Spatiotemporal distributions and ecological risk of polycyclic aromatic hydrocarbons in the surface seawater of Laizhou Bay, China

The spatial-temporal distribution, source, and potential ecological risk of polycyclic aromatic hydrocarbons (PAHs) in surface seawater from Laizhou Bay were investigated. The total PAH (ΣPAH) concentrations ranged from 277 to 4393 ng/L with an average of 1178 ng/L, thereby suggesting a relatively moderate to high PAH exposure level in Laizhou Bay in comparison to other bays in the world. The composition patterns and source apportionment results revealed that the coal, biomass burning, diesel emissions, and petroleum combustion as well as the combination of these processes were the dominant sources of PAHs in the surface water, which were closely associated with sail process and sewage effluents. The ecological risk assessment indicated that benzo(a)pyrene (BaP), phenanthrene (Phe), luoranthene (Flua), and naphthalene (Nap) would exist ecological risks in most of surface seawater sites, but the probabilistic risk assessment (PRA) results showed that the current level of risk is not as severe as the risk quotient (RQ) results revealed.

Cumulated influence of natural and anthropogenic drivers on surface seawater barium: Evidence from a high-resolution coral record in the northern South China Sea

Barium (Ba) plays a crucial role as a tracer element in elucidating essential marine biogeochemical processes. However, the limited knowledge regarding Ba sources and variations impedes our comprehension of the diverse array of processes occurring in the marine environment. Although coral Ba/Ca ratios have demonstrated potential as a tracer of oceanic Ba, there remains a scarcity of long-term and high-resolution records to fully utilize this technique. Here, we presented a 32-year record of monthly coral Ba/Ca ratios and δ18O from the Weizhou Island in the northern South China Sea to elucidate the sources and the influence factors on surface seawater Ba. The results indicated no significant correlation between coral Ba/Ca and sea surface temperature or growth rate, implying that coral Ba/Ca ratios could serve as a dependable proxy for surface seawater Ba concentrations. Significant increases and abrupt fluctuations in coral Ba/Ca ratios were observed during the period of oil drilling exploration and engineering construction, indicating that anthropogenic activities might lead to an elevation of surface seawater Ba levels, subsequently affecting coral Ba/Ca ratios. The winter coral Ba/Ca peaks on monthly timescales were confirmed to be caused by resuspended sediment driven by the winter monsoon. Extreme peaks of coral Ba/Ca occurring during the wet season demonstrated the potential of coral Ba/Ca to record tropical cyclones, which has not been found in low-resolution scale studies. The continuous, long-term, and high-resolution coral Ba/Ca time series provides compelling evidence for the combined influence of both natural and anthropogenic factors on seawater Ba concentrations. These findings significantly contribute to the comprehension of the intricate biogeochemical cycling of marine Ba.

Microbial degradation mechanisms of surface petroleum contaminated seawater in a typical oil trading port

Petroleum hydrocarbons are significant new persistent organic pollutants for marine oil spill risk areas. Oil trading ports, in turn, have become major bearers of the risk of offshore oil pollution. However, studies on the molecular mechanisms of microbial degradation of petroleum pollutants by natural seawater are limited. Here, an in situ microcosm study was conducted. Combined with metagenomics, differences in metabolic pathways and in the gene abundances of total petroleum hydrocarbons (TPH) are revealed under different conditions. About 88% degradation of TPH was shown after 3 weeks of treatment. The positive responders to TPH were concentrated in the genera Cycloclasticus, Marivita and Sulfitobacter of the orders Rhodobacterales and Thiotrichales. The genera Marivita, Roseobacter, Lentibacter and Glaciecola were key degradation species when mixing dispersants with oil, and all of the above are from the Proteobacteria phylum. The analysis showed that the biodegradability of aromatic compounds, polycyclic aromatic hydrocarbon and dioxin were enhanced after the oil spill, and genes with higher abundances of bphAa, bsdC, nahB, doxE and mhpD were found, but the photosynthesis-related mechanism was inhibited. The dispersant treatment effectively stimulated the microbial degradation of TPH and then accelerated the succession of microbial communities. Meanwhile, functions such as bacterial chemotaxis and carbon metabolism (cheA, fadeJ and fadE) were better developed, but the degradation of persistent organic pollutants such as polycyclic aromatic hydrocarbons was weakened. Our study provides insights into the metabolic pathways and specific functional genes for oil degradation by marine microorganisms and will help improve the application and practice of bioremediation.

The broad-scale microplastic distribution in surface water and sediments along Northeastern Mediterranean shoreline

Plastics manufactured to fulfil the unique demands of civilization accumulate in the sea due to their durability. Microplastics (MP) pose a greater threat than macroplastics as they can easily enter the aquatic environment and be hard to detect. MPs potentially impact several components of the marine life and food chain. This study determined MP distribution and characterization by collecting sediment from 47 different stations and surface seawater (SSW) from 29 stations in 2019 along the Turkish coast of the Eastern Mediterranean Sea. Potential MP particles were stained with Nile-Red and verified using ATR-FTIR. While MP abundance in the sediment ranged between 118 ± 97 and 1688 ± 746 MPs kg^-1, it varied between 0.18 ± 0.10 MPs m^-3 and 2.21 ± 1.75 MPs m^-3 in SSW. The MP abundance showed significant spatial variation (p < 0.05). The polymer type in the samples was determined by ATR-FTIR. In both water and sediments, polyethylene was the most common MP type (>59 %), while fragment was the most common MP form (>57.6 %), and >65 % of overall MPs were <1500 μm. The spatial pattern of MPs in the sediments and SSW was affected by the population, the magnitude of the tourism sector, the rim current, and circulation. The monitoring data presented here can provide a remarkable projection of the current trend and form a basis for future MP pollution prevention.

