High Arctic seawater and coastal soil microbiome co-occurrence and composition structure and their potential hydrocarbon biodegradation.

The accelerated decline in Arctic sea-ice cover and duration is enabling the opening of Arctic marine passages and improving access to natural resources. The increasing accessibility to navigation and resource exploration and production brings risks of accidental hydrocarbon releases into Arctic waters, posing a major threat to Arctic marine ecosystems where oil may persist for many years, especially in beach sediment. The composition and response of the microbial community to oil contamination on Arctic beaches remain poorly understood. To address this, we analyzed microbial community structure and identified hydrocarbon degradation genes among the Northwest Passage intertidal beach sediments and shoreline seawater from five high Arctic beaches. Our results from 16S/18S rRNA genes, long-read metagenomes, and metagenome-assembled genomes reveal the composition and metabolic capabilities of the hydrocarbon microbial degrader community, as well as tight cross-habitat and cross-kingdom interactions dominated by lineages that are common and often dominant in the polar coastal habitat, but distinct from petroleum hydrocarbon-contaminated sites. In the polar beach sediment habitats, Granulosicoccus sp. and Cyclocasticus sp. were major potential hydrocarbon-degraders, and our metagenomes revealed a small proportion of microalgae and algal viruses possessing key hydrocarbon biodegradative genes. This research demonstrates that Arctic beach sediment and marine microbial communities possess the ability for hydrocarbon natural attenuation. The findings provide new insights into the viral and microalgal communities possessing hydrocarbon degradation genes and might represent an important contribution to the removal of hydrocarbons under harsh environmental conditions in a pristine, cold, and oil-free environment that is threatened by oil spills.

Photobacterium pectinilyticum sp. nov., a novel bacterium isolated from surface seawater of Qingdao offshore.

A Gram-staining-negative, facultative aerobic, motile strain, designated strain ZSDE20T, was isolated from the surface seawater of Qingdao offshore. Phylogenetic analysis of the 16S rRNA gene of strain ZSDE20T, affiliated it to the genus Photobacterium. It was closely related to Photobacterium lutimaris DF-42 T (98.92% 16S rRNA gene sequence similarity). Growth occurred at 4-28ºC (optimum 28ºC), pH 1.0-7.0 (optimum 7.0) and in the presence of 1-7% (w/v) NaCl (optimum 3%). The dominant fatty acids were summed feature 3 (C16:1 ω7c or/and C16:1 ω6c, 34.23%), summed feature 8 (C18:1 ω7c and C18:1 ω6c, 10.36%) and C16:0 (20.05%). The polar lipids of strain ZSDE20T comprised phosphatidylethanolamine, phosphatidylcholine, lyso-phosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol dimannoside, phosphatidylinositol mannosides and two unknown lipids. The major respiratory quinone was ubiquinone-8 (Q-8). The DNA G + C content of strain ZSDE20T was 45.6 mol%. Average nucleotide identity (ANI) values between ZSDE20T and its reference species were lower than the threshold for species delineation (95-96%); in silico DNA-DNA hybridization further showed that strain ZSDE20T had less than 70% similarity to its relatives. Based on the polyphasic evidences, strain ZSDE20T is proposed as representing a novel species of the genus Photobacterium, for which the name Photobacterium pectinilyticum sp. nov. is proposed. The type strain is ZSDE20T (= MCCC 1K06283T = KCTC 82885 T).

Flagellimonas baculiformis sp. nov. and Flagellimonas crocea sp. nov., isolated from surface seawater of the Pacific Ocean.

Two Gram-negative, non-spore-forming, non-motile, non-flagellated bacteria, designated strains D6T and DH64T, were isolated from surface water of the Pacific Ocean. For strain D6T, growth occurred at 10-40 °C, pH 5.5-9.0 and in the presence of 0-8.0 % NaCl (w/v). For strain DH64T, growth occurred at 10-40 °C, pH 5.5-8.5 and in the presence of 0.5-8.0 % NaCl (w/v). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strains D6T and DH64T both belonged to the genera Flagellimonas, with the highest sequence identities to Flagellimonas taeanensis JCM 17757T (98.2 %) and Flagellimonas marinaquae JCM 11811T (98.6 %), respectively. The 16S rRNA gene sequence identity between strains D6T and DH64T was 95.9 %. The average amino acid identity and digital DNA-DNA hybridization values between the two strains and the nearest phylogenetic neighbours were 66.7-93.3 % and 16.1-38.5 %, respectively. The major respiratory quinone of both strains was menaquinone-6. The major polar lipid was phosphatidylethanolamine. The major fatty acids were identified similarly as iso-C15 : 1 G, iso-C15 : 0 and iso-C17 : 0 3-OH. The genomic G+C contents of strains D6T and DH64T were determined to be 45.5 and 42.6 mol%, respectively. The combined genotypic and phenotypic data show that the strains represent two novel species within genera Flagellimonas, for which the names Flagellimonas baculiformis sp. nov. and Flagellimonas crocea sp. nov. are proposed, with type strains D6T (=MCCC M28982T=KCTC 92604T) and DH64T (=MCCC M28986T=KCTC 92975T).

