Surface Seawater Samples Research Articles

Inter-annual variation and comprehensive evaluation of organophosphate esters (OPEs) in the Yellow Sea, China

Considering the extensive production and continuous usage of organophosphate esters (OPEs) around the urbanized coasts in recent years, the inter-annual variation and the ecological risks of OPEs in the Yellow Sea (YS), China were systematically evaluated in summer 2015 and 2019. The major component of OPEs, halogenated-OPEs in 78 surface and bottom seawater samples collected from 39 locations in the YS in 2019 were compared with 62 samples at 31 sites conducted in the same periods and similar stations in 2015. The average concentration of halogenated-OPEs increased 1.57, 2.50 folds in the surface and bottom seawater, respectively, in recent 5 years. The proportion of TCPP to halogenated-OPEs exhibited an increasing trend from 56.49% in 2015 to 79.95% in 2019. The peak values of halogenated-OPEs changed from the nearshore regions (33°N-38°N) in 2015 to the nearshore and offshore regions (33°N-35°N) in 2019, implying the growing terrigenous emission sources, especially some large OPEs producers nearby the coastal zones in the northern area of Jiangsu province. The targeted halogenated-OPEs posed no significant or low ecological risks to the aquatic organisms in 2015 and 2019, however, the values of RQ showed an elevated trend in 2019. Therefore, the ecological risks of OPEs in this region still need continuous concern due to the gradually increasing OPEs usage and production.

Biogeochemical controls on ammonium accumulation in the surface layer of the Southern Ocean

Abstract. The production and removal of ammonium (NH4+) are essential upper-ocean nitrogen cycle pathways, yet in the Southern Ocean where NH4+ has been observed to accumulate in surface waters, its mixed-layer cycling remains poorly understood. For surface seawater samples collected between Cape Town and the Marginal Ice Zone in winter 2017, we found that NH4+ concentrations were 5-fold higher than is typical for summer and lower north than south of the Subantarctic Front (0.01–0.26 µM versus 0.19–0.70 µM). Our observations confirm that NH4+ accumulates in the Southern Ocean's winter mixed layer, particularly in polar waters. NH4+ assimilation rates were highest near the Polar Front (12.9 ± 0.4 nM d−1) and in the Subantarctic Zone (10.0 ± 1.5 nM d−1), decreasing towards the Marginal Ice Zone (3.0 ± 0.8 nM d−1) despite the high ambient NH4+ concentrations in these southernmost waters, likely due to the low temperatures and limited light availability. By contrast, rates of NH4+ oxidation were higher south than north of the Polar Front (16.0 ± 0.8 versus 11.1 ± 0.5 nM d−1), perhaps due to the lower-light and higher-iron conditions characteristic of polar waters. NH4+ concentrations were also measured along five transects of the Southern Ocean (Subtropical Zone to Marginal Ice Zone) spanning the 2018/19 annual cycle. These measurements reveal that mixed-layer NH4+ accumulation south of the Subantarctic Front derives from sustained heterotrophic NH4+ production in late summer through winter that, in net, outpaces NH4+ removal by temperature-, light-, and iron-limited microorganisms. Our observations thus imply that the Southern Ocean becomes a biological source of CO2 to the atmosphere in autumn and winter not only because nitrate drawdown is weak but also because the ambient conditions favour net heterotrophy and NH4+ accumulation.

Fulvivirga lutea sp. nov., a marine bacterium isolated from seawater.

A strictly aerobic, Gram-stain-negative, gliding, rod-shaped bacteria, designated strain S481T, was isolated from a surface seawater sample collected at Gunsan marina, in the West Sea of the Republic of Korea. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain S481T formed a monophyletic clade with members of the genus Fulvivirga, showing 93.7-95.8% sequence similarity to the type strains. Strain S481T has a single circular chromosome of 4.13 Mbp with a DNA G+C content of 37.3 mol%. The values of average nucleotide identity, average amino acid identity and digital DNA-DNA hybridization between strain S481T and all genome-sequenced species of the genus Fulvivirga were below 71.2%, 68.6% and 18.9%, respectively, indicating lower values than the standard cut-offs for species delineation. Growth was observed at 20-42 °C (optimum, 37 °C), at pH 6-8 (optimum, pH 7) and with 0 - 6 % NaCl (optimum, 1-2 %). The major fatty acids (>10%) were iso-C15:0, iso-C15:1 G and C16:1ω5c. The respiratory quinone was MK-7. The major polar lipids were identified as phosphatidylethanolamine, three unidentified aminolipids and five unidentified lipids. Based on the results of phenotypic characterization, phylogenetic analysis and genome-based comparison, strain S481T represents a novel species in the genus Fulvivirga, for which we propose the name Fulvivirga lutea sp. nov. The type strain is S481T (=KCTC 82209T=JCM 34505T).

Fate and ecological risks of current-use pesticides in seawater and sediment of the Yellow Sea and East China Sea

With the frequent use of chemical pesticides, the current-use pesticides (CUPs) emerge and concentrate in the sea. The partition between the sediment and seawater is essential for understanding the environmental fate of CUPs. However, there is little research on this topic. In the present study, seventeen CUPs were screened in seawater and sediment samples collected from the Yellow Sea and East China Sea. Total concentration of 17 CUPs in surface seawater samples ranged from 9.5 to 267.3 ng/L, with 6 CUPs presenting 100% detection frequency. Carbendazim, tricyclazole, tebuconazole, atrazine and imidacloprid accounted for >80% of all CUPs, which was due to their large application in the local agriculture and fishing activities. Higher concentration sites were located near the shore and Yangtze river estuary, indicating intense human activities and riverine input that elevated the level of CUPs in marginal sea. The pesticides in seawater were mainly found in the surface followed by the bottom layer, which indicated that atmospheric deposition and re-suspension played key roles for their vertical distribution characteristics. The high fugacity fraction ratios (ff > 0.5) indicated the non-equilibrium state of pesticides that might have been transferred from sediment to seawater at most sites. These 17 detectable pesticides in seawater were at low levels, presenting ignorable or low toxic effects to aquatic organisms.

Seasonality of phytoplankton community and dynamics of autotrophic carbon in a cold temperate port (Argentina)

The changes within and between seasons in phytoplankton composition and abundance determine the carbon biomass available for upper levels of the food web. Temporal changes in phytoplankton community and environmental parameters in a port in Puerto Madryn, Southwest Atlantic were analysed. During an annual period (2011–2012), samples of surface seawater were collected approximately monthly. We determined phytoplankton community structure (species composition and abundance) and biomass (determined by carbon content and chlorophyll a (Chl a)). Water temperature, salinity and transparency were measured when sampling the surface water and local meteorological data were considered. The main groups observed were diatoms (Bacillariophyta; the most abundant during the concentration peaks of Chl a), dinoflagellates (Dinophyta) and flagellates, which mainly included species of Cryptophyta and Chlorophyta. Diatoms exhibited blooms in March (summer–autumn) and September (spring), represented by Skeletonema costatum and Pseudo-nitzschia spp. respectively. Dinoflagellates contributed to the highest carbon biomass, with peaks in January (summer) and April (autumn), exemplified by Prorocentrum micans and Scrippsiella acuminata, respectively. Temporal differences in community composition were related to the seasonal changes in temperature, solar irradiance, precipitation, salinity and wind velocity. The environmental conditions seem not only to determine the species composition but also cell size distribution: nanoplanktonic (≤ 20 µm) species dominated mainly during late spring, summer and early winter while microplanktonic species (> 20 µm) during late winter and early spring. Our results showed within-season changes and show that not only Chl a, but also carbon content can be considered, as the former is a biased estimator of phytoplankton biomass. This study provides the first seasonally resolved estimation in the area of the carbon biomass available for upper levels of the food web and a necessary information for future scenarios prediction. HIGHLIGHTS• Two diatom blooms were followed by an increase in dinoflagellate abundance.• Annual environmental conditions drive the phytoplankton community structure.• First seasonally estimation of autotrophic biomass availability for Patagonian trophic web.