Impacts of terrestrial input on the distribution characteristics of microplastics in the East China Sea characterized by chromophoric dissolved organic matter (CDOM) analysis

Large quantities of microplastics are found in the East China Sea (ECS), however, the impacts of complicated terrestrial input on the distribution characteristics of microplastics have not been studied. Hence, we aimed to characterize the microplastic distribution in the ECS combined with the fluorescence characteristics of chromophoric dissolved organic matter (CDOM), a sensitive technique to trace terrestrial substances in seawater. The average microplastic abundance in the surface seawater of ECS was 34.73 ± 4.05 items/m³ and sites in the north ECS had a higher microplastic abundance (55.90 ± 2.47 items/m³) than those in the southern region (11.22 ± 4.01 items/m³), due to its proximity to the Yangtze River estuary and Hangzhou Bay. Polyethylene (PE, 44.2 %) was the most abundant microplastic type in the northern region, whereas polyethylene terephthalate (PET, 28.4 %) had a higher proportion in the south ECS. Besides, sites in the north ECS had a higher diversity index of microplastics, suggesting various sources of microplastic pollution. Interestingly, a stronger correlation with the diversity index was found for protein-like component C3 (R² = 0.56) in northern regions compared to fulvic-like component C1 (R² = 0.32) and humic-like component C2 (R² = 0.28), suggesting the significant impact of anthropogenic discharge. Moreover, no correlation between fluorescence components and microplastic diversity index was found in the south ECS, indicating that CDOM can reflect the impact range of terrestrial input on the distribution characteristics of microplastics. This research might be useful in assessing and reducing the impact of terrestrial input on the distribution characteristics of microplastics in the ECS.

Spatial distribution, vertical profiles and transport of legacy and emerging per- and polyfluoroalkyl substances in the Indian Ocean

The contamination status and transport of per- and polyfluoroalkyl substances (PFASs) in the seawater of the Indian Ocean (IO) and an adjacent subregion of the Northwest Pacific Ocean (NWPO) were investigated. Eight legacy PFASs were widely distributed in the surface seawater, and perfluoroheptanoic acid (PFHpA) and perfluorooctanoic acid (PFOA) were the two predominant PFASs. ΣPFAS concentration decreased in the following order: NWPO>Joining area of Asia and Indian-Pacific Oceans (JAIPO)>Northeast Indian Ocean>Southwest Indian Ocean. Hexafluoropropylene oxide-dimer acid, a replacement surfactant for PFOA was extensively detected in the IO (~34.8 pg/L) for the first time, showing an early sign of emerging PFAS spread in global open oceans. Eight depth profiles across the JAIPO (down to 5433 m depth) revealed a "surface-enrichment" and "depth-depletion" pattern for PFASs in the water column, and two noticeable fluctuations were mainly located at depths of 150-200 and 200-500 m. Physical processes, including eddy diffusion, and the origin and trajectory of water mass were crucial factors for structuring PFAS vertical profiles. Mass transport estimates revealed a remarkable PFOA contribution through the JAIPO to IO carried by the Indonesian Throughflow, and a nonnegligible PFHpA contribution from Antarctic Immediate Water to deep water of the JAIPO driven by thermohaline circulation.

Microplastics in the surface waters of the South China sea and the western Pacific Ocean: Different size classes reflecting various sources and transport

Microplastic transport in the marginal seas is a key process influencing their ultimate fate in the open oceans. In the present study, we collected seawater samples from the western Pacific Ocean (WP) and the South China Sea (SCS) to investigate the distribution, transport, and possible sources for microplastics. Generally, the range of microplastic levels were 187-1816, 146-1563, and 34.2-622 particles/m³ (averaged in 797 ± 512, 744 ± 330, and 201 ± 134 particles/m³) for the northern SCS, the western SCS, and the WP, respectively. Based on the size distribution, the highest value (390 ± 288 particles/m³) was found for 100-200 μm, followed by 200-500 μm (131 ± 155 particles/m³), and 500-1000 μm (29.7 ± 39.2 particles/m³), with the lowest for 1-5 mm (13.6 ± 14.2 particles/m³). Granule, yellow, and size <1000 μm were their most prevalent characteristics. The main polymer types of microplastics were polyester, rayon, and nylon. A negative correlation between microplastic proportion and particle size was observed in the SCS and the WP. Furthermore, the main sources of microplastics in the northern SCS probably came from the Pearl River. Surface currents and the vertical mixing processes might be two different mechanisms that affect microplastic transport from the WP and the SCS. Future comparison to measured particle size distributions data allows us to explain size-selective microplastic transport in the marine environment, and probably provide guidance on microplastic longevity.

