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The nutrient regime has changed significantly in the Bohai Sea (BS) during the past six decades because of anthropogenic perturbations. Specifically, the concentration of DIN increased by about 7-fold from the end of the 1950s to the mid-2010s, while DIP and DSi concentrations decreased from the end of the 1950s to the beginning of the 1990s, and have since increased again. Unsynchronized changes in nutrient levels have led to changes in the nutrients structure, which has caused a series of ecological effects. Phytoplankton biomass increased by 6-fold from the 1960s to the mid-2010s. Additionally, phytoplankton composition shifted from a diatom-dominated to a dinoflagellate-dominated system, and the dominant species of macrozoobenthos changed. Red tides rarely occurred before the 1980s, but have occurred periodically and frequently since the 1990s. Finally, the BS ecosystem has shifted from an N-limited oligotrophic state before the 1990s to a potentially P-limited eutrophic state. • Dissolved inorganic nitrogen increased by 7-fold over the past 60 years in Bohai Sea • Dissolved inorganic phosphorus, dissolved silica decreased first and then increased • Phytoplankton biomass increased by 6-fold and the dominant species changed • Bohai Sea shifted from N-limited oligotrophic state to P-limited eutrophic state [ABSTRACT FROM AUTHOR]

Vanadium is a component of different natural and industrial products and a widely used metal, which, nonetheless, has only garnered attention in recent years owing to its potential risks. Six sampling trips were conducted over different seasons and years, collecting 108 samples from rivers and 232 from the bays and analyzed using high-precision inductively coupled plasma mass spectrometry. This study investigated the sources, spatiotemporal characteristics, and risks of vanadium in the aquatic ecosystems of two typical bays of the Northwest Pacific that have strong links with vanadium-related industries. Likewise, the health and ecological risks were assessed using probabilistic and deterministic approaches. Overall, vanadium concentrations were higher in Jiaozhou Bay (JZB: 0.41–52.7 μg L−1) than in Laizhou Bay (LZB: 0.39–17.27 μg L−1), with concentrations higher than the majority of the worldwide studies. Vanadium-realted industries significantly impacted (p < 0.05) the metal concentrations in the rivers with 54.22% (40.73–150%) and 54.45% (27.66%–68.87%) greater concentrations in JZB and LZB rivers. In addition, vanadium exhibited significant seasonal variation, and higher values were quantified during the monsoon period at LZB owing to the greater catchment area. Impacted by smaller freshwater inputs, the post-monsoon period had substantial impacts on JZB, and vanadium in the rivers and bays was significantly higher during the winter. Despite some concentrations being higher than that indicated in the drinking water guidelines established by China, vanadium presents low to null risks to the population as per both approaches. Last, species with limited resilience are likely to face medium to high risks, with an incidence of 65–93% using the probabilistic method and 52–97% using the deterministic assessment. [Display omitted] • Concentrations in water near vanadium-related industries are up to 54.45% higher. • Seasonal variations in the vanadium concentrations linked with vanadium adsorption capacity. • Vanadium concentrations in both study areas higher than those found across China. • Medium and high ecological risks were estimated for both bays. [ABSTRACT FROM AUTHOR]

To investigate the long-term effects of urbanization and industrialization on coastal trace metal contamination, two sediment cores, Q21 (representing 1965–2018) and Q23 (representing 1986–2018), collected from the adjacent coasts of the east old town and west new area of Qingdao were analyzed. Although the concentrations of As, Cd, Co, Cr, Cu, Ni, Pb, Sc, and Zn were higher in Core Q21, the increasing trends in their concentrations and contamination levels were more obvious in Q23, especially since the 2000s. Moreover, the urbanization rates of the new area (1978–2017) were significantly positively correlated with the historical metal concentrations in Q23. Affected by the rapid socio-economic development in the new area, the combined excessive concentrations of the eight metals (excluding Sc) increased faster in Q23 (0.14–78.4 mg/kg) than Q21 (0.58–45.3 mg/kg). Overall, the sediment Core Q23 experienced higher trace metal contamination and ecological risks than Core Q21. • Historical records of nine metals in two cores of Jiaozhou Bay were investigated. • Excessive concentrations of metals in the sediment cores were quantified. • Rapid urbanization in the western bay accelerated metal enrichment in sediments. • Severe metal contamination could occur in western bay owing to rapid urbanization. [ABSTRACT FROM AUTHOR]