Pseudidiomarina fusca sp. nov., Isolated from the Surface Seawater of the Western Pacific Ocean.

The Gram-negative marine bacterium GXY010T, which has been isolated from the surface seawater of the western Pacific Ocean, is aerobic, non-motile and non-flagellated. Strain GXY010T exhibits growth across a temperature range of 10-42 °C (optimal at 37 °C), pH tolerance from 7.0 to 11.0 (optimal at 7.5) and a NaCl concentration ranging from 1.0 to 15.0% (w/v, optimal at 5.0%). Ubiquinone-8 (Q-8) was the predominant isoprenoid quinone in strain GXY010T. The dominant fatty acids (>10%) of strain GXY010T were iso-C15:0 (14.65%), summed feature 9 (iso-C17:1ω9c and/or 10-methyl C16:0) (12.41%), iso-C17:0 (10.85%) and summed feature 3 (C16:1ω7c and/or C16:1ω6c) (10.41%). Phosphatidylethanolamine (PE), phosphatidylglycerol (PG), diphosphatidylglycerol (DPG), unidentifiable glycolipid (GL) and four non-identifiable aminolipids (AL1-AL4) were the predominant polar lipids of strain GXY010T. The genomic DNA G+C content was identified as a result of 48.0% for strain GXY010T. The strain GXY010T genome consisted of 2,766,857 bp, with 2664 Open Reading Frames (ORFs), including 2586 Coding sequences (CDSs) and 78 RNAs. Strain GXY010T showed Average Nucleotide Identity (ANI) values of 73.4% and 70.6% and DNA-DNA hybridization (DDH) values of 19.2% and 14.5% with reference species Pseudidiomarina tainanensis MCCC 1A02633T (=PIN1T) and Pseudidiomarina taiwanensis MCCC 1A00163T (=PIT1T). From the results of the polyphasic analysis, a newly named species, Pseudidiomarina fusca sp. nov. within the genus Pseudidiomarina, was proposed. The type strain of Pseudidiomarina fusca is GXY010T (=JCM 35760T = MCCC M28199T = KCTC 92693T).

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.

Distribution Characteristics of Microplastics in Surface Seawater off the Yangtze River Estuary Section and Analysis of Ecological Risk Assessment.

Microplastics are widespread in the oceans as a new type of pollutant. Due to the special geographical environment characteristics, the Yangtze River estuary region become hotspot for microplastics research. In 2017 and 2019, surface seawater microplastics samples were collected from five stations off the Yangtze River estuary during four seasons (spring, summer, autumn, and winter). The abundance and characteristics of microplastics in seawater were researched. The results showed that microplastics widely existed in surface seawater; the average abundance of microplastics in seawater was (0.17 ± 0.14) items/m3 (0.00561 ± 0.00462) mg/m3; and accounting for 80% of the total plastic debris, the abundance of microplastics was at moderately low levels compared to national and international studies. The particle size of most microplastics was between 1 mm to 2 mm, accounting for 36.1% of the total microplastics. The main shapes of microplastics were fiber, flake, and line, accounting for 39.5%, 28.4%, and 20.8%, respectively. Polypropylene, polyethylene terephthalate, and polyethylene were the main components of microplastics, accounting for 41.0%, 25.1%, and 24.9%, respectively. Yellow, green, black, and transparent were the most common colors, accounting for 21.9%, 19.6%, 16.5%, and 15.7%, respectively. This study shows that the spatial distribution of microplastics in the surface waters off the Yangtze River estuary shows a decreasing trend from nearshore to farshore due to the influence of land-based inputs, hydrodynamics, and human activities; the distribution of microplastics has obvious seasonal changes, and the level of microplastic pollution is higher in summer. The potential ecological risk of microplastics in the surface waters off the Yangtze River estuary is relatively small.

Vibrio methylphosphonaticus sp. nov., a methylphosphonate-decomposing bacterium isolated from surface seawater in the Xisha Islands, PR China.