Correction to: Altererythrobacter flava sp. nov., a new member of the family Erythrobacteraceae, isolated from a surface seawater sample

Correction to: Altererythrobacter flava sp. nov., a new member of the family Erythrobacteraceae, isolated from a surface seawater sample

Physical Characterization and Spatial Variability of Microplastics in Coastal Surface Waters in Roxas,Palawan, Philippines

Surface seawater samples gathered from 13 sites in Roxas, Palawan, were subjected to on-site sieving and microplastics visual identification. All samplings contained microplastics, with blue fiber-shaped particles being abundant. The localized terrain, wind patterns, tributaries, and ocean wave path influenced the microplastic particle transport concentration across sampling sites. As a result, local authorities need to develop strategies to reduce microplastics usage and raise citizen consciousness of environmental issues.

Spatial distribution and origin of organic matters in an Arctic fjord system based on lipid biomarkers (n-alkanes and sterols)

The concentration of n-alkanes (C17–C35) and sterols in marine particulate matter were investigated to trace the origin of organic carbon in Kongsfjorden in early spring (April). The spatial distributions of environmental factors (seawater temperature, salinity, density, turbidity, chlorophyll a (chl. a) and particulate organic carbon (POC) concentrations) and the cell density of phytoplankton differed between the inner and outer fjord regions. In addition, brassicasterol, diatom biomarker, showed a high concentration in the outer fjord and positive correlations with the chl. a and POC concentrations in the water column. In contrast, some sterols originating from terrestrial organic matter (OM), such as stigmasterol and campesterol, showed relatively higher concentrations in the inner fjord than in the outer fjord. Based on the distance-based redundancy analysis (db-RDA) result, the distributions of organic compounds are predominantly controlled by the water density and the POC and chl. a concentrations, and these distributions allowed us to divide the inner and outer fjord regions. However, the hierarchical clustering of principal components (HCPC) results obtained based on principal component analysis (PCA) using lipid biomarkers (C17–C35 alkanes and sterols) and environmental factors indicated that the clusters were distinguished by surface (0 m) and subsurface (>4 m) seawater samples rather than by any regional division. Notably, the concentration of relatively short-chain alkanes (average chain length (ACL): 24.6 ± 3.7) without a carbon preference for odd numbers (carbon preference index (CPI): 0.97 ± 0.11) in the sea surface layer was significantly higher than that of subsurface seawater (ACL: 31.1 ± 0.5 and CPI: 1.06 ± 0.03) in the early spring. This suggests the potential of these compounds as indicators for tidewater glacier-derived OM and freshwater input by snow melt into the fjord system. Hence, these results demonstrate that the distributions of lipid biomarkers in the water column possibly provide important information for a comprehensive understanding of the origin and transport of OM in an Arctic fjord.

Microplastics in biota and surface seawater from tropical aquaculture area in Hainan, China

Microplastic pollution is a growing global concern and a serious threat to aquatic life. Microplastics (MPs) have been found in the natural environment in the last few years. However, levels of microplastic pollution in aquaculture areas of Hainan Island have been less studied than in wild environments. Xincun bay (XC) and Gangmen bay (GM) are lagoons that are rich in fishery resources. Here, we investigated microplastic pollution in 8 surface seawater samples, 17 species of fish, and mussel samples from XC bay and GM bay, Hainan, China. The MPs were isolated from surface seawater, organisms and identified by microscopic, Raman spectroscopic and micro-Fourier Transform Infrared spectrometer methods. The mean abundance of MPs in seawater samples was 523 items/m3 and that of fish was 7.1 items/individual and the percentages of microplastics detected in the gastrointestinal tracts (GITs) and gill were 99% and 1%, respectively. MPs were also observed in the soft tissues of mussel samples with a mean abundance of 0.36 ± 0.81 items/individual. Most MPs were identified as polystyrene and their sizes ranged between 0.5 and 5 mm in both seawater and organism samples. Our results indicate that the uptake of microplastics by organisms was closely related to microplastic pollution in the aquaculture environment. Foam pollution is common in organisms and surface seawater in the aquaculture area of our study region, which provides a way for human exposure.

Spatial and temporal dynamics of SAR11 marine bacteria across a nearshore to offshore transect in the tropical Pacific Ocean.