The occurrence, spatiotemporal variations, influence factors and environmental risks of eight common neonicotinoids (NEOs), fipronil, and three fipronil metabolites (fipronil and its metabolites are collectively referred to as FIPs) in different seasons from the estuary to the inner area of Jiaozhou Bay, China were comprehensively investigated. First- and second-generation NEOs were found to be the predominant pesticides in this area. The average contents of ∑NEOs and ∑FIPs from the estuary to the inner bay decreased from 12.99 ng/L to 0.82 ng/L and from 1.10 ng/L to 0.17 ng/L, respectively. NEO and FIP concentrations were higher in summer and autumn. High ∑NEO content is distributed in main inflow rivers, such as Dagu River and Licun River, which are influenced by pesticide application. NEO concentrations in all rivers were high upstream and low downstream because of the influence of heavy rainfall and seawater dilution in summer. NEO concentrations were high along the coast and low at the mouth and center of Jiaozhou Bay in summer and autumn and evenly distributed in winter and spring. Temperature has a great influence on most NEOs and FIPs owing to its effect on their degradation. Nitrogen-containing nutrients have an important influence on the distribution of fipronil and acetamiprid, which may be due to the activity of nitrogen-containing functional groups in their structure. Only Licun River, Dagu River and Haibo river sewage treatment plant in summer posed a certain risk of chronic toxicity for NEOs using the new threshold established by the species sensitive distribution (SSD) method for Chinese native aquatic lives. These findings should arouse people's attention. [ABSTRACT FROM AUTHOR]

Endocrine-disrupting chemicals (EDCs) in water are receiving particular attention as they pose adverse effects on aquatic systems, even at trace concentrations. A comprehensive study was conducted on 14 EDCs (five estrogens and nine household and personal care products (HPCPs)) in the water of the urbanized Jiaozhou Bay in the Yellow Sea during summer and winter. Results showed that the total concentration of 14 EDCs ranged from 100 to 658 ng L−1 and 56.7–212 ng L−1 in the estuarine and bay water, respectively. The average total concentration of five estrogens in summer was significantly (p < 0.05) lower than that in winter due to the higher precipitation dilution and degradations during summer, whereas the average total concentration of nine HPCPs was significantly (p < 0.05) higher during the summer than that during the winter because of the higher usage and emissions during the summer. Estrogens and HPCPs were dominated by 17α-ethinylestradiol and p-hydroxybenzoic acid (PHBA), respectively. High PHBA concentrations may be related to the hydrolysis of parabens. The total concentrations of EDCs were higher in the eastern coastal seawater of the bay due to the strong influence of domestic and industrial wastewater discharge. Estrogens may interfere with the endocrine system of aquatic organisms in the bay because the total estradiol equivalent concentration exceeded 1 ng L−1. 17α-ethinylestradiol was the main contributor to the estrogenic activity. The EDC mixtures posed high risks (RQ > 1) to mollusks, crustaceans, and fish, and low to moderate risks (RQ < 1) to algae. Fish was the most sensitive aquatic taxon to the EDC mixtures. Given the concentration and frequency of EDCs, the optimized risk quotient method revealed that 17α-ethinylestradiol, estrone, triclocarban, triclosan, and 17β-estradiol should be prioritized in ecological management because of their high risks (prioritization index of >1). [Display omitted] • Endocrine-disrupting chemicals (EDCs) are widely detected in an urbanized bay. • Estrogen concentration is lower in summer due to high rainfall and degradation. • Household and personal care products (HPCPs) was high in summer due to high use. • Impacted by riverine input, EDC concentration was high in the eastern bay coast. • Five priority EDCs with high ecological risks were identified. [ABSTRACT FROM AUTHOR]

Identifying trophic status shift and developing nutrient criteria were considered important for controlling coastal eutrophication. Based on data from 1980 to 2018, we used sequential t -test analysis of regime shifts and assessment of coastal trophic status models to detect regime shifts in trophic status in Bohai Bay (China). We identified four distinct periods: unimpaired (1980–1984), minimally impacted (1985–1994), tipping point (1995–1999) and severely degraded (2000–2018). Using the reference conditions at different trophic status, a frequency distribution analysis was performed to develop candidate nutrient criteria. By considering other factors, such as the quantity and quality of data and long-term nutrient variations, we determined recommended criteria for dissolved inorganic nitrogen (15.3 μmol L−1) and phosphorus (0.42 μmol L−1) in Bohai Bay. This study provides a novel and feasible approach to determine reference conditions for the determination of nutrient criteria for coastal waters. Regime shift in trophic status of Bohai Bay during different time periods. [Display omitted] • Four distinct periods of trophic status were identified in Bohai Bay in the past four decades. • The reference conditions were determined based on the combined results of STARS and ASSETS models. • The regionally specific nutrient criteria were developed for Bohai Bay. [ABSTRACT FROM AUTHOR]