Microplastics in the surface seawater of Bandon Bay, Gulf of Thailand

This study aimed to evaluate the microplastics abundance, composition and distribution in Bandon Bay's surface seawater, in southern Thailand. Samples of microplastics were collected from 48 transects using a surface manta trawl at four different estuaries that support human activities. The results showed that the highest microplastic abundance occurred in the fishery and aquaculture areas with a mean abundance of 0.33 particles/m³. Fragments were the dominant form at all stations. Microplastics with <1 mm were the dominant size, and white was the colour most found in all stations. Polypropylene was the major type of microplastic, accounting for 57% overall. This study is an important reference for understanding the microplastics status in the surface seawater of Bandon Bay, as it will allow relevant agencies to accurately assess the pollution level of microplastics in the bay. It is of practical significance to understand the sources and sinks of microplastics.

Microplastic pollution in the surface seawater in Zhongsha Atoll, South China Sea

The prevalence of microplastics in the marine environment has attracted extensive attention. So far, no information is known regarding the temporal and spatial variations of microplastics in Zhongsha Atoll. This study, for the first time, comprehensively investigated the occurrence and distribution of microplastics in the surface seawater in Zhongsha Atoll based on two ocean cruises. The abundances of microplastics measured in the surface seawater of Zhongsha Atoll were in the ranges of not detected (ND) to 67 items/m³, and ND to 160 items/m³ in 2019 and 2020, respectively. All microplastics detected in Zhongsha Atoll were fibers, most of which were transparent and less than 2 mm. Polyethylene terephthalate was the dominating composition of microplastics. These results suggested that sewage, surface runoff, atmospheric deposition by neighboring land, and fishing activities may be the primary pollution sources. This study provides critical information on microplastic pollution in Zhongsha Atoll for the first time, calling for more research in the management of marine plastic debris in the future.

Legacy and emerging per- and poly-fluoroalkyl substances in surface seawater from northwestern Pacific to Southern Ocean: Evidences of current and historical release

Knowledge on distribution of per- and poly-fluoroalkyl substances (PFASs) in open oceans is limited. By taking part in the 32nd Chinese Antarctic Research Expedition, 41 surface seawater samples were collected in the northwestern Pacific Ocean (NW-PO), eastern Indian Ocean (E-IO) and Southern Ocean (SO), and 23 PFASs comprised of legacy perfluoroalkyl carboxylic acids, perfluoroalkyl sulfonate acids and some new emerging homologs such as 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) were measured. The concentrations of the total PFASs decreased in the order of NW-PO>E-IO>SO. Perfluorooctanoic acid (PFOA) was the most dominant, followed by perfluorooctane sulfonate (PFOS). The PFOA concentration declined exponentially with the offshore distance, while such trend was not obvious for PFOS and other legacy PFASs, suggesting that PFOA was mainly derived from the ongoing land-based emissions, while PFOS was mainly from historical residues. 6:2 Cl-PFESA was identified (<11.1-170 pg/L) in the oceanic waters with relatively high level at the sites near Australia. Multiple receptor models indicated that PFASs in the SO were mainly contributed by atmosphere input, while those in the NW-PO and E-IO were originated from land sources. Isomeric profiles of PFOA showed that telomere-based source became more outstanding than electrochemical fluorinated production in recent years.

Microplastics and microfibers in surface waters of Monterey Bay National Marine Sanctuary, California

Despite a recent report of high concentrations of microplastics and microfibers in the mesopelagic waters of Monterey Bay National Marine Sanctuary (MBNMS), little is known about these particles in surface waters. From 2017 to 2019, we sampled two nearshore and two offshore locations within MBNMS using a manta trawl and analyzed these samples for microplastics and microfibers. We found an average concentration of 1.32 ± 0.70 (SE) particles per m³. We found the highest concentration of particles closest to shore, and the lowest concentration above the remote Davidson Seamount. Fiber-like debris was more common in offshore, as compared to nearshore, sites. Overall, particles in our samples were primarily buoyant synthetic polymers, including polypropylene and polyethylene. Our results provide baseline data on the degree of microplastic and microfiber pollution in MBNMS surface waters and confirm that this pollution can be found in waters from the surface to at least 1000 m depth.

Iodidimonas gelatinilytica sp. nov., aerobic iodide-oxidizing bacteria isolated from brine water and surface seawater

Chemo-organotrophic iodide (I^-)-oxidizing bacterial strains Hi-2^T and Mie-1 were isolated from iodide-rich natural gas brine water in Chiba and surface seawater in Mie, Japan, respectively. Cells of strains Hi-2^T and Mie-1 were aerobic, Gram-negative and rod-shaped (0.3-0.5 µm width and 1.2-4.4 µm in length). Two isolates grew optimally at 30 °C, pH 7.5 and with 3% NaCl (w/v). Iodide oxidation to form molecular iodine (I₂) was a biochemically unique trait for strains Hi-2^T and Mie-1. The major cellular fatty acids are C_18:1ω7c, C_16:1ω5c and C_18:1 2-OH. A phylogenetic analysis based on the 16S rRNA gene sequence revealed that strains Hi-2^T and Mie-1 were located near Iodidimonas muriae C-3^T with 99.2% sequence similarity. The calculated digital DNA-DNA hybridization (dDDH) value of 65.7-65.9% between the two isolates and I. muriae C-3^T was lower than the threshold of 70%, which was used for prokaryotic species delineation. Strains Hi-2^T and Mie-1 differed in the hydrolysis of aesculin, the hydrolysis of gelatin and the major cellular fatty acids composition from I. muriae C-3^T. Considering these biochemical properties, the major cellular fatty acids composition and dDDH value, a novel species is proposed for strains Hi-2^T (= JCM 17844^T = LMG 28661^T) and Mie-1 (= JCM 17845 = LMG 28662), to be named Iodidimonas gelatinilytica.

