China after an accident of oil pipeline explosion.

The 2013 "Qingdao oil pipeline explosion" contaminated about 2.5 km of shoreline in the Jiaozhou Bay area and aroused widespread concern because of the serious casualties even though it was not the most severe oil-spill contamination in China. To evaluate the long-term impact, we collected thirty-three surface sediment samples after 3 years of the accident, with sixteen polycyclic aromatic hydrocarbons (PAHs) detected. Spatial-temporal variation in PAHs revealed that a minimal impact might still be present after 3 years. Source analysis combined with a one-way ANOVA showed that pyrolytic sources were consistently predominant. The environmental impact was already minimal 3 years later and negligible thereafter. Although the cancer risk has decreased over the years, there has always been a potential hazard to human for specific occupation, with all of the risk values exceeded 10-6. This study offers a reference for assessing the long-term impact of oil spills in similar bay areas.

Effects of methyl halide flux characteristics following Spartina alterniflora invasion in a seaward direction in a temperate salt marsh, China.

In this study, we explored the source-sink characteristics of methyl halide (CH3X; X = Cl, Br, I) in coastal wetlands located in temperate regions, and identified key factors affecting the spatio-temporal variation of CH3X during the invasion of Spartina alterniflora. We used static chamber-gas chromatography to monitor CH3X fluxes in the S. alterniflora area and bare flat area of the Jiaozhou Bay salt marsh for a long time from August 2015 to May 2017. Our results indicated that CH3X emissions showed obvious seasonal and diurnal variations. The S. alterniflora area was a source of CH3X, with higher fluxes in the spring and autumn seasons. CH3X fluxes were higher during the daytime than at night, and the diurnal difference in CH3Br was the most significant (4.51 times). The bare flat area was mainly a sink for CH3X, and the maximum absorption flux occurred in summer. At this time, the microbial activity was greater, and the consumption rate during the day was higher than that at night. Extreme linear correlations existed between the fluxes of CH3Cl, CH3Br, and CH3I (P < 0.01), indicating that the production and consumption of the three gases were likely to have similar mechanisms and were affected by the same factors. S. alterniflora invasion increased CH3X emissions and shifted the original bare flat area from a sink to a source of CH3X. The biomass of S. alterniflora, especially the leaf, significantly affects CH3X fluxes. Additionally, S. alterniflora increased the content of total organic carbon, total sulfur, available sulfur, and iron (III) in the soil, which were the main factors promoting the source-sink transformation of CH3X. Based on the current invasive area of S. alterniflora in China, we estimated that the annual emissions of CH3Cl, CH3Br, and CH3I from S. alterniflora into the troposphere were 9.04 × 106, 2.42 × 105 and 2.06 × 105 mol, respectively.

Distribution, sources, and ecological risk of organophosphate esters in the urbanized Jiaozhou Bay, East China.

Organophosphate esters (OPEs), substitutes of polybrominated diphenyl ethers, have been found in a variety of marine environmental matrices, whereas little is known about the feature and sources of seawater OPEs from the environments simultaneously affected by multiple anthropogenic activities. Jiaozhou Bay is one typical bay heavily disturbed by human activities, which was semi-enclosed and surrounded by large amounts of discharged rivers and catchments, various types of ports, and aquaculture farms. This study found that concentrations of Σ13OPEs ranged from 23.90 to 366.40 ng/L (median: 37.76 ng/L) in the seawater and from 90.15 to 1183.14 ng/L (median: 940.61 ng/L) in the inflowing river water. Tris (2-chloroisopropyl) phosphate, triethyl phosphate, and tris (2-chloroethyl) phosphate were the predominant congener, with the percentage of 43.76%, 22.80%, and 14.01%, respectively, in the bay water and 52.47%, 11.31%, and 23.66% in the river water. The overall spatial distribution was characterized by a higher concentration of Σ13OPEs and halogenated-OPEs in the nearshore sites and in the inflowing rivers, which were surrounded by urbanized areas with dense anthropogenic activities, especially along the eastern coast. Effluent discharge and vehicular and marine traffic emissions were distinguished as two main plausible sources of OPEs to Jiaozhou Bay, based on the principal component analysis and Spearman correlations. Ecological risk analysis indicated that Σ13OPEs posed a low risk to aquatic organisms in the bay and low-to-medium risks in the inflowing rivers.