Arsenic (As) and antimony (Sb) are toxic metalloids widely distributed in coastal sediments, but are seldom studied for their geochemical baselines. In this study, sediment samples were collected from Jiaozhou Bay (JZB) to evaluate their baselines, contamination, and ecological risk. Results showed that the As and Sb concentrations were between 3.15 and 11.94 mg/kg and 0.20–0.61 mg/kg, respectively. Sc and Fe showed good performance in developing geochemical baseline functions for the metalloids. Organic matter content and clay had significant positive correlations with metalloid abundance in sediments (p < 0.01). In the JZB, As and Sb were not enriched in the sediments, with the enrichment factors below 1. Furthermore, the contamination degrees of As and Sb were low in the JZB. In addition, the ecological risks of As and Sb were relatively low in the JZB, with the risk index between 4.02 and 12.70 and 1.68–5.09, respectively. • Geochemical baseline functions of As and Sb were developed in a semi-enclosed bay. • Organic matter and clay were significantly relevant with metalloids in sediments. • As and Sb were not enriched in the sediments of the JZB. • The contamination degrees and risk levels of As and Sb were low in the JZB. [ABSTRACT FROM AUTHOR]

Fourteen perfluoroalkyl substances (PFASs) in fishery organism, surface seawater, river water, rainwater, and wastewater samples collected from Jiaozhou Bay (JZB) in China and its surrounding area were determined to understand their contamination status, sources, health risk, and causes of spatiotemporal variations in the aquatic environment of a temperate bay adjacent to a metropolis. The total concentration of PFASs in 14 species of fishery organisms ranged from 1.77 ng/g to 31.09 ng/g wet weight, and perfluorooctane sulfonate (PFOS) was the dominant PFAS. ∑PFASs concentration in surface seawater ranged from 5.54 ng/L to 48.27 ng/L over four seasons, and dry season (winter and spring) had higher levels than wet season (summer and autumn). Perfluorooctanoic acid (PFOA) was the predominant individual PFAS in seawater, indicating that notorious C8 homologs remained the major PFASs in this region. The seasonal variation in seawater concentrations of three major PFASs, namely, PFOA, perfluoroheptanoic acid, and perfluorononanoic acid, was similar to that of ∑PFASs. However, the seasonal variation of PFOS concentration was different from that of ∑PFASs, with the lowest in winter and the highest in spring. In general, seasonal variations of terrigenous input and water exchange capacity were the main reasons for the spatiotemporal variation of PFASs in the aquatic environment of JZB. Moreover, bioselective enrichment for individual PFAS affected the partition of PFASs in different environment medium. Wet precipitation, sewage discharge, and surface runoff were the main sources of PFASs in this area. Nevertheless, the contribution of different sources to individual PFAS indicated a clear difference, and wastewater and river water were not consistently the most important source for every PFAS. Preliminary risk assessment revealed that the consumption of seafood, especially fish, from JZB might pose a certain extent of health risk to local consumers based on their estimated daily intake of PFASs. Image 1 • Various PFASs occurred in the fishery organisms and aquatic environment of Jiaozhou Bay. • Notorious C8 homologs (PFOA and PFOS) were still the dominant PFASs. • The levels of PFASs in seawater evidently varied with the season and location. • Terrigenous input, tide, and rainfall affected the spatiotemporal variation of PFASs. • Health risks for PFAS exposure via fishery organism intake cannot be ignored. [ABSTRACT FROM AUTHOR]

Coppicing is a highly effective method of producing a great deal of fast growing, sustainable timber without the need for replanting. Tamarix chinensis , a native salt-tolerant species, plays an important role in the ecosystems of arid saline alkali soil and coastal wetlands in northern China. In this study, we conducted a coppicing field experiment on T. chinensis to study the vigor of resprouting over a 4-year monitoring period in the coastal wetland of Laizhou Bay, China. Results of this study show that the growth of coppiced T. chinensis was vigorous and conformed to an "S-curve" type growth pattern. The height and crown of coppiced T. chinensis recovered quickly to the initial level by the 2nd year of regrowth and its aboveground biomass regained 93.5% of the previous level by the 4th year. The carbon stock in the T. chinensis wetland was significantly increased by the coppicing operation. Carbon stocks in the aboveground parts and soil (0–100 cm) increased by 222.6 g m−2 and 588.9 g m−2, respectively, during the 4-year experimental period. These values are 43% and 74% higher, respectively, than those in the control plot over the same period. These results indicate that coppicing provides a practical means for promoting regeneration and rejuvenation of Tamarix spp. forests as well as a new approach to increasing biomass and carbon stocks in the coastal wetlands of northern China. [ABSTRACT FROM AUTHOR]

