Polycyclic aromatic hydrocarbons (PAHs) in surface sediment and oysters (Crassostrea rhizophorae) from mangrove of Guadeloupe: levels, bioavailability, and effects

Deciphering environmental forcings in the distribution of meiofauna and nematodes in mangroves of the Atlantic-Caribbean-East Pacific and Indo-West Pacific regions

Mangroves develop under environmental conditions and anthropogenic pressures whose impact on benthic meiofauna remains poorly understood. It is unclear how meiofauna communities are structured according to local sedimentary conditions. This study was designed to characterize the community structure of meiofauna and nematodes (dominant taxa) and the associated environmental forcings in intertidal mangrove sediments from Mayotte (Indo-West-Pacific), Martinique and Guadeloupe (Caribbean). Sediment cores were sampled at the end of the dry season at low tide on adult mangrove stands with similar immersion time. In each sediment layer, we analyzed redox potential, pH, porewater salinity, grain size, organic matter, metals, organic contaminants, prokaryotes and meiofauna. Our results show that sediments far from cities and agricultural fields trapped site-specific contaminants due to local water transport processes. Some metals, PAHs or pesticides exceeded toxicity thresholds in most of the studied stations, thus being harmful to benthic fauna. The sedimentary environment acts as a filter selecting specific meiofauna communities at station scale only in the Caribbean. In Mayotte, horizontal homogeneity contrasts with vertical heterogeneity of the sedimentary environment and the meiofauna. Nematode genera showed particular distribution patterns horizontally and vertically, suggesting the presence of sediment patches suitable for a restricted pool of genera on each island. Results in the Caribbean are consistent with nested diversity patterns due to environmental filtering. Conversely, horizontal homogeneity at Mayotte would reflect greater dispersal between stations or more spatially homogeneous anthropogenic pressures. The nematode genera present at depth may not be the most specialized, but the most versatile, capable of thriving in different conditions. Terschellingia and Daptonema showed contrasted responses to environmental forcing, likely due to their versatility, while Desmodora showed uniform responses between study areas, except when toxicity thresholds were exceeded. Our results emphasize that a given genus of nematode may respond differently to sedimentary conditions depending on sites.

Bioaccumulation of PAHs in marine bivalves of the Santos Estuary (Brazil) associated with the evaluation of human consumption

The present study aimed to evaluate concentrations of 16 priority PAHs in the mussel Perna perna and oyster Crassostrea rhizophorae of the Santos Estuary (Brazil) and the potential risk to human health associated with the consumption of these species. The levels of ΣPAHs in the tissues of bivalves ranged from 96.94 to 988.76 μg/kg for mussels and from 88.38 to 138.62 μg/kg for oysters. A general trend of higher concentrations of PAHs was observed according to the increase in log Kow values in both species. The estimated amount of ΣPAHs via mussel and oyster intake ranged from 1.0 to 3.2 ng/kg and from 0.4 to 1.2 ng/kg of body weight per day, respectively. The calculated THQs, HI and CRs for the regular consumption of raw bivalves followed the internationally acceptable limits and represent a low risk to human health.

Does mangrove leave falling dominate the bury of polycyclic aromatic hydrocarbons in the mangrove of China?

Mangrove wetlands are vital coastal ecosystems that can absorb and accumulate pollutants. Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants that pose potential risks to ecosystems and human health. However, their source and transport fate in mangrove areas are poorly understood. This study investigates 29 PAHs pollution of water and sediment in Zhangjiangkou Mangrove Wetland, the northernmost large-scale mangrove wetland reserve in China. We examine the distribution, source, transport mechanisms and risk assessment of PAHs. The results show that the concentrations of PAHs in mangrove sediment range from 55.62 to 347.36 ng/g (DW), with 5-ring PAHs being the dominant species. While the concentrations of PAHs in surface water range from 10.61 to 46.39 ng/L, with 2-ring PAHs and alkylated PAHs being the dominant species. The PAHs concentrations in surface water and sediment of river are higher than those in mangrove area, indicating that mangrove water could receive PAHs through tidal exchange. Based on diagnostic ratios (DRs), principal component analysis (PCA), and positive matrix factorization (PMF), we infer that the leaf deposition (48.55%) could be an important pathway of PAHs in mangrove sediment except for river water transport (51.45%), while the PAHs in estuary water originate mainly from point sources such as biomass burning (50.96%) and traffic emission (49.04%). The range of toxic equivalents in surface water and sediment was 2.73-16.09 ng TEQ g-1 and 0.03-3.63 ng/L, respectively. Although the ecological risk assessment suggests that the PAHs pollution in surface water and sediment poses a low risk, we recommend more attention to the protection of the mangrove ecosystem. This study reveals that mangrove leaf falling might be a significant mechanism of PAH sequestration in the mangrove system, which deserves more attention in future research.

Polycyclic aromatic hydrocarbons distribution in fish tissues and human health risk assessment on consumption of four fish species collected from Lagos Lagoon, Nigeria

Lagos Lagoon is a very popular lagoon in Lagos state that receives effluents from neighboring industries. These effluents tend to increase the level of contaminants in the lagoon, thereby creating more stressors for aquatic animals. Determination of polycyclic aromatic hydrocarbons (PAHs) in four commonly consumed fish species from the lagoon and the prediction of possible health risks associated with their consumption were performed in this study. Various levels of PAH were detected in the fish tissues with the highest total concentration of PAH in Sarothoredon melanotheron. High concentrations of benzo(a)pyrene were noticed in Sarothoredon melanotheron and Ethmalosa fimbriata, and their values were above the guideline value of 0.002 μg/g. The dietary daily intake (DDI) value in S. melanotheron 82.00 ×10-5 μg/g/day was highest. Carcinogenic toxic equivalents (TEQ) showed that consumption of S. melanotheron had higher potential to pose carcinogenic risks, while the excess cancer risk (ECR) index for the PAHs in all the assessed fish species was beyond threshold values indicating potential carcinogenic risk from their consumption. No significant association was found between the concentration of PAHs and the size of the fish. Target hazard quotient (THQ) results suggested absence of potential non-carcinogenic risk if individual PAH in the fish are consumed frequently. The study however established possible carcinogenic human health risk from consumption of the fish obtained from Lagos Lagoon. The study recommends monitoring of contamination and consumption of fish from harvest sites within the study region.

Integrating chemical and biological data by chemometrics to evaluate detoxification responses of a neotropical bivalve to metal and metalloid contamination

Mangroves represent a challenge in monitoring studies due to their physical and chemical conditions under constant marine and anthropogenic influences. This study investigated metals/metalloids whole-body bioaccumulation (soft tissues) and the risk associated with their uptake, biochemical and morphological detoxification processes in gills and metals/metalloids immobilisation in shells of the neotropical sentinel oyster Crassostrea rhizophorae from two Brazilian estuarine sites. Biochemical and morphological responses indicated three main mechanisms: (1) catalase, superoxide dismutase and glutathione played important roles as the first defence against reactive oxygen species; (2) antioxidant capacity against peroxyl radicals, glutathione S-transferase, metallothionein prevent protein damage and (3) metals/metalloids sequestration into oyster shells as a mechanism of oyster detoxification. However, the estimated daily intake, target hazard quotient, and hazard index showed that the human consumption of oysters would not represent a human health risk. Among 14 analysed metals/metalloids, chemometrics indicate that Mn, As, Pb, Zn and Fe overload the antioxidant system leading to morphological alterations in gills. Overall, results indicated cellular vacuolization and increases in mucous cell density as defence mechanisms to prevent metals/metalloids accumulation and the reduction in gill cilia; these have long-term implications in respiration and feeding and, consequently, for growth and development. The integration of data from different sites and environmental conditions using chemometrics highlights the main biological patterns of detoxification from a neotropical estuarine bivalve, indicating the way in which species can cope with metals/metalloids contamination and its ecological consequences.

Aliphatic and polycyclic aromatic hydrocarbons in surface sediments as a tool for the assessment of the contamination status of mangrove forests in Rio de Janeiro (Brazil)

The distribution of aliphatic and polycyclic aromatic hydrocarbons (PAHs) in surface sediments from mangrove forests of the Rio de Janeiro State was investigated. Ten sampling stations were selected in the mangroves of Sepetiba Bay and the Jacarepaguá Lagoon Complex (JLC), which are areas affected by multiple human activities. The total aliphatic hydrocarbons concentrations showed marked variation between samples (27-407 μg g^-1), mostly related to the total organic carbon contents. The total PAHs concentration ranged between 38 and 792 ng g^-1. Diagnostic indices and statistical analysis showed that the mangrove forests can be divided into three groups: the western portion of Sepetiba Bay with the lowest level of contamination; the inner portion of the bay with the most intense presence of local sources of contamination, especially of pyrolytic character; and the JLC with a greater accumulation of hydrocarbons, mainly derived from petroleum combustion, resultant from the intense urbanization.

Environmental risk assessment of petrogenic hydrocarbon spills in mangrove ecosystems: the Tumaco case study as a baseline, Colombian Pacific

Petrogenic hydrocarbon spills (PHS) are harmful to mangrove ecosystems along tropical coastlines in the short and long term. The aim of this study was to assess the environmental risk of recurrent PHS on mangrove ecosystems in Tumaco municipality, Colombian Pacific. Mangrove characteristics and management aspects led to subdividing the study area into 11 units-of-analysis (UAs) for which threats, vulnerability, potential impacts, and risks were assessed based on environmental factors and the formulation and use of indicators in a rating scale with five categories, which are very low, low, moderate, high, and very high. The results showed that all UAs are highly (64%; 15,525 ha) or moderately (36%; 4,464 ha) threatened by PHS, highly (45%; 13,478 ha) or moderately (55%; 6,511 ha) vulnerable to this kind of pollution, and susceptible to high (73%; 17,075 ha) or moderate (27%; 2,914 ha) potential impacts. The environmental risk was high in 73% (17,075 ha) of the UAs, indicating likely irreversible damage to mangrove ecosystems by PHS, thus pointing to the need of urgent intervention by responsible authorities to ease their recovery and conservation. The methodology and results of this study become technical inputs that serve for environmental control and monitoring, which can be incorporated into contingency and risk management plans.

Baseline distribution of petroleum hydrocarbon contamination in the marine environment around the coastline of Qatar

Levels of organic contaminants (TPHs, PAHs) were simultaneously determined in both abiotic (sediments, seawater) and biotic (Pinctada radiata oysters) samples at four sites along the coastline of Qatar (Arabian Gulf) in 2017-2018. TPHs and PAHs were more frequently detected in oyster tissues than sediment and seawater samples collected from the same areas. While levels of TPHs and PAHs in seawater and sediments were lower than previous local studies and worldwide studies, PAHs levels observed in pearl oyster tissue (25.9-2240 μg/kg) were relatively higher than in previous studies in Qatar. In general, eight PAHs compounds were detected in oyster tissue, with benzo(a)pyrene displaying the highest concentration. The coast of Qatar could be affected by seasonal patterns of pollutants, where TPHs and PAHs levels increased in winter compared to summer. These results provide key information on the use of the pearl oyster as a bioindicator species and Qatar's marine environment.

A baseline study of polycyclic aromatic hydrocarbons distribution, source and ecological risk in Zhanjiang mangrove wetlands, South China

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental contaminants and pose a severe threat to human health. Here, 38 surface sediment samples collected from the Gaoqiao mangrove wetland in Zhanjiang, south China, were analyzed to determine 16 Environmental Protection Agency (EPA) priority PAHs. Total PAHs concentrations ranged from 33.5 µg/kg to 404.8 µg/kg with an average of 147.7 ± 77.7 µg/kg, inferring a moderate pollution level. Three and four-ring compounds dominated the PAHs composition patterns. Significant positive correlations were observed between the PAHs and the physicochemical properties of the sediments. According to the characteristic molecular ratio method, PAHs in sediments were mainly derived from combustion sources, including the incomplete combustion of liquid fossil fuels, grass, wood, and coal. The result based on the PMF model indicates that the primary combustion sources of PAHs are coal combustion, diesel-powered vehicles, biomass combustion and gasoline-powered vehicles, with a share of 39.01%, 25.21%, 12.72% and 10.48%, respectively. The petrogenic source contributes 12.58% PAHs to the sediments. The mean effects range median quotient (m-ERM-Q) and toxic equivalent method (TEQ) indicate a low comprehensive ecological risk of PAHs in the study area. Still, the evaluation results of effects range low (ERL) suggest that PAHs in the sediment would occasionally have adverse biological effects. Therefore, this situation demands attention and calls for protection strategies in the processes of urbanization and industrialization in south China.

Bioaccumulation and trophic transfer of PAHs in tropical marine food webs from coral reef ecosystems, the South China Sea: Compositional pattern, driving factors, ecological aspects, and risk assessment

Multiple environmental pressures caused by global warming and human activities have aroused widespread concern about PAHs pollution in tropical marine coral reef regions (CRRs). However, the trophodynamics of PAHs in the food webs of the CRRs and the related influence factors have not been reported. This study investigated the occurrence, trophic amplification, and transmission of PAHs in various organisms selecting between at least representative species for each level in CRRs of the South China Sea (SCS); revealed their driving mechanisms; and explored the trophodynamics of PAHs in the food web of the coral reef ecosystem. Results showed that more PAHs can be accumulated in the mantle tissue of Tridacnidae, and the proportion of mantle tissue of Tridacnidae increases with the increase of latitude (y = 0.01x + 0.17, R² = 0.49, p < 0.05). Latitude drives the differential occurrence level and bioaccumulation of PAHs in tropical marine organisms, and also affects the trophodynamics of PAHs in aquatic ecosystem food webs. PAHs undergo trophic amplification in the food webs of tropical marine ecosystems represented by coral reefs, thus further aggravating the negative environmental impact on coral reef ecosystems. The cancer risk caused by accidental ingestion of PAHs by humans through consumption of seafood in CRRs is very low, but we should be alert to the biomagnification effect of PAHs.

Polycyclic aromatic hydrocarbons (PAHs) in mangrove ecosystems: A review

Polycyclic aromatic hydrocarbons (PAHs) are organic pollutants of increasing concern in the different fields of the environment and human health. There are 16 of them that are recognized as priority pollutants by the US environmental protection agency due to their mutagenic and carcinogenic potentials. Due to their hydrophobicity and stability, they are persistent in the environment and can be transported over long distances. Their toxicological effects on multiple species, including humans, as well as their bioaccumulation in the food web became major topics in organic pollutants research this last decade. In the environment, multiple studies have been conducted on their accumulation in the soil and their degradation processes resulting in numerous review papers. However, the dynamics of PAHs in mangrove ecosystems is not yet completely understood. In this review paper, an exhaustive presentation of what is known about PAHs and their transfer, accumulation, and degradation in mangrove ecosystems is offered. This article brings to light the knowledge already acquired on the subject and the perspective research necessary to fully comprehend PAHs dynamics in mangrove ecosystems.

Monitoring metallothionein-like protein concentrations and cholinesterase activity in tropical cup oysters as biomarkers of exposure to metals and pesticides in the southern Caribbean, Colombia

Metallothionein-like protein concentrations (MT) and three functionally defined fractions of cholinesterase activity (ChE) were quantified in gill and digestive gland homogenates of tropical cup oysters from 5 nearshore locations in the Colombian Caribbean and correlated with sediment and tissue metal (9 metals) and pesticide (22 organophosphates, OPs, and 20 organochlorines-OCPs), as well as water physical-chemical parameters (salinity, pH, temperature, and dissolved oxygen). Tissue and sediment pesticide concentrations were below detection limits in all samples, whereas sediment and tissue metal concentrations exceeded environmental thresholds at several locations. Tissue MT and ChE biomarkers varied by a factor of 5-6 between locations. Inhibition of cholinesterase activity was negligible for all 5 sites, despite spatial-temporal variation in ChE activity, consistent with below-detection OP concentrations. Tissue MT and ChE biomarkers correlated with tissue and metal sediment concentrations, yet, statistically significant covariance between biomarkers and water chemistry parameters was also observed, indicating that both, metal concentrations and physical-chemical variables, are likely to be responsible for generating the observed spatial-temporal variations in biomarker patterns.

Assessment of polycyclic aromatic hydrocarbons in three environmental components from a tropical estuary in Northeast Brazil

The evaluation of occurrence, risk quotient (RQ), bioaccumulation factor (BAF), and sources of PAH was conducted in Sergipe-Poxim estuarine system. PAH distribution that ranged from 7.1 to 30.9 ng L^-1 (surface water, SW), 5.4 to 19.5 ng g^-1 (sediment, S), and 4.3 to 18.1 ng g^-1 (oyster, O), characterized the environment with low contamination; 2-3 (SW), 5-6 (S), and 4 (O) PAH rings accounted for 54.5%, 68.7%, and 87.7%, respectively, along with naphthalene (SW), dibenzo(a,h)anthracene (S), and pyrene (O) as the prevailing compounds. PCA suggested the predominance of particular groups related to SW (LMW-PAH), S (HMW-PAH), and O (pyrene and fluoranthene). Furthermore, one sample of O presented a high PAH bioavailability as shown through the BAF, with emphasis on pyrene (BAF = 26.8). The RQ showed a low to moderate range in SW and S; hence, in-depth information about the possible toxic effect in organisms of this region is required.

Twists and turns of an oyster's life: effects of different depuration periods on physiological biochemical functions of oysters

Aquaculture activities are often established in the vicinity of highly populated, potentially contaminated areas. Animals cultured at such locations, namely bivalves, are frequently used as test organisms in ecotoxicological testing. In this case, a period of depuration is required to allow the normalization of physiological processes, which are likely to be altered after exposure to a multiplicity of waterborne contaminants occurring in the wild. One of the most important species in modern marine aquaculture is the oyster species Crassostrea gigas. The aim of this study was to assess if the current depuration time frame of 24 h (adopted by most aquaculture facilities), is long enough to permit oysters to revert potential toxic effects exerted by environmental contaminants, allowing their use in laboratory-based ecotoxicological studies. The selected approach involved the monitoring of biochemical (antioxidant defence, oxidative damage, phase II metabolism, and neurological homeostasis) and physiological (condition index) parameters, along a period of 42 days. The obtained results showed that a period of 24 h does not revert any of the potential toxic effects caused by environmental contaminants to which animals may have been previously subjected; even a period of 42 days was not long enough for the oysters to completely normalize the levels of their antioxidant defences, namely total GPx activity, which increased over time. Lipid peroxidation was also increased during the depuration period, and the activity of the metabolic isoenzymes GSTs was significantly decreased. Furthermore, AChE activity measured in the adductor muscle of oysters was increased over time. These assumptions suggest that a period of depuration longer than 24 h is mandatory to obtain adequate test organisms of this oyster species, to be used for ecotoxicological testing purposes.

Biological responses of mangrove oysters (Crassostrea rhizophorae) and mercury contamination in an urban tropical estuary

This study aimed to assess the biological responses of oysters from an urban estuary in Northeast Brazil, through the evaluation of biochemical and physiological biomarkers, and integrate these responses with the investigation of mercury seasonal contamination. Oysters and sediment were collected from three sites in the estuary of the Ceará River during dry and rainy seasons. Biomarkers (AchE, CaE, GST, CAT, and Condition Index) were analyzed in different tissues. Hg bioaccumulation was higher in animals sampled in the rainy season, with increases varying from 5% to 136%, compared to the dry season. The changes in biomarkers highlight already elevated stresses for the organisms at the inner portion of the estuary, near the confluence with the Maranguapinho River, mainly during the rainy season, corroborating other studies that showed ecotoxicological effects with water and sediment samples. Finally, no correlation between Hg in sediment/oyster and biomarker results was observed.

The biological pump effects of phytoplankton on the occurrence and benthic bioaccumulation of hydrophobic organic contaminants (HOCs) in a hypereutrophic lake

The distribution of hydrophobic organic contaminants (HOCs) in eutrophic ecosystems has been widely studied, but how phytoplankton blooms affect their occurrence and benthic bioaccumulation is poorly understood. To fill this knowledge gap, the biological pump effects of phytoplankton on the fate of organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) in sediments and benthos (Corbicula fluminea) from Lake Taihu, a hypereutrophic lake in China, were identified. The spatial-temporal distribution of HOCs suggests that higher phytoplankton biomass, coupled with sediment organic matter (SOM) content, greatly increased the concentration of HOCs in sediments in both winter and summer seasons. This could be attributed to the biological pump effects sequestering more HOCs from water to sediments with settling phytoplankton, especially during the summer. The biological pump effects further promoted the uptake of sediment-bound HOCs by benthos. The significant positive relationships between concentrations of HOCs in sediments and benthos were observed during the winter dormancy phase of benthos. Furthermore, the benthic bioaccumulation of HOCs could be strengthened by phytoplankton, due to their contribution to SOM and the following increased bioavailability of HOCs in sediments. Further research is needed to elucidate the phytoplankton biological pump effects on the fate of HOCs in benthic food chain, especially for hypereutrophic waters.

The Utility of Electrochemical Systems in Microbial Degradation of Polycyclic Aromatic Hydrocarbons: Discourse, Diversity and Design

Polycyclic aromatic hydrocarbons (PAHs), especially high molecular weight PAHs, are carcinogenic and mutagenic organic compounds that are difficult to degrade. Microbial remediation is a popular method for the PAH removal in diverse environments and yet it is limited by the lack of electron acceptors. An emerging solution is to use the microbial electrochemical system, in which the solid anode is used as an inexhaustible electron acceptor and the microbial activity is stimulated by biocurrent in situ to ensure the PAH removal and avoid the defects of bioremediation. Based on the extensive investigation of recent literatures, this paper summarizes and comments on the research progress of PAH removal by the microbial electrochemical system of diversified design, enhanced measures and functional microorganisms. First, the bioelectrochemical degradation of PAHs is reviewed in separate and mixed PAH degradation, and the removal performance of PAHs in different system configurations is compared with the anode modification, the enhancement of substrate and electron transfer, the addition of chemical reagents, and the combination with phytoremediation. Second, the key functional microbiota including PAH degrading microbes and exoelectrogens are overviewed as well as the reduced microbes without competitive advantage. Finally, the typical representations of electrochemical activity especially the internal resistance, power density and current density of systems and influence factors are reviewed with the correlation analysis between PAH removal and energy generation. Presently, most studies focused on the anode modification in the bioelectrochemical degradation of PAHs and actually more attentions need to be paid to enhance the mass transfer and thus larger remediation radius, and other smart designs are also proposed, especially that the combined use of phytoremediation could be an eco-friendly and sustainable approach. Additionally, exoelectrogens and PAH degraders are partially overlapping, but the exact functional mechanisms of interaction network are still elusive, which could be revealed with the aid of advanced bioinformatics technology. In order to optimize the efficacy of functional community, more advanced techniques such as omics technology, photoelectrocatalysis and nanotechnology should be considered in the future research to improve the energy generation and PAH biodegradation rate simultaneously.

Bioavailability of polycyclic aromatic compounds (PACs) to the Sydney rock oyster (Saccostrea glomerata) from sediment matrices of an economically important Australian estuary

Improving risk assessment and remediation rests on better understanding of contaminant bioavailability. Despite their strong toxicological attributes, little is known about the partitioning behaviour and bioavailability of polar polycyclic aromatic hydrocarbons (PAHs) in aquatic environments. The present study provides an insight into the bioavailable fractions of polar PAHs and their parent analogues in the tissues of the Sydney rock oyster, Saccostrea glomerata, a model aquatic bio-indicator organism. The concentration and distribution patterns of parent and polar PAHs including oxygenated PAHs (oxyPAHs), nitrated PAHs (NPAHs) and heterocyclic PAHs (HPAHs) were determined in water, sediment and oysters from an ecologically and economically important estuary of New South Wales, Australia. Total concentrations of PAHs, oxyPAHs, NPAHs and HPAHs were higher in sediments compared to oyster tissue and water. For most polar PAHs, total concentrations for water, sediment and oyster samples were <1 μg/g (μg/l for water) while parent PAH concentrations were several orders of magnitude higher. Computed biota-sediment accumulation factors (BSAFs) on lipid-normalized oyster concentrations revealed that while ∑oxyPAHs and ∑HPAHs exhibited low accumulation from sediment to oyster tissues (BSAF <1), ∑PAHs and ∑NPAH were found to be accumulated at high levels (BSAF >1). BSAF individual computation showed that bioaccumulation of nine investigated HPAHs in oyster tissues were relatively low and only 2-EAQ (oxyPAH) and 1N-NAP (NPAH) showed high levels of accumulation in oyster tissues, similar to parent PAHs. To the best of our knowledge, this is the first known study on the bioavailability of polar and non-polar PAHs in an Australian aquatic environment. The outcome of this study might be a useful indicator of the potential risks of polar PAHs to humans and other living organisms.

Toxicities of Polycyclic Aromatic Hydrocarbons for Aquatic Animals

Polycyclic aromatic hydrocarbons (PAHs) are organic compounds that are widely distributed in the air, water, and soil. Recently, the amount of PAHs derived from fuels and from incomplete combustion processes is increasing. In the aquatic environment, oil spills directly cause PAH pollution and affect marine organisms. Oil spills correlate very well with the major shipping routes. Furthermore, accidental oil spills can seriously impact the marine environment toxicologically. Here, we describe PAH toxicities and related bioaccumulation properties in aquatic animals, including invertebrates. Recent studies have revealed the toxicity of PAHs, including endocrine disruption and tissue-specific toxicity, although researchers have mainly focused on the carcinogenic toxicity of PAHs. We summarize the toxicity of PAHs regarding these aspects. Additionally, the bioaccumulation properties of PAHs for organisms, including invertebrates, are important factors when considering PAH toxicity. In this review, we describe the bioaccumulation properties of PAHs in aquatic animals. Recently, microplastics have been the most concerning environmental problem in the aquatic ecosystem, and the vector effect of microplastics for lipophilic compounds is an emerging environmental issue. Here, we describe the correlation between PAHs and microplastics. Thus, we concluded that PAHs have a toxicity for aquatic animals, indicating that we should emphasize the prevention of aquatic PAH pollution.

Concentration and distribution of polycyclic aromatic hydrocarbons in oysters from Todos os Santos Bay (Bahia, Brazil)

The aim of the present study was to evaluate the presence of polycyclic aromatic hydrocarbons (PAHs) in oysters (Crassostrea rhizophorae) collected from Todos os Santos Bay (Bahia, Brazil). The total PAH concentration was highest in Madre de Deus (36.3 to 37.8 ng g^-1 in dry weight, dw), which is located near a petrochemical complex, oil refinery, and commercial port. In the Paraguaçu river estuary, PAH concentrations varied between 23.2 and 25.7 ng g^-1 dw. The lowest concentrations (1.55 ng g^-1 dw) were found in the Jaguaribe river estuary, which can be considered a relatively preserved area. The main source of PAHs in the study areas was observed to be pyrogenic. Values of benzo[a]pyrene toxic equivalent ranged from 0.28 to 4.20. The concentrations of PAHs in oysters from the Paraguaçu river estuary and in Madre de Deus indicate the possible lifetime risk of developing cancer in humans who feed on it.

Occurrence and distribution of anthropogenic persistent organic pollutants in coastal sediments and mud shrimps from the wetland of central Taiwan

Sediment profile and mud shrimp (Austinogebia edulis) from the coastal wetland of central Taiwan in 2017 and 2018 were analyzed for concentration, source, and composition of persistent organic pollutants (POPs) including polycyclic aromatic hydrocarbon (PAHs), polybrominated diphenyl ethers (PBDEs), organochlorine pesticides (OCPs; DDT and HCB), and polychlorinated biphenyls (PCBs). Sediment profiling indicated PAH concentrations reaching 254.38 ng/g dw in areas near industrial areas and PAH concentrations of 41.8 and 58.42 ng/g dw in sampling areas further from industrial areas, suggesting that the determining factor for spatial distribution of POPs might be proximity to contaminant sources in industrial zones. Based on molecular indices, PAHs were substantially of both pyrolytic and petrogenic origins. The main sources for PCBs were Aroclor 1016 and 1260 and the congener BDE-209 was the dominant component among PBDE congeners. While we were unable to obtain live mud shrimp samples from the heavily contaminated areas, in samples from less contaminated areas, the risk assessment on mud shrimp still illustrated a borderline threat, with DDT concentrations almost reaching standardized values of Effects Range-Low (ERL). Bioaccumulation factors for DDTs and PCBs (17.33 and 54.59, respectively) were higher than other POPs in this study. Further study is essential to assess and understand the impact of these chemicals on the wetland ecosystem near this heavily industrialized area.

Assessment of brazilian mangroves hydrocarbon contamination from a latitudinal perspective

The present study investigated the contamination of Brazilian mangroves sediments by aliphatic hydrocarbons (AHs) and polycyclic aromatic hydrocarbons (PAHs). Samples were obtained from mangroves located along the brazilian coast, between the northern coast and the austral limit of the occurrence of this ecosystem. Total AH ranged from 1.9 to 311.3 μg g^-1 and compound distribution pointed to biogenic sources, mainly from mangrove forests, and petrogenic sources, with a significant presence of an unresolved complex mixture in some areas. PAH values (34.4-977.3 ng g^-1) indicated low to moderate contamination levels in mangrove sediments, reflecting the socioeconomic diversity observed along the Brazilian coast. The predominant PAH sources ranged from pyrolytic to petrogenic. According to sediment quality reference values, the evaluated sediments are not likely to cause biological effects, but deserve attention due to the current expansion scenario of oil prospecting activities off the Brazilian coast.

Reduced bioavailability and ecological risks of polycyclic aromatic hydrocarbons in Yangshan port of East China Sea: Remediation effectiveness in the transition from construction to operation

To assess the remediation effectiveness of ecological restoration in the transition period from construction to operation of Yangshan Port, the largest deepwater port of East China Sea, we employed equilibrium passive sampling and partitioning theory to assess the changing bioavailability and flux of polycyclic aromatic hydrocarbons (PAHs) in relation to bioaccumulation and ecological risks in marine organisms. Due to the ecological restoration efforts, both the bulk and bioavailable concentrations of PAHs in sediment and surface seawater samples decreased dramatically after the port entered the operation phase, as compared with those reported during the last construction phase. PAH concentrations in the marine organisms also showed a dramatic decline, and corresponded to the change in the freely dissolved fractions of PAHs in sediment/surface water according to their thermodynamic potential for bioaccumulation. While trophic magnification of ΣPAHs was observed in the pelagic communities, concentrations of PAHs in benthic species were relatively consistent across multiple trophic levels, and were generally higher than those in pelagic species. The differing bioaccumulation between benthic and pelagic species may be related to the habitat-specific bioavailability of PAHs and the prey-predator relations among different species. The incremental lifetime cancer risks (ILCR) of PAHs in marine organisms also dropped by nearly three orders of magnitude, and were lower than the guideline (1 × 10^-6) proposed by the U.S. EPA, except for several species at higher trophic levels. Overall, our study highlights an integrated use of passive sampling and equilibrium partitioning theory as a robust tool that can be applied to assess the effectiveness of ecological remediation in the port environment with quantitative, mechanistic insights from bioavailability to bioaccumulation.

Distribution and sources of organic contaminants in surface sediments of Hooghly river estuary and Sundarban mangrove, eastern coast of India

This study investigated polycyclic aromatic hydrocarbons (PAHs) and organochlorine compounds such as polychlorinated biphenyls (PCBs) and DDT-related pesticides in surface sediments of Hooghly estuary and the Sundarban mangrove wetlands. Concentrations of ∑₁₇PAH, ∑₁₈₂PCB and ∑₆DDT ranged from 15.4 to 1731, not detected (nd) to 13.5 and nd to 8.97 ng g^-1 dry weight, respectively. Low levels of PCBs and low to moderate concentrations of DDTs and PAHs reflected recent development in West Bengal, which was dominated by agriculture and multifarious industries in the past. Diagnostic ratios suggested that major sources of PAHs are combustion processes, DDTs are input by agriculture, antifouling paints and public health campaigns, and organochlorines are predominantly from industrial origin. Heavier PCB congeners suggest local sources and short-range transport of such chemicals. Decision makers may use these findings for managing the Hooghly River watershed in order to promote a sustainable development on the eastern coast of India.

Using multi-integrated biomarker indexes approach to assess marine quality and health status of marine organism: a case study of Ruditapes philippinarum in Laizhou Bay, China

With the progress of technology and the deepening of understanding of biological monitoring, much more attention has been paid to the multiple evaluation of marine pollution monitoring. In view of this, our study aimed at establishing a multi-integrated biomarker indexes approach to evaluate marine condition systematically and comprehensively. In the current study, sampling was conducted in Laizhou Bay, China (S1, S2, and S3) in May, August, and October of 2015. And then, multi-integrated biomarker indexes approach was applied to assess marine PAHs pollution, select appropriate biomarkers, and evaluate marine environmental quality and health status of the clams of Ruditapes philippinarum. As the results showed, S2 was the most PAHs-polluted site while S1 was the least polluted site, and the levels of tPAHs in seawater and sediments ranged from 69.78 to 315.30 ng/L and 163.19 to 565.17 ng/g d.w., respectively. And all three sampling sites had different sources of PAHs. IBR represented DNA damage (F value), the expression of SOD, EROD activity, GST activity, and LPO could be served as biomarkers to monitor the PAHs pollution in Laizhou Bay. And MPI suggested the quality of all three sites: S1 was generally favorable, S2 was moderately polluted, and S3 was lightly polluted. BRI values showed that the order of health status of R. philippinarum was S1 > S3 > S2.

State of the art and future challenges for polycyclic aromatic hydrocarbons is sediments: sources, fate, bioavailability and remediation techniques

Polycyclic aromatic hydrocarbons (PAHs) are amongst the most abundant contaminants found in the aquatic environment. Due to their toxicity and carcinogenicity, their sources, fate, behaviour, and cleanup techniques have been widely investigated in the last several decades. When entering the sediment-water system, PAH fate is determined by particular PAH and sediment physico-chemical properties. Most of the PAHs will be associated with fine-grained, organic-rich, sediment material. This makes sediment an ultimate sink for these pollutants. This association results in sediment contamination, and in this manner, sediments represent a permanent source of water pollution from which benthic organisms may accumulate toxic compounds, predominantly in lipid-rich tissues. A tendency for biomagnification can result in critical body burdens in higher trophic species. In recent years, researchers have developed numerous methods for measuring bioavailable fractions (chemical methods, non-exhaustive extraction, and biomimetic methods), as valuable tools in a risk-based approach for remediation or management of contaminated sites. Contaminated sediments pose challenging cleanup and management problems, as conventional environmental dredging techniques are invasive, expensive, and sometimes ineffective or hard to apply to large and diverse sediment sites. Recent studies have shown that a combination of strategies including in situ approaches is likely to provide the most effective long-term solution for dealing with contaminated sediments. Such in situ approaches include, but are not limited to: bioaugmentation, biostimulation, phytoremediation, electrokinetic remediation, surfactant addition and application of different sorbent amendments (carbon-rich such as activated carbon and biochar) that can reduce exposure and limit the redistribution of contaminants in the environment.

Abundance and characteristics of microplastics in the mangrove sediment of the semi-enclosed Maowei Sea of the south China sea: New implications for location, rhizosphere, and sediment compositions

Microplastic pollution of intertidal mangrove ecosystems is receiving growing attention, and scientists suspect that the microplastic pollution of semi-enclosed seas is significantly different from that of other coastal types because of their unique geographical features. However, data on the distributions and characteristics of microplastics in the mangrove sediment of semi-enclosed seas are very limited. This study selected the Maowei Sea, a typical semi-enclosed sea, as its representative study site. The analysis revealed that the microplastic abundances in the river estuaries were much lower than those at the oceanic entrance zones, with values ranging from 520 ± 8 to 940 ± 17 items/kg. Polyethylene (PE)/polypropylene (PP)/polystyrene (PS), white/transparent, and <1 mm were the dominant type, colour, and size of the microplastics, respectively, in the observed mangrove sediments. Moreover, some other factors, including the rhizosphere/non-rhizosphere and the proportion of organic matter, codetermined the distribution and characteristics of microplastics. Specifically: (1) the percentage of colorful microplastics were higher in the rhizosphere due to the microbial activities and (2) positive linear relationships were found between the pore volume (PV) values of the free particulate organic matter (FPOM), occluded particulate organic matter (OPOM) (1.6-2.0 g/cm³ and >2.0 g/cm³), and the abundance of very small microplastics (<1 mm).

Polycyclic aromatic hydrocarbons in sediments of the Amazon River Estuary (Amapá, Northern Brazil): Distribution, sources and potential ecological risk

The distribution, sources and potential ecological risk of priority polycyclic aromatic hydrocarbons (PAHs) in sediment from the Amazon River Estuary (Macapá and Santana, Amapá, Northern Brazil) were investigated. The total PAHs concentration (∑PAH) ranged from 22.2 to 158.9 ng g^-1 dw (mean value 49.4 ng g^-1 dw). PAHs levels in the study area were relatively low than those in nearby areas and other coastal zones worldwide, and could be considered as baseline for PAHs in Amazonic sediments. PAHs ratios and the statistical analysis showed that fossil fuel and biomass combustions, primarily from local sources, were the dominant PAHs origins. The potential ecological risk was assessed on the basis of the sediment quality guidelines, and it was found that PAHs in the sediments of the Amazon River Estuary do not cause adverse effects on living organisms; however, the abundance of naphthalene and the presence of dibenzo[a,h]anthracene and benzo[a]pyrene deserve more attention.

Bioaccumulation and Cycling of Polycyclic Aromatic Hydrocarbons (PAHs) in Typical Mangrove Wetlands of Hainan Island, South China

Mangrove wetlands are important coastal ecosystems in tropical and subtropical regions, and mangrove sediments and tissues often are the pollutant sinks due to their high organic matter contents. Polycyclic aromatic hydrocarbons (PAHs) in the mangrove sediments and tissues of nine species from three typical mangrove wetlands of Hainan Island were studied. The average concentration of PAHs in all mangrove tissues was 403 ng g^-1 dw, with PAHs concentrations in leaf, branch, root, and fruit of 566, 335, 314, and 353 ng g^-1 dw, respectively. PAHs levels were much higher in leaf than in other mangrove tissues, which may be caused partly by atmospheric deposition of PAHs. The dominant individual PAH compounds in mangrove tissues were phenanthrene (41.3%), fluoranthene (14.7%), and pyrene (11.4%), while in sediments were naphthalene (73.4%), phenanthrene (3.9%), and pyrene (3.6%), respectively. The biota-sediment accumulation factors of PAH congeners in the mangrove wetlands showed different patterns, with the most predominant of phenanthrene. The cycling of PAHs in the mangrove wetlands of Hainan Island also were estimated, and the results showed that the standing accumulation, the annual absorption, the annual net retention, the annual return, and the turnover period in all mangrove tissues of the community were 2228 µg m^-2, 869 µg m^-2 a^-1, 206 µg m^-2 a^-1, 663 µg m^-2 a^-1, and 3.4 a, respectively. These results indicated that mangroves are playing an important role in retaining PAHs.

Chemical contamination assessment in mangrove-lined Caribbean coastal systems using the oyster Crassostrea rhizophorae as biomonitor species

This paper aims to contribute to the use of mangrove cupped oyster, Crassostrea rhizophorae, as a biomonitor species for chemical contamination assessment in mangrove-lined Caribbean coastal systems. Sampling was carried out in eight localities (three in Nicaragua and five in Colombia) with different types and levels of contamination. Oysters were collected during the rainy and dry seasons of 2012-2013 and the tissue concentrations of metals, polycyclic aromatic hydrocarbons (PAHs), and persistent organic pollutants (POPs) were determined. Low tissue concentrations of metals (except Hg) and PAHs; moderate-to-high tissue concentrations of Hg, hexachlorocyclohexanes (HCHs), and dichlorodiphenyl-trichloroethanes (DDTs); detectable levels of chlorpyrifos, polychlorinated biphenyls (PCBs) (mainly CB28, CB118, CB138 and CB 153) and brominated diphenyl ethers 85 (BDE85); and negligible levels of musks were recorded in Nicaraguan oysters. A distinct profile of POPs was identified in Colombia, where the tissue concentrations of PCBs and synthetic musk fragrances were low to moderate, and Ag, As, Cd, Pb, and PAHs ranged from moderate to extremely high. Overall, the values recorded for HCHs, DDTs and PCBs in Nicaraguan mangrove cupped oysters greatly exceeded the reference values in tissues of C. rhizophorae from the Wider Caribbean Region, whereas only the levels of PCBs were occasionally surpassed in Colombia. Different contaminant profiles were distinguished between oysters from Nicaragua and Colombia in radar plots constructed using the main groups of contaminants (metals, PAHs, musks, PCBs, and organochlorine pesticides (OCPs)). Likewise, integrated pollution indices revealed differences in the levels of contaminants. Moreover, the profiles and levels in oyster tissues also varied with season. Thus, principal component analysis clearly discriminated Nicaraguan and Colombian localities and, especially in Colombia, seasonal trends in chemical contamination and differences amongst localities were evidenced. The geographical and environmental disparity of the studied scenarios may represent to a large extent the diversity of mangrove-lined Caribbean coastal systems and therefore the present results support the use of C. rhizophorae as suitable biomonitor species at Caribbean regional scale, where seasonal variability is a major factor controlling pollutant mobility and bioavailability.

Concentration, distribution and source apportionment of polycyclic aromatic hydrocarbons (PAH) in Poxim River sediments, Brazil

The individual concentrations, total amount and sources of 16 priority polycyclic aromatic hydrocarbons (PAH) in sediments collected along of the Poxim River, Aracaju, Brazil, were for the first time determined. The ΣPAH ranged between 2.2±1.5ngg^-1 and 28.4±6.9ngg^-1, with a mean value of 14.4±9.3ngg^-1. The Pearson correlation test and Principal component analysis (PCA) were used to assess the correlation between the PAH, organic matter and grain size; and to differentiate the sampling stations. Diagnostic ratios presented predominance of pyrogenic sources. Therefore, the PAH quantified showed the influence of anthropogenic activities near of the Poxim River.

Occurrence survey and spatial distribution of perfluoroalkyl and polyfluoroalkyl surfactants in groundwater, surface water, and sediments from tropical environments

The occurrence and spatial distribution of 22 selected perfluoroalkyl and polyfluoroalkyl substances (PFASs) in surface water (n=75), groundwater (n=80) and surficial sediment (n=15) were investigated for the first time in the tropical areas constituted by the French Overseas Territories (French Guiana, Guadeloupe, Martinique, Mayotte and Reunion). Descriptive statistics and correlations between PFASs were evaluated through the use of specific statistical treatments to handle left-censored data ("non-detects"). PFASs were ubiquitous in these samples and detection frequencies as high as 79% for perfluorooctane sulfonate (PFOS) and 65% for perfluorooctanoate (PFOA) were reported in surface waters. ∑PFASs was in the range<LOD-77ngL^-1 (median=1.8ngL^-1) in surface waters and <LOD-638ngL^-1 (median=0.56ngL^-1) in groundwater. PFOS and PFOA dominated PFAS composition profiles in surface water, while shorter-chain compounds prevailed in groundwater, highlighting their higher transfer potential through infiltration processes and the possible influence of precursors. Elevated levels of 6:2 fluorotelomer sulfonate (6:2 FTSA) and short-chain perfluoroalkyl carboxylates were found in groundwater near several industrial facilities such as oil refineries or electricity power plants. This may be related to the existence of firefighting operations involving the use of aqueous film forming foams (AFFFs) that contain precursors to such compounds. These findings would also tend to confirm recent trends regarding the increasing proportion of C₄- or C₆-based perfluoroalkyl acids, their precursors, or even shorter-chain congeners at PFAS hot spots.

Multi-biomarker approach in the scallop Chlamys farreri to assess PAHs pollution in Qingdao coastal areas of China

A multi-biomarker approach was conducted in the scallop Chlamys farreri from three sites, denoted here as S1, S2, and S3, in Qingdao coastal areas of China in March, June, September and December 2014 to assess pollution from polycyclic aromatic hydrocarbons (PAHs) and to select appropriate biomarkers. A suite of biological responses of the gills and digestive glands of the scallops was assayed, including: (i) phase I detoxification enzymes of 7-ethoxyresorufin-O-deethylase (EROD), epoxide hydrolase (EH), and dihydrodiol dehydrogenase (DD) and phase II detoxification enzymes of glutathione-S-transferase (GST) and sulfotransferase (SULT); (ii) antioxidant enzymes: catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx); (iii) oxidative damage parameters: lipid peroxidation (LPO) expressed by malondialdehyde (MDA) contents, protein carbonylation (PC) and DNA damage (F value); and (iv) the metabolism-related genes of EH, DD, GST, SULT and SOD. Simultaneously, the concentrations of total PAHs along with 16 types of PAHs previously identified by the US Environmental Protection Agency (USEPA) and environmental parameters, including temperature and salinity together with pH, were measured. Using Principle Component Analysis (PCA), it was revealed that S2 was the most PAH-contaminated site, while S1 was identified as the least PAH-polluted site, which was consistent with the results utilizing the Biomarker Response Index (BRI); in other words, the biological health status of S2 was worse than S1 and S3. Moreover, the most suitable biomarkers to assess PAH pollution in Qingdao coastal areas proved to be DD mRNA expression and the F value in both the gills and digestive glands for the total PAHs, DD activity and PC contents or PC and MDA contents in the gills or digestive glands for 5 + 6 rings PAHs and DD mRNA expression in both the gills and digestive glands for 2 + 3 rings and 4 rings PAHs. Moreover, this study highlighted the possible use of the scallop Chlamys farreri for studying contamination due to PAHs and provided valuable information on environmental assessment.

Evaluation of the impact of bioaccumulation of PAH from the marine environment on DNA integrity and oxidative stress in marine rock oyster (Saccostrea cucullata) along the Arabian sea coast

Marine pollution due to oil spills is of great concern globally for their impact on the health of marine ecosystems. We assessed the genotoxic effects and oxidative stress due to genotoxic pollutants accumulated from the ambient marine environment in the tissues of marine rock oyster, Saccostrea cucullata along the Arabian Sea coast around Goa, India. The extent of DNA damage in S. cucullata was determined by comet assay as variation of comet parameter: mean % tail DNA along the coast with respect to that at the reference site (Tiracol, Goa, India). In addition, the oxidative stress responses of rock oysters exposed to marine pollutants such as polycyclic aromatic hydrocarbons (PAHs) were assessed as a function of variation in antioxidant enzyme activities such as glutathione-s-transferase (GST), catalase (CAT) and superoxide dismutase (SOD) along the coast. Spearman correlation analysis showed significant correlation between different components of PAHs (viz., 2-3-PAH, 4-6-PAH and oxy-PAH) in the tissues of the rock oysters and the antioxidant enzyme activities. The antioxidant enzyme activities in S. cucullata increased with increasing concentrations of PAHs in tissues in the following order of sampling sites: Tiracol < Arambol < Betul < Velsao. Among the PAHs, oxy-PAH was found to be most predominant in causing DNA damage in S. cucullata. These results provide an insight into environmental genotoxicity and oxidative stress induced by PAHs along the Arabian Sea coast, India.

Hemolymph and gill carbonic anhydrase are more sensitive to aquatic contamination than mantle carbonic anhydrase in the mangrove oyster Crassostrea rhizophorae

Carbonic anhydrase (CA) is a ubiquitous metalloenzyme of great importance in several physiological processes. Due to its physiological importance and sensitivity to various pollutants, CA activity has been used as biomarker of aquatic contamination. Considering that in bivalves the sensitivity of CA to pollutants seems to be tissue-specific, we proposed here to analyze CA activity of hemolymph, gill and mantle of Crassostrea rhizophorae collected in two tropical Brazilian estuaries with different levels of anthropogenic impact, in dry and rainy season. We found increased carbonic anhydrase activity in hemolymph, gill and mantle of oysters collected in the Paraíba Estuary (a site of high anthropogenic impact) when compared to oysters from Mamanguape Estuary (inserted in an area of environmental preservation), especially in the rainy season. CA of hemolymph and gill were more sensitive than mantle CA to aquatic contamination. This study enhances the suitability of carbonic anhydrase activity for field biomarker applications with bivalves and brings new and relevant information on hemolymph carbonic anhydrase activity as biomarker of aquatic contamination.

Ecotoxicological and Health Risk Assessment of Polycyclic Aromatic Hydrocarbons (PAHs) in Short-Neck Clam (Paphia undulata) and Contaminated Sediments in Malacca Strait, Malaysia

The distribution, sources, and human health risk assessment of polycyclic aromatic hydrocarbons (PAHs) in surface sediment and the edible tissue of short-neck clam (Paphia undulata) from mudflat ecosystem in the west coast of Malaysia were investigated. The concentrations of ∑₁₆ PAHs varied from 347.05 to 6207.5 and 179.32 to 1657.5 ng g^-1 in sediment and short-neck clam samples, respectively. The calculations of mean PEL quotients (mean-PELQs) showed that the ecological risk of PAHs in the sediment samples was low to moderate-high level, whereas the total health risk through ingestion and dermal contact was considerably high. The PAHs biota sediment accumulation factors data for short-neck clam were obtained in this study, indicating a preferential accumulation of lower molecular weight PAHs. The source apportionment of PAHs in sediment using positive matrix factorization model indicated that the highest contribution to the PAHs was from diesel emissions (30.38%) followed by oil and oil derivate and incomplete coal combustion (23.06%), vehicular emissions (16.43%), wood combustion (15.93%), and natural gas combustion (14.2%). A preliminary evaluation of human health risk using chronic daily intake, hazard index, benzo[a]pyrene-equivalent (BaP_eq) concentration, and the incremental lifetime cancer risk indicated that PAHs in short-neck clam would induce potential carcinogenic effects in the consumers.

A multi-biomarker approach in scallop Chlamys farreri to assess the impact of contaminants in Qingdao coastal area of China

A multi-biomarker approach was carried out to classify the environmental quality and the adverse effects of contaminants on scallop Chlamys farreri. The scallops were collected from three sampling stations in Qingdao coastal area of China in March, May, August and October of 2015. A suite of environmental factors and biomarkers, including temperature, salinity, pH, the concentrations of polycyclic aromatic hydrocarbons (PAHs), tetrabromobisphenol A (TBBPA) and metals (Cr, Mn, Cu, Zn, Cd, Pb, As) in seawater and soft tissue, mRNA expression of aryl hydrocarbon receptor (AhR) and P-glycoprotein (P-gp), 7-ethoxyresorufin O-deethylase (EROD), glutathione-S-transferase (GST), uridine-diphosphate-glucuronyl-transferase (UGT), sulfotransferase (SULT), metallothionein (MT), Superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), lipid peroxidation (LPO) and protein carbonyl (PC) contents and DNA strand breaks, were measured in the gill and digestive gland. The results showed that S2 was the most polluted while S1 was identified the least polluted. Despite the differentiation of pollution levels and environmental parameters the selected biomarkers responded efficiently to contaminants. Principal component analysis (PCA) revealed that EROD for PAHs, AhR for TBBPA, MT for Cr, Pb and Mn, LPO and PC for Zn were the effective biomarkers respectively. This study demonstrated that the application of multi-biomarker approach in conjunction with the traditional analysis of environmental parameters and contaminants provided valuable information in environmental risk assessment.

Polycyclic Aromatic Hydrocarbons in Mussels from a South American Estuary

Bivalves, especially mussels, have been pointed as putative species to monitor polycyclic aromatic hydrocarbons (PAHs) in marine environment. After several environmental PAHs baseline reports, the present study was conducted to assess for the first time the levels of PAHs in native mussels (Brachidontes rodriguezii) collected from a critical industrialized estuary of Argentina. Under this objective, after an 18-month sampling period, 34 pools of mussels were assessed for 17 PAHs, including the 16 compounds prioritized by United States Environmental Protection Agency. By means of gas chromatography-mass spectrometry analysis, results showed total PAHs concentrations in mussel's tissue ranged from under laboratory detection limits to 482.4 ng/g dry weight. Mussel body burdens were dominated by lower molecular weight PAHs, such as phenanthrene, naphthalene, and pyrene, whereas the overall PAHs profile suggested the predominance of petrogenic sources. Finally, the potential ecotoxicological impact was evaluated by applying Environmental Assessment Criteria and benzo[a]pyrene toxic equivalent factors.

Combined exposure to pyrene and fluoranthene and their molecular effects on the Sydney rock oyster, Saccostrea glomerata

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitously detected in the water column, associated with particulate matter or in the tissue of marine organisms such as molluscs. PAH exposure and their resultant bioaccumulation in molluscs can cause a range of serious physiological effects in the affected animals. To examine the molecular response of these xenobiotics in bivalves, Sydney rock oysters (Saccostrea glomerata) were exposed to pyrene and fluoranthene for seven days. Chemical analysis of the soft-tissue of PAH stressed S. glomerata confirmed that pyrene and fluoranthene could be bioaccumulated by these oysters. RNA-Seq analysis of PAH-exposed S. glomerata showed a total of 765 transcripts differentially expressed between control and PAH-stressed oysters. Closer examination of the transcripts revealed a range genes encoding enzymes involved in PAH detoxification (e.g. cytochrome P450), innate immune responses (e.g. pathogen recognition, phagocytosis) and protein synthesis. Overall, pyrene and fluoranthene exposure appears to have resulted in a suppression of pathogen recognition and some protein synthesis processes, whereas transcripts of genes encoding proteins involved in clearance of cell debris and some transcripts of genes involved in PAH detoxification were induced in response to the stressors. Pyrene and fluoranthene exposure thus invoked a complex molecular response in S. glomerata, with results suggesting that oysters focus on removing the stressors from their system and dealing with the downstream effects of PAH exposure, potentially at the exclusion of other, less immediate concerns (e.g. protection from infection).

Polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs in the coastal seawater, surface sediment and oyster from Dalian, Northeast China

A total of 46 polycyclic aromatic hydrocarbons (PAHs, 21 parent and 25 alkylated) were determined in seawater, surface sediment and oyster from coastal area of Dalian, North China. The concentration of Σ46PAHs in seawater, sediment, and oyster were 136-621 ng/L, 172-4700 ng/g dry weight (dw) and 60.0-129 ng/g wet weight (ww) in winter, and 65.0-1130 ng/L, 71.1-1090 ng/g dw and 72.8-216 ng/g ww in summer, respectively. High PAH levels were found in industrial area both in winter and summer. Selected PAH levels in sediments were compared with Sediments Quality Guidelines (ERM-ERL, TEL-PEL indexes) for evaluation probable toxic effects on marine organism and the results indicate that surface sediment from all sampling sites have a low to medium ecotoxicological risk. Daily intake of PAHs via oyster as seafood by humans were estimated and the results indicated that oyster intake would not pose a health risk to humans even 30 days after a oil spill accident near by. Water-sediment exchange analysis showed that, both in winter and summer, the fluxes for most high molecular weight PAHs were from seawater to sediment, while for low molecular weight PAHs, an equilibrium was reached between seawater and sediment.

Effects of flooding and aging on phytoremediation of typical polycyclic aromatic hydrocarbons in mangrove sediments by Kandelia obovata seedlings

A laboratory experiment was conducted to evaluate the effects of flooding and aging on the phytoremediation of naphthalene (Nap), anthracene (Ant) and benzo[a]pyrene (B[a]P) in mangrove sediment by Kandelia obovata (K. obovata) Druce seedlings. Flooding increased dissipation efficiency in the rhizosphere zone from 69.47% to 82.45%, 64.27% to 80.41%, and 61.55% to 78.31% for Nap, Ant and B[a]P, respectively. Aging decreased dissipation efficiency significantly. Further investigation demonstrated that increased enzyme activity was one of important factors for increasing PAHs dissipation rates in flooded mangrove sediments. Moreover, a novel method for in situ quantitative investigation of PAHs distribution in root tissues was established using microscopic fluorescence spectra analysis. Subsequently, the effects of flooding and aging on the distribution of PAHs in root tissues were evaluated using this established method. The order of bioavailable fractions of PAHs after phytoremediation was as follows: non-aging/non-flooding>flooding>aging.

Level of contamination by metallic trace elements and organic molecules in the seagrass beds of Guadeloupe Island

Seagrass bed ecosystems occupy the most important part of coastal shelf in the French West Indies. They also constitute nurseries for many invertebrates and fishes harvested by local fisheries. In Guadeloupe, coastal fish stocks are declining meanwhile several agroecosystems revealed to be heavily contaminated by pollutants (agricultural lands, rivers, mangroves, seagrass beds, and coral reefs). Considering these facts, a study of the contamination of seagrass beds (8000 ha) of the Grand Cul-de-Sac Marin (GCSM) bay was conducted on their sediments and marine phanerogams. The analyses concerned six metals (Cd, Cu, Hg, Pb, V, Zn), tributyltin, 18 polycyclic aromatic hydrocarbons (PAHs), eight polybrominated diphenyl ethers (PBDEs), 38 polychlorobiphenyls (PCBs), dithiocarbamates (CS2 residues), and 225 pesticide molecules.Overall, the level of contamination of the seagrass beds was low for both sediments and phanerogams. Metallic trace elements were the main pollutants but with higher concentrations recorded in coastal sites, and their distribution can be explained by the proximity of river mouths and current patterns. The level of contamination was lower in plants than in sediments. However, the level of contamination between these two compartments was significantly correlated. The conclusion of this study is that, unlike other coastal ecosystems of Guadeloupe such as mangroves, the seagrass beds in the GCSM present a low degree of pollution. The observed level of contaminants does not seem to threaten the role of nursery played by the seagrass beds and does not likely present a risk for the reintroduction of manatees.

Evaluation of impacted Brazilian estuaries using the native oyster Crassostrea rhizophorae: Branchial carbonic anhydrase as a biomarker

In this study, we investigated the use of branchial carbonic anhydrase activity in a sessile filter feeding species, the oyster Crassostrea rhizophorae, as a biomarker. The oysters were collected in three human impacted Brazilian estuaries, following a crescent latitudinal gradient: in Pernambuco state (Itamaracá), in Espírito Santo state (Piraquê), and in Paraná state (Paranaguá), in August/2003 (Winter in the southern hemisphere) and February/2004 (Summer). Three sites were chosen in each estuary for oyster sampling: Reference (R), Contaminated 1 (C1, close to industrial/harbor contamination), and Contaminated 2 (C2, near to sewage discharges). Comparing to values in oysters sampled in reference sites, there was apparent inhibition in carbonic anhydrase activity (CAA) in gills of oysters from C1 of Itamaracá and from C2 of Piraquê, both cases in Summer. On the other hand, increased CAA was noted in C2 oysters of Itamaracá in winter, and of Paranaguá, in both seasons. Branchial CAA in C. rhizophorae was thus very responsive to coastal contamination. Data are consistent with its usefulness as a supporting biomarker for inexpensive and rapid analysis in the assessment of estuaries using a sessile osmoconformer species, but preferably allied to other biomarkers and with knowledge on the suite of contaminants present.

Distribution and accumulation of polycyclic aromatic hydrocarbons (PAHs) in the food web of Nansi Lake, China

The concentrations of polycyclic aromatic hydrocarbons (PAHs) were analyzed in water, sediment, and biota (aquatic plant, shrimp, and fish) of Nansi Lake by gas chromatography-mass spectrometry (GC-MS). The concentrations of total PAHs were 27.54-55.04 ng L(-1) in water, 80.31-639.23 ng g(-1) dry weight (dw) in sediments, 20.92-192.78 ng g(-1) dw in aquatic plants, and 67.3-533.9 ng g(-1) dw in fish and shrimp muscles. The ratios of phenanthrene to anthracene (Ph/An), fluoranthene to pyrene (Flu/Pyr), and low molecular weight to high molecular weight (LMW/HMW) in sediment indicated that the sources of the PAHs were a mixture of pyrolytic and petrogenic contamination at most sampling sites in Nansi Lake. The composition profile of PAHs in plants was similar to that in water and animals with 2-3 ring PAHs being dominant. The 4-6 ring PAHs were the dominant PAH compounds in sediment. There is a positive correlation between sediment and aquatic plants, but their PAH composition profiles were different, implying that aquatic plant absorption of PAHs from sediment is selective and the accumulation of PAHs in aquatic plants is different. The concentration of PAHs in fish showed a positive correlation with plants, reflecting that the PAHs in fish are mainly absorbed from aquatic plants rather than directly from the water. Bioaccumulation of LMW PAHs in aquatic biota was higher than HMW PAHs. The biota-sediment accumulation factor (BSAF) values of total PAHs in the plants Potamogeton lucens Linn and Ceratophyllum demersum Linn were higher than that in most animals. The BSAF values of total PAHs in animals were in the following order: Cyprinus carpio>Macrobrachium nipponense>Carassius auratus>Channa argus. There was no significant relationship between PAH bioaccumulation and trophic levels in Nansi Lake. Risk assessment of PAHs in water, sediment, and animals indicated that the water environment of Nansi Lake is safe at present. It is worthwhile to note that benzo [a] anthracene (BaA), benzo [a] pyrene (BaP), indeno [1,2,3-cd] pyrene (InP), dibenz [a, h] anthracene (DBA), and benzo [ghi] perylene (BghiP) were detected in sediment, plants, and animals at all sampling sites, and they have potential carcinogenicity to the organisms of Nansi Lake.

Polycyclic aromatic hydrocarbons (PAHs) in Crassostrea rhizophorae and Cathorops spixii from the Caroni Swamp, Trinidad, West Indies

Dietary exposure to polycyclic aromatic hydrocarbons (PAHs) may pose serious threats to human health. However, within the Caribbean, quantitative assessments regarding the risks associated with dietary PAH exposure remain sparse. This study investigated PAH presence in edible biota from the Caroni Swamp and quantitatively assessed the potential health threat to human consumers. Mangrove oysters (Crassostrea rhizophorae) and Madamango sea catfish (Cathorops spixii) collected from seven sites in the Caroni Swamp were analysed for 16 priority PAHs. Total PAH levels ranged from 109 ± 18.4 to 362 ± 63.0 ng/g dry wt. in Crassostrea rhizophorae and 7.5 ± 0.9 to 43.5 ± 25.5 ng/g dry wt. in Cathorops spixii (average ± standard deviation). Benzo[a]pyrene levels in Crassostrea rhizophorae at all sites exceeded international guidelines from British Colombia (Canada) and the European Union (EU). Incremental lifetime cancer risk (ILCR) values based on the ingestion of Crassostrea rhizophorae ranged from 8.4 × 10(-6) to 1.6 × 10(-5) and slightly exceeded the commonly used 1 × 10(-6) acceptable level of risk. Information from this study is important in understanding the potential health risks posed by PAHs, it is critical towards the protection of public health, and it serves as a useful baseline for comparison with future work.