Implications from a field study regarding the relationship between polycyclic aromatic hydrocarbons and glutathione S-transferase activity in mussels

An aluminium smelter on the west coast of Scotland discharges an aqueous effluent containing polycyclic aromatic hydrocarbons (PAHs) at the head of Loch Leven. The loch also supports two mussel (Mytilus edulis) farms. Data are presented on burdens of PAHs in the soft tissues of mussels and the effect of these contaminants on glutathione S-transferase (GST) activity in mussel hepatopancreas. GST activity is shown to be correlated with total PAH burden and also with the concentrations of certain individual PAHs. These field data show that high molecular weight PAHs are closely correlated to GST activity, whereas low molecular weight PAHs are not. This suggests that 5- and 6-ring PAHs have a more pronounced role than 2- to 4-ring compounds in inducing GST activity in mussels from Loch Leven. It is proposed that it may be more appropriate to link GST activity with 5- and 6-ring compounds only, rather than with the total PAH burden.     

Different levels of mussel (Mytilus edulis) DNA strand breaks following chronic field and acute laboratory exposure to polycyclic aromatic hydrocarbons

Levels of polycyclic aromatic hydrocarbons (PAHs) including benzo[a]pyrene (B[a]P) were at least seven-fold higher in mussels sampled from a polluted site (Loch Leven, in Scotland, UK) compared to a nearby clean reference site (Loch Etive) throughout the year 2000. Levels of DNA strand breaks (alkaline COMET assay) using both gill and digestive gland nuclei were similar at both sites despite the difference in contaminant load (total PAH). In contrast, mussels collected from a reference site (Port Quin, Cornwall, UK) had an increase in DNA strand breaks in digestive gland cells following laboratory exposure to B[a]P-dosed Isochrysis galbana. However, after 14 days high dose (20 ppb-exposed diet) animals had returned to levels similar to the controls. There was no evidence of increased necrosis or apoptosis after treatments. The results from these two studies suggest that an adaptive response may prevent ongoing DNA damage in mussels exposed to high levels of B[a]P and PAH contamination.     

Oil well produced water discharges to the North Sea. Part II: comparison of deployed mussels (Mytilus edulis) and the DREAM model to predict ecological risk

Large volumes of water often are produced with oil and gas from offshore platforms. The produced water is separated from the oil and gas and either reinjected into a deep formation or discharged to the ocean. The Norwegian oil and gas industry advocates ecological risk assessment as the basis for managing produced water discharges to the North Sea. In this paper, we compare estimates of ecological risks to water-column communities based on data on hydrocarbon residues in soft tissues of blue mussels deployed for a month near offshore platforms and based on predictions of the Dose related Risk and Effect Assessment Model (DREAM). The study was performed near produced water discharges to the Tampen and Ekofisk Regions of the Norwegian Sector of the North Sea. Because polycyclic aromatic hydrocarbons (PAH) are considered the most important contributors to the ecological hazard posed by produced water discharges, comparisons made here focus on this group of compounds. The mussel approach is based on predicted environmental concentrations (PECs) of individual PAH, estimated from PAH residues in mussels following deployment for a month near several produced water discharges, and predicted no effects concentrations (PNECs) based on a K(ow) regression model. In the DREAM method, PECs for three PAH fractions are estimated in the three-dimensional area around produced water discharge with the DREAM model. PNECs for each fraction are based on the chronic toxicity of a representative PAH from each fraction divided by an assessment factor to account for uncertainty in the chronic value. The mussel method gives much lower estimates of ecological risk than the DREAM method. The differences are caused by the much lower PNECs used in DREAM than derived from the regression model, and by the lower concentrations of aqueous PAH predicted by DREAM than estimated from PAH residues in mussel tissues. However, the two methods rank stations at different distances from produced water discharges in the same order and both identify 2- and 3-ring PAHs as the main contributors to the ecological risk of produced water discharges. Neither method identifies a significant ecological risk of PAH in the upper water column of the oil fields. The DREAM model may produce an overly conservative estimate of ecological risk of produced water discharges to the North Sea.     

Mussels document loss of bioavailable polycyclic aromatic hydrocarbons and the return to baseline conditions for oiled shorelines in Prince William Sound, Alaska

Polycyclic aromatic hydrocarbons (PAH) were measured in mussels (Mytilus trossulus) collected between 1990 and 2002 from 11 sites on the shores of Prince William Sound (PWS), Alaska, that were heavily oiled by the 1989 Exxon Valdez oil spill (EVOS). This study, utilizing the methods of the NOAA Status and Trends Mussel Watch Program, found that concentrations of PAH released from spill remnants have decreased dramatically with time and by 2002 were at or near the range of total PAH (TPAH) of 3-355 ng/g dry weight obtained for mussels from unoiled reference sites in PWS. Time-series TPAH data indicate a mean TPAH half-life in mussel tissues of 2.4 years with a range from 1.4 to 5.3, yielding an annual mean loss of bioaccumulated TPAH of 25%. The petroleum-derived TPAH fraction in mussel tissues has decreased with time, reflecting the decreasing release of EVOS residues in shoreline sediments. These results show that PAH from EVOS residues that remain buried in shoreline sediments after the early 1990s are in a form and at locations that have a low accessibility to mussels living in the intertidal zone.     

Influence of parasitism in controlling the health, reproduction and PAH body burden of petroleum seep mussels

Petroleum seep mussels are often exposed to high hydrocarbon concentrations in their natural habitat and, thus, offer the opportunity to examine the relationship between parasitism, disease and contaminant exposure under natural conditions. This is the first report on the histopathology of cold-seep mussels. Seep mussels were collected by submersible from four primary sites in the Gulf of Mexico, lease blocks Green Canyon (GC) 184, GC-234, GC-233, and Garden Banks 425 in 550–650 m water depth. Five types of parasites were identified in section: (1) gill “rosettes” of unknown affinity associated with the gill bacteriocytes, (2) gill “inclusions” similar to chlamydia/rickettsia inclusions, (3) extracellular gill ciliates, (4) body “inclusions” that also resemble chlamydial/rickettsial inclusions, and (5) Bucephalus-like trematodes. Comparison to shallow-water mytilids demonstrates that: (1) both have similar parasite faunas; (2) seep mytilids are relatively heavily parasitized; and (3) infection intensities are extremely high in comparison to shallow-water mytilids for Bucephalus and chlamydia/rickettsia. In this study, the lowest prevalence for chlamydia/rickettsia was 67%. Prevalences of 100% were recorded from three populations. Bucephalus prevalence was 70% in three of 10 populations. The parasite fauna was highly variable between populations. Some important parasites were not observed in some primary sites. Even within primary sites, some important parasites were not observed in some populations. Bucephalus may exert a significant influence on seep mussel population dynamics. Forty percent of the populations in this study are severely reproductively compromised by Bucephalus infection. Only a fraction of petroleum seep mussel populations are maintaining the entire beta-level population structure of this species. Variation in two parasites, gill ciliates and Bucephalus, explained most of the variation in PAH body burden between mussel populations. PAHs are known to be sequestered preferentially in gametic tissue. Bucephalus would be expected to reduce overall body burden, at high infection intensities, by replacing gametic tissue. PAH concentrations exceeded 1 ppm in 4 of 9 populations, a ratio significantly higher than the 8 of 30 mussel locales in the NOAA Mussel Watch Program. Only five Mussel Watch locales exceeded the highest value for a petroleum seep population. Digestive gland and gill tissue atrophy were not significantly correlated with PAH body burden, even though some populations were characterized by body burdens exceeding 1 ppm, suggesting that seep mussels may not be as sensitive to PAH exposure as are some shallow-water mytilid populations.     

Polycyclic aromatic hydrocarbons in surface seawater and in indigenous mussels (Mytilus galloprovincialis) from coastal areas of the Saronikos Gulf (Greece)

Polycyclic aromatic hydrocarbons (PAHs) were identified and measured in surface seawater and in the tissues (gills and mantle) of indigenous black mussels, Mytilus galloprovincialis, collected from three coastal sites of Saronikos Gulf (Greece), a gulf that exhibits high levels of pollution. The total PAHs measured by spectrofluorometry in the surface seawater were found in the range of 425–459 ng L⁻¹ at the most polluted sites 1 and 2 (Elefsis Bay–Salamis Island) and in the range of 103–124 ng L⁻¹ at site 3 (Aegina Island). PAHs' sources in seawater were identified by application of specific PAH ratios, such as phenanthrene/anthracene and fluoranthene/pyrene. Levels of PAHs in soft tissues (gills and mantle) of indigenous mussels were much higher than those reported for seawater. Total PAH concentrations in mantle tissues were in the range of 1300–1800 ng g⁻¹ dry weight (dw) tissue at sites 1 and 2 and approximately 380 ng g⁻¹ dw at site 3. In gill tissues total PAH concentrations were in the range of 1480–2400 ng g⁻¹ dw at sites 1 and 2 and approximately 430 ng g⁻¹ dw at site 3. PAHs composition was dominated by two-, three- and four-ring compounds in seawater, where 17 different PAH compounds were identified and measured in mussel tissues. Mussels can be used as sentinel organisms to monitoring PAHs' contamination, since they concentrate PAHs from the surrounding water media and therefore making the chemical analysis simpler and less prone to error than that for water. In surface seawater possible weathering and photodegradation due to hot climates contribute to reduced PAHs concentrations.     

DNA adducts and polycyclic aromatic hydrocarbon (PAH) tissue levels in blue mussels (Mytilus spp.) from Nordic coastal sites

DNA adducts in gills and digestive gland, as well as polycyclic aromatic hydrocarbon (PAH) tissue levels were analysed in blue mussels (Mytilus spp.) from Nordic coastal areas (Iceland, Norway and Sweden) with diffuse or point sources of PAHs of various origins. Both DNA adduct and PAH tissue levels were generally low, indicating low PAH exposure to the mussels in the areas studied. DNA adducts were found to be higher in gills than in digestive gland of the mussels at all sites studied. Elevated DNA adduct levels in gills were found at 6 sites out of 18 compared to reference sites in respective coastal zones. Adduct levels ranged from 0.5 to 10 nmol adducts/mol normal nucleotides, being highest in mussels from Reykjavík harbour, Iceland (intertidal mussels), and from Fiskaatangen, Norway (subtidal mussels). Total PAH tissue levels in the mussels ranged between 40 and 11,670 ng/g dry wt., and were significantly correlated with DNA adduct levels (r(2)=0.73, p<0.001). PAH ratio values indicated that the PAHs were in most cases of pyrolytic origin, but with petrogenic input near harbours and an oil refinery.     

珠江虎门潮汐水道水体中多环芳烃的分布及季节变化

采用GF/F玻璃滤膜对珠江虎门潮汐水道6个表层水样进行过滤分离出多环芳烃的颗粒相和溶解相,并根据美国EPA标准对多环芳烃进行了定量分析.结果显示,洪、枯季水体中16种优先控制多环芳烃总量分别是223～614,6 559～20 031 ng/dm3;洪、枯季多环芳烃总量分别为786～2 098,11 360～34 338 ng/dm3;广州前航道的污染较狮子洋严重.珠江虎门潮汐水道水体中多环芳烃的含量、分布具有明显的季节变化特征,枯季多环芳烃的浓度高于洪季1个数量级以上,且二环多环芳烃的含量占95%以上,主要呈溶解相形式出现;洪季高环多环芳烃的含量明显升高,主要呈颗粒相形式输运.     

Biochemical responses in farmed mussel Perna perna transplanted to contaminated sites on Santa Catarina Island, SC, Brazil.

The effects of contaminants on the biochemical parameters of the intensively farmed mussel Perna perna, are unknown. The aim of this study was to compare biochemical responses in mussels held in clean and contaminated sites in Santa Catarina Island, Brazil. Mussels were transplanted from a farming area, Ratones Grande Island (RGI), to two contaminated sites, Itacorubi (ITAC) and Hercílio Luz Bridge (HLB). A reference group was kept at RGI. After 150 and 180 days of exposure, the digestive glands of the mussels were analyzed for catalase, glucose 6-phosphate dehydrogenase (G6PDH) and glutathione S-transferase (GST) activities. No changes were observed in the catalase activity, in both periods. Low G6PDH activity was observed in mussels transplanted for 150 days at the ITAC site. Increased GST activity was observed in mussels from ITAC and HLG sites after 180 days. These responses are probably related to the augmented discharges of domestic effluents associated with elevated rainfall index.     

Enhancement of polycyclic aromatic hydrocarbons in estuarine invertebrates by surface runoff at a decommissioned military fuel depot

Accumulation of polycyclic aromatic hydrocarbons (PAHs) was determined in blue mussels (Mytilus spp.) and shore crabs (Hemigrapsus sp.) at a recently closed military fuel depot in central San Francisco Bay, California. In April 1996, during a period of above average precipitation, specimens were collected at the depot, near the depot, and at sites 10 and 20 km south of the depot. Four weeks after the rains ended, blue mussels were again collected at the depot, and at two additional sites in the central Bay region. In April, total PAHs in mussels from the depot were significantly higher only than that in mussels collected 20 km from the depot; however, seven specific, substituted PAHs were higher at the depot than at all other sites. In June, only two of the 38 PAHs common in mussels in April were detected at the depot; these concentrations were comparable to ambient concentrations in mussels at the Bay. It seemed that bioavailability of PAHs at the depot was enhanced by rainfall, probably due to the mobilization of PAHs via groundwater into the Bay. Concentrations in mussels from chronically contaminated sites were about five times higher than mussels collected from the depot. Low PAH concentrations were detected in shore crabs near the depot, and the highest levels were not associated with the depot. Observed PAH concentrations are discussed in relation to upper trophic organisms.     

Correlation of CYP1A1 induction, as measured by the P450 RGS biomarker assay, with high molecular weight PAHs in mussels deployed at various sites in San Diego Bay in 1993 and 1995

In 1993 collections of marine mussels (Mytilus galloprovincialis) were deployed 1 m from the water surface at six sites in San Diego Bay for 88 days. A similar mussel deployment was conducted in 1995, except the animals were deployed 1 m off the bottom and only for 32 days. After recovery from the sites, tissue was extracted with dichloromethane and the solvent extracts analyzed for chemical contaminant content and the ability to produce CYP1A1 induction in a transgenic cell line (TV101L cells). The cells used in the assay (P450 RGS) are stably transfected with a plasmid containing firefly luciferase linked to human CYP1A1 promoter sequences. Induction (fold increase compared to control) was determined by luminometry 16 h after application of small volumes (2–10 μl) of solvent extracts to cultured cells. Small mussels deployed in the Naval Station (NAV) in 1993 exhibited very high bioaccumulation of polycyclic aromatic hydrocarbons (PAHs; 52 μg/g) and polychlorinated biphenyls (PCBs), in addition to very strong induction of CYP1A1 measured by reporter gene system (RGS) responses. Large mussels deployed at the NAV station in 1993 and intermediate-sized animals placed at three stations within the NAV station in 1995 accumulated 13–29 μg PAH/g and exhibited relatively high RGS responses. Correlation of RGS responses for all mussel samples to the measured PAH concentrations was 0.85 (r²). When the concentrations of seven specific PAHs found in the samples are converted to benzo[a]pyrene equivalents, from previously derived toxic equivalency factors (TEFs) for this test system, and compared to measured RGS responses, the correlations are approximately 0.9. The results of these studies indicate that the RGS biomarker can be used as a screening tool for detection of CYP1A1-inducing compounds in tissues, and an estimate of potential human health or ecological risk from ingestion of contaminated organisms. Positive RGS responses can be followed by detailed chemical analyses of PAHs and coplanar PCBs using the same extract.     

The effect of long-term depuration on phase I and phase II biotransformation in mullets (Mugil cephalus) chronically exposed to pollutants in River Douro Estuary, Portugal

Pollutants such polycyclic aromatic hydrocarbons (PAHs) are released into the environment by urban communities and industries and the enzymes that catalyse the biotransformation of pollutants play a key role regarding the accumulation of these compounds in fish species inhabiting these areas. In this study the relationship between phase I (EROD activity) and phase II (GST activity) and PAH metabolites was measured in grey mullet (Mugil cephalus) after capture in the Douro estuary, and after long-term depuration in an unpolluted laboratory environment. The results showed a significant decrease in EROD activity after 1 month and in bile metabolites after 4 months in captivity, with both maintaining reduced levels at 4 and 8 months depuration. Liver GST activity did not showed significant changes. This study provides evidence that Douro estuary waters contain bioavailable PAHs that can be associated with the induction of cytochrome P450, and that mullets have the ability to metabolise and eliminate PAHs.     

Oil well produced water discharges to the North Sea. Part I: comparison of deployed mussels (Mytilus edulis), semi-permeable membrane devices, and the DREAM model predictions to estimate the dispersion of polycyclic aromatic hydrocarbons

The oil companies operating in the Norwegian sector of the North Sea have conducted field studies since the mid-1990s to monitor produced water discharges to the ocean. These studies have been used to refine monitoring methods, and to develop and validate a dispersion and impact assessment model. This paper summarizes monitoring data from surveys conducted in two major oil and gas production areas, and compares the results to concentrations of polycyclic aromatic hydrocarbons (PAH) in surface waters predicted by the dose-related risk and effect assessment model (DREAM). Blue mussels and semi-permeable membrane devices (SPMDs) were deployed in the Ekofisk and Tampen Regions and analyzed for more than 50 PAH. PAH concentrations in ambient seawater were estimated based on the mussels and SPMD concentrations, and compared to model predictions. Surface water total PAH concentrations ranged from 25 to 350 ng/L within 1 km of the platform discharges and reached background levels of 4-8 ng/L within 5-10 km of the discharge; a 100,000-fold dilution of the PAH in the discharge water. The PAH concentrations in surface water, predicted by three methods, compared well for the Ekofisk Region. The model predicted higher concentrations than the field-based methods for parts of the Tampen Region; particularly the most tidally influenced areas. Tidally-mediated fluctuations in PAH concentrations in surface water must be considered because they affect the estimation of PAH concentrations from mussel and SPMD residue data, and the predictions by the DREAM model. Predictions using mussels, SPMDs, and modeling support and complement each other; all are valuable tools for estimating the fate and impact of chemical contaminants in produced water that are discharged to the ocean.     

PAH-biodegradation potential of indigenous microorganisms: evidence from the respiratory activity of surface sediments in the Quanzhou Bay in China

Seven stations were established in the Quanzhou Bay (24.73°-24.96°N, 118.50°-118.70°E) in China on three cruises to determine the concentrations of polycyclic aromatic hydrocarbons (PAHs) and the numbers of PAH-degrading bacteria in surface sediments. Assessing the biodegradation poten- tial of indigenous microorganisms by measuring the respiratory intensity with the addition of PAHs in sediment samples was also one of the aims of this study. The results show that the total PAH concentrations of the sedimen...     

Effects of environmental pollution in caged mussels (Mytilus galloprovincialis)

Biological effects of environmental pollution, mainly related to presence of PAHs, were assessed in mussels Mytilus galloprovincialis caged in Priolo, an anthropogenically-impacted area, and Vendicari, a reference site, both located along the eastern coastline of Sicily (Italy). PAHs concentration and histopathological changes were measured in digestive gland tissues. Expression of cytochrome P4504Y1 (CYP4Y1) and glutathione S-transferase (GST), indicative of xenobiotic detoxification, and activity of catalase (CAT) as oxidative stress index, were evaluated.The results show a direct correlation between the high concentrations of PAHs in digestive glands of mussels from Priolo and the significantly altered activity of phase I (P < 0.001) and phase II (P < 0.0001) biotransformation enzymes, along with increased levels of CAT activity (P < 0.05). These findings show the enhancement of the detoxification and antioxidant defense systems. The mussel caging approach and selected biomarkers demonstrated to be reliable for the assessment of environmental pollution effects on aquatic organisms.     

Phase I and II biotransformation enzymes and polycyclic aromatic hydrocarbons in the Mediterranean mussel (Mytilus galloprovincialis,Lamarck, 1819) collected in front of an oil refinery

The aim of the present study was to investigate the responses of phase I and II biotransformation enzymes and levels of PAHs in the Mediterranean mussel (Mytilus galloprovincialis, Lamarck, 1819) collected from three sites at different distance from an oil refinery. Phase I enzyme activities as NAD(P)H-cyt c red, NADH ferry red, B(a)PMO and phase II as UDPGT, GST were measured in digestive gland while 16 PAHs (US-EPA) in whole soft tissue. An added value to the data obtained in the present study rely on the RDA analysis which showed close correlations between PAHs levels and phase I enzyme activities in mussels collected in front of the refinery. And again a significant spatial correlation between B(a)P levels and NADPH-cyt c red activities was observed using linear models. No differences among sites for B(a)PMO and phase II GST activities were observed, while the application of UDPGT as biomarkers requires further investigation.     

Polycyclic aromatic hydrocarbons in surface sediments of the Zhelin Bay in the South China Sea

This study examined the concentrations of polycyclic aromatic hydrocarbons (PAHs) in surface sediments collected in July 2004 from eight stations in the Zhelin Bay, one of the most important bays for large-scale mariculture in Guangdong Province. Thirteen individual parent PAH compounds were identified using high performance liquid chromatography with UV detection. The overall average concentration of total PAHs was 477.0 ng/g, ranging from 146.1 to 928.8 ng/g. Low molecular mass PAHs with two to three rings (e.g., acenaphthene) were dominant in each sample. The PAH concentration varied among sampling stations, with the highest concentration observed at bay outlets and the lowest found at stations outside the bay. Ratios of low to high molecular mass PAHs and fluoranthene to pyrene were used to determine the origin of PAHs, and results indicated mainly petroleum-derived contamination. Compared with other bays and harbors around the world, the total concentrations of PAHs in surface sediments at the Zhelin Bay are moderate, but this does not exclude the possibility of potential impact on human consumers because some strong carcinogenic PAHs with high molecular mass were found at the station with a nearby caged-fish and oyster farm. Long-term monitoring of PAH contamination in the Zhelin Bay is recommended to reduce the potential toxicological effects on aquatic organisms and humans.     

Polycyclic aromatic hydrocarbon (PAH) burden of mussels (Mytilus sp.) in different marine environments in relation with sediment PAH contamination, and bioavailability

Sediments and mussels (Mytilus edulis, Mytilus galloprovincialis) were sampled in different European coastal environments (Germany, France, Spain) and analysed for their polycyclic aromatic hydrocarbon (PAH) content by Gas Chromatography/Mass Spectrometry (GC-MS). Bioaccumulation factors of individual compounds from the sediment were calculated and discussed according to the compound solubility. The mussels showed different accumulation patterns according to the pollution source they were exposed to (dissolved fraction of PAHs, particulate fraction, petroleum present in the water column). The exposure source also depends on the geographical location of the mussels. In the Mediterranean Sea, the bivalves were mainly exposed to the dissolved fraction of PAHs, while in the Baltic Sea and in the Atlantic Ocean, the PAHs associated to the particles were significant sources.     

The PAH composition of surface sediments from Stagnone coastal lagoon, Marsala (Italy)

This paper examines the presence, distribution, nature and sources of 22 Aromatic Hydrocarbons (PAHs), which are important environmentally and toxicologically, in sediments from the Stagnone coastal lagoon at Marsala (Italy). Analysis was performed by gas chromatography/mass spectrometry (GC/MS) with selected ion monitoring (SIM). The total concentration of polycyclic aromatic hydrocarbons ranged from 72 to 18381 μg/kg of dry matrix. The relative standard deviation (RSD) of the replicates on the concentrations of individual compounds ranged from 5% to 20%. The accuracy of method was estimated by analyzing “blank” samples added of known quantities of analytes and the recover percentage was 88 ± 9%. The detection limit (LOD) of analytical procedure was less than 0.2 μg/kg d.w. for all analytes. The quantification limit (LOQ) of analytical procedure was less than 0.7 μg/kg d.w.The resulting distributions and weight ratios of specific compounds are discussed in terms of sampling location and origin of organic matter. A comparison with other studies of total PAHs suggests that the levels are within the concentration ranges already reported by other authors. From an eco-toxicological point of view, total PAH concentrations at seven out of the eight sites studied represent a relatively clean environment when compared to other sites.Organic matter content and PAH concentrations were found to be correlated and the compounds present in Stagnone sediments were shown to be mainly of pyrolitic origin, while a negligible quantity of PAHs may derive from biogenic sources since all the sediments contain perylene traces. There is no evidence of coal-tar contamination.Cluster analysis was carried out in order to discriminate between different PAH origins.     

Biota: sediment partitioning of aluminium smelter related PAHs and pulp mill related diterpenes by intertidal clams at Kitimat, British Columbia

The question of polycyclic aromatic hydrocarbon (PAH) bioavailability and its relationship to specific PAH sources with different PAH binding characteristics is an important one, because bioavailability drives PAH accumulation in biota and ultimately the biochemical responses to the PAH contaminants. The industrial harbour at Kitimat (British Columbia, Canada) provides an ideal location to study the bioavailability and bioaccumulation of sediment hydrocarbons to low trophic level biota. Samples of soft shell clams (Mya arenaria) and intertidal sediment collected from multiple sites over six years at various distances from an aluminium smelter and a pulp and paper mill were analysed for 106 PAHs, plant diterpenes and other aromatic fraction hydrocarbons. Interpretation using PAH source ratios and multivariate data analysis reveals six principal hydrocarbon sources: PAHs in coke, pitch and emissions from anode combustion from the aluminium smelter, vascular plant terpenes and aromatised terpenes from the pulp and paper mill, petroleum PAHs from shipping and other anthropogenic activities and PAHs from natural plant detritus. Harbour sediments predominantly contain either pitch or pyrogenic PAHs from the smelter, while clams predominantly contain plant derived PAHs and diterpenes from the adjacent pulp mill. PAHs from the smelter have low bioavailability to clams (Biota-Sediment Accumulation Factors; BSAFs <1 for pitch and coke; <10 for anode combustion, decreasing to ∼0.1 for the mass 300 and 302 PAHs), possibly due to binding to pitch or soot carbon matrices. Decreases in PAH isomer ratios between sediments and clams likely reflect a combination of variation in uptake kinetics of petroleum PAHs and compound specific metabolism, with the importance of petroleum PAHs decreasing with increasing molecular weight. Plant derived compounds exhibit little natural bioaccumulation at reference sites, but unsaturated and aromatised diterpenes released from resins by industrial pulping processes are readily accumulated by the clams (BSAFs >500). Thus while most of the smelter associated PAHs in sediments may not be bioavailable to benthic organisms, the plant terpenes (including retene, totarol, ferruginol, manool, dehydroabietane and other plant terpenes that form the chemical defence mechanism of conifers) released by pulp mills are bioavailable and possess demonstrated toxic properties. The large scale release of plant terpenes by some of the many pulp mills located in British Columbia and elsewhere represents a largely undocumented risk to aquatic biota.