Preliminary study of the source apportionment and diversity of microplastics: Taking floating microplastics in the South China Sea as an example

At present, the study of microplastic sources is in a relatively preliminary stage due to the complexity of microplastic features in the environment. Based on a literature review, we developed a source-specific classification system for the quantitative analysis of microplastic sources. The classification system includes ten types of microplastics based on morphology and composition and can identify their main sources and the associated probabilities. To reflect the complexity of types and sources in the regional combination of microplastics, we first propose a microplastic diversity index (D_1-D'(MP)). We use the South China Sea as an example to carry out quantitative source analysis and calculate the diversity index. Eight types of microplastics were found, mainly consisting of maritime coatings (type "Gran_coat") (33.0%) and synthetic fibers (type "Fib_thin") (29.6%). We also found that the diversity increased with offshore distance. In addition, we partitioned surface microplastics globally according to a two-dimensional microplastic abundance-diversity index. We believe that these indicators can effectively reflect pollution status and ultimately lead to different types of control measures. In the future, additional indicators for the characterization of microplastics must be included in the classification system to establish a one-to-one source analysis system for microplastic characteristics and source apportionment. In general, our study may provide new insights into the establishment of more accurate and quantitative source apportionment techniques and effective pollution control.

Lost but can't be neglected: Huge quantities of small microplastics hide in the South China Sea

Large quantities of microplastics with small particle sizes were found in the South China Sea (SCS). The abundances of microplastics in seawater were 0.045±0.093and 2569±1770particles/m³ according to the bongo net and pumping sampling methods, respectively. Smaller-size fractions (size<0.3mm) contributed 92% of the number of microplastics to the total load. Continental slope is the largest reservoir of microplastics with an inventory of 295tons. 21 polymer types were found in the samples using the micro Fourier Transform Infrared Spectroscopy (FTIR), among which alkyds (22.5%) and polycaprolactone (PCL) (20.9%) accounted for almost half of the total polymer content. Lighter plastics would not only concentrate upon the coastal area, being more likely to drift further into open seas with ocean currents. The distribution characteristics showed that it was mainly controlled by terrestrial input of the Pearl River. This study, as the first report from SCS on microplastics in water for its distribution and influence factors, provided impetus for further research on the transportation fate and the behavior of this emerging pollutant from coastal zone to the open oceans.

Atmospheric microplastic over the South China Sea and East Indian Ocean: abundance, distribution and source

At present, microplastic (MP) is pervasive globally and has a regional difference. Recent studies have identified MP in the terrestrial atmospheric environment. However, the connection between terrigenous atmospheric MP emissions and impacts over the ocean is not well known. Here, we present the distribution of atmospheric MP abundance over the ocean based on a transoceanic survey conducted across 21 sampling transects from the Pearl River Estuary (PRE) to the South China Sea (SCS) and then to the East Indian Ocean (EIO). The abundance of atmospheric MP over the PRE (4.2 ± 2.5 items/100 m³) was significantly higher than that over the EIO (0.4 ± 0.6 items/100 m³). However, the abundance of atmospheric MP in the SCS (0.8 ± 1.3 items/100 m³) was not significantly different from the EIO and PRE. This result revealed that MP undergoes long-range transport, more than 1000 km away, through the atmosphere, but atmospheric MP transmission as the main source of oceanic MP based on transoceanic studies is not a plausible assumption. Furthermore, backward trajectory model analysis of 21 sampling transects preliminary showed the potential sources of atmospheric MP over the PRE, SCS, and EIO.

Microplastic ingestion in deep-sea fish from the South China Sea

Monitoring the ingestion of microplastics by fish in the environment is crucial to understanding the risks posed by microplastics in the marine ecosystem. In this study, we investigated the ingestion of microplastics in deep-sea fish from the northern continental slope of the South China Sea. All fish samples were contaminated by microplastics, reflecting a high level of microplastic pollution in this region. The average abundance of microplastics in the stomachs of sampled fish was 1.96 ± 1.12 items/individual and 1.53 ± 1.08 items/g, and levels in the intestines of sampled fish were 1.77 ± 0.73 items/individual and 4.82 ± 4.74 items/g. Fish were collected from depths of 200 to 209 m and 453 to 478 m, and no significant difference in the quantity of microplastics ingested was detected among different depths in this range. The microplastics ingested by fish were dominated by plastics that were <1 mm in size, film-like in shape, transparent in color and composed of cellophane. Our results suggest that the ingestion of microplastics by fish is closely related with the microplastic pollution in the marine environment.

