Differences in PAH tolerance between Capitella species: underlying biochemical mechanisms

Microbial Hydrocarbon Degradation in Guaymas Basin-Exploring the Roles and Potential Interactions of Fungi and Sulfate-Reducing Bacteria

Hydrocarbons are degraded by specialized types of bacteria, archaea, and fungi. Their occurrence in marine hydrocarbon seeps and sediments prompted a study of their role and their potential interactions, using the hydrocarbon-rich hydrothermal sediments of Guaymas Basin in the Gulf of California as a model system. This sedimented vent site is characterized by localized hydrothermal circulation that introduces seawater sulfate into methane- and hydrocarbon-rich sediments, and thus selects for diverse hydrocarbon-degrading communities of which methane, alkane- and aromatics-oxidizing sulfate-reducing bacteria and archaea have been especially well-studied. Current molecular and cultivation surveys are detecting diverse fungi in Guaymas Basin hydrothermal sediments, and draw attention to possible fungal-bacterial interactions. In this Hypothesis and Theory article, we report on background, recent results and outcomes, and underlying hypotheses that guide current experiments on this topic in the Edgcomb and Teske labs in 2021, and that we will revisit during our ongoing investigations of bacterial, archaeal, and fungal communities in the deep sedimentary subsurface of Guaymas Basin.

Off-Target Stoichiometric Binding Identified from Toxicogenomics Explains Why Some Species Are More Sensitive than Others to a Widely Used Neonicotinoid

Neonicotinoids are currently licensed for use in 120 countries, making accurate nontarget species sensitivity predictions critical. Unfortunately, such predictions are fraught with uncertainty, as sensitivity is extrapolated from only a few test species and neonicotinoid sensitivities can differ greatly between closely related taxa. Combining classical toxicology with de novo toxicogenomics could greatly improve sensitivity predictions and identify unexpectedly susceptible species. We show that there is a >30-fold differential species sensitivity (DSS) for the neonicotinoid imidacloprid between five earthworm species, a critical nontarget taxon. This variation could not be explained by differential toxicokinetics. Furthermore, comparing key motif expression in subunit genes of the classical nicotinic acetylcholine receptor (nAChR) target predicts only minor differences in the ligand binding domains (LBDs). In contrast, predicted dissimilarities in LBDs do occur in the highly expressed but nonclassical targets, acetylcholine binding proteins (AChBPs). Critically, the predicted AChBP divergence is capable of explaining DSS. We propose that high expression levels of putative nonsynaptic AChBPs with high imidacloprid affinities reduce imidacloprid binding to critical nAChRs involved in vital synaptic neurotransmission. This study provides a clear example of how pragmatic interrogation of key motif expression in complex multisubunit receptors can predict observed DSS, thereby informing sensitivity predictions for essential nontarget species.

Comparative biomarker responses to urban pollution in three polychaete species: Perinereis cultrifera, Diopatra neapolitana, and Marphysa sanguinea from the lagoon of Tunis

Coastal lagoons are among the most vulnerable ecosystems as they are often exposed to different anthropogenic activities. The Polychaetes, which are dominant components in macrobenthic community, are particularly exposed to contamination. The current study was designed to assess and compare the sensitivity of different polychaetes species towards urban pollution. To do this, three polychaete species: Perinereis cultrifera, Diopatra neapolitana, and Marphysa sanguinea, were collected from the Tunis South Lagoon during summer 2013. A set of biomarkers indicative of genotoxicity (DNA damage), biotransformation, and oxidative stress (glutathione S-transferase, GST) as well as immune response (cyclooxygenase activity (COX), lysozyme activity, and nitric oxide level (NOx)), was used. The results revealed that D. neapolitana and P. cultrifera exhibited higher genetic alteration and GST activity and more prominent immune response when compared with M. sanguinea. These findings denote of the higher sensitivity of D. neapolitana and P. cultrifera to urban pollution and suggest their possible use in environmental biomonitoring programs.

Effect of fluoranthene on antioxidative defense in different tissues of Lymantria dispar and Euproctis chrysorrhoea larvae

This study examined the effect of long-term exposure to environmentally relevant concentrations of dietary fluoranthene (6.7 and 67 ng / g dry food weight) on defense mechanisms of the polyphagous forest insects Lymantria dispar L. and Euproctis chrysorrhoea L. The activities and expression of isoforms of superoxide dismutase (SOD) and catalase (CAT), the activities of glutathione S-transferase (GST) and glutathione reductase (GR), and total glutathione content (GSH) were determined in the whole midgut and midgut tissue, while SOD and CAT activities were assessed in hemolymph of the larvae. The results showed significant changes of enzyme activities, with more pronounced responses in larval midgut tissues, and between-species differences in patterns of response. Significantly increased activity of SOD was recorded in the whole midgut and midgut tissue of L. dispar larvae, as well as in midgut tissue of E. chrysorrhoea larvae. Fluoranthene increased CAT activity in midgut tissue of L. dispar larvae, and in the whole midgut and midgut tissue of E. chrysorrhoea larvae. Different expression patterns were detected for enzyme isoforms in tissues of larvae exposed to dietary fluoranthene. Total GSH content and GST activity increased in E. chrysorrhoea larval midgut tissue. Significantly decreased SOD activity in hemolymph of L. dispar larvae, and opposite changes in CAT activity were recorded in the hemolymph of larvae of two insect species. The tissue-specific responses of enzymes to dietary fluoranthene, recorded in each species, enabled the larvae to overcome the pollutant induced oxidative stress, and suggest further assessment of their possible use as early-warning signals of environmental pollution.

Unraveling the performance of the benthic index AMBI in a subtropical bay: The effects of data transformations and exclusion of low-reliability sites

We investigated the relationship between the AMBI index and different contamination proxies in an urbanized bay in South America (SE Brazil), and the effect of (a) abundance data transformation and (b) exclusion of low-reliability sites (high SD; low N) on the index' performance. Poor ecological quality and opportunistic species were related to an increase in contaminants concentrations and mud content. Good ecological status and sensitive species (EG I) were mainly related to increased hydrodynamics. Data transformation caused minimal changes to the overall relationships, but exclusion of low-reliability sites improved the relationship between ecological groups and contamination proxies. Our results show that AMBI is robust in detecting effects of different contaminants in the area and reinforce the importance of the index as a tool for coastal management, but local joint efforts are needed to improve and adjust local species classification in ecological groups to improve the index' performance.

Metal residues, histopathology and presence of parasites in the liver and gills of fourhorn sculpin (Myoxocephalus quadricornis) and shorthorn sculpin (Myoxocephalus scorpius) near a former lead-zinc mine in East Greenland

Fourhorn sculpins (Myoxocephalus quadricornis) and shorthorn sculpins (Myoxocephalus scorpius) have been considered suitable local bioindicators for environmental monitoring studies in the Arctic. Because these species share many characteristics, data from the two species have previously been pooled when assessing marine metal contamination. A chemical and histological study was conducted on fourhorn and shorthorn sculpins collected around a contaminated lead-zinc mine at East Greenland to investigate whether there were any differences in the residues of metals, histopathology and parasites in liver and gills between the two sculpin species. The results demonstrated that concentrations of copper (Cu), zinc (Zn), mercury (Hg) and lead (Pb) were significantly higher in the fourhorn sculpins (p<0.001) while there were no significant differences for arsenic (As) or cadmium (Cd). Furthermore, density of blood vessel fibrosis (p=0.028), prevalence and density of chondroplasia (p=0.002 and p=0.005, respectively), number of mucin-containing mucous cells (p<0.001) and chloride cells (p<0.001) and mean intensity of colonial Peritricha (p<0.001) were significantly higher in fourhorn sculpin. Based on these results we suggest that pooling the two species when conducting environmental assessments is not recommended as it can lead to incorrect conclusions. We propose that a larger study investigating the biological effects of zinc-lead mining in Greenland is needed.

Cu/Zn superoxide dismutase (SOD) and catalase (CAT) response to crude oil exposure in the polychaete Perinereis aibuhitensis

Cu/Zn superoxide dismutase (SOD) and catalase (CAT) cDNAs from the polychaete Perinereis aibuhitensis were cloned and characterized in order to investigate the relationship between crude oil exposure and stress response in this worm. The full length of PaSOD was 870 bp and PaCAT was 1967 bp encoding 150 and 506 amino acids, respectively. Gene expression and enzyme activity of Cu/Zn SOD and CAT in response to crude oil contaminated soil (500, 1500, and 3000 mg/kg) were measured. The results showed that expression of the CAT gene and enzyme activity in P. aibuhitensis was positively correlated to the concentration of crude oil and reached a maximum at 15 days of exposure to 3000 mg/kg crude oil. The expression of the SOD gene and enzyme activity of SOD in P. aibuhitensis also increased during exposure to crude oil and reached a maximum at 10 days of exposure to 3000 mg/kg crude oil. These results indicated that SOD and CAT are important for maintaining the balance of cellular metabolism and protecting P. aibuhitensis from crude oil toxicity.

Evaluation of bioremediation potential of three benthic annelids in organically polluted marine sediment

This study aimed to evaluate the possible remedial effects of three marine benthic annelids on organically polluted sediments from the waters of Hatsukaichi Marina, Hiroshima, Japan. Two polychaetes, Perinereis nuntia and Capitella cf. teleta, and an oligochaete, Thalassodrilides sp., were incubated in sediments for 50 days. Their effects on physicochemical properties such as organic matter (loss on ignition), redox potential (Eh), acid volatile sulfides (AVS), and degradation of polycyclic aromatic hydrocarbons (PAHs) were assessed. The polychaetes P. nuntia and C. cf. teleta significantly increased Eh level and decreased AVS level compared with the oligochaete Thalassodrilides sp. and control (without benthic organisms). Total PAH concentration significantly decreased from the initial level with all three groups; Thalassodrilides sp. had a marked ability to reduce PAHs in sediment. These results indicate that benthic organisms have species-specific remediation properties and ecological functions in organically polluted sediments.

Accumulation and effects of sediment-associated silver nanoparticles to sediment-dwelling invertebrates

Sediment is increasingly recognized as the major sink for contaminants including nanoparticles (NPs). Thus, sediment-living organisms are especially susceptible to NP exposure. Studies of the fate and effects of NPs in the sediment matrix are still in their infancy, and data from such studies are in high demand. Here, we examine the effects of exposure to sediment mixed with either aqueous Ag (administered as AgNO3) or Ag NPs (13nm, citrate-capped) at a nominal exposure concentration of 100μg Ag/g dry weight sediment on four benthic invertebrates: two clones of the gastropod Potamopyrgus antipodarum (clones A and B) and two polychaete species (Capitella teleta, Capitella sp. S). Our results show that both species sensitivity and Ag form (aqueous Ag, Ag NPs) play a role in bioaccumulation and effects. Following two weeks of exposure, both clones of P. antipodarum were found to be insensitive towards both Ag forms (generally low Ag accumulation, no toxicity). In contrast, the two Capitella species varied widely with respect to Ag uptake and observed toxicity. Capitella sp. S was adversely affected by both aqueous Ag (mortality) and Ag NPs (growth), whereas C. teleta was not affected by either Ag form. For neither polychaete species was the observed toxicity directly related to bioaccumulation. Therefore, future nano-ecotoxicological research should focus on understanding differences in uptake and handling mechanisms among species and the relationship between bioaccumulation and toxicity.

The Cytochrome P450 superfamily complement (CYPome) in the annelid Capitella teleta

The Cytochrome P450 super family (CYP) is responsible for a wide range of functions in metazoans, having roles in both exogenous and endogenous substrate metabolism. Annelids are known to metabolize polycyclic aromatic hydrocarbons (PAHs) and produce estrogen. CYPs are postulated to be key enzymes in these processes in annelids. In this study, the CYP complement (CYPome) of the annelid Capitella teleta has been robustly identified and annotated with the genome assembly available. Phylogenetic analyses were performed to understand the evolutionary relationships between CYPs in C. teleta and other species. Predictions of which CYPs are potentially involved in both PAH metabolism and steroidogensis were made based on phylogeny. Annotation of 84 full length and 12 partial CYP sequences predicted a total of 96 functional CYPs in C. teleta. A further 13 CYP fragments were found but these may be pseudogenes. The C. teleta CYPome contained 24 novel CYP families and seven novel CYP subfamilies within existing families. A phylogenetic analysis identified that the C. teleta sequences were found in 9 of the 11 metazoan CYP clans. Two CYPs, CYP3071A1 and CYP3072A1, did not cluster with any metazoan CYP clans. We found xenobiotic response elements (XREs) upstream of C. teleta CYPs related to vertebrate CYP1 (CYP3060A1, CYP3061A1) and from families with reported transcriptional upregulation in response to PAH exposure (CYP4, CYP331). C. teleta had a CYP51A1 with ∼65% identity to vertebrate CYP51A1 sequences and has been predicted to have lanosterol 14 α-demethylase activity. CYP376A1, CYP3068A1, CYP3069A1, and CYP3070A1 were the most appropriate candidates for steroidogenesis genes based on their phylogeny and warrant further analyses, though no specific aromatase (estrogen synthesis) candidates were found. Presence of XREs upstream of C. teleta CYPs may indicate a functional aryl hydrocarbon receptor in C. teleta and candidate CYPs for studies of PAH metabolism.

Effects of Barcelona harbor sediments in biological responses of the polychaete Capitella teleta

Marine ecosystems are increasingly exposed to a multitude of anthropogenic contaminants. Harbor environments are permanently subjected to such contaminants and bottom sediments are considered as the final repository. Filter-feeding and burrowing organisms, such as some polychaete communities, are among the most exposed organisms. This study aimed to assess the toxicity of Barcelona harbor sediments to the polychaete Capitella teleta by assessing and linking individual-level responses such as body weight (growth) and egestion rate (feeding) with subcellular-level responses including antioxidant (catalase and superoxide dismutase) and neurotransmission related (acetyl cholinesterase) enzyme activities. Sediments were collected from three different locations of the Barcelona (Spain) harbor with a positive gradient of metallic and organochlorine pollution from the mouth of the harbor towards the innermost zone. Sub-cellular and individual behavior of C. teleta exposed to Barcelona harbor sediments allowed the discrimination of toxic responses across sediments. Behavior responses were better correlated to chemical contamination than those of biomarkers. Harbor sediments produced neurotoxicity, promoted oxidative stress and reduced egestion and growth rates in exposed worms. These results indicate that biological responses of C. teleta worm can be used as early-warning tools to assess pollution effects on marine soft-bottom macrobenthonic communities.

Detecting benthic community responses to pollution in estuaries: a field mesocosm approach

Biological stress responses in individuals are used as indicators of pollution in aquatic ecosystems, but detecting ecologically relevant responses in whole communities remains a challenge. We developed an experimental approach to detect the effects of pollution on estuarine communities using field-based mesocosms. Mesocosms containing defaunated sediments from four estuaries in southeastern Australia that varied in sediment contamination were transplanted and buried in sediments of the same four estuaries for six weeks. Mesocosm sediment properties and metal concentrations remained representative of their source locations. In each estuary, fauna communities associated with sediments derived from the site with the highest metal concentrations were significantly different from other communities. This pattern was evident for some of the individual taxa, in particular the polychaete Capitella sp. Consistent responses across estuaries suggest numbers of individuals, and especially Capitella sp., could be used to identify contaminated sediments in estuaries with similar fauna and site characteristics.

Subcellular distribution of fluoranthene in Chlorella vulgaris with the presence of cetyltrimethylammonium chloride

This study explored the possible mechanism of the joint toxicity of binary mixtures of cetyltrimethylammonium chloride (CTAC) and fluoranthene (Flu) to the green alga Chlorella vulgaris by examining the subcellular distribution of Flu within the alga. The joint action of CTAC (100 μg L(-1)) and Flu (0-200 μg L(-1)) on the algae changed from a synergetic effect (0-50 μg L(-1)) to an antagonistic effect (50-200 μg L(-1)) with an increase of the Flu concentration. The Flu uptake was enhanced by the presence of CTAC through the intracellular detection of Flu. Furthermore, the highest amount of Flu bound to the cytosol, whereas the least amount bound to the cellular debris when synergistic effect was observed at 2.5 μg L(-1) Flu. However, the highest amount of Flu bound to the cellular debris, whereas the least amount bound to the organelles when antagonistic effect was displayed at 200 μg L(-1) Flu. The different subcellular distribution of Flu may affect the uptake of the highly toxic CTAC by the algae in the binary mixture, and consequently lead to a different level of CTAC toxicity. The abovementioned results indicate that the subcellular distribution of chemicals can be used to elucidate possible mechanisms for the joint toxicity of their binary mixtures to aquatic organisms.

Fate and effects of acetyl cedrene in sediments inhabited by different densities of the deposit feeder, Capitella teleta

Fragrance materials, such as acetyl cedrene (AC), are of environmental concern because they are continuously released to aquatic systems down the drain. In the present study, Capitella teleta (formerly Capitella capitata species I) was exposed to AC-amended sediment at two population densities corresponding to 44,000 and 88,000 worms/m(2). The fate of AC in systems with worms was compared to that in identical systems without worms. We examined the toxicity of AC on worm survival, growth, and feeding rate, and quantified the fate of AC in exposure systems by mass balance. Worm survival was close to 100% in all treatments. Acetyl cedrene had some positive effects on worm growth, but not feeding, whereas density had negative effects on both growth and feeding rates. After 14 d, the sediment concentration of AC was reduced by 88 to 99% in the presence of worms, whereas sediment AC concentration was reduced by 13 to 31% or less in the absence of worms. Acetyl cedrene was detected in fecal pellets, at low concentrations compared to the initial concentration in the sediment, but not in worm tissue, suggesting that ingested AC is bioavailable to Capitella teleta and that worms can biotransform sediment-associated AC effectively.

Estimating chemical biotransformation rates from food web concentrations

Biotransformation is widely recognized as the most important and most uncertain determinant of bioaccumulation. A step-wise method for estimating organism-specific biotransformation half-lives from field observations and using established food web modeling is developed. As a proof of concept, the method is applied to the case of nine polycyclic aromatic hydrocarbons (PAHs) in a well-studied food web in Bohai Bay, China. The estimated half-lives are in good agreement with the existing literature. The proposed biotransformation estimation method, through data mining, for sufficiently defined ecosystems, may greatly reduce the necessary animal testing involved in chemical assessments by providing useful guidance to experimentalists and regulators.

Inhibition of pyrene biotransformation by piperonyl butoxide and identification of two pyrene derivatives in Lumbriculus variegatus (Oligochaeta)

Using the freshwater annelid Lumbriculus variegatus (Oligochaeta), the presence of cytochrome P450 (CYP) isozymes was investigated by analyzing metabolites of the polycyclic aromatic hydrocarbon (PAH) pyrene in treatments with and without the CYP inhibitor piperonyl butoxide (PBO). The results show a low biotransformation capability of L. variegatus (7% of total pyrene body burden as metabolites at 168 h). Addition of PBO resulted in a significant reduction of metabolites, suggesting the presence of a CYP in L. variegatus. Besides 1-hydroxypyrene, three peaks representing unknown metabolites were detected in LC-FLD (liquid chromatography with fluorescence detection) chromatograms of L. variegatus. Deconjugations showed that sulfonation and glucosidation are involved in the formation of these unknowns. Further studies with the time of flight mass analyzer provided the identification of the glucose-sulfate conjugate of 1-hydroxypyrene. The same metabolites were detected in the solvent-nonextractable fraction by incubation of the tissue residues with proteinase K, suggesting that part of these metabolites are bound to proteins. Overall, the slow biotransformation of pyrene by L. variegatus (involving CYP) supports the use of this species in standard bioaccumulation tests; however, the tissue-bound metabolite fraction described in the current study deserves further investigation for its toxicity and availability to upper trophic levels through diet.

Characteristics of immune-competent amoebocytes non-invasively retrieved from populations of the sentinel earthworm Lumbricus rubellus (Annelida; Oligochaeta; Lumbricidae) inhabiting metal polluted field soils

Lumbricus rubellus is a cosmopolitan earthworm devoid of riboflavin-storing eleocytes; its immune competent coelomocytes are predominantly amoebocytes. Our aim was to determine whether amoebocyte cytometrics in L. rubellus are robust biomarkers for innate immunological responses to environmental pollutants. Investigations were conducted on populations inhabiting three unpolluted and five metalliferous (mainly Pb+Zn+Cd) habitats in the UK and Poland. Inter-population differences in worm mass and amoebocyte numbers did not consistently reflect soil or tissue metal concentrations. Flow cytometry indicated that autofluorescence of the amoebocytes differs between cells from the unpolluted and metal-polluted worms, and pinocytosis of neutral red by amoebocytes was lower (especially at 15 versus 60 min incubation) in worms from the polluted Poland site compared with the reference population. To conclude, amoebocyte cytometrics and functionality are potentially useful for environmental diagnostics; deployment is contingent on better understanding potential confounders.

Transcriptomic underpinning of toxicant-mediated physiological function alterations in three terrestrial invertebrate taxa: a review

Diverse anthropogenic activities often lead to the accumulation of inorganic and organic residues in topsoils. Biota living in close contact with contaminated soils may experience stress at different levels of biological organisation throughout the continuum from the molecular-genetic to ecological and community levels. To date, the relationship between changes at the molecular (mRNA expression) and biochemical/physiological levels evoked by exposures to chemical compounds has been partially established in a limited number of terrestrial invertebrate species. Recently, the advent of a family of transcriptomic tools (e.g. Real-time PCR, Subtractive Suppressive Hybridization, Expressed Sequence Tag sequencing, pyro-sequencing technologies, Microarray chips), together with supporting informatic and statistical procedures, have permitted the robust analyses of global gene expression changes within an ecotoxicological context. This review focuses on how transcriptomics is enlightening our understanding of the molecular-genetic responses of three contrasting terrestrial macroinvertebrate taxa (nematodes, earthworms, and springtails) to inorganics, organics, and agrochemicals.

Molecular genetic differentiation in earthworms inhabiting a heterogeneous Pb-polluted landscape

A Pb-mine site situated on acidic soil, but comprising of Ca-enriched islands around derelict buildings was used to study the spatial pattern of genetic diversity in Lumbricus rubellus. Two distinct genetic lineages ('A' and 'B'), differentiated at both the mitochondrial (mtDNA COII) and nuclear level (AFLPs) were revealed with a mean inter-lineage mtDNA sequence divergence of approximately 13%, indicative of a cryptic species complex. AFLP analysis indicates that lineage A individuals within one central 'ecological island' site are uniquely clustered, with little genetic overlap with lineage A individuals at the two peripheral sites. FTIR microspectroscopy of Pb-sequestering chloragocytes revealed different phosphate profiles in residents of adjacent acidic and calcareous islands. Bioinformatics found over-representation of Ca pathway genes in EST(Pb) libraries. Subsequent sequencing of a Ca-transport gene, SERCA, revealed mutations in the protein's cytosolic domain. We recommend the mandatory genotyping of all individuals prior to field-based ecotoxicological assays, particularly those using discriminating genomic technologies.

A multibiomarker approach using the polychaete Arenicola marina to assess oil-contaminated sediments

BACKGROUND, AIM AND SCOPE

Marine and coastal sediments can accumulate substantial concentrations of metals and hydrocarbons, yet the consequences of this contamination for exposed biota in situ can be difficult to establish. Here, we examine the hypothesis that exposure to contaminated sediments can lead to detrimental effects in sediment-dwelling species. The combination of chemical and biological assessment allows the identification of the impact of chemical contamination, and their use as assessment tools is becoming increasingly important.

MATERIALS AND METHODS

The study was applied to marine sediments from the Bay of Algeciras (S Spain) impacted by multiple, low-level contaminant inputs, and the Galician Coast (NW Spain), historically impacted by an oil spill (Prestige 2002), with two reference sites selected in UK and Spain. The common lugworm Arenicola marina was exposed in the laboratory for 14 days to the marine sediments, and a suite of biomarkers of sublethal toxicity was combined with analytical chemistry to test for relationships between sediment contamination and effect.

RESULTS

Moderate to strong correlations between organics, metals, and biological responses were observed, with DNA damage as measured using the Comet assay forming the largest contribution toward the observed differences (p < 0.05). The responses of worms from sites experiencing different contamination loads were clearly distinguishable.

DISCUSSION

We show how a combination of multibiomarkers with analytical chemistry can be used to investigate the toxicity of marine sediments, enabling the differentiation of sites showing different types of contamination. There are clear relationships in sublethal assays that can be related to the putative mode of toxicity of the contaminants.

CONCLUSIONS

The use of A. marina in this way provides a sensitive, holistic approach to sediment toxicity assessment, enabling comparisons between oil-polluted sites to be quantified.

RECOMMENDATIONS AND PERSPECTIVES

These tools provide a relatively simple, rapid, and economic way to test the environmental status of oil-contaminated sediment.

Effects of black carbon on pyrethroid availability in sediment

Pyrethroids are widely used synthetic insecticides with the characteristics of high hydrophobicity and broad-spectrum aquatic toxicity. Many studies indicate that black carbon (BC) plays an important role in the bioavailability of hydrophobic compounds such as polycyclic aromatic hydrocarbons and polychlorinated biphenyls in soils and sediments. However, the effect of BC on bioavailability of other compounds such as pyrethroids in sediments is less known. In this study, we simultaneously measured pyrethroid uptake into polydimethylsiloxane (PDMS) fibers and 24 h bioaccumulation in Chironomus tentans in a sediment amended with a charcoal at different rates. There were significant negative correlations between the accumulation of pyrethroids in PDMS fibers (C(PDMS)) and the charcoal level in sediment. When the charcoal content was increased from 0 to 1.0%, C(PDMS) decreased by 5.7-9.1%. Amendment of 1.5% charcoal to the original sediment decreased biota sediment accumulation factor (BSAF) of (14)C-permethrin in C. tentans from 2.8 to 1.7. The effect of charcoal was further found to be similar for the different subcellular fractions of C. tentans, including cell debris, organelles and proteins, and granules. The overall effect of charcoal on pyrethroid availability, however, was modest, and adsorption of pyrethroids on pure charcoal was found to be similar to that on sediment organic carbon. The relatively weak sorption on charcoal was likely due to the large molecular weight and sizes of pyrethroids, which might hinder their diffusion into charcoal nanopores.

Using the polychaete Arenicola marina to determine toxicity and bioaccumulation of PAHS bound to sediments

The present study was conducted to evaluate a sediment toxicity and bioavailability test with the polychaete Arenicola marina as a potential tool to assess sediments contaminated by oil spills. A bioassay using the lugworm Arenicola marina was carried out in order to determine toxicity and bioaccumulation associated with the contaminants present in the fuel oil extracted from a sank tanker. After 10 and 21 days of exposure to sediments with different proportions of fuel oil (0.5, 1, 2, 4 and 8%) polychaetes were sampled to determine the mortality and the levels of individual PAHs in the organisms. During the experiment, mortality was recorded and the concentration (percentage of fuel oil) that provokes the mortality of the 50% of the Arenicola marina population exposed was calculated for both sampling dates (LC50(10) = 6.4%; LC50(21) = 2.4%). Bioaccumulation was mainly produced for fluoranthene, pyrene, benzo(b)fluoranthene and benzo(k)fluoranthene, whereas phenantrene and anthracene where initially accumulated and then metabolized. The results obtained in the present study suggest Arenicola marina can be a suitable species for assessing PAHs toxicity and bioaccumulation as part of oil spill management.

Biotransformation of polycyclic aromatic hydrocarbons in marine polychaetes

Deposit-feeding polychaetes constitute the dominant macrofauna in marine environments that tend to be depositional centers for organic matter and contaminants. Polychaetes are known to accumulate polycyclic aromatic hydrocarbons (PAHs) from both particulate and dissolved phases but less is known about the mechanisms underlying elimination of accumulated PAHs. An important pathway of elimination is through biotransformation which results in increased aqueous solubility of the otherwise hydrophobic PAHs. Biotransformation in marine polychaetes proceeds in a two phased process similar to those well studied in vertebrates, phase I enzymes belonging to the Cytochrome P450 (CYP) enzyme family, along with a few phase II enzymes have been identified in marine polychaetes. In this review we aim at highlighting advances in the mechanistic understanding of PAH biotransformation in marine polychaetes by including data obtained using analytical chemistry and molecular techniques. In marine polychaetes induction of CYP enzyme activity after exposure to PAHs and the mechanism behind this is currently not well established. Conflicting results regarding the inducibility of CYP enzymes from polychaetes have led to the suggestion that induction in polychaetes is mediated through a different mechanistic pathway, which is corroborated by the apparent lack of an AhR homologous in marine polychaetes. Also, none of the currently identified CYP genes from marine polychaetes are isoforms of those regulated by the AhR in vertebrates. Relatively few studies of phase II enzymes in marine polychaetes are currently available and most of these studies have not measured the activity of specific phase II enzymes and identified phase II metabolites but used an extraction technique only allowing determination of the overall amount of phase II metabolites. Studies in insects and various marine invertebrates suggest that in invertebrates, enzymes in the important phase II enzyme family, UDP-glucuronosyl transferases primarily use glucoside as co-substrate as opposed to the vertebrate cosubstrate glucuronic acid. Recent studies in marine polychaetes have however identified glucuronidation of PAHs indicating no mechanistic difference in co-substrate preference among UDP-glucuronosyl transferases between vertebrates and marine polychaetes but it might suggest a mechanistic difference between marine polychaetes and insects.

The determination of earthworm species sensitivity differences to cadmium genotoxicity using the comet assay

The concept of species sensitivity differences is important in ecotoxicology and environmental risk assessment, but testing usually focuses on lethality of toxicants. The effects on the suborganismal level are mostly ignored; therefore, the present study assessed a biomarker of genotoxicity (the alkaline comet assay) to compare species sensitivities. Five earthworm species (Amynthas diffringens, Aporrectodea caliginosa, Dendrodrilus rubidus, Eisenia fetida and Microchaetus benhami) were exposed for 48 h to sublethal concentrations of cadmium sulphate in reconstituted soil water and DNA integrity was evaluated with the parameter Tail DNA %. Significant amounts of DNA damage were detected in three (A. caliginosa, D. rubidus and E. fetida) species. E. fetida exhibited the highest level of DNA damage, although D. rubidus showed the highest increase (3-fold) in DNA damage from the control. All exposed earthworms accumulated Cd, although body loads did not correspond with DNA damage levels; most of the Cd was probably sequestrated and rendered harmless.

Influence of biotransformation on trophic transfer of the PAH, fluoranthene

The persistence of polycyclic aromatic hydrocarbons (PAHs) in marine sediments may be influenced by benthic invertebrate bioturbation. Through processes such as deposit-feeding and enhancement of microbial metabolic activity PAHs may be remobilized from the sediment compartment, and either transferred to organisms at higher trophic levels or to the overlying water column, both processes inevitably changing the bioavailability of the PAH. Accumulation of contaminants from one level in the food chain to the next depends on feeding rate and assimilation efficiency, two factors that basically vary with food quality and contaminant type. Though it is generally believed that pre-consumptive biotransformation will reduce bioavailability due to the more polar nature of the metabolites compared to the unchanged parent compound, theoretically the decrease in lipophilicity will increase the sediment/food desorption rate in the intestine, and some metabolites will still be lipophilic enough to be absorbed by passive diffusion. We examined the trophic transfer of the PAH, fluoranthene from two closely related polychaete species (i.e., Capitella sp. I and Capitella sp. S), differing in their biotransformation ability, to the predatory polychaete, Nereis virens. We found that N. virens fed the biotransforming species, Capitella sp. I, accumulated significantly more Flu equivalents compared to worms fed Capitella sp. S, which have a very limited biotransformation ability. The dose-specific increase in N. virens intestinal Flu concentration was approximately twice as high in worms fed Capitella sp. I (equation: gut content=7.3 x dose-3.9) compared to worms fed Capitella sp. S (equation: gut content=3.2 x dose+0.6). In addition, we measured DNA damage, using the comet assay, in N. virens intestinal cells after feeding with the two prey species. We did not detect DNA damage above 'background' levels for worms fed either of the two Capitella species, possibly due to relatively low intestinal Flu concentrations in N. virens. Our results indicate that accumulation of PAHs by infaunal organisms may play an important role in the transfer of this type of contaminant to higher trophic levels. Moreover, we observed differences in transfer potential between parent compounds and their respective metabolites, which may influence the fate of these compounds in marine ecosystems. However, from the present study it cannot be concluded whether differences in biotransformation ability among prey species can lead to different effects in their predators.