Surveys of microbial communities across transitions coupled with contextual measures of the environment provide a useful approach to dissect the factors determining distributions of microorganisms across ecological niches. Here, monthly time-series samples of surface seawater along a transect spanning the nearshore coastal environment within Kāneʻohe Bay on the island of Oʻahu, Hawaiʻi, and the adjacent offshore environment were collected to investigate the diversity and abundance of SAR11 marine bacteria (order Pelagibacterales) over a 2-year time period. Using 16S ribosomal RNA gene amplicon sequencing, the spatiotemporal distributions of major SAR11 subclades and exact amplicon sequence variants (ASVs) were evaluated. Seven of eight SAR11 subclades detected in this study showed distinct subclade distributions across the coastal to offshore environments. The SAR11 community was dominated by seven (of 106 total) SAR11 ASVs that made up an average of 77% of total SAR11. These seven ASVs spanned five different SAR11 subclades (Ia, Ib, IIa, IV, and Va), and were recovered from all samples collected from either the coastal environment, the offshore, or both. SAR11 ASVs were more often restricted spatially to coastal or offshore environments (64 of 106 ASVs) than they were shared among coastal, transition, and offshore environments (39 of 106 ASVs). Overall, offshore SAR11 communities contained a higher diversity of SAR11 ASVs than their nearshore counterparts, with the highest diversity within the little-studied subclade IIa. This study reveals ecological differentiation of SAR11 marine bacteria across a short physiochemical gradient, further increasing our understanding of how SAR11 genetic diversity partitions into distinct ecological units.

Seasonal and Temporal Influence on Polycyclic Aromatic Hydrocarbons in the Red Sea Coastal Water, Egypt

This study investigated seasonal variation, spatial distribution, sources, composition and potential ecological risks of 16 polycyclic aromatic hydrocarbons (PAHs) in Red Sea coastal water. Surface seawater samples were collected at fourteen different locations. The sum of 16 PAHs concentrations in Red Sea showed clear variation between seasons, ranged from 1.08–6.10, 0.79–50.86, 1.37–54.47 and 0.21–7.18 μg/L in summer, autumn, winter, and spring respectively. PAHs levels in Red Sea coastal waters were relatively high at certain sites during autumn and winter seasons. They could be classified as highly polluted by PAHs contaminants (>10 μg/L). According to the diagnostic ratios measured, the majority of PAHs in this study originated from pyrogenic sources, while minor amounts originated from petrogenic sources. Four rings PAHs accounted for more than 64% of the total PAHs studied. PAHs pose a high ecological risk along the period of study, according to the ecological risk assessment by Risk quotients (RQNCs and RQMPCs).

Cultivable Winogradskyella species are genomically distinct from the sympatric abundant candidate species

Winogradskyella is a genus within the phylum Bacteroidetes with a clear marine origin. Most members of this genus have been found associated with marine animals and algae, but also with inorganic surfaces such as sand. In this study, we analyzed genomes of eleven species recently isolated from surface seawater samples from the North Sea during a single spring algae bloom. Corresponding metagenomes yielded a single Candidatus species for this genus. All species in culture, with the exception of W. ursingii, affiliated with a Winogradskyella lineage characterized by large genomes (~4.3 ± 0.4 Mb), with high complexity in their carbohydrate and protein degradation genes. Specifically, the polysaccharide utilization loci (PULs) were diverse within each individual strain, indicating large substrate versatility. Although present in the North Sea, the abundances of these strains were at, or below, the detection limit of the metagenomes. In contrast, the single species, classified as Candidatus W. atlantica, to which all North Sea MAGs belonged, affiliated with a lineage in which the cultivated representatives showed small genomes of ~3.0–3.5 Mb, with the MAGs having ~2.3 Mb. In Ca. W. atlantica, genome streamlining has apparently resulted in the loss of biosynthesis pathways for several amino acids including arginine, methionine, leucine and valine, and the PUL loci were reduced to a single one for utilizing laminarin. This as-yet uncultivated species seems to capitalize on sporadically abundant substrates that are released by algae blooms, mainly laminarin. We also suggest that this streamlined genome might be responsible for the lack of growth on plates for this Candidatus species, in contrast to growth of the less abundant but coexisting members of the genus.