Spatio-temporal comparison of neustonic microplastic density in Hong Kong waters under the influence of the Pearl River Estuary

Rivers are recognised as an important source of plastic debris in the open sea. The Pearl River in China is estimated to transport 0.1milliontonnes of plastic waste to the open sea annually. However, no empirical study has been conducted to assess the plastic contamination levels in the Pearl River Estuary. Hong Kong is situated in the east of the Pearl River Estuary; its western waters are strongly influenced by river discharge, whereas the eastern waters are unaffected by the freshwater plume. In this study, we quantified the neustonic plastic debris density in the western and eastern waters of Hong Kong. The mean microplastic (0.355-4.749mm) and large plastic debris (≥4.75mm) densities in the western side were 3.627 and 0.758n/m³, respectively. Seasonal comparisons indicated that both size classes of plastic debris were significantly more abundant by number in the rainy season than the dry season (p<0.001). However, the influence of rivers on plastic density at the sea surface may be highly restricted to the estuarine delta, as no significant spatial difference was found between the western and eastern waters.

Heavy metal concentrations in wild fishes captured from the South China Sea and associated health risks

Heavy metal concentrations were measured in 29 marine wild fish species from the South China Sea. Concentrations (wet weight) were 0.51-115.81 ng/g (Cd), 0.54-27.31 ng/g (Pb), 0.02-1.26 μg/g (Cr), 8.32-57.48 ng/g (Ni), 0.12-1.13 μg/g (Cu), 2.34-6.88 μg/g (Zn), 2.51-22.99 μg/g (Fe), and 0.04-0.81 μg/g (Mn), respectively. Iron concentrations in all and Mn in some fish species were higher than the acceptable daily upper limit, suggesting human consumption of these wild fish species may pose a health risk. Human health risk assessment, however, indicated no significant adverse health effects with consumption.

Occurrence and distribution of conventional and new classes of per- and polyfluoroalkyl substances (PFASs) in the South China Sea

Concentrations of 23 per- and polyfluoroalkyl substances (PFASs), including new classes of PFASs, in seawater samples were investigated for their occurrence and the interaction of the ocean currents with the distribution of PFASs in the South China Sea. This study revealed that socio-economic development was associated with the PFAS contamination in coastal regions of South China. Significant correlations between concentration of total PFASs with gross domestic product (GDP) per capita and population density were found in the areas, suggesting that the influence of intense human activities in these areas may have resulted in higher PFAS contamination to the adjacent environment. Di-substituted polyfluoroalkyl phosphate (diPAP), one of the potential replacements for PFASs, was only detected in the heavily developed region, namely Pearl River Delta (PRD). Total PFAS concentrations, ranging from 195 to 4925 pg/L, were detected at 51 sampling stations of the South China Sea. The results also confirmed that PFAS contamination in the South China Sea is strongly affected by the ocean currents. In comparison to perfluoroactane sulfonate (PFOS) concentrations measured nine years ago at the same locations, the concentrations in this study were found to be two times higher. This indicated that the use and production of perfluoroalkyl sulfonates (PFSAs) has been continuing in the region.

Pseudonocardians A-C, new diazaanthraquinone derivatives from a deap-sea actinomycete Pseudonocardia sp. SCSIO 01299

Pseudonocardians A–C (2–4), three new diazaanthraquinone derivatives, along with a previously synthesized compound deoxynyboquinone (1), were produced by the strain SCSIO 01299, a marine actinomycete member of the genus Pseudonocardia, isolated from deep-sea sediment of the South China Sea. The structures of compounds 1–4 were determined by mass spectrometry and NMR experiments (¹H, ¹³C, HSQC, and HMBC). The structure of compound 1, which was obtained for the first time from a natural source, was confirmed by X-ray analysis. Compounds 1–3 exhibited potent cytotoxic activities against three tumor cell lines of SF-268, MCF-7 and NCI-H460 with IC₅₀ values between 0.01 and 0.21 μm, and also showed antibacterial activities on Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212 and Bacillus thuringensis SCSIO BT01, with MIC values of 1–4 μg mL⁻¹.