A Gram-stain-negative, facultative anaerobic, methylphosphonate-decomposing, motile by a polar flagellum and rod-shaped marine bacterium, designated S4B1T, was isolated from the surface seawater collected from the Yongle Atoll (Xisha Islands, PR China). The pairwise alignment showed the highest sequence similarity of 97.5 and 96.6 % to Vibrio aestuarianus subsp. cardii 12_122_3T3T and Vibrio atypicus HHS02T, respectively. Phylogenetic analysis based on 16S rRNA gene and the phylogenomic analysis of single-copy genes showed that strain S4B1T belonged to the genus Vibrio and formed a close branch with Vibrio qingdaonensis ZSDZ65T. Growth of strain S4B1T occurred at 4-30 °C (optimum, 28 °C), at pH 6.0-8.0 (optimum, pH 7.0) and in the presence of 2-7 % (w/v) NaCl (optimum, 3 %). The predominant fatty acids (>10 %) were C16 : 0, iso-C16 : 0 and summed feature 3 (C16 : 1 ω7c or/and C16 : 1 ω6c). The DNA G+C content of the assembled genomic sequence was 44.3 mol%. Average nucleotide identity (ANI) values between S4B1T and its reference species were lower than the threshold for species delineation (95-96 %), in which its highest ANI value with V. qingdaonensis ZSDZ65T was 87.0 %. In silico DNA-DNA hybridization further showed that strain S4B1T had less than 70 % similarity to its relatives. On the basis of the polyphasic evidence, strain S4B1T is proposed to represent a novel species of the genus Vibrio, for which the name Vibrio methylphosphonaticus sp. nov. is proposed. The type strain is S4B1T (=KCTC 92311T=MCCC 1K06168T).

Galbibacter pacificus sp. nov., isolated from surface seawater of the western Pacific Ocean and transfer of Joostella marina to the genus Galbibacter as Galbibacter orientalis nom. nov. and emended description of the genus Galbibacter.

Two Gram-stain-negative, non-motile, non-spore-forming, strictly aerobic and rod-shaped bacterial strains, CMA-7T and CAA-3, were isolated from surface seawater samples collected from the western Pacific Ocean. Phylogeny of 16S rRNA gene sequences indicated they were related to the genera Galbibacter and Joostella and shared 95.1, 90.9 and 90.8% sequence similarity with G. mesophilus Mok-17T, J. marina DSM 19592T and G. marinus ck-I2-15T, respectively. Phylogenomic analysis showed that the two strains, together with the members of the genera Galbibacter and Joostella, formed a monophyletic clade that could also be considered a monophyletic taxon. This distinctiveness was supported by amino acid identity and percentage of conserved proteins indices, phenotypic and chemotaxonomic characteristics and comparative genomics analysis. Digital DNA‒DNA hybridization values and average nucleotide identities between the two strains and their closest relatives were 18.0-20.8 % and 77.7-79.3 %, respectively. The principal fatty acids were iso-C15 : 0, iso-C17 : 0 3-OH, iso-C15 : 1 G, Summed Feature 3 (C16 : 1 ω7c/C16 : 1 ω6c or C16 : 1 ω6c/C16 : 1 ω7c), Summed Feature 9 (iso-C17 : 1 ω9c or C16 : 0 10-methyl), and C15 : 0 3-OH. The predominant respiratory quinone was MK-6. The polar lipids were phosphatidylethanolamine, aminolipid, aminophospholipid, phospholipid, phosphoglycolipid, glycolipid and unknown polar lipid. The genomic DNA G+C content of strains CMA-7T and CAA-3 was both 38.4 mol%. Genomic analysis indicated they have the potential to degrade cellulose and chitin. Based on the polyphasic evidence presented in this study, the two strains represent a novel species within the genus Galbibacter, for which the name Galbibacter pacificus sp. nov. is proposed. The type strain is CMA-7T (=MCCC M28999T = KCTC 92588T). Moreover, the transfer of Joostella marina to the genus Galbibacter as Galbibacter orientalis nom. nov. (type strain En5T = KCTC 12518T = DSM 19592T=CGMCC 1.6973T) is also proposed.

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.

Vibrio amylolyticus sp. nov. and Vibrio gelatinilyticus sp. nov., two marine bacteria isolated from surface seawater of Qingdao.