Heterogeneous ice nucleation ability of aerosol particles generated from Arctic sea surface microlayer and surface seawater samples at cirrus temperatures

Abstract. Sea spray aerosol particles are a recognised type of ice-nucleating particles under mixed-phase cloud conditions. Entities that are responsible for the heterogeneous ice nucleation ability include intact or fragmented cells of marine microorganisms as well as organic matter released by cell exudation. Only a small fraction of sea spray aerosol is transported to the upper troposphere, but there are indications from mass-spectrometric analyses of the residuals of sublimated cirrus particles that sea salt could also contribute to heterogeneous ice nucleation under cirrus conditions. Experimental studies on the heterogeneous ice nucleation ability of sea spray aerosol particles and their proxies at temperatures below 235 K are still scarce. In our article, we summarise previous measurements and present a new set of ice nucleation experiments at cirrus temperatures with particles generated from sea surface microlayer and surface seawater samples collected in three different regions of the Arctic and from a laboratory-grown diatom culture (Skeletonema marinoi). The particles were suspended in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud chamber and ice formation was induced by expansion cooling. We confirmed that under cirrus conditions, apart from the ice-nucleating entities mentioned above, also crystalline inorganic salt constituents can contribute to heterogeneous ice formation. This takes place at temperatures below 220 K, where we observed in all experiments a strong immersion freezing mode due to the only partially deliquesced inorganic salts. The inferred ice nucleation active surface site densities for this nucleation mode reached a maximum of about 5×1010 m−2 at an ice saturation ratio of 1.3. Much smaller densities in the range of 108–109 m−2 were observed at temperatures between 220 and 235 K, where the inorganic salts fully deliquesced and only the organic matter and/or algal cells and cell debris could contribute to heterogeneous ice formation. These values are 2 orders of magnitude smaller than those previously reported for particles generated from microlayer suspensions collected in temperate and subtropical zones. While this difference might simply underline the strong variability of the number of ice-nucleating entities in the sea surface microlayer across different geographical regions, we also discuss how instrumental parameters like the aerosolisation method and the ice nucleation measurement technique might affect the comparability of the results amongst different studies.

Assessing the utility of barium isotopes to trace Eurasian riverine freshwater inputs to the Arctic Ocean

Tracing riverine freshwater transport pathways within the Arctic Ocean is key to understanding changes in Arctic Ocean freshwater inventories. Dissolved Ba concentrations have been used in this capacity but are compromised by non-conservative processes. To assess the potential for Ba isotopes to provide insights into the impact of such processes on Arctic Ocean dissolved Ba inventories, Ba concentration and isotope data for surface seawater samples from the Siberian Shelf and Bering Sea/Strait are presented. These samples capture the mixing of riverine freshwater discharged by the rivers Yenisey, Lena and Ob, with Atlantic and Pacific derived seawater, which are traced by relationships between salinity, Ba concentration and δ138/134Ba. The δ138/134Ba of net river inputs, following modification by estuarine processes, are constrained to be 0.31 ± 0.04‰, 0.20 ± 0.06‰ and 0.23 ± 0.04‰, for the rivers Yenisey, Lena and Ob respectively. These values are used to estimate an average δ138/134Ba for Eurasian river freshwater input to the Arctic Ocean of 0.23 ± 0.04‰. The Ba concentration and δ138/134Ba of Lena River freshwater transported across the Laptev Sea are modified by non-conservative processes. These non-conservative processes do not result in distinctive modification of dissolved Ba concentration-δ138/134Ba mixing relationships between Eurasian riverine freshwater and Arctic seawater, which unfortunately limits the potential of Ba isotopes to improve tracing riverine freshwater sources in the central Arctic Ocean basins using dissolved Ba inventories. More generally the results of this study help advance understanding of Ba isotope cycling in the environment and their development as an emerging tracer of marine processes.