Paracoccus amoyensis sp. nov., isolated from the surface seawater along the coast of Xiamen Island, China

Strain 11-3^T was isolated from the surface seawater along the coast of Xiamen Island, China. Cells were Gram-stain-negative, oxidase- and catalase-positive, short and rod-shaped, nonmotile, 0.5-1.0 μm in width and 1.0-2.0 μm in length. Growth of strain 11-3^T was at temperature of 15-37°C (optimum 28-35°C), at pH of 5.0-11.0 (optimum 7.0-9.0) and at salinity range of 0-10 (optimum 0.5-1). Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain 11-3^T belonged to the genus Paracoccus and had the highest similarity with Paracoccus caeni MJ17^T (98.1 %), followed by Paracoccus xiamenensis 12-3^T (97.1 %), Paracoccus zeaxanthinifaciens ATCC 21588^T (97.1 %), Paracoccus aestuarii DSM 19484^T (97.0 %), Paracoccus liaowanqingii 2251^T (97.0 %), Paracoccus fistulariae KCTC 22803^T (97.0 %) and other species of the genus Paracoccus (95.2-96.8 %). The DNA-DNA hybridization values between strain 11-3^T and the selected strains (P. caeni MJ17^T, P. xiamenensis 12-3^T, P. zeaxanthinifaciens ATCC 21588^T, P. aestuarii DSM 19484^T and P. liaowanqingii 2251^T) were 19.4, 19.5, 21.6, 19.3 and 19.8 %, respectively. Corresponding, their ANI values were 77.53, 75.61, 75.36, 75.73 and 75.33 %, respectively. The major fatty acid was summed feature 8 (C_18:1 ω6c/ω7c). The major respiratory quinone was Q10. The polar lipids included phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), diphosphatidylglycerol (DPG), unidentified glycolipid (GL) and unidentified aminolipid (AL). The DNA G+C content of strain 11-3^T was 60.1 %. Based on results of the phylogenetic analysis, phenotypic and chemotaxonomic characteristics, strain 11-3^T represents a novel species of the genus Paracoccus, for which the name Paracoccus amoyensis sp. nov. is proposed. The type strain is 11-3^T (=MCCC 1A16380^T=KCTC 72689^T).

Microplastic pollution in surface seawater of Sanggou Bay, China: Occurrence, source and inventory

Microplastic pollution in marine environments has become a major global environmental issue. However, the source of microplastics in marine environments is poorly understood. Here, we investigated the distribution and the source of microplastics in surface seawater from Sanggou Bay, China. The results showed that the average abundance of microplastics was 20.06 ± 4.73 items/L, which represented a medium and high level relative to other sea areas. Microplastics of <0.5 mm dominated. Most particles were granular and transparent, and polyethylene was the dominant polymer. We estimated that 62.76% of the microplastics originated from mariculture facilities, an indication that mariculture contributes significantly to microplastics pollution, and calculated that 96.15 kg was present in surface seawater of Sanggou Bay. Our findings indicated that more attention should be paid to mariculture-derived microplastics pollution in the future.

Assessing the potential risk and relationship between microplastics and phthalates in surface seawater of a heavily human-impacted metropolitan bay in northern China

The impacts of microplastics (MPs) and phthalates (PAEs), a class of MP-associated contaminants, on the marine environment are not thoroughly understood despite concern over their adverse effects on humans and ecosystems. Field studies linking MPs and PAEs in seawater have not yet been reported. We investigate for the first time the correlation between MPs contamination and the presence of PAEs in the surface seawater of Jiaozhou Bay (JZB), a semi-enclosed metropolitan bay in northern China heavily impacted by human activity. The abundance of MPs, dominated by polyethylene and polyethylene terephthalate mostly smaller than 2 mm, ranged between 24.44 items/m³ and 180.23 items/m³, with the majority being black and transparent fibers and fragments. Concentrations of PAEs varied from 129.96 ng/L to 921.22 ng/L. Relatively higher abundances of MPs and higher concentrations of PAEs were generally found in areas near riverine inputs and sewage treatment plants. There was a strong correlation between PAEs concentration and MPs abundance, suggesting that they are closely linked. In a risk assessment combining PAEs and MPs, the risk quotients (RQs) indicated that the ecological risk of di-n-butyl phthalate in JZB was relatively high (0.046<RQ < 0.516); the risk of the other PAEs were low. The overall ecological hazard index (HI) of PAEs was low to medium (0.098<HI < 0.897). The risk of MPs pollution in JZB, as indicated by Pollution Load Index (PLI), was moderate (PLI_JZB = 11.76), and mainly due to polyvinyl chloride.