Two Gram-stain-negative, oxidase-positive, facultative anaerobic and rod-shaped motile bacteria, designated strains ZSDZ34 and ZSDE26, were isolated from offshore surface seawater collected near Qingdao. Phylogenetic analysis based on 16S rRNA gene sequences placed ZSDE26T and ZSDZ34T within the genus Vibrio, family Vibrionaceae, class Gammaproteobacteria. Strain ZSDE26T was most closely related to Vibrio gallaecicus VB 8.9T with 97.3 % sequence similarity, whereas ZSDZ34T was most closely related to Vibrio aestuarianus subsp. cardii DSM 109723T with 97.8 % sequence similarity. Strain ZSDE26T grew with 1-5 % (w/v) NaCl (optimum, 4 %), at 16-28 °C (optimum, 28 °C) and at pH 6.0-9.0 (optimum, pH 7.0). Growth of strain ZSDZ34T occurred with 1-6 % (w/v) NaCl (optimum, 3 %), at 16-37 °C (optimum, 28 °C) and at pH 6.0-9.0 (optimum, pH 7.0). Both strains shared the same major fatty acid components (more than 10 % of total fatty acids) of summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c) and C16 : 0. Additionally, strain ZSDZ34T contained a higher proportion of iso-C16 : 0. The DNA G+C contents of strains ZSDE26T and ZSDZ34T were 42.8 and 44.5 mol%, respectively. On the basis of the results of polyphasic analysis, ZSDE26T and ZSDZ34T are considered to represent novel species within the genus Vibrio, for which the names Vibrio amylolyticus sp. nov. (type strain, ZSDE26T=KCTC 82890T=MCCC 1K06290T) and Vibrio gelatinilyticus sp. nov. (type strain, ZSDZ34T=KCTC 82888T=MCCC 1K06292T) are proposed, respectively.

Vibrio sinus sp. nov., a marine bacterium isolated from coastal seawater.

A Gram-straining-negative, facultatively anaerobic, motile by means of a polar flagellum and rod-shaped marine bacterium, designated S4M6T, was isolated from surface seawater collected in Dongshan Bay (Fujian, PR China). Phylogenetic analysis based on 16S rRNA genes, phylogenomic analysis of single-copy gene families and whole genome data indicated that S4M6T represented a member of the genus Vibrio. The closest phylogenetic relatives of S4M6T were Vibrio marisflavi CGMCC 1.8994T (97.8 % 16S rRNA gene sequence pairwise similarity), Vibrio variabilis LMG 25438T (96.9 %), Vibrio gangliei SZDIS-1T (96.2 %) and Vibrio aestivus M22T (96.1 %). The growth of S4M6T occurred at 15-35 °C (optimum 28 °C), pH 4.0-9.0 (optimum 5.0-7.0) and in the presence of 2-5 % (w/v) NaCl (optimum 3 %). The predominant fatty acids (>10 %) are C16 : 0, summed feature 3 (C16 : 1ω7c and/or C16 :  1ω6c) and summed feature 8 (C18 : 1ω7c and/or C18 :  1ω6c). The DNA G+C content of the assembled genomic sequences was 43.4 % for S4M6T. Average nucleotide identity (ANI) values between S4M6T and the reference species were lower than the threshold for species delineation (95-96 %); in silico DNA-DNA hybridization further indicated that S4M6T had less than 70 % similarity to its relatives. On the basis of the polyphasic evidence, strain S4M6T is proposed to represent a novel species of the genus Vibrio, for which the name Vibrio sinus sp. nov. is proposed. The type strain is S4M6T (= KCTC 92312T= MCCC 1K06167T).

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 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.

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.

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.

Zunongwangia pacifica sp. nov., isolated from surface seawater of the Western Pacific Ocean.

Zunongwangia is a group of marine bacteria with important industrial application potential and ecological functions. In this study, a Gram-stain-negative, rod-shaped, non-motile, strictly aerobic and bright yellow pigmented bacterial strain within this genus, designated C2-37M9T, was isolated from a surface seawater sample from the Philippine Basin in the Western Pacific Ocean. Strain C2-37M9T grew at 10-44 °C (optimum, 28-30 °C), pH 6-9 (pH 7) and in the presence of 0-12 % NaCl (w/v; 2-3 %). Phylogenetic analysis based on 16S rRNA gene sequences indicated that it belonged to the genus Zunongwangia and had 95.7-98.7 % sequence similarity to all type strains of this genus, with the highest value corresponding to Zunongwangia profunda (98.7 %). Digital DNA-DNA hybridization, average nucleotide identity and average amino acid identity values between strain C2-37M9T and all valid type strains were 27.5-32.3, 83.8-86.7 and 86.9-89.0 %, respectively. The principal fatty acids (>5 %) were iso-C15 : 0, iso-C17 : 0 3-OH, anteiso-C15 : 0, summed feature 9 (C16 : 0 10-methyl and/or iso-C17 : 1 ω9c), iso-C15 : 1 G and summed feature 3 (C16 : 1 ω6c and/or C16 : 1 ω7c). The predominant respiratory quinone was MK-6. The polar lipids were one phosphatidylethanolamine, two unknown glycolipids, three unidentified aminolipids and six unidentified lipids. The genomic DNA G+C content of strain C2-37M9T was 36.7 mol%. Based on phylogenetic results and genomic-based relatedness indices, as well as phenotypic and genotypic characteristics, strain C2-37M9T represents a novel species within the genus Zunongwangia, for which the name Zunongwangia pacifica sp. nov. is proposed. The type strain is C2-37M9T (=MCCC M21534T=KCTC 82852T).