Microplastics in seawater and zooplankton: A case study from Terengganu estuary and offshore waters, Malaysia

Widespread accumulation and distribution of microplastics at the sea surface raise concerns as the habitat is a feeding ground for zooplankton. As primary consumers, these organisms are closely connected to microplastic input in the marine food chain. Little comparative information currently exists about this problem in estuary and offshore systems. This study investigates microplastic distribution in the surface water and the potential ingestion of microplastics in selected taxonomic groups of zooplankton from the Terengganu Estuary to offshore waters, Malaysia. In the surface water, three types of microplastics were found (fibres, fragments and pellets). Fibres made up the highest percentage, comprising 80.8% and 73.8% of microplastics in offshore waters and estuaries, respectively. The highest total density of microplastics was found in the Terengganu Estuary (545.8 particles m^-3). Microplastics sampled from the offshore waters were identified as polyamide, polyethylene, and polypropylene, which possibly originated from secondary microplastic sources. Two types of microplastics were detected in zooplankton: fibres and fragments. Fibres were the most commonly ingested microplastic type in zooplankton collected from offshore waters (94%) and estuaries (77.7%). The average sizes of ingested fibres and fragments were 361.7 ± 226.8 μm and 96.8 ± 28.1 μm, respectively, with a wider range of sizes ingested observed in offshore waters than in estuaries. The concentration of microplastics in seven zooplankton groups varied from 0.01 ± 0.002 particles ind.^-1 (Harpacticoida) to 0.2 ± 0.14 particles ind.^-1 (Aphragmophora). Notwithstanding the conformity of our results (increased anthropogenic activities led to greater plastic pollution within the estuary), no significant correlation was observed between the levels of microplastic ingestion and microplastic concentration in the surface water within both areas. Our results provide an important baseline reference on microplastic pollution from estuary to offshore waters, as well as proving that zooplankton act as a repository for microplastic in the marine ecosystem.

Microplastic pollution around remote uninhabited coral reefs of Nansha Islands, South China Sea

Microplastic (MP) pollution is a growing environmental problem in the global oceans. However, there is relatively little evidence of the extent of MP pollution around remote islands, such as coral reefs, in the open ocean. In this study, we conducted a large-scale investigation of MP pollution in the surface waters around the remote uninhabited coral reefs of Nansha Islands in South China Sea. Microplastics were widespread in the surface waters with an average abundance of 0.0556 ± 0.0355 items/m³, although this varied among the coral reefs. The MPs were predominantly composed of polypropylene (PP) and polyethylene (PE), and > 70% of them were <3 mm in size. Fragments and fibers comprised the most common MP types. The similarity between macro plastic and MP compositions provided evidence for the tracing of MP sources in the study area. The main pollutants (transparent PP fibers and PE fibers) around these remote coral reefs may originate from fishing gear abrasions. The plastic waste released from nearby residential islands and high-intensity fishing activities around Nansha Islands likely represented important local sources. Overall, the abundance of MPs found in the surface waters surrounding these remote coral reefs in the South China Sea was relatively low; however, these levels of MP pollution should not be disregarded given the importance of coral reef ecosystems.

Polycyclic aromatic hydrocarbons (PAHs) in wild marine organisms from South China Sea: Occurrence, sources, and human health implications

Concentrations of 16 US EPA priority polycyclic aromatic hydrocarbons (PAHs) were measured in 15 marine wild organism species from South China Sea. The concentration (dry weight) of 16 PAHs ranged from 94.88 to 557.87ng/g, with a mean of 289.86ng/g. The concentrations of BaP in marine species were no detectable. The composition of PAHs was characterized by the 2- and 3-ring PAHs in marine species, and NA, PHE and FA were the dominant constituents. PAHs isomeric ratios indicated PAHs mainly originated from grass, wood and coal combustion, and petroleum. The human health risk assessment based on the excess cancer risk (ECR) suggested the probability of PAHs posing carcinogenic risk to human beings with consumption of marine organisms were negligible (probability<1×10^-6).