Occurrence, distribution and risk assessment of organophosphate ester flame retardants and plasticizers in surface seawater of the West Pacific

Twenty-eight samples of surface seawater were collected from the West Pacific Ocean during 2019 using a high-volume solid-phase extraction with high-throughput organic analysis (Hi-throat/Hi-volume SPE) method, and concentrations of 10 organophosphate ester flame retardants and plasticizers (OPEs) were determined. The total OPE concentration in the samples was 3.02–48.4 ng L−1 (mean 25.0 ± 10.5 ng L−1), with tris(2-chloroethyl) phosphate (TCEP) being the largest contributor. Cluster analysis results showed off-shore input from the coast of East and Southeast Asia was an important source of these chemicals. Tri-p-tolyl phosphate (TpTP) should also be considered for long-term monitoring, because of its high detection frequency. Results of a risk assessment indicated low ecological risk to species in the West Pacific Ocean for TPhP and ΣOPEs. Hazard quotients (HQs) were all <1, indicating that the health risk to humans from these chemicals was at acceptable levels.

Study on microplastic pollution in the coastal seawaters of selected regions along the northern coast of Kerala, southwest coast of India

Coastal areas are one of the most significant ecosystems, sustaining rich bioresources. Coastal seawaters are subjected to human interferences that lead to pollution and pose serious environmental issues. The current study attempts to categorize and quantify microplastics from selected regions of the northern coast of Kerala, located in the Southwest coast of India. In this study, surface seawater samples were collected from five sampling sites for three months. The five sampling regions selected were marked with GPS (Global Positioning System) and replicates of surface seawater samples (top ⁓10 cm) were collected from the selected transects by using a zooplankton net of mesh size 240 μm that was hauled in water for 20 min. In this study, deep coloured fibres (< 2 mm in size) were predominant and these were observed in the range of 0.80–6.99 items/m3. An analysis of the chemical composition of the microplastic particles by micro-Raman Spectroscopy (HORIBA Scientific LabSpec 6) revealed that polypropylene (PP) was the dominant (31–52% of the randomly selected subset (10%) of total fibre particles) among the five polymer types collected. Poly (ethylene-co-vinyl acetate) or PEVA, polyamide (PA), polybutadiene (BR) and polyethylene (PE) were the other polymer types observed and the presence of these particles in the coastal seawaters causes a lot of harm as these areas comprise rich fauna that plays a significant role in the food web. The current study will provide the impetus to conduct similar studies in seawaters and other aquatic environments in India and the threat microplastic particles impose on the ecological community could also be better estimated by understanding their status. This quantitative study opens the door for further research on the distribution of microplastic particles in the system and the adsorption of organic pollutants and their leaching effects on fauna.

Antifouling paint biocides (Irgarol 1051 and diuron) in the selected ports of Peninsular Malaysia: occurrence, seasonal variation, and ecological risk assessment.

Irgarol 1051 and diuron are photosystem II inhibitors in agricultural activities and antifouling paints in the shipping sector. This study focused on three major ports (western, southern, and eastern) surrounding Peninsular Malaysia to construct the distribution of both biocides on the basis of the seasonal and geographical changes. Surface seawater samples were collected from November 2011 to April 2012 and pretreated using the solid-phase extraction technique followed by quantification with GC-MS and LC-MS-MS for Irgarol 1051 and diuron, respectively. Generally, the distribution of Irgarol 1051 was lowest during November 2011 and highest during April 2012, and similar patterns were observed at all ports, whereas the distribution of diuron was rather vague. The increasing pattern of Irgarol 1051 from time to time is probably related to its accumulation in the seawater as a result of its half-life and consistent utilization. On the basis of the discriminant analysis, the temporal distribution of Irgarol 1051 varied at Klang North Port, Klang South Port, and Pasir Gudang Port, whereas diuron was temporally varied only at Kemaman Port. Furthermore, Irgarol 1051 was spatially varied during November 2011, whereas diuron did not show any significant changes throughout all sampling periods. Ecological risk assessment exhibited a high risk for diuron and Irgarol 1051, but Irgarol 1051 should be of greater concern because of its higher risk compared to that of diuron. Thus, it is recommended that the current Malaysian guidelines and regulations of biocide application should be reevaluated and improved to protect the ecosystem, as well as to prevent ecological risks to the aquatic environment.

Distribution characteristics and risk assessment of TBBPA in seawater and zooplankton in northern sea areas, China.