Coastal zone use influences the spatial distribution of microplastics in Hangzhou Bay, China

Microplastic pollution in estuarine and coastal environments has recently been characterised in several countries but few researchers have addressed the influence of different forms of coastal zone use on the distribution of microplastic. Here, microplastic particles were sampled in Hangzhou Bay, which is heavily influenced by a range of human activities, and their abundance, size, and polymer type characterised. The abundance of microplastics was 0.14 ± 0.12 items/m³ in water, 84.3 ± 56.6 items/kg dry weight of sediment, and between 0.25 ± 0.14 and 1.4 ± 0.37 items/individual in biota. These results show that Hangzhou Bay has a low level of microplastic contamination compared to other coastal systems in China, although abundance was spatially variable within the bay; relatively higher microplastic abundances were found in the southern area of the bay, which has adjacent industrial and urban land-use zones, while lower abundances were observed in the central and northern bay areas where mariculture, fisheries, and mineral and energy industries are most common. The relatively low microplastic abundance observed in the biota samples is consistent with the generally low values for the seawater and sediment samples. Pellets were the most common of four particle-shape classes (fibres, fragments, films, and pellets) in surface seawater, while fibres were most abundant in sediment and biota. Smaller-sized microplastics (<1.0 mm) were dominant in all samples. Microplastics in the surface seawater were dominated by low-density polypropylene and polyethylene particles, while rayon was dominant in the sediment and biota samples. Our results demonstrate that regional variability in anthropogenic activity and land-use are important controls on the spatial pattern of microplastic pollution in Hangzhou Bay.

First dataset of 236U and 233U around the Greenland coast: A 5-year snapshot (2012-2016)

We report the first combined dataset of ²³⁶U and ²³³U in the Greenland marine environment during the period of 2012-2016. Results are discussed in terms of time evolution and spatial distribution of ²³⁶U concentration, and atomic ratios of ²³⁶U/²³⁸U and ²³³U/²³⁶U. ²³⁶U concentrations along the Greenland coast are distributed within a relatively narrow range of (0.7-12.9) × 10⁷ atom/L, corresponding to ²³⁶U/²³⁸U atomic ratios of (1.1-15.5) × 10^-9. The ²³³U/²³⁶U atomic ratios obtained vary from 0.12 × 10^-2 to 1.16 × 10^-2, with the majority distributed in the range of (0.2-0.7) × 10^-2. We applied ²³³U/²³⁶U and ²³⁶U/²³⁸U atomic ratios in a binary mixing model to identify possible ²³⁶U source terms. The results indicate that anthropogenic ²³⁶U and ²³³U in Greenland surface seawater originated from the direct global fallout (DGF) and the Sellafield and La Hague reprocessing plants (RP) is diluted by a third endmember, mostly likely natural ocean water (NOW), containing marginal ²³⁶U and ²³³U. A preliminary estimation of the source terms of ²³⁶U using ²³³U/²³⁶U atomic ratios indicate that, for both eastern and western Greenland seawater, contributions from global fallout (GF) constitute about 30% of ²³⁶U. The dominating source for ²³⁶U, i.e. 70 %, is associated to reactor ²³⁶U including discharges from RP and local reactor input in the Arctic Ocean.

Diverse and unique viruses discovered in the surface water of the East China Sea

Background

Viruses are the most abundant biological entities on earth and play import roles in marine biogeochemical cycles. Here, viral communities in the surface water of the East China Sea (ECS) were collected from three representative regions of Yangshan Harbor (YSH), Gouqi Island (GQI), and the Yangtze River Estuary (YRE) and explored primarily through epifluorescence microscopy (EM), transmission electron microscopy (TEM), and metagenomics analysis.

Results

The virus-like particles (VLPs) in the surface water of the ECS were measured to be 10⁶ to 10⁷ VLPs/ml. Most of the isolated viral particles possessed a head-and-tail structure, but VLPs with unique morphotypes that had never before been observed in the realm of viruses were also found. The sequences related to known viruses in GenBank accounted for 21.1–22.8% of the viromic datasets from YSH, GQI, and YRE. In total, 1029 viral species were identified in the surface waters of the ECS. Among them, tailed phages turn out to make up the majority of viral communities, however a small number of Phycodnaviridae or Mimiviridae related sequences were also detected. The diversity of viruses did not appear to be a big difference among these three aquatic environments but their relative abundance was geographically variable. For example, the Pelagibacter phage HTVC010P accounted for 50.4% of the identified viral species in GQI, but only 9.1% in YSH and 11.7% in YRE. Sequences, almost identical to those of uncultured marine thaumarchaeal dsDNA viruses and magroviruses that infect Marine Group II Euryarchaeota, were confidently detected in the ECS viromes. The predominant classes of virome ORFs with functional annotations that were found were those involved in viral biogenesis. Virus-host connections, inferred from CRISPR spacer-protospacer mapping, implied newly discovered infection relationships in response to arms race between them.

Conclusions

Together, both identified viruses and unknown viral assemblages observed in this study were indicative of the complex viral community composition found in the ECS. This finding fills a major gap in the dark world of oceanic viruses of China and additionally contributes to the better understanding of global marine viral diversity, composition, and distribution.

Chemical fate of persistent organic pollutants in the arctic: Evaluation of simplebox

Persistent organic pollutants (POPs) are of great concern for decades due to their persistence, bioaccumulation and long-range transport potential. Multimedia fate models are useful scientific and decision-support tools for predicting the chemical fate in the environment. The SimpleBox multimedia fate model (v4.0) was used in this study to estimate the impact of POP emissions from the European and North American mainland on POP contamination in the Arctic. The purpose of the study was to evaluate the performance of SimpleBox by comparing estimations to measurements. Model performance for the air compartment was reasonable as estimated concentrations were generally within a factor of five of measured concentrations. SimpleBox suggested higher POP concentrations in Arctic oceans than in temperate oceans, contrary to the few measured data. Discrepancies between estimations and measurements may be attributed to the variability in emission estimates and degradation rates of POPs, representativeness of monitoring data, and a missing snow and ice environmental compartment in SimpleBox. Emission rates and degradation rate constants were the most influential input parameters in SimpleBox based on sensitivity analysis. Suggestions for improvements of SimpleBox refining POP risk assessment are provided.

Assessment of seawater pollution of the Al-Khafji coastal area, Arabian Gulf, Saudi Arabia

Twenty-seven coastal seawater samples were collected to assess seawater pollution and document the possible sources at Al-Khafji coastal area, Arabian Gulf, Saudi Arabia. Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Sr, Cd, Hg, and Pb were analyzed using inductively coupled plasma mass spectrometer (ICP-MS). The results revealed the following order of concentration: Sr > Ni > V > Cu > As > Zn > Al > Fe > Cr > Mn > Pb > Co > Cd > Hg. Most metals exhibited a fluctuated pattern within the studied sites without obvious trend, except Sr and Ni, which showed a fluctuated pattern with increasing trend southwards. The studied sites were classified into polluted, slightly polluted, and non-polluted ones based on HCA analyses. The higher levels of metals in the seawater of the polluted sites may be attributed to atmospheric input and oil spills from underwater pipelines, off offshore oil wells, loading and handling operations, oil terminals, and oil tanker incidents in the Arabian Gulf in general and many other anthropogenic sources in Al-Khafji area in particular such as desalination plant, landfilling due to new constructions, industrial sewage, and the Khafji Joint Operations (KJO).

Distribution, sources and ecological risk assessment of PAHs in surface seawater from coastal Bohai Bay, China

The distribution, composition, potential sources and ecological risk of 16 US EPA priority polycyclic aromatic hydrocarbons (PAHs) were investigated in surface water from coastal Bohai Bay. The PAH concentrations ranged from 48.0 to 607 ng L^-1 with the mean value of 267 ng L^-1 in dissolved phase and 198 to 935 ng L^-1 with the mean value of 424 ng L^-1 in particle-associated phase, and decreased following the order: Qinhuangdao (QHD) > Caofeidian (CFD) > Huanghuagang (HHG). The 2-3 ring PAHs accounted for 79.9% to 86.2% in particle-associated phase and 65.6% to 73.2% in dissolved phase of total 16 PAHs, in which naphthalene (Nap) was the most dominant compound. The PAHs in surface seawater mainly originated from petrogenic sources according to the molecular ratios of benzo[a]anthracene/228 and fluoranthene/202. Risk quotients indicated that there was potential ecological risk for PAHs in surface seawater, especially for pyrene and fluorene.

Variation in microbial community structure in surface seawater from Pearl River Delta: Discerning the influencing factors

Contamination of perfluoroalkyl acids (PFAAs) is ubiquitously detected in various environments. However, their potential effects on microbial communities remain largely unknown. In this study, surface seawater of the Pearl River Delta (PRD) is sampled to measure PFAA concentrations and profile the structure of free-living microbial community. Total PFAAs concentrations range from 131 to 1563 pg L^-1 in surface seawater. PFOS (16-470 pg L^-1), PFOA (27-272 pg L^-1), PFHpA (18-201 pg L^-1) and PFBA (25-152 pg L^-1) are the major homologues, indicating continued industrial application or release of PFOS and a gradual shift towards using shorter-chain PFAAs. Concentrations of PFAAs from this recent cruise are much lower than previous reports, which may be due to the effective management of PFAA usage around PRD region. In addition, the microbial community in PRD surface seawater is predominantly colonized by the Proteobacteria phylum (27.2 to 61.5%) and the Synechococcus genus (5.6 to 38.6%). The structure of the microbial communities varies among stations, mainly resulting from different abundances of Synechococcus, Prochlorococcus and Nitrosopumilus. Geochemical parameters (e.g., nutrients and salinity) and phytoplankton are significantly associated with the microbial community dynamics in surface seawater. In the interactive network of microbiota, a subset of bacteria (i.e., Fluviicola, Nitrosopumilus, Limnohabitans, Sediminibacterium, C39 and Polynucleobacter) shows significantly positive correlations with PFAAs (R > 0.6; P < 0.001). Overall, this study gives a timely monitoring of PFAA pollution around PRD area. Shift in environmental microbiota by geochemical factors and phytoplankton is also observed, which may affect biogeochemical cycling.

