The toxic mechanisms of BDE-47 to the marine diatom Thalassiosira pseudonana-a study based on multiple physiological processes

Influence of perfluoroalkyl substances, with focus on perfluorobutanoic acid on the responding characteristics and molecular mechanisms of Thalassiosira pseudonana

Perfluoroalkyl substances (PFAS) are widely dispersed persistent organic pollutants (POPs) throughout marine ecosystems. Due to ban of traditional long-chain PFAS, the emerging short-chain ones showed increased environmental detection as substitutes. As the foundation of aquatic food webs, microalgae play a pivotal role in the stability of marine environments. However, the toxicity of those short-chain PFAS was lack of investigation. Therefore, we chose 4C PFAS perfluorobutanoic acid (PFBA) and the marine model diatom Thalassiosira pseudonana as research targets, comprehensively studied the toxicity of PFBA to T. pseudonana in terms of the population growth, photosynthetic physiology and oxidative stress. Our results characterized the inhibited growth, inhibited photosynthetic parameters, increased reactive oxygen species (ROS) levels and activated antioxidant system under PFBA exposure. Further transcriptome analysis revealed the underlying molecular mechanisms: photosynthetic genes were slightly down-regulated and the expression of oxidative stress-related genes was enhanced; significant up-regulation of genes related to the DNA excision repair and replication-coupled DNA repair pathways; the expression of carbon metabolisms-related genes was increased, including the Calvin cycle, glycolysis, pentose phosphate pathway, tricarboxylic acid (TCA) cycle and fatty acid biosynthesis, that could provide sufficient energy for the recovery processes of microalgal cells. This study elucidated the underlying toxic mechanisms of PFBA on phytoplankton, and provided novel insights for assessing the environmental risks of PFAS.

Effects of marine phycotoxin dinophysistoxin-1 on the growth and cell cycle of Isochrysis galbana

The phycotoxin dinophysistoxins are widely distributed in the global marine environments and potentially threaten marine organisms and human health. The mechanism of the dinophysistoxin toxicity in inhibiting the growth of microalgae is less well understood. In this study, effects of the dissolved dinophysistoxin-1 (DTX1) on the growth, pigment contents, PSII photosynthetic efficiency, oxidative stress response and cell cycle of the marine microalga Isochrysis galbana were investigated. Growth of I. galbana was significantly inhibited by DTX1 with 0.6-1.5 μmol L-1 in a 96-h batch culture, corresponding the 96 h-EC50 of DTX1 at 0.835 μmol L-1. The maximum quantum yield of PSII (Fv/Fm), and light utilization efficiency (α) were obviously reduced by DTX1 at 1.5 μmol L-1 during 96-h exposure. Contents of most of pigments were generally reduced by DTX1 with a dose-depend pattern in microalgal cells except for diatoxanthin. The ROS levels were increased by DTX1 with 0.6-1.5 μmol L-1 after 72-h exposure, while the contents or activities of MDA, GSH, SOD and CAT were significantly increased by DTX1 at 1.5 μmol L-1 at 96 h. The inhibitory effect of DTX1 on the growth of I. galbana was mainly caused by the production of ROS in the cells. Cell cycle analysis showed that the I. galbana cell cycle was arrested by DTX1 at G2/M phase. This study enhances the understanding of the chemical ecology effects of DTX1 on marine microalgae and also provides fundamental data for deriving water quality criteria of DSTs for marine organisms.

Photosynthetic response mechanism to polybrominated diphenyl ether exposure in Chlorella pyrenoidosa

Polybrominated diphenyl ether (PBDE) contamination is common in aquatic environments and can severely damage aquatic organisms. However, there is a lack of information on the response and self-adaptation mechanisms of these organisms. Chlorella pyrenoidosa was treated with 2,2',4,4'-tetrabromodiphenyl ether (BDE47), causing significant growth inhibition, pigment reduction, oxidative stress, and chloroplast atrophy. Photosynthetic damage contributed to inhibition, as indicated by Fv/Fm, Chl a fluorescence induction, photosynthetic oxygen evolution activity, and photosystem subunit stoichiometry. Here, Chl a fluorescence induction and quinone electron acceptor (QA-) reoxidation kinetics showed that the PSII donor and acceptor sides were insensitive to BDE47. Quantitative analyses of D1 and PsaD proteins illustrated that PSII and PSI complexes were the main primary targets of photosynthesis inhibition by BDE47. Significant modulation of PSII complex might have been caused by the potential binding of BDE47 on D1 protein, and molecular docking was performed to investigate this. Increased activation of antioxidant defense systems and photosystem repair as a function of exposure time indicated a positive resistance to BDE47. After a 5-day exposure, 23 % of BDE47 was metabolized. Our findings suggest that C. pyrenoidosa has potential as a bioremediator for wastewater-borne PBDEs and can improve our understanding of ecological risks to microalgae.

Cell cycle of microalga Isochrysis galbana arrested by neurotoxin β-N-methylamino-l-alanine and corresponding molecular mechanisms

The phycotoxin β-N-methylamino-l-alanine (BMAA) has attracted attention due to its risks to marine organisms and human health. In this study, approximately 85 % of synchronized cells of the marine microalga Isochrysis galbana were arrested at the cell cycle G1 phase by BMAA at 6.5 μM for a 24-h exposure. The concentration of chlorophyll a (Chl a) gradually decreased, while the maximum quantum yield of PSII (F_v/F_m), the maximum relative electron transport rate (rETR_max), light utilization efficiency (α) and half-saturated light irradiance (I_k) reduced early and recovered gradually in I. galbana exposed to BMAA in 96-h batch cultures. Transcriptional expression of I. galbana analyzed at 10, 12, and 16 h disclosed multiple mechanisms of BMAA to suppress the microalgal growth. Production of ammonia and glutamate was limited by the down-regulation of nitrate transporters, glutamate synthase, glutamine synthetase, cyanate hydrolase, and formamidase. Diverse extrinsic proteins related to PSII, PSI, cytochrome b6f complex, and ATPase were influenced by BMAA at transcriptional level. Suppression of the DNA replication and mismatch repair pathways increased the accumulation of misfolded proteins, which was reflected by the up-regulated expression of proteasome to accelerate proteolysis. This study improves our understanding of the chemical ecology impacts of BMAA in marine ecosystems.

Toxicity of 2, 2', 4, 4'-tetrabromodiphenyl ether (BDE-47) on the green microalgae Chlorella sp. and the role of cellular oxidative stress

Polybrominated diphenyl ethers (PBDEs) are toxic to marine organisms including the major primary producer phytoplankton, while the toxic mechanisms haven't yet been fully clarified. Therefore, we comprehensively studied the toxic mechanisms of BDE-47 on the marine chlorophyte Chlorella sp., with a focus on the role of cellular oxidative stress. The results indicate that BDE-47 stress resulted in the inhibition of population growth as well as cell death and programmed cell death. The antioxidant system was activated in both low and high BDE-47 treatments, but only microalgal cells in the high BDE-47 treatment showed cellular oxidative stress. By adding ROS inhibitor, the relief of photosynthetic inhibition, Ca²⁺ overproduction and cell death was found. Therefore, we conclude that photosynthetic damage, cell death and cellular oxidative stress were the major mechanisms of BDE-47 toxicity to Chlorella sp., and that cellular oxidative stress played an important role in mediating the other mechanisms.

Toxicity Effects of Combined Mixtures of BDE-47 and Nickel on the Microalgae Phaeodactylum tricornutum (Bacillariophyceae)

Nickel and 2,2’,4,4’-tetrabromodiphenyl ether (BDE-47) are two environmental pollutants commonly and simultaneously present in aquatic systems. Nickel and BDE-47 are individually toxic to various aquatic organisms. However, their toxicity mechanisms are species-dependent, and the toxic effects of combined mixtures of BDE-47 and nickel have not yet been investigated. The present study investigated the toxic effects of combined mixtures of BDE-47 and nickel in the diatom Phaeodactylum tricornutum. BDE-47 and nickel mixtures significantly decreased cell abundance and photosynthetic efficiency, while these cells’ reactive oxygen species (ROS) production significantly increased. The EC₅₀-72 h for BDE-47 and mixtures of BDE-47 and nickel were 16.46 ± 0.93 and 1.35 ± 0.06 mg/L, respectively. Thus, combined mixtures of the two pollutants enhance their toxic effects. Interactions between BDE-47 and nickel were evaluated, revealing synergistic interactions that contributed to toxicity in P. tricornutum. Moreover, transcriptomic analyses revealed photosynthesis, nitrogen metabolism, the biosynthesis of amino acids, the biosynthesis of secondary metabolites, oxoacid metabolism, organic acid metabolism, carboxylic acid metabolism, and oxidation-reduction processes were considerably affected by the mixtures. This study provides evidence for the mechanisms of toxicity from combined BDE-47 and nickel exposure while also improving our understanding of the ecological risks of toxic chemicals on microalgae.

The effects of two sized polystyrene nanoplastics on the growth, physiological functions, and toxin production of Alexandrium tamarense

Micro- and nano-plastics (MNPs) are increasingly prevalent pollutants in marine ecosystems and result in various deleterious effects on marine organisms. There have been studies evaluated the toxic effects of MNPs on marine microalgae, but few of them focused on the effects of MNPs on dinoflagellate species and their toxins production, which could have significant implications on human health and ecological safety in coastal areas. In this study, the common harmful algal blooms-causing dinoflagellate Alexandrium tamarense was exposed to 0.1 and 1 μm sized polystyrene nanoplastics (NPs) to investigate the responding patterns of population growth, multiple physiological functions, as well as the intracellular paralytic shellfish toxins (PSTs) productions. The results indicated the population growth, photosynthetic parameters, nutrients (nitrate and phosphate) uptake rates and extracellular carbonic anhydrase activities (CA_ext) were all inhibited by the two sized NPs, accompanied by the prolonged and more aggregated microalgal cells under the observation of scanning electron microscope (SEM), and the inhibition effects were more severe under 1 μm sized NPs than 0.1 μm sized NPs. Finally, we found the intracellular PSTs contents increased 73.59% exposed to 0.1 μm sized NPs while decreased 85.50% exposed to 1 μm sized NPs comparing the controls at 96 h, without significant changes of relative compositions. These results provided evidence that MNPs were toxic to A. tamarense and affected their intracellular PSTs productions within 96 h, which is critical to consider when evaluating the potential risks of MNPs in marine ecosystems.

Toxic effect of BDE-47 on the marine alga Skeletonema costatum: Population dynamics, photosynthesis, antioxidation and morphological changes

The toxic effects of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) on the marine alga Skeletonema costatum were studied, including the population dynamics, chlorophyll fluorescence characteristics, pigment content, superoxide dismutase (SOD) activity, malondialdehyde (MDA) content and morphology. High doses (200-600 μg L^-1) of BDE-47 significantly suppressed the population growth of S. costatum, with a 96 h EC₅₀ value of 293 μg L^-1. Photosynthetic parameters (F_v/F_m, rETR_max and Φ_PSⅡ) of photosystem II (PSII) were significantly inhibited with increasing BDE-47 concentrations. The chlorophyll c (chl c) concentration was also inhibited by exposure to BDE-47. In contrast, chl a and carotenoid concentrations were elevated after exposure to high concentrations of BDE-47 for 72 and 96 h. The SOD activity was generally higher at concentrations of 100-600 μg L^-1 than those of the control when the exposure time was less than 48 h. With increasing time, the SOD activity generally decreased, and significantly higher SOD activity only occurred in the treatment with high doses of BDE-47. High MDA contents occurred after exposure for 96 h in all BDE-47 treatments. With increasing BDE-47 concentrations, drastic deformation of the silicious valve and detachment of the strutted processes were found. In addition, drastic decreases in the BDE-47 concentration in culture medium indicated the bioaccumulation of BDE-47 by S. costatum. Our results revealed multiple responses of S. costatum to BDE-47 exposure, and indicated the potential risk of BDE-47 in the East China Sea based on these responses.

Screening and application of Chlorella strains on biosequestration of the power plant exhaust gas evolutions of biomass growth and accumulation of toxic agents

To use microalgae for the biosequestration of carbon dioxide (CO₂) emitted from the coal-fired power plants, the screening of high CO₂ tolerant microalgae and their accumulation of toxic agents have attracted significant research attention. This study evaluated 10 Chlorella strains for high CO₂ tolerance using combined growth rates and growth periods subjected to logistic parameters. We selected LAMB 31 with high r (0.89 ± 0.10 day^-1), high k (6.51 ± 0.19), and medium Tp (5.17 ± 0.15 day) as a candidate for CO₂ biosequestration. Correspondingly, six genes involving carbon fixation and metabolism processes were upregulated in LAMB 31 under high CO₂ conditions, verifying its high CO₂ tolerant ability. LAMB 31 cultures exposed to exhaust gas of power plant under different flow rates grew well, but the high flow rate (0.6 L/h) showed inhibition effects compared with low flow rates (0.2 and 0.3 L/h) at the end of the culturing period. The toxic agents in the exhaust gas including sulfur, arsenic, and mercury accumulated in LAMB 31 biomass but were deemed safe for use in the production of both human food and animal feed based on the National Food Safety Standard in China. This study showed a complete process involving high CO₂ tolerant microalgae screening, high CO₂ tolerant verification, and in situ application in a power plant. Data results provide valuable information as the basis for future research studies in microalgae application on CO₂ mitigation at emission sources.

Molecular mechanism of oil induced growth inhibition in diatoms using Thalassiosira pseudonana as the model species

The 2010 Deepwater Horizon oil-spill exposed the microbes of Gulf of Mexico to unprecedented amount of oil. Conclusive evidence of the underlying molecular mechanism(s) on the negative effects of oil exposure on certain phytoplankton species such as Thalassiosira pseudonana is still lacking, curtailing our understanding of how oil spills alter community composition. We performed experiments on model diatom T. pseudonana to understand the mechanisms underpinning observed reduced growth and photosynthesis rates during oil exposure. Results show severe impairment to processes upstream of photosynthesis, such as light absorption, with proteins associated with the light harvesting complex damaged while the pigments were unaffected. Proteins associated with photosynthetic electron transport were also damaged, severely affecting photosynthetic apparatus and depriving cells of energy and carbon for growth. Negative growth effects were alleviated when an organic carbon source was provided. Further investigation through proteomics combined with pathway enrichment analysis confirmed the above findings, while highlighting other negatively affected processes such as those associated with ferroxidase complex, high-affinity iron-permease complex, and multiple transmembrane transport. We also show that oxidative stress is not the primary route of negative effects, rather secondary. Overall, this study provides a mechanistic understanding of the cellular damage that occurs during oil exposure to T. pseudonana.

The molecular response mechanisms of a diatom Thalassiosira pseudonana to the toxicity of BDE-47 based on whole transcriptome analysis

Polybrominated diphenyl ethers (PBDEs) are ubiquitously distributed persistent organic pollutants (POPs) in marine environments. Phytoplankton are the entrance of PBDEs entering to biotic environments from abiotic environments, while the responding mechanisms of phytoplankton to PBDEs have not been full established. Therefore, we chose the model diatom Thalassiosira pseudonana in this study, by integrating whole transcriptome analysis with physiological-biochemical data, to reveal the molecular responding mechanisms of T. pseudonana to the toxicity of BDE-47. Our results indicated the changes of genes expressions correlated to the physiological-biochemical changes, and there were multiple molecular mechanisms of T. pseudonana responding to the toxicity of BDE-47: Gene expressions evidence explained the suppression of light reaction and proved the occurrence of cellular oxidative stress; In the meanwhile, up-regulations of genes in pathways involving carbon metabolisms happened, including the Calvin cycle, glycolysis, TCA cycle, fatty acid synthesis, and triacylglycerol synthesis; Lastly, DNA damage was found and three outcome including DNA repair, cell cycle arrest and programmed cell death (PCD) happened, which could finally inhibit the cell division and population growth of T. pseudonana. This study presented the most complete molecular responding mechanisms of phytoplankton cells to PBDEs, and provided valuable information of various PBDEs-sensitive genes with multiple functions for further research involving organic pollutants and phytoplankton.

Evaluation of the toxic response induced by BDE-47 in a marine alga, Phaeodactylum tricornutum, based on photosynthesis-related parameters

The pollution of polybrominated diphenyl ethers (PBDEs) is becoming a pressing environmental problem in aquatic environments, and its threat to aquatic organism has received much attention. In this study, Phaeodactylum tricornutum was treated with 0.8 and 4 mg L^-1 2,2',4,4'-tetrabrominated biphenyl ether (BDE-47), the most toxic PBDEs, for 96 h. BDE-47 inhibited cell growth in a time- and concentration-dependent manner. Observation of cell ultrastructure suggested the damage of the chloroplasts morphology. BDE-47 also decreased the chlorophyll content and the oxygen evolution rate, and altered the performance of photosystems. Transcriptomic analysis revealed differential expression of 62 genes related to photosynthesis in BDE-47 treatments (4 mg L^-1) and transcription suppression of 58 genes involved in chlorophyll synthesis, antenna proteins, oxygen evolution, electron transport and downstream carbon fixation, implying potential toxicity targets in cells. Additionally, the levels of reactive oxygen species (ROS) and lipid peroxidation increased under BDE-47 stress and were positively correlated with photosynthesis inhibition. Pretreatment with the ROS scavenger N-acetyl-l-cysteine reduced the extent of inhibition, suggesting that ROS was responsible for these effects. Another experiment with the electron transport chain inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea showed that the generation of ROS was partially blocked, primarily indicating that photosynthetic inhibition induced by BDE-47 contributed to ROS overproduction. Thus, BDE-47 inhibited the photosynthesis by down-regulating the gene expression. This change stimulated ROS production, further leading to chloroplast membrane damage to aggravate this inhibition via a feedback loop. These effects of BDE-47 had adverse outcomes on the entire physiological state and the population growth of the microalgae.

ROS-mediated programmed cell death (PCD) of Thalassiosira pseudonana under the stress of BDE-47

Polybrominated diphenyl ethers (PBDEs) are a series of highly persistent organic pollutants (POPs) ubiquitously distributed in marine environments. As key primary producers, microalgae are the start of PBDEs bioaccumulations and vulnerable to their toxicities. In order to deeply investigate the toxic mechanism of PBDEs on microalgal cells, the occurrence of programmed cell death (PCD) in a model diatom Thalassiosira pseudonana and its possible mediating mechanism were studied. The results indicated: cell death of T. pseudonana happened under the stress of BDE-47, which was proved to be PCD based on the correlations with three biochemical markers (DNA fragmentation, phosphatidylserine externalization and caspase activity) and three molecular markers [Metacaspase 2 gene (TpMC2), Death-associated protein gene (DAP3) and Death-specific protein 1 gene (TpDSP1)]; Furthermore, the changes of cellular ROS levels were correlated with the PCD markers and the dead cell rates, and the cell membrane and the chloroplast were identified as the major ROS production sites. Therefore, we concluded that PCD might be an important toxic mechanism of PBDEs on microalgal cells, and that chloroplast- and cell membrane-produced ROS was an important signaling molecule to mediate the PCD activation process. Our research firstly indicated microalgal PCD could be induced by PBDEs, and increased our knowledge of the toxic mechanisms by which POPs affect microalgal cells.

Effects of florfenicol on growth, photosynthesis and antioxidant system of the non-target organism Isochrysis galbana

Florfenicol (FFC) is one of the most universally used antibiotics in aquaculture, which is substitute for chloramphenicol extensively, while the massive residues in aquatic environment were assumed to threaten the non-target organisms. Present research investigated the effects of florfenicol on growth, chlorophyll content, photosynthesis, and antioxidant ability of Isochrysis galbana. The results showed that FFC at 0.001-1 mg/L stimulated the growth of I. galbana and increased the content of chlorophyll. In addition, photosynthesis of I. galbana was inhibited and the photosynthetic parameters were uplifted with the increased exposure duration and FFC concentration. Furthermore, superoxide dismutase (SOD), catalase (CAT) activity significantly dropped at 0.01-20 mg/L FFC, while the contents of malondialdehyde (MDA), glutathione (GSH) and reactive oxygen species (ROS) increased after 72 h exposure, indicating that FFC at high concentrations caused a serious oxidative stress on algae. The simultaneous increase of ROS disrupted the equilibration between oxidants and antioxidant systems. Under the high concentration of FFC, the excessive of ROS was generated in algae which affected the membrane permeability and further decreased the cell biomass. Present study showed that acute exposure (72 h) at the environmental relevant concentration (0.01 mg/L) cannot induce the physiological dysfunction of the microalgae I. galbana, but the feeding concentration (20 mg/L) can. Additionally, this study hinted the possible negative impacts on ecosystems with the chronic exposure even at low FFC concentration or with the uncontrolled use of FFC.

The toxicity, bioaccumulation and debromination of BDE-47 and BDE-209 in Chlorella sp. under multiple exposure modes

Polybrominated diphenyl ethers (PBDEs) are a series of important persistent organic pollutants (POPs) in marine environments. Microalgae are the start of PBDEs bioaccumulated and bioconcentrated along the marine food web. In order to investigate the variations of PBDEs bioaccumulation by microalgae and its influencing factors, we set up a series of experiments with Chlorella sp. under different BDE-47 or BDE-209 exposure modes to measure their toxicity, bioaccumulation and degradation patterns. The inhibition effect on cell growth was much more obvious in BDE-47 than BDE-209, with the EC₅₀ values at 96 h calculated as 64.7 μg L^-1 and 4070 μg L^-1, respectively. Microalgal uptake rates showed BDE-209 diffused less into cells than BDE-47, with highest measured uptake rates of 0.145 × 10^-7 μg h^-1 cell^-1 and 0.45 × 10^-7 μg h^-1 cell^-1, respectively. The bioaccumulation amount by unit microalgal cell varied with PBDE concentrations and culture time, which appeared to be related to the changes of extracellular polymeric substances (EPS) and cellular neutral lipids under the toxicity of PBDEs. Finally, we found Chlorella sp. delayed the debromination patterns of BDE-209 compared to seawater. This study linked the toxicity, microalgal bioaccumulation and metabolism of PBDEs, provided new insights in the research of POPs by microalgae and marine food webs.

The regulating mechanisms of CO2 fixation and carbon allocations of two Chlorella sp. strains in response to high CO2 levels

The extreme high CO₂ in industrial exhaust gas cannot be tolerated by microalgae is the key challenge for the application of microalgae in CO₂ bio-sequestration. To provide better insights for this challenge, we chose one high CO₂ tolerant (Chlorella sp. LAMB 31) and non-tolerant (Chlorella sp. LAMB 122) Chlorella sp. to examine their different CO₂ fixation and carbon allocation responses to 40% CO₂. The results indicated LAMB 31 had a 24-h "lag phase" of biomass increase, during which the transition from PSII-PSI and the increase of lipid synthesis happened to acclimate high CO₂ conditions, followed by the increase of pigments synthesis, carbon fixation rates and polysaccharide productions. However, no acclimating mechanism was observed in LAMB 122, whose biomass, photosynthesis and material synthesis were all gradually collapsed under 40% CO₂. Finally, four parameters including Chl a, polysaccharides, carbon fixation rates and MDA were selected to be good physiological biomarkers for high CO₂ tolerant strains screenings in the future.

Trait-dependent variability of the response of marine phytoplankton to oil and dispersant exposure

The Deepwater Horizon oil spill released millions of barrels of crude oil into the Gulf of Mexico, and saw widespread use of the chemical dispersant Corexit. We assessed the role of traits, such as cell size, cell wall, motility, and mixotrophy on the growth and photosynthetic response of 15 phytoplankton taxa to oil and Corexit. We collected growth and photosynthetic data on five algal cultures. These responses could be separated into resistant (Tetraselmis astigmatica, Ochromonas sp., Heterocapsa pygmaea) and sensitive (Micromonas pusilla, Prorocentrum minimum). We combined this data with 10 species previously studied and found that cell size is most important in determining the biomass response to oil, whereas motility/mixotrophy is more important in the dispersed oil. Our analysis accounted for a third of the variance observed, so further work is needed to identify other factors that contribute to oil resistance.

Occurrence and congener profiles of polybrominated diphenyl ethers in green mussels (Perna viridis) collected from northern South China Sea and the associated potential health risk

Polybrominated diphenyl ether (PBDE) contamination has become a major concern over the effects on human health. In the present study, we collected widely consumed green mussels (Perna viridis) samples from the northern South China Sea (NSCS) to investigate the occurrence, spatial distribution, congener profiles as well as potential risk of 18 PBDEs. All the target PBDEs were detected in green mussel samples, indicating their ubiquitous distribution. The concentrations of the total 18 PBDE_S (ΣPBDEs) in all samples varied from 6.96 to 55.6 ng/g lipid weight (lw), with BDE-47 and BDE-209 being the predominant PBDE congeners. Overall, the ΣPBDEs pollution in green mussels from NSCS was at a moderate to high level in comparison with the PBDEs pollution worldwide. The dietary exposure of the local population in South China to PBDEs via consuming green mussels was estimated to be 0.30-0.80 ng/kg body weight (bw)/day. Evaluation of the exposure risk for BDE-47, 99, 153 and 209 indicated that health risks due to green mussel consumption are substantially lower than the U.S. EPA minimum concern level.