Tetrabromobisphenol-A (TBBPA) is a typical persistent organic pollutant (POP) that is harmful to the environment and organisms. It easily accumulates in organisms and is transmitted along the food chain or food web for long distances and long periods of time. The experiment was designed to assess the TBBPA pollution levels in marine environments via environmental sample testing and risk assessment. TBBPA levels in seawater and zooplankton samples at each station (n = 38) were detected, whereafter the bioaccumulation factor (BAF) and risk quotient (RQ) were calculated to evaluate the potential bioaccumulation and ecological risk of TBBPA to zooplankton, respectively. The results showed that TBBPA was widely detected in surface seawater and zooplankton samples in the Yellow Sea and Bohai Sea, with levels ranging from ND (non-detected) to 0.46μg/L and ND to 9.83μg/kg (wet weight), respectively. In both the Yellow Sea and Bohai Sea, the distance from the shore was one of the main factors affecting the TBBPA concentration in seawater, regardless of visibility. The BAF was significantly correlated with the TBBPA content in zooplankton samples (P < 0.01), which ranged from 372.32 to 29,941.55, indicating that TBBPA exhibits an obvious bioaccumulation risk to marine zooplankton. The ecological risk assessment indicated that TBBPA levels in seawater pose a high ecotoxicity risk to zooplankton (RQ > 1). This finding suggests that both the significant bioaccumulation of TBBPA in marine ecosystems and its potential ecological risks cannot be ignored.

Trophic transfer and dietary exposure risk of mercury in aquatic organisms from urbanized coastal ecosystems

In this study, 26 surface seawater samples, 26 surface sediment samples and 114 organisms were collected to study the trophic transfer and dietary exposure risk of mercury (Hg) in organisms from the Jiaozhou Bay, which is a typical semi-enclosed urbanized bay. The total mercury (THg) and methylmercury (MeHg) concentrations did not exceed the threshold limits and performed as: fish > crustaceans > mollusks. The trophic level values (TLs) were less than 3 in all the groups, indicating simple structure of food chain. With the increasing δ15N value, THg and MeHg were significantly biomagnified in the mollusks and fish but not in the crustaceans. In addition, the bioaccumulation and biomagnification of MeHg were higher than inorganic mercury (IHg) in the aquatic food chain. Target hazard quotient (THQ) and provisional tolerable weekly intake (PTWI) indicated that Hg exposure via consumption of seafood from the Jiaozhou Bay did not pose significant health risks for general population. Consuming fish will face the higher health risk than crustaceans and mollusks, especially in urban regions. Moreover, the risk of MeHg caused by intaking seafood deserved more attention. Trophic transfer function (TTF) explicated the transfer of Hg in the ecosystem and higher trophic transfer efficiency of MeHg than IHg. TTF interpreted the terrestrial input of Hg should be controlled to ensure the safety of consuming seafood from the Jiaozhou Bay.

Lateral variations of 134Cs and 228Ra concentrations in surface waters in the western North Pacific and its marginal sea (2018–2019): Implications for basin-scale and local current circulations

Lateral variations in 134Cs, 137Cs, and 228Ra concentrations (activities) in surface waters off the northeastern coast of Japan, including the subarctic Oyashio Current, subtropical Kuroshio Current, East Sakhalin Current (ESC), and Soya Warm Current (SWC), were examined from July to October in 2018 and 2019. The 134Cs concentrations in the surface seawater samples, decay-corrected to the date of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, were in the range of 0.2–0.9 mBq/L, whereas those transported to the study area with basin-scale currents varied between 0.2 and 1.3 mBq/L; this included the East Kamchatka Current (EKC) for 8 years following the FDNPP accident. Combined with the 228Ra (0.1–1.4 mBq/L) and 137Cs (1.0–1.7 mBq/L) concentrations and the salinity (32.4–34.6), the distribution of 134Cs concentrations indicated that FDNPP-derived radiocesium in this study area was partially transported with the EKC from the northeastern North Pacific. Based on a simple three-component (SWC, ESC, and EKC) mixing model that uses the salinity and 134Cs concentration, the fractions of the EKC showed a maximum value of ~ 0.4 off the southeastern Hokkaido, Japan.