Paracoccus indicus sp. nov., isolated from surface seawater in the Indian Ocean

Strain IO390502^T, isolated from surface seawater in the Indian Ocean, was characterised using a polyphasic taxonomy approach. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strain IO390502^T belongs to the genus Paracoccus and is closely related to Paracoccus seriniphilus DSM 14827^T (97.6%), followed by P. zeaxanthinifaciens JCM 21774^T (97.5%), P. homiensis DSM 17862^T (97.3%), P. marcusii DSM 11574^T (97.2%), P. haeundaensis BC 74171^T (97.0%) and P. carotinifaciens E-396^T (97.0%). Cells are Gram-negative, aerobic, poly-β-hydroxybutyrate-accumulating, motile, rod-shaped, and forms creamy-white colonies. Optimal growth occurred at 25-30 °C, pH 5-8, and in the presence of 3-8% NaCl. The genome of strain IO390502^T has a G+C content of 64.9 mol% and a 3.5 Mb chromosome. The in silico DNA-DNA hybridisation and average nucleotide identity values between strain IO390502^T and the three closely related taxa, P. seriniphilus DSM 14827^T, P. zeaxanthinifaciens JCM 21774^T and P. homiensis DSM 17862^T, are 19.6%, 21.9% and 20.6%, and 76.0%, 79.9% and 77.8%, respectively. Phosphatidylglycerol is the major lipid present, ubiquinone-10 (Q-10) is the sole isoprenoid quinone, and the major cellular fatty acid is C_18:1ω7c. Based on data from phenotypic tests and genotypic differences between strain IO390502^T and its close phylogenetic relatives, strain IO390502^T represents a new species belonging to the genus Paracoccus, for which the name Paracoccus indicus sp. nov. is proposed. The type strain is IO390502^T (= JCM 32637^T = CCTCC AB 2018071^T).

Toxic metals in Perna viridis mussel and surface seawater in Pasir Gudang coastal area, Malaysia, and its health implications

Contamination of toxic metals in P. viridis mussels has been prevalently reported; hence, health risk assessment for consuming this aquaculture product as well as the surrounding surface seawater at its harvesting sites appears relevant. Since Kampung Pasir Puteh, Pasir Gudang is the major harvesting site in Malaysia, and because the last heavy metal assessment was done in 2009, its current status remains unclear. Herein, flame atomic absorption spectrometry and flow injection mercury/hydride system were used to determine the concentrations of Pb, Cd, Cu and total Hg in P. viridis mussels and surface seawater (January-March 2015), respectively. Significantly higher concentrations of these metals were found in P. viridis mussels (p < 0.05) than that of surface seawater samples. The concentrations for Pb (4.27-6.55 μg/g) and Cd (1.55-2.21 μg/g) in P. viridis mussels exceeded the maximum permitted proportion prescribed by the Malaysian law. The concentrations of all metals in surface seawater also violated the Malaysia Marine Water Quality Criteria and Standards. Significant (p < 0.05) and high strength of association (r = 0.787) observed between Pb concentration in P. viridis mussel with the surface seawater indicates its possible application for inferring Pb concentrations in the mussel. Since both the calculated target hazard quotient and hazard index for Pb and Cd exceeded 1, the possible detrimental health impacts on human for consuming P. viridis mussels from this rearing site cannot be ignored. Hence, promoting continuous monitoring programmes and developing efficient toxic metal removal techniques prior to entering the market are required.

Microplastic pollution in North Yellow Sea, China: Observations on occurrence, distribution and identification

Microplastics are emerging contaminants and have attracted widespread environmental concerns about their negative effects on the marine ecosystems. In this study, we investigated the abundances, distributions and characteristics of microplastics in surface seawater and sediments from the North Yellow Sea. The results showed that the abundance of microplastics was 545 ± 282 items/m³ in surface seawater and 37.1 ± 42.7 items/kg dry weight in sediments, representing a medium microplastic pollution level compared with other sea areas. Small microplastics (<1 mm) made up >70% of the total microplastic numbers. Films and fibers were the dominant shapes of microplastics in both the surface seawater and sediments. Transparent microplastics were generally more common than microplastics of other colors. Based on the identification by a Fourier transform infrared microscope, polyethylene (PE) was the dominant composition of microplastics in surface seawater, while polypropylene (PP) was the most common polymer type in sediments. These results will improve our understanding of the environmental risks posed by microplastics to marine ecosystems.

Sources of plutonium isotopes and 137Cs in coastal seawaters of Liaodong Bay and Bohai Strait, China and its environmental implications

In order to investigate the sources of plutonium in seawaters of Liaodong Bay and Bohai Strait, China, surface seawater samples were collected and analyzed for ^239+240Pu and ¹³⁷Cs by radiochemical separation combined with ICP-MS and γ-spectrometry, respectively. A large variation of ^239+240Pu activities was observed, ranging from 1.993 to 29.677 mBq/m³ in the Liaodong Bay and from 0.932 to 10.183 mBq/m³ in the Bohai Strait. ¹³⁷Cs activities showed little variation between the investigated locations, which was attributed to the different behavior characteristics of ^239+240Pu and ¹³⁷Cs in seawaters. The ²⁴⁰Pu/²³⁹Pu atom ratios showed a significant variation between the Liaodong Bay (0.185) and Bohai Strait (0.225), indicating that Pu derived from the Pacific Proving Grounds might have been transported to the Bohai Strait but not yet to the Liaodong Bay, which could further provide valuable reference for evaluating the seawater exchange cycle between the Bohai Sea and Yellow Sea.