Phthalate esters in seawater and sediment of the northern South China Sea: Occurrence, distribution, and ecological risks

In this study, the occurrence and distribution of 15 phthalate esters (PAEs) in seawater and sediment from the northern South China Sea (NSCS) were investigated for the first time to improve understanding on the contamination status of PAEs in this region. The concentrations of total PAEs (∑₁₅ PAEs) were found to range from 68.8 to 1500 ng/L, 46.0 to 7800 ng/L, and 49.2 to 440 ng/g dry weight in surface seawater, bottom seawater, and sediment, respectively. Among the 15 PAEs, dibutyl phthalate (DBP) and bis(2-ethylhexyl) phthalate (DEHP) were the predominant PAE congeners, with mean contributions of 44.7% and 24.0% in surface water, and 42.7% and 25.8% in bottom water, respectively. Moreover, diisobutyl phthalate (DiBP) constituted the majority of ∑15 PAEs in the sediment (61.3%). Comparatively high concentrations of Σ15 PAEs were observed in seawater at the sites within the western NSCS, whereas relatively higher concentrations of Σ15 PAEs were detected in sediments at the eastern NSCS. River input and atmospheric deposition could be the main sources of PAEs in the NSCS. Preliminary risk assessment implied that DBP, DiBP, and DEHP posed low to high potential risks for marine organisms at different trophic levels. These results would be valuable for implementing effective control measures and remediation strategies for PAEs contamination in the region.

Mercury pollution in fish from South China Sea: levels, species-specific accumulation, and possible sources

Both total mercury (THg) and methylmercury (MeHg) levels in fish collected from South China Sea (SCS) were studied to understand Hg pollution in Chinese tropical marine ecosystems. The average THg concentrations in fish species ranged from 39.6 μg/kg for rabbitfish (Siganus fuscessens) to 417 μg/kg for thornfish (Terapon jarbua), while those of MeHg varied from 13 μg/kg (rabbitfish) to 176 μg/kg (thornfish). The median values of MeHg/THg ratios in different fish species ranged from 36 to 85%. Significant inter-species differences of THg and MeHg in fish were observed due to feeding habits and fish sizes. Overall, carnivorous fish had higher levels of THg, MeHg and MeHg/THg ratios than omnivorous and herbivorous fish. High Hg levels in fish of the SCS were probably related to Hg input from atmospheric deposition and anthropogenic activities.

Persistent organic pollutants in marine fish from Yongxing Island, South China Sea: levels, composition profiles and human dietary exposure assessment

Little data is available on the bioaccumulation of persistent organic pollutants (POPs) in marine organisms from South China Sea (SCS). Five marine fish species were collected from Yongxing Island, SCS to investigate the presence of polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane and its metabolites (DDTs). PBDEs, PCBs, and DDTs concentrations ranged from 2.0-117, 6.3-199, and 9.7-5831 ng g(-1) lw, respectively. In general, contaminants measured in this study were at the lower end of the global range. Concentrations of PBDEs and PCBs were significantly correlated in fish samples, implying that PBDEs are as prevalent as PCBs in Yongxing Island. Among the five fish species studied, yellow striped goatfish had the highest concentrations of PBDEs, PCBs, and DDTs, probably attributed to its different living and feeding habits. The contaminant distribution pattern indicated that agrochemical source is more important than industrial source in Yongxing Island, SCS. The average estimated daily intakes of PBDEs, PCBs, and DDTs via fish consumption by local residents in the coastal areas of South China ranged from 1.42-5.91, 3.20-13.3, and 8.08-33.6 ng d(-1), which were lower than those in previous studies, suggesting that consumption of marine fish in Yongxing Island, SCS, might not subject local residents to significant health risk as far as POPs are concerned. This is the first study to report the occurrence of POPs in marine biota from SCS.

Bioaccessibility and human health implications of heavy metals in different trophic level marine organisms: A case study of the South China Sea

This study investigated the total concentrations and bioaccessibility of heavy metals in edible tissues and trophic levels of 12 marine organism species in the South China Sea. The results were used to estimate health risks to humans. Of the heavy metals detected, nickel (Ni) was present at the highest concentrations, followed in descending, order by iron (Fe), zinc (Zn), manganese (Mn), chromium (Cr), copper (Cu), cadmium (Cd) and lead (Pb). Cd had the highest percentage bioaccessibility (61.91%). There were no correlations between log-transformed total metal concentrations and trophic level values, nor between log-transformed bioaccessibility metal concentrations and trophic level values. This indicates there is no biomagnification among these trace metals. The carcinogenic risk probabilities for Pb and Cr to urban and rural residents were below the acceptable level (< 1 × 10^-4). The target hazard quotient (THQ) value for each metal and the total THQ values for all metals studied indicated no significant risk of non-carcinogenic effects to urban and rural residents from consuming marine organisms from the South China Sea.