Cadmium isotopes in Bahamas platform carbonates: A base for reconstruction of past surface water bioproductivity and their link with chromium isotopes.

The distribution of cadmium (Cd) within the oceans strongly suggests that it is used as a nutrient by marine phytoplankton. Biologically induced removal of Cd from modern surface waters is accompanied by an isotopic fractionation leaving surface-waters enriched in isotopically heavy Cd. This first study focusses on tying the Cd isotopic record preserved in modern shallow platform carbonates of the Great Bahama Bank (GBB) to conditions in the upper water column, and provides a base for future studies aiming at reconstructing past bioproductivity levels in ancient ocean/basin surface waters. In addition, we compare δ114Cd values with previously published chromium (Cr) isotope values and link signals of bioproductivity with redox conditions in the surface waters. The GBB core samples yield [Cd] (21-188 µg/kg), which increases with depth alongside changes in carbonate mineralogy related to sediment supply and diagenesis. The δ114Cd values of these carbonates are mainly positively fractionated with an average of 0.11‰ ± 0.17 (2σ; n = 17) relative to the NIST 3108 reference standard. Unlike previously observed for Cr isotopes, there is no control of δ114Cd values by relative abundances of the carbonate polymorphs aragonite and calcite in the studied profile. Likewise, δ114Cd values are not correlated to major and trace element (e.g. Ca, Mg, Mn and Sr) contents. We postulate that the burial and diagenetic processes of carbonate cannot modify the Cd isotope signals. Using the experimental fractionation factor for Cd into calcite (-0.45‰), calculated seawater δ114Cd of +0.56 ± 0.17‰ is in agreement with values for modern North Atlantic Surface Seawater. This study's results suggest that δ114Cd values in carbonates are a reliable tool for reconstruction of bioproductivity levels in past surface seawaters, and open new possibilities in combination with Cr isotopes to link these with past ocean redox.

Pontibacter cellulosilyticus sp. nov., a carboxymethyl cellulose-hydrolysing bacterium isolated from coastal water.

A Gram-stain-negative, rod-shaped, non-motile, red-pink bacterium designated SD6T was isolated from coastal marine water at Sadong Beach, Ulleung Island, South Korea. Cells of SD6T grew at 10-42 °C (optimum, 30 °C), pH 5.0-9.0 (optimum, pH 6.0-7.0) and at 0-8.0 % (w/v) NaCl (optimum, 0-3 %). Moreover, 16S rRNA gene sequence analysis indicated that strain SD6T was a member of the genus Pontibacter, sharing similarities to Pontibacter aydingkolensis XAAS-1T (98.0 %), Pontibacter amylolyticus 9-2T (97.3 %), Pontibacter korlensis X14-1T (97.2 %) and Pontibacter soli HYL7-26T (96.8 %). The predominant fatty acids of strain SD6T were identified as iso-C15 : 0 and summed feature 4 (comprising anteiso-C17 : 1 B and/or iso-C17 : 1 I) and the sole respiratory quinone was identified as MK-7 (menaquinone 7). Major polar lipids included phosphatidylethanolamine, one unidentified phosphoglycolipid, two unidentified glycolipids and one unidentified lipid. The average nucleotide identity and in silico DNA-DNA hybridization values of strain SD6T with its closely related strains were 72.8-79.8 % and 19.2-22.6 %, respectively. The genomic DNA G+C content was 45.4 mol%. In accordance with the results of phenotypic, chemotaxonomic and phylogenetic data, strain SD6T represents a novel species of the genus Pontibacter, for which the name Pontibacter cellulosilyticus sp. nov. is proposed. The type strain is SD6T (=KACC 21543T=NBRC 114313T=JCM 31022T).