Temporal and spatial variations of 134Cs and 137Cs levels in the Sea of Japan and Pacific coastal region: Implications for dispersion of FDNPP-derived radiocesium

To investigate the dispersion of Fukushima Dai-ichi Nuclear Power Plant (FDNPP)-derived radiocesium in the Sea of Japan and western Pacific coastal region and determine the sources of radiocesium in these areas, we examined the temporal and spatial variations of ¹³⁴Cs and ¹³⁷Cs concentrations (activities) during 2011-2016 in seawaters around the western Japanese Archipelago, particularly in the Sea of Japan. In May 2013, the surface concentration of ¹³⁴Cs was ∼0.5 mBq/L (decay-corrected to March 11, 2011), and that of ¹³⁷Cs exceeded the pre-accident level in this study area, where the effects of radiocesium depositions just after the FDNPP accident disappeared in surface waters in October 2011. Subsequently, radiocesium concentrations gradually increased during 2013-2016 (∼0.5-1 mBq/L for ¹³⁴Cs), exhibiting approximately homogeneous distributions in each year. The temporal and spatial variations of ¹³⁴Cs and ¹³⁷Cs concentrations indicated that FDNPP-derived radiocesium around the western Japanese Archipelago, including the Sea of Japan, has been supported by the Kuroshio Current and its branch, Tsushima Warm Current, during 2013-2016. However, in the Sea of Japan, the penetration of ¹³⁴Cs was limited to depths of less than ∼200 m during three years following the re-delivery of FDNPP-derived radiocesium.

Metal pollution in Al-Khobar seawater, Arabian Gulf, Saudi Arabia

In order to assess heavy metals pollution along the Al-Khobar coastline, 30 seawater samples and 15 sediment ones were collected for Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Cd, Hg and Pb analysis by Inductively Coupled Plasma-Mass Spectrometer (ICP-MS). The analysis indicated a southward decreasing pattern in most heavy metal concentrations and the average values of Zn, Fe, Mn, Cu, As and Cr were higher than the ones reported from some worldwide seas and gulfs. Most of the highest levels were recorded within the bays and were related with in situ under sediments especially that composed of clays and very fine sands, and in localities characterized with anthropogenic activities like landfilling, desalination plants, fishing boats, oil spills and solid rubbish. The results of the present study provide useful background for further marine investigation and management in the Arabian Gulf region.

A semi-automated Raman micro-spectroscopy method for morphological and chemical characterizations of microplastic litter

Every step of microplastic analysis (collection, extraction and characterization) is time-consuming, representing an obstacle to the implementation of large scale monitoring. This study proposes a semi-automated Raman micro-spectroscopy method coupled to static image analysis that allows the screening of a large quantity of microplastic in a time-effective way with minimal machine operator intervention. The method was validated using 103 particles collected at the sea surface spiked with 7 standard plastics: morphological and chemical characterization of particles was performed in <3h. The method was then applied to a larger environmental sample (n=962 particles). The identification rate was 75% and significantly decreased as a function of particle size. Microplastics represented 71% of the identified particles and significant size differences were observed: polystyrene was mainly found in the 2-5mm range (59%), polyethylene in the 1-2mm range (40%) and polypropylene in the 0.335-1mm range (42%).

Spatial distribution, sources and ecological risk assessment of polycyclic aromatic hydrocarbons in surface seawater from Yangpu Bay, China

The occurrence of 14 polycyclic aromatic hydrocarbons (PAHs) listed by the United States Environmental Protection Agency was investigated in surface seawater of Yangpu Bay, China in November 2013 (winter) and May 2014 (summer). Seventy-two samples were collected from 12 sampling sites. The total concentrations of PAHs in Yangpu Bay showed obvious variations in different seasons, which varied from 582.8 to 2208.3 ng L(-1) in winter and 952.4 to 1201.7 ng L(-1) in summer, respectively. Two-ring PAHs accounted for more than 91.6% of total PAHs in winter, and three-ring PAHs were dominant with 81.6% of total PAHs in summer. Molecular indices analyses indicated that the main source of PAHs in Yangpu Bay could be petrogenic contamination. The ecological risk assessment by Risk quotients (RQNCs and RQMPCs) showed a potential ecological risk of PAHs in Yangpu Bay, indicating a close attention should be paid to pollution of PAHs in the coastal area of Yangpu.

A method for molecular analysis of catalase gene diversity in seawater

Catalase plays an important role in the metabolism of marine bacteria and has potential impact on the marine environment. Four PCR primers were designed to amplify the catalase gene fragments in marine bacteria by applying metagenomic DNA from Yellow Sea surface water as the template. Of the four reproducible target PCR products, the longest one with 900 bp were chosen for catalase gene library construction by the T-vector and the white Escherichia coli colonies in the library was screened through restriction-digesting the reamplified insert fragments by the selected restriction endonuclease MboI, and then the bands of the resulting products were displayed in the agarose gel by electrophoresis. The unique restriction fragment length polymorphism (RFLP) pattern was selected and the corresponding catalase gene fragments were sequenced, which verified that every unique RFLP pattern represented one type of catalase. This PCR-RFLP method above was established to investigate the bacterial catalase diversity in seawater.