Surface O3 photochemistry over the South China Sea: Application of a near-explicit chemical mechanism box model

A systematic field measurement was conducted at an island site (Wanshan Island, WSI) over the South China Sea (SCS) in autumn 2013. It was observed that mixing ratios of O₃ and its precursors (such as volatile organic compounds (VOCs), nitrogen oxides (NO_x = NO + NO₂) and carbon monoxide (CO)) showed significant differences on non-episode days and episode days. Additional knowledge was gained when a photochemical box model incorporating the Master Chemical Mechanism (PBM-MCM) was applied to further investigate the differences/similarities of O₃ photochemistry between non-episode and episode days, in terms of O₃-precursor relationship, atmospheric photochemical reactivity and O₃ production. The simulation results revealed that, from non-O₃ episode days to episode days, 1) O₃ production changed from both VOC and NO_x-limited (transition regime) to VOC-limited; 2) OH radicals increased and photochemical reaction cycling processes accelerated; and 3) both O₃ production and destruction rates increased significantly, resulting in an elevated net O₃ production over the SCS. The findings indicate the complexity of O₃ pollution over the SCS.

Occurrence, sources and transport of antibiotics in the surface water of coral reef regions in the South China Sea: Potential risk to coral growth

Laboratory research has indicated that antibiotics had negative effects on coral growth by disturbing natural microbiota; however, no field studies have reported antibiotic contamination levels and their influence on coral growth in natural coral reef regions (CRRs). This study investigated antibiotic occurrence and sources in the surface water from CRRs that have suffered from rapid coral degradation and evaluated their risk to coral growth. These regions are in the South China Sea, including four coastal and two offshore CRRs. The results show that 13 antibiotics were detected in the coastal CRRs with concentrations ranging from 10^-2-10⁰ ng L^-1, while 5 antibiotics occurred in offshore CRRs (300-950 km from the mainland), with concentrations ranging from 10^-2 to 10^-1 ng L^-1. Their concentrations decreased gradually from the coast to offshore in the transport process. However, Yongxing Island, which is approximately 300 km from the mainland, was an exception with relatively higher concentrations than the surrounding reefs because of the ever-increasing human activity on the island. The presence of anthropogenic contaminants antibiotics in CRRs may be a potential risk to coral growth.

Occurrence of polycyclic aromatic hydrocarbons (PAHs) in coral reef fish from the South China Sea

Little data are available on the bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) in coral reef fish from the South China Sea (SCS). In this study, we collected 21 coral reef fish species from the Xisha and Nansha Islands in the SCS to investigate the occurrence of 16 US-EPA PAHs. The total PAH concentrations (ΣPAH) in the collected fish ranged from 12.79 to 409.28 ng/g dry weight (dw, Xisha Islands) and from 32.71 to 139.09 ng/g dw (Nansha Islands), respectively. The ΣPAH concentration of Scarus niger collected from the Xisha Islands (237.13 ng/g dw) was about twofold higher than that of Scarus niger collected from the Nansha Islands (139.09 ng/g dw). The dominant compounds were found to be 2-ring and 3-ring PAHs. Based on qualitative and quantitative analyses, the main PAH sources were found to be coal and biomass combustion (50.43%), petroleum sources (25.86%), and vehicular emissions (16.10%).

Organic ultraviolet (UV) filters in the South China sea coastal region: Environmental occurrence, toxicological effects and risk assessment

Organic ultraviolet (UV) filters are common ingredients of personal care products and occur ubiquitously in the aquatic environment; however, little is known about their distribution in and potential effects to the marine environment. This study reports the occurrence, toxicological effects and risk assessment of eleven commonly consumed UV filters in marine surface water collected from the South China Sea (SCS) coastal region. The concentrations of UV filters ranged from <MDL to 145 ng/L in the SCS, in which benzophenone-3, octocrylene and butyl methoxydibenzoylmethane were the most dominant compounds with their detection frequencies over 97%. Relatively higher levels of total UV filters were found near the highly industrialized and urbanized Pearl River Estuary (PRE) and the concentrations gradually decreased towards the SCS. In general, the environmental levels of UV filters were higher at the western marine waters in Hong Kong than the eastern marine waters. Significant negative correlations were observed between benzophenone-4 and water temperature, as well as ethylhexyl methoxycinnamate and salinity (P < 0.001; r < -0.5). Immobilization test of barnacle nauplius larvae (Balanus amphitrite) was conducted to assess the acute toxicity of organic UV filters to marine organisms. Benzophenone-8 and 4-methylbenzylidene camphor showed relatively higher toxicity with the 50% effect concentrations (EC₅₀) of 2.2 and 3.9 mg/L, respectively. A preliminary risk assessment was conducted by the results obtained from our field and laboratory studies. Results showed that the risk to cause immobilization in barnacle nauplius larvae in associated with exposure to current levels of organic UV filters in the SCS was minimal.

Distribution characteristics of microplastics in Zhubi Reef from South China Sea

As a new type of emerging pollutant in the ocean, microplastics have received global attention in recent years. Considering the increasing amount of human activities around the South China Sea, it is important to determine the current status of microplastic pollution in this region. In this study, we analyzed the abundance and distribution of microplastics at Zhubi Reef in the South China Sea. Microplastic abundance ranged from 1400 to 8100 items/m³ of surface water, which was much higher than the values reported from other ocean areas. About 80% of the microplastics were smaller than 0.5 mm in size. Fibers and pellets comprised the most common microplastic types. The dominant microplastics were transparent or blue in color. The main polymer types were polypropylene (25%) and polyamide (18%). In general, our results revealed Zhubi Reef was contaminated with microplastics, which were likely derived from the intensive fisheries in the area and emissions from coastal cities. This study also provides baseline data that are useful for additional studies of microplastics in the South China Sea.

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.

Distinct Bacterial Communities Associated with Massive and Branching Scleractinian Corals and Potential Linkages to Coral Susceptibility to Thermal or Cold Stress

It is well known that different coral species have different tolerances to thermal or cold stress, which is presumed to be related to the density of Symbiodinium. However, the intrinsic factors between stress-tolerant characteristics and coral-associated bacteria are rarely studied. In this study, 16 massive coral and 9 branching coral colonies from 6 families, 10 genera, and 18 species were collected at the same time and location (Xinyi Reef) in the South China Sea to investigate the bacterial communities. The results of an alpha diversity analysis showed that bacterial diversities associated with massive corals were generally higher than those with branching corals at different taxonomic levels (phylum, class, order, and so on). In addition, hierarchical clustering tree and PCoA analyses showed that coral species were clustered into two large groups according to the similarity of bacterial communities. Group I consisted of massive Goniastrea, Plesiastrea, Leptastrea, Platygyra, Echinopora, Porites, and Leptoria, and group II consisted of branching Acropora and Pocillopora. These findings suggested that both massive corals and branching corals have their own preference for the choice of associated bacteria, which may be involved in observed differences in thermal/cold tolerances. Further analysis found that 55 bacterial phyla, including 43 formally described phyla and 12 candidate phyla, were detected in these coral species. Among them, 52 phyla were recovered from the massive coral group, and 46 phyla were recovered from the branching coral group. Formally described coral pathogens have not been detected in these coral species, suggesting that they are less likely to be threatened by disease in this geographic area. This study highlights a clear relationship between the high complexity of bacterial community associated with coral, skeletal morphology of coral and potentially tolerances to thermal or cold stress.

Scopararanes C-G: new oxygenated pimarane diterpenes from the marine sediment-derived fungus Eutypella scoparia FS26

Five new oxygenated pimarane diterpenes, named scopararanes C–G (1–5) were isolated from the culture of a marine sediment-derived fungus Eutypella scoparia FS26 obtained from the South China Sea. The structures of these compounds were established on the basis of extensive spectroscopic analysis. The absolute configurations of compounds 1–5, were determined by CD spectroscopic analysis and comparison with literature data. All isolated compounds (1–5) were evaluated for their cytotoxic activities against MCF-7, NCI-H460, and SF-268 tumor cell lines by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) method.

Antibiotics in coral reef fishes from the South China Sea: Occurrence, distribution, bioaccumulation, and dietary exposure risk to human

Coral reef fishes are about 10% of commercial fishes worldwide. Their pollution is close to human's health. Antibiotics are one group of emerging organic pollutants in the marine environment. However, little data is available on the bioaccumulation and dietary risks of antibiotics in coral reef fish from the South China Sea (SCS) or any other parts of the global coral reef environment. In this study, we examined 19 antibiotics in 18 species of coral reef fish collected from coastal and offshore regions in the SCS. The results revealed that 17 antibiotics were detected in the fishes. Their average concentrations ranged from 1.3 × 10^-5 to 7.9 × 10^-1 ng/g ww, which were at the lower end of the global range about antibiotic levels in fish. The average total antibiotic concentrations (∑₁₉ABs) were significantly higher in the offshore fish (1.2 ng/g ww) than in the coastal fish (0.16 ng/g ww). Different fish species or the protection of mucus produced by coastal fish at severe environmental stress may cause the differences. Fluoroquinolones (FQs) accounted for 89% and 74% of the average ∑₁₉ABs in the offshore and coastal fish, respectively. It may relate to their relative high aqueous solubility and adsorption ability to particles. The log BAFs (bioaccumulation factors) of the antibiotics ranged from -0.34 to 4.12. Norfloxacin, dehydrated erythromycin (DETM), and roxithromycin were bioaccumulative in some offshore fish samples with their log BAFs higher than 3.7. The results of trophic magnification factors (TMFs) demonstrated that DETM underwent significant trophic dilution while enoxacin underwent trophic magnification in the food web of coral reef fishes. The estimated daily intakes of antibiotics via fish consumption by China residents ranged from 2.0 × 10^-4 to 2.7 ng/kg weight body/day, which was 3 to 8 orders of magnitude lower than the respective acceptable daily intakes.

Occurrence of Pseudo-nitzschia species and associated domoic acid production along the Guangdong coast, South China Sea

The diatom genus Pseudo-nitzschia, which has been associated with amnesic shellfish poisoning events globally, is also one of the key harmful microalga groups in Guangdong coastal waters, off the north coast of the South China Sea. In order to explore the diversity and toxigenic characteristics, Pseudo-nitzschia isolates were established. Based on a combination of morphological and molecular features, in total 26 different Pseudo-nitzschia taxa were identified, including two new species, P. uniseriata H.C. Dong & Yang Li and P. yuensis H.C. Dong & Yang Li. Morphologically, P. uniseriata is unique by having striae mainly comprising one row of poroids, which are simple without divided hymen internally, and each poroid containing one, seldom two sectors. Pseudo-nitzschia yuensis is characterized by having striae comprising one to two rows of poroids. In biseriate striae, the poroids are polygonal and irregularly distributed, and a discontinuous row of poroids may be present in the middle. In uniseriate striae, the poroids usually contain 1-5 sectors. Both taxa are well differentiated from other Pseudo-nitzschia species in phylogenetic analyses inferred from ITS2 sequence-structure information. Pseudo-nitzschia uniseriata is sister to P. lineola, whereas P. yuensis forms a group together with P. micropora and P. delicatissima. When comparing ITS2 secondary structure, two hemi-compensatory base change (HCBCs) are found between P. uniseriata and P. lineola. One compensatory base change (CBC) and four HCBCs are found between P. yuensis and P. delicatissima, and there is one CBC and five HCBCs between P. yuensis and P. micropora. The ability of cultured strains to produce particulate DA (pDA) revealed production of pDA in twenty-nine strains belonging to seven species: P. bipertita, P. caciantha, P. cuspidata, P. fraudulenta, P. fukuyoi, P. lundholmiae and P. multiseries. This is the first report of P. bipertita being toxic, with pDA content of 15.6 ± 2.1 fg cell^-1. The presence of brine shrimps significantly increased pDA content in P. cuspidata, P. fukuyoi, P. lundholmiae and P. multiseries 1.4 to 7 times, and induced pDA production in P. fraudulenta from below detection limit to 17.5 ± 1.6 fg cell^-1. The highest pDA concentration, 4830.5 ± 120.3 fg cell^-1, was detected in P. multiseries, a level much lower than previous reports on P. multiseries from North America and Europe. Overall, the cellular toxin levels in Pseudo-nitzschia spp. were low in Guangdong coastal isolates.