The composition, distribution, origin, and influencing factors of lipophilic marine algal toxins (LMATs) in surface seawater and phytoplankton in Laizhou Bay, China, were comprehensively investigated for the first time. Okadaic acid (OA), pectenotoxin-2 (PTX2), dinophysistoxin-1 (DTX1), dinophysistoxin-2 (DTX2), and pectenotoxin-2 seco acid (PTX2 SA) were discovered in surface seawater, whereas PTX2, OA, 7-epi-PTX-2 SA, DTX1, PTX2 SA, PTX11, and DTX2 were found in phytoplankton in a decreasing concentration order. ∑LMAT concentrations in seawater and phytoplankton were 1.08–35.66 ng/L (mean: 7.31 ng/L) and 0–3609.75 ng/L (mean: 191.38 ng/L), respectively. LMAT contents in seawater and phytoplankton exhibited the highest levels in the southeastern mouth of Laizhou Bay and decreased toward the inner and outer bays. Dinophysis fortii , D. acuminata , D. rotundata , Procentrum lima , and P. minimum were identified as the potential origins of LMATs in Laizhou Bay. Moreover, increased nutrient level and decreased pH in seawater could increase LMAT content. • Lipophilic marine algal toxins in Laizhou Bay were investigated comprehensively. • Various toxins were detected, and okadaic acid and pectenotoxins were the dominant. • High level of toxins was observed in the southeastern mouth of Laizhou Bay. • Dinophysis spp. and Procentrum spp. were identified as the main sources of toxins. • The levels of these toxins will increase under the influence of global change. [ABSTRACT FROM AUTHOR]

Lipophilic marine algal toxins (LMATs) pose a potential threat to the health of marine shellfish consumers and marine breeding industries. In this study, LMATs in dissolved phases (DP) and particulate phases (PP) in the seawater of Jiaozhou Bay were accurately determined over four seasons to understand their composition, level, phase partitioning, spatiotemporal variation, and potential sources in aquatic environments of a typical semi-closed mariculture bay. Various LMATs, such as okadaic acid (OA), dinophysistoxin-1 (DTX1), dinophysistoxin-2 (DTX2), gymnodimine (GYM), 13-desmethyl spirolide C (SPX1), pectenotoxin-2 (PTX2), pectenotoxin-2 seco acid (PTX2 SA), and pectenotoxin-11 (PTX11), were detected in DP and PP; of these, OA and PTX2 were the dominant LMATs in DP and PP, respectively. The average proportion of ΣLMATs in DP (97.5%) was significantly higher than that in PP (2.5%), which indicates that LMATs are predominantly partitioned into DP. The total concentrations of LMATs in DP ranged from 4.16 ng/L to 23.19 ng/L (mean, 13.35 ng/L) over four seasons. The highest levels of LMATs in DP and PP were found in summer (mean, 16.71 ng/L) and spring, respectively, while the maximum variety of LMATs was found in autumn. This result suggests that seasonal changes could influence the composition, concentration, and phase partitioning of LMATs in aquatic environments of a coastal semi-closed mariculture bay. ΣLMAT concentrations were higher in the western region than in the eastern region of the bay, where shellfish may have a greater risk of exposure. Dinophysis acuminata , Dinophysis fortii , and Prorocentrum minimum were the potential sources of LMATs in the aquaculture seawater. Overall, various LMATs occurred in the semi-closed mariculture bay, and the persistence and bioavailability of these toxins in aquaculture seawater should be determined in future research. Image 1 • LMATs in aquatic environments of Jiaozhou Bay in China, a typical mariculture bay, were accurately measured. • While several LMATs were found in both dissolved and particulate phases, these were dominant in the former. • The composition and level of LMATs in aquaculture seawater evidently varied with the season. • Spatial variations in LMAT level in the seawater of the coastal semi-closed bay were not remarkable. • Dinophysis acuminata , Dinophysis fortii , and Prorocentrum minimum may be the main sources of LMATs in Jiaozhou Bay. Various LMATs both in dissolved and particulate phases were distributed in the aquatic environments of a typical semi-closed mariculture bay. [ABSTRACT FROM AUTHOR]

• PPCPs decreased gradually in detection rates and levels from rivers to coastal seas. • Amoxicillin and p-hydroxybenzoic acid accounted for over 50% of the total PPCPs. • Southeastern waters outside the yangtze estuary had higher PPCP concentrations. • PPCP mixtures posed medium to high risks to different aquatic organisms. • Priority PPCPs with high ecological risks were identified. Pharmaceuticals and personal care products (PPCPs) have captured global concern due to their detrimental effects on aquatic organisms. Thirty PPCPs were analyzed in the water of the Jiaozhou Bay watershed, the Yellow Sea (YS) and the East China Sea (ECS) in China to investigate the distribution and risk of PPCPs from rivers to coastal seas, which are not yet well documented. The results showed the prevalence of the target PPCPs with a downward trend in detection frequencies and total concentrations from rivers (675 ng/L on average) to bay (166 ng/L) and to coastal seas (103 ng/L). Antibiotics and personal care products (PCPs) were dominated by amoxicillin (AMOX) and p-hydroxybenzoic acid, respectively, while the dominant estrogens were inconsistent in different regions. Spatially, the total PPCP concentrations were higher in the ECS than that in the YS due to the larger quantity of sewage flowing into the ECS. Additionally, higher total PPCP concentrations were appeared in the southeastern waters outside the Yangtze estuary and Hangzhou Bay of the ECS. The PPCP mixtures might pose medium to high risk to aquatic organisms in general. The total risk quotient (RQ T) of antibiotics and PCPs to algae was higher than that to crustacean and fish, while estrogens may cause the greatest damage to fish. Despite the higher PPCP concentrations in river water than in seawater, the RQ T of PPCPs in bay water was generally higher than that in river water, which may be associated with the susceptibility of marine organisms. Furthermore, the high-risk pollutants that need special concern in different regions were clarified, showing that AMOX, 17ß-estradiol, and estriol deserve the highest-priority in rivers, bay, and coastal waters, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

• Yellow River PAH input & sea currents determined PAH spatial distribution in the sea. • Yellow River alluvial loess solid dilution effect led to lower PAH levels in the sediment. • Yellow River & Yellow Sea water dilution effect led to lower PAH levels in the water. • PAH properties decided its partitions in surface/bottom water & bottom water/sediment. • PAH ecological risks in both water and sediment were negligible or acceptable. The marginal Bohai Sea, connected to the northwestern Pacific Ocean, is threatened by human activity. The Yellow River, the second largest river in China, drains large amounts of water, silts, and polycyclic aromatic hydrocarbons (PAHs) into the southern Bohai Sea; however, to what extent the Yellow River inputs influence the spatial distributions and partitions of PAHs in the southern Bohai Sea is not well known. Therefore, this study collected surface water, bottom water, and sediment samples from the southern Bohai Sea and analyzed them to examine the spatial distributions and partitions of 15 priority PAHs. The results showed that PAH concentrations ranged from 26.9 to 50.1 ng L–1 in surface water, 18.8 to 44.1 ng L–1 in bottom water, and 7.4 to 143.9 ng g–1 in sediment, with higher proportions of four-, five-, and six-ring PAHs in sediment than in water. PAH inputs from the Yellow River and sea coastal currents determined the spatial distribution of PAH concentrations in water and sediment, with an overall decrease from the estuary to the southeast. However, the solid dilution effect of input silts from the Yellow River and the liquid dilution effect of water from the Yellow River and Yellow Sea led to lower PAH concentrations in the water and sediment of the southern Bohai Sea than those in other areas of the Bohai Sea. PAH exchange between the atmosphere and seawater led to significantly higher individual PAH concentrations (except for acenaphthylene) in the surface water than in the bottom water, with ratios significantly related to the PAH n-octanol-water partition coefficient, organic carbon-water partition coefficient, and Henry's law constants. These parameters also determined PAH partitioning between the bottom water and sediment. Individual and total PAH concentrations in the sediment were significantly correlated with organic matter, clay, and silt contents. Therefore, the partitions and spatial distributions of PAHs in the southern Bohai Sea comprehensively depend on PAH properties, PAH inputs from the Yellow River and the atmosphere, sea currents, and seawater and sediment properties. The ecological risks posed by individual PAHs in both water and sediment were negligible or acceptable. [Display omitted] [ABSTRACT FROM AUTHOR]

In the previous decade, neonicotinoids (NEOs) and fipronil (FIP) have received increasing attention as environmental pollutants because the high toxicity of these insecticides to nontarget arthropods has been recognized. In this study, a new method was developed for the simultaneous determination of seven NEOs and FIP and its metabolites (FIPs) in seawater and river water samples using disk-based solid-phase extraction (SPE) and high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS). The optimization of disk-based SPE extraction and HPLC separation parameters of target analytes was investigated. Under optimal conditions, the low limit of quantitation (LOQ) of 11 target analytes in actual water samples ranged from 0.05 ng/L to 0.50 ng/L. Satisfactory absolute recoveries (58.9%–109.9%), precision (relative standard deviations, ≤13.3%), and linearity (R 2 ≥ 0.995) were also achieved, thereby indicating that the developed method would be suitable to determine the target NEOs and FIPs in seawater and river water. Finally, the proposed method was applied to determine the amounts of these insecticides in authentic environmental water samples collected from Jiaozhou Bay, China, and its adjacent rivers. Nitenpyram, thiamethoxam, imidacloprid, clothianidin, and acetamiprid were detected, as well as FIPs in seawater and river water samples. This study is the first to report that NEOs and FIPs are detected in the coastal seawater. The total concentration of these insecticides ranged from ≤LOD to 11.19 ng/L, which indicates that these pesticides are eventually discharged into the marine environment. Therefore, it is necessary to investigate the temporal spatial distribution, migration and transformation, environmental fate, and bioavailability of these pesticides in further studies. Image 1 • SPE disk had favorablerecoveries for simultaneous enrichment of trace NEOs and FIPs. • A reliable analytical method was developed for NEOs and FIPs in water samples. • Several NEOs, FIP, and its metabolites were detected in Jiaozhou Bay coastal water. • The analysis of NEOs and FIPs in seawater was reported for the first time. • More attention has to be focused on environmental risks of the coastal area posed by NEOs and FIPs. [ABSTRACT FROM AUTHOR]

Paralytic shellfish toxins (PSTs) producing algae are widely distributed in the global coastal aquatic environment, posing a threat to coastal ecosystem health and mariculture safety. However, the levels and potential environmental risks of PSTs frequently detected in shellfish remain largely unexplored in seawater of mariculture zones. In this study, a new method for trace detection of 13 common PSTs (<1.0 ng/L) in seawater was established based on off-line solid phase extraction (SPE) and on-line SPE-liquid chromatography-tandem mass spectrometry (on-line SPE-LC-MS/MS), and a systematic investigation of PSTs in seawater of the Laizhou Bay, a typical aquaculture bay in China, was conducted to understand their pollution status, environmental impact factors and ecological risks for the first time. Eleven PSTs were detected in the seawater of Laizhou Bay with total concentrations ranging from 0.75 to 349.47 ng/L (mean, 176.27 ng/L), which indicates the rich diversity of PSTs in the mariculture bay and demonstrates the reliability of the proposed analytical method. C1, C2, GTX2, GTX3, dc GTX2, and dc GTX3 were found to be the predominant PSTs, which refreshed the knowledge of PST contamination in the coastal aquatic environment. PST levels in seawater exhibited the highest levels in the southeastern mouth of Laizhou Bay and decreased toward the inner bay. Correlation analyses showed that climatic factors, nutrient status and hydrological conditions had significant effects on the distribution of PST in mariculture bay. Preliminary environmental risk assessments revealed that aquatic organisms throughout the waters of Laizhou Bay are at risk of chronic PST toxicity. These findings imply that the risk of PST in seawater of mariculture bay has previously been grossly underestimated, and that the coastal aquatic environment in North China and even the world may be at more serious risk of PST pollution, which should be taken seriously. [Display omitted] • A new analytical method was developed for 13 trace PSTs in seawater (<1.0 ng/L). • Various PSTs widely distributed in nearshore water was reported for the fist time. • GTXs, dc GTXs, and C-toxins are the predominant PSTs in mariculture seawater. • Aquatic organisms in the Laizhou Bay are generally at risk of chronic PST toxicity. • Nutrient and hydrological conditions affect the distribution of PST in Laizhou Bay. [ABSTRACT FROM AUTHOR]

We investigated the spatiotemporal distributions, risks, and prioritization of 15 widely used antibiotics in Laizhou Bay (LZB). Water samples (145) were collected from LZB and its estuaries and analyzed. Twelve antibiotics, with total concentrations of 241–1450 and 69–289 ng L−1 in estuarine water and seawater, respectively, were detected, with the contributions of norfloxacin, ciprofloxacin, and amoxicillin exceeding 70%. Amoxicillin was firstly determined, which contributed to 20% and 46% of the total antibiotics during summer and spring, respectively. Higher antibiotic concentrations were observed in the sea located adjacent to aquaculture bases and the Yellow River Estuary, which are significantly influenced by mariculture and riverine inputs, respectively. Veterinary antibiotics showed higher total concentrations in summer compared to spring, indicating a higher degree of their usage in mariculture in summer. The antibiotic mixtures posed high risk to algae and low to medium risks to crustaceans and fish. Amoxicillin and norfloxacin were identified as high-risk pollutants. Additionally, amoxicillin and ciprofloxacin showed medium to high resistance development risks. Previous studies on antibiotics in the LZB did not determined amoxicillin and thus underestimated antibiotic contamination, ecological risk, and resistance development risk. Amoxicillin, norfloxacin, and ciprofloxacin should be prioritized in risk management. [Display omitted] • Amoxicillin in the Laizhou Bay water was firstly determined. • Norfloxacin and amoxicillin concentrations were higher than other compounds. • Mariculture & Yellow River inputs affected antibiotic spatiotemporal distribution. • Veterinary antibiotics showed higher concentrations in summer than in spring. • Priority antibiotics with high ecological and/or resistance risks were identified. [ABSTRACT FROM AUTHOR]

• Historical evolution of coastal eutrophication in China exhibited two periods. • Nutrient composition and stoichiometry in coastal waters were significantly changed. • Increased N and P are mainly from river input, atmosphere deposition and SGD. • Changed nutrients have resulted in distinctly varied harmful algal blooms. • Eutrophication combined with climate change continually impact coastal ecosystems. Eutrophication in coastal waters caused by excess nutrient inputs has occurred widely on a global scale. Due to the rapid economic development over the last four decades, most of the Chinese coastal waters have experienced a eutrophic process. Major observed trends of coastal eutrophication include two periods, a slow development from the 1970s to 1990s and a fast development after 2000, with major contributions of increased nitrogen (N) and phosphorus (P) from river inputs, atmospheric deposition, and submarine groundwater discharge (SGD). Nutrient composition and stoichiometry have been significantly changed, including increased ammonium, bioavailable organic N and P, and asymmetric ratios between N, P and silicate (Si). Most of these changes were related to the rapid increases in population density, fertilizer application, sewage discharge, aquaculture and fossil fuel combustion, and have resulted in distinctly increased harmful algal blooms. Coastal eutrophication combined with the effects of climate change is projected to continually grow in coming decades. Targeted research is therefore needed on nitrogen reduction and control, potential adaptation strategies and the consequences for ecosystems and economic sustainability. [ABSTRACT FROM AUTHOR]

[Display omitted] Atrazine, a potent herbicide for weeds removal during the growing season, has been widely used in China. It is known to be distributed in aquatic ecosystems with a long half-life, thus presenting a potential risk to species and consumers. This study analyzed the concentrations of degraded atrazine residues in marine organisms (N = 129) including 3 species of mollusks, 2 species of crustaceans, and 15 species of fish from a semi-enclosed bay, Jiaozhou Bay (JZB), adjacent to the Northwest Pacific Ocean in China. The corresponding trophic magnification factors (TMF), bioaccumulation factors (BCFs), and subsequent risks to final consumers were also determined. The results showed an average atrazine concentration of (0.301 ± 0.03) ng g−1 and (0.305 ± 0.04) ng g−1 in fish and invertebrates, respectively. The BCFs were (5.23 ± 1.75) L kg−1 and (5.81 ± 1.31) L kg−1 for fish and invertebrates, respectively. Atrazine was significantly bio-diluted in JZB through the sampled marine organisms with increasing trophic levels, with a TMF value below 1 (P < 0.01). An analysis of the species sensitivity distribution (SSD) predicted that<0.02% of species were exposed to a dissolved concentration of atrazine (57.88 ng L−1) that would lead to detrimental effects, while risk quotients predicted low long-term risks for species in the bay. Finally, people with a diet limited to species from JZB were found to face no associated health risk due to a significantly small daily intake and target hazard quotient of atrazine. The corresponding non-carcinogenic effect showed no significant risk from seafood consumption. [ABSTRACT FROM AUTHOR]

Lipophilic marine algal toxins (LMATs) are highly toxic secondary metabolites produced by marine microalgae that pose a great threat to marine aquaculture organisms and human health. In this study, a novel and automated method for the simultaneous determination of six groups of LMATs in seawater was developed by on-line solid phase extraction (SPE) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Condition optimization and method validation were performed, and the recoveries of all 14 target LMATs featuring different properties ranged from 83.5% to 96.0%. The limits of detection of most target compounds were within ≤3.000 ng/L with good precision (relative standard deviation ≤ 12.1%) and linearity (R 2 ≥0.9916). Compared with off-line SPE methods, the proposed on-line SPE method has better recovery, sensitivity, repeatability, and throughput; in addition, the volume of seawater sample necessary to conduct determinations is greatly reduced in the present method. Finally, the method was applied to determine LMATs in actual seawater samples collected from the Bohai and South Yellow Seas of China in summer, and okadaic acid and pectenotoxin-2 were detected in all seawater samples. The highest concentration of ∑LMATs (22.23 ng/L) occurred in the coastal mariculture area of Shandong Province. Therefore, routine monitoring of LMATs in seawater of the coastal mariculture zone is necessary to prevent shellfish contamination especially in summer, and the proposed on-line SPE-LC-MS/MS method is a powerful way for direct and automatic detection of various LMATs in coastal mariculture area. A quantitative strategy of 14 common LMATs in seawater was developed with online-SPE-UHPLC-MS/MS using MRM mode. Image 1 • A novel and automated method was developed to detect LMATs in seawater simultaneously. • On-line SPE-LC-MS/MS could achieve the rapid detection of 6 groups of typical LMATs. • A single injection requires only 2.4 mL of seawater and a total analytical time of 25 min. • The method was successfully applied to detect LMATs in the Yellow and Bohai Seas in China. • Considerable attention should be paid to the occurrence of LMATs in mariculture zone. [ABSTRACT FROM AUTHOR]

• Arsenic was the most enriched in the crustaceans compared with molluscs and fish. • Arsenic content in marine organisms was higher in the northern coasts of China. • Arsenic was slightly biodiluted in marine organisms with increasing values of δ15N. • Health risk of eating crustaceans was the highest especially for urban households. China has been the major fishery producer in the Northwest Pacific Ocean for decades and the seafood safety deserves continuous concern. In this study, 188 organism and 27 sediment samples were collected from the Jiaozhou Bay, a typical semi-enclosed bay adjacent to the Northwest Pacific Ocean, to study the arsenic (As) pollution level and trophodynamics in the coastal regions of China combined with a meta-analysis. Results showed that arsenic was the most abundant in crustaceans with the average of 28.84 ± 4.95 mg/kg in dry weight, in comparison with molluscs (18.68 ± 2.51 mg/kg) and fish (9.31 ± 1.45 mg/kg). Additionally, based on a meta-analysis, arsenic in coastal organisms generally decreased from north to south in China. With increasing values of δ15N, arsenic was significantly biomagnified in the molluscs but bio-diluted in the groups of crustaceans and fish. When all the species were taken into consideration, overall bio-dilution of As was observed through the simplified food chain in the Jiaozhou Bay. Based on the target hazard quotient (THQ), the health risk of consuming seafood from the Jiaozhou Bay was not significant except for several kinds of crustaceans. The smaller THQs indicated lower health risk of eating molluscs and fish than crustaceans. Besides, urban households tended to undertake much higher risk than rural households. Based on our results, it is recommended for urban citizens to reduce the frequency of consuming crustaceans and give preference to fish when choosing seafood. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• The urbanized bay was heavily contaminated by amoxicillin and fluoroquinolones. • Total antibiotic concentrations were 71.8~840 ng L −1 for the estuarine water and 38.7~181 ng L −1 for the bay water. • Total antibiotic concentrations in the bay water were significantly higher in winter than in summer. • Spatiotemporal changes in antibiotics were driven by their sources and runoff dilution. • Amoxicillin and enrofloxacin presented high risks to algae in the urbanized bay. The occurrence, temporal variation, and spatial variation of antibiotics in coastal bays and estuaries worldwide are not well documented or understood. Fifteen target antibiotics within the five classes of β-lactams, amphenicols, macrolides, fluoroquinolones, and sulfonamides were measured during the summer and winter in the water of Jiaozhou Bay in China, which is a semi-enclosed urbanized bay. Fourteen antibiotics (excluding tylosin) were detected, thus demonstrating the widespread occurrence of their residues in the bay. The total antibiotic concentration ranged from 71.8 ng L −1 to 840 ng L −1 for the estuarine water, which was significantly higher than that for the bay water (38.7–181 ng L −1). The antibiotic classes in the bay water were dominated by fluoroquinolones and β-lactams, which accounted for nearly 90% of the total antibiotic concentration. In addition, amoxicillin contamination was the most prominent among the 14 detected antibiotics as it accounted for ~44% of the total antibiotic concentration. The concentrations of amoxicillin, leucomycin, enrofloxacin, and sulfamonomethoxine in the bay water were usually higher than those reported for coastal bays and estuaries worldwide. The average total antibiotic concentration in the bay water was 84.7 ng L −1 during the summer, which was significantly lower than that during the winter (129.0 ng L −1). This was mainly due to high dilution by runoff during the summer. The florfenicol concentration in the bay water was significantly higher during the summer than in winter due to its higher usage in aquaculture during the summer. Spatially, the total antibiotic concentration (both summer and winter) was higher in the water along the eastern coast of the bay, where the population and hospital densities are high. However, the sum of the veterinary antibiotic concentrations was higher in the northeastern aquaculture area of the bay during the summer. A risk assessment revealed that amoxicillin and enrofloxacin could pose high risks (risk quotient of > 1) to algae in the bay. The synergic effects of pharmaceutical mixtures and the bioaccumulation of antibiotics through the food web should be considered in future studies. Image, graphical abstract [ABSTRACT FROM AUTHOR]