Integrative sediment quality assessment using a biomarker approach: review of 3 years of field research

Integrated Genomic and Bioinformatics Approaches to Identify Molecular Links between Endocrine Disruptors and Adverse Outcomes

Exposure to Endocrine Disrupting Chemicals (EDC) has been linked with several adverse outcomes. In this review, we examine EDCs that are pervasive in the environment and are of concern in the context of human, animal, and environmental health. We explore the consequences of EDC exposure on aquatic life, terrestrial animals, and humans. We focus on the exploitation of genomics technologies and in particular whole transcriptome sequencing. Genome-wide analyses using RNAseq provides snap shots of cellular, tissue and whole organism transcriptomes under normal physiological and EDC perturbed conditions. A global view of gene expression provides highly valuable information as it uncovers gene families or more specifically, pathways that are affected by EDC exposures, but also reveals those that are unaffected. Hypotheses about genes with unknown functions can also be formed by comparison of their expression levels with genes of known function. Risk assessment strategies leveraging genomic technologies and the development of toxicology databases are explored. Finally, we review how the Adverse Outcome Pathway (AOP) has exploited this high throughput data to provide a framework for toxicology studies.

The use of a Weight-of-Evidence approach to address sediment quality in the Odiel River basin (SW, Spain)

The fluvial systems of the Iberian Pyrite Belt (SW Iberian Peninsula) are affected by acid mine drainage (a lixiviate residue product of mining activities derived from sulfide oxidation). The high acidity and high concentrations of sulfates and metal(loid)s are the main causes of the environmental degradation of the Odiel River basin. The use of weight of evidence approach in areas of the Odiel River basin implies the integration of different lines of evidence (chemistry, toxicity and bioaccumulation) using the freshwater clam Corbicula fluminea as target species. The integration of the results from the application of the different lines of evidence showed that the index of pollution was higher downvalley (Ptriad=12,312), moderate after mining effluent discharges (Ptriad=13.9) and very low where the Odiel River sources (Ptriad=6.31). The multivariate analysis indicated that variables and chemicals were associated with geochemical matrix and background levels (% of fines and toxic metal(loid) concentrations), toxic effects, and metal(loid) bioaccumulation reflecting the geographical distribution of the contamination towards the estuary. Metal(loid) thresholds were calculated for the study area as site-specific values of interim freshwater sediment quality values: As≥171; Cd≥0.48; Co≥8.82; Cr≥38.4; Cu≥451; Ni≥18.4; Pb≥377; Sb≥17.7; Zn≥221mg/kg of freshwater fluvial dry sediment. These results revealed the possibility of using the TEL values proposed by the USEPA and the NOAA for sediments from this site, and proposed lower PEL values for the Iberian Pyrite Belt as result of toxicity effects found in the Asian clam due to the combination of extreme acidity and high metal(loid) concentrations.

Effect of different river flow rates on biomarker responses in common carp (Cyprinus carpio)

The present study investigated effects of different river flow rates on basal activities of selected biomarkers and the occurrence of oxidative stress in the common carp (Cyprinus carpio). Juvenile carp were exposed to different river flow rates (5-120 cm/s) by caging for 3 weeks. After this period, one half of the fish were sacrificed and used for analysis. The other half received a single intraperitoneal injection of 3-methylcholanthrene (3-MC) and after 6 days were sacrificed and used for analysis. In order to investigate whether the physical activity of carp in the environment will influence the condition status of carp, following biomarkers were measured - activities of glutathione S-transferase (GST), catalase (CAT) and ethoxyresorufin-O-deethylase (EROD) and concentration of protein carbonyls (PC). The results showed that different flow rates significantly influenced biochemical biomarkers. The basal activity of GST did not change significantly after exposure to different river flow rates, whereas the activity of CAT increased with increasing river flow rates. The application of 3-MC caused significant increases in GST and CAT activities, but there were no difference between 3-MC control and 3-MC different flow rates. The occurrence of oxidative stress as a result of exposure to increased physical activity, i.e. increased river flow rates, was confirmed by measurement of PC levels - the level of PC increased with increasing river flow rates. Measurement of EROD basal activity showed that at lower river flow rates the EROD activity increased and at higher river flow rates decreased towards control levels demonstrating a close relationship between oxidative stress, PC levels and EROD activity. Obviously, biomarker responses in carp of different condition status can differ substantially. It can be concluded that flow rate may be an important factor in biomonitoring of rivers using biomarkers and since at different locations river water flow rate can vary significantly, the site selection is extremely important for proper design of river biomonitoring studies involving caging.

Impact of dredged urban river sediment on a Saronikos Gulf dumping site (Eastern Mediterranean): sediment toxicity, contaminant levels, and biomarkers in caged mussels

Impacts of chemical contaminants associated with dumping of dredged urban river sediments at a coastal disposal area in Saronikos Gulf (Eastern Mediterranean) were investigated through a combined approach of sediment toxicity testing and active biomonitoring with caged mussels. Chemical analyses of aliphatic hydrocarbons (AHs), polycyclic aromatic hydrocarbons (PAHs), Cu, and Zn in combination with the solid phase Microtox® test were performed on sediments. Concentrations of PAHs, AHs, Cu, and Zn as well as multiple biomarkers of contaminant exposure and/or effects were measured in caged mussels. Sediments in the disposal and neighboring area showed elevated PAHs and AHs concentrations and were characterized as toxic by the solid-phase Microtox® test during and after dumping operations. Biomarker results in the caged mussels indicated sublethal effects mainly during dumping operations, concomitantly with high concentrations of PAHs and AHs in the caged mussel tissues. Cu and Zn concentrations in sediments and caged mussels were generally not elevated except for sediments at the site in the disposal area that received the major amount of dredges. High PAHs and AHs levels as well as sublethal effects in the caged mussels were not persistent after termination of operations. The combined bioassay-biomarker approach proved useful for detecting toxicological impacts of dredged river sediment disposal in sediments and the water column. Nevertheless, further research is needed to evaluate whether sediment toxicity will have long-term effects on benthic communities of the disposal area.

Integration of sediment contamination with multi-biomarker responses in a novel potential bioindicator (Sepia officinalis) for risk assessment in impacted estuaries

For the purpose of biomonitoring, species that combine ecological and commercial importance may provide a link between ecological and human health risk. The common cuttlefish, Sepia officinalis, holds both characteristics in south-western Europe, albeit remaining unsurveyed in ecotoxicological studies. Cuttlefish collected from an impacted estuary in SW Portugal and a reference location off the coast were analysed for a battery of biomarker responses in the digestive gland and gills. The contrast to reference animals revealed that biomarker responses, especially those related to oxidative stress, were consistent with sediment contamination by PAHs, even in a situation that combines complex toxicant mixtures, moderate levels of contamination and high ecotoxicological diversity. However, environmental parameters related to the differences between shore and estuarine habitats should not be overruled. Also, digestive gland metallothionein retained significant specificity to metals even though previous studies in the area with clams and fish failed to trigger a conclusive response. The highest net differences in biomarker responses were detected in the gills, likely indicating higher sensitivity to environmental stressors. Still, the digestive gland responses were overall the most consistent with sediment contamination and effectively differentiated between estuarine industrial- and rural-impacted sites. The results indicate that S. officinalis may be a candidate to meet the European Union's requirements for efficient biomonitoring programmes, with the additional importance of being cosmopolitan, abundant, commercially valuable and combining the molluscan biology that has been granting bivalves their high value for biomonitoring with foraging behaviour, thus better able to reflect anthropogenic stressors impacting a wider area than sedentary organisms. Nevertheless, further investigations in unpolluted sites are needed to better evaluate the background levels of biomarker responses in the species.

Environmental harm assessment of a wastewater discharge from Hammerfest LNG: a study with biomarkers in mussels (Mytilus sp.) and Atlantic cod (Gadus morhua)

Biologically treated wastewater (WW) from the Hammerfest LNG (liquefied natural gas) plant is discharged to the sea. A study using biomarkers in mussels and Atlantic cod was performed to examine whether this discharge meets a zero harmful emission requirement. Caging of mussels close to the outfall and exposure of mussels and fish to WW in the laboratory were conducted, and a suite of contaminant responsive markers was assessed in exposed animals. In mussels the markers included chemical contaminant levels, haemocyte lysosomal instability and nucleus integrity, cellular energy allocation, digestive gland and gonad histopathology and shell-opening behaviour. In fish, biliary PAH metabolites and gill histopathology biomarkers were measured. A consistent cause-effect relationship between WW treatments and markers measured in test animals was not found. The results therefore indicate that the WW emission is unlikely to represent a significant stress factor for the local marine environment under the conditions studied.

Bioavailability and oxidative stress of cadmium to Corbicula fluminea

This work set out to study the effects of cadmium (Cd) in sediments on the antioxidant enzyme activities in the digestive gland of Asian clam Corbicula fluminea and to explore the potential for applying these responses to evaluate the Cd-contaminated sediment. Additionally, diffusive gradients in thin-films (DGT) technique was used to predict the response of its antioxidant defense system. The sediments, collected from Taihu Lake, were spiked with Cd at different concentrations (0.72, 0.91, 1.62, 2.59, 11.2, 20.4 and 40.6 mg kg(-1), dry weight). Asian clam was cultivated for 28 days. Concentrations of Cd in the body of Asian clam had a good relationship with concentrations of Cd in overlying water and sediments, as measured by DGT. Cd affected these biochemical parameters significantly, especially for superoxide (SOD), peroxidase (POD) and glutathione (GSH), which began to show higher sensitivity and have a significant difference in low dosage (0.91 mg Cd kg(-1)) compared with blank. Contents of MDA and MT, which were induced by Cd, increased with the increasing Cd concentration in sediments and reached peak values at 11.2 and 20.4 mg kg(-1), respectively, after 28 days exposure. All of these results suggested that biochemical responses cooperated in detoxifying and maintaining cellular metabolic homeostasis. The R(2) of regression analysis between the contents of MT and the concentrations of Cd measured by DGT, in sediments and soft body were 0.71, 0.94 and 0.88 after 28 days exposure. This suggested that DGT measurement could predict the response of MT. Cd accumulation, GSH and MT were indispensable biomarkers and the MDA content and DGT appeared to be promising biomarkers. The results clearly indicated that Cd could induce oxidative stress in the digestive gland of Asian clam. The combination of biomonitors with DGT can obtain different information about Cd bioavailability and confirm the significance of applying a suite of biomarkers rather than a selective index to assess the sublethal effect. It also offered theoretical methods for the prediction of sediment Cd pollution.

Impact of remobilized contaminants in Mytilus edulis during dredging operations in a harbour area: bioaccumulation and biomarker responses

Dredging operations in harbours are recurrent to maintain accessibility and navigational depths. One of the main environmental risks of these operations is the remobilization of contaminants trapped in the sediments, rendering them more bioavailable to the biota. However, regulatory policies regarding the contamination risk of dredging chiefly apply to the disposal of dredged materials rather than the direct impact of the procedure itself. In order to assess the ecotoxicological risk of harbour dredging operations in a polluted estuary (the Tagus, W Portugal), the present study compared bioaccumulation and biomarker responses in field-deployed mussels before and after the beginning of operations, complemented by sediment characterization and risk analysis based on standardized sediment quality guidelines. The results revealed a very significant increase in genotoxicity and oxidative stress from the beginning of dredging onwards, which was accompanied by increased bioaccumulation of toxicants, especially polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). Overall, the results indicate the importance of surveying the direct impacts of these procedures on local contamination, especially considering these sediments had been previously classified as "trace contaminated", according to normative guidelines, and therefore safe for disposal. This study shows the importance of obtaining both chemical and biological data in standard monitoring procedures and that the remobilization of contaminants by dredging operations may be grossly underestimated, which calls for caution when assessing the impact of these activities even in low to moderately polluted areas.

Application of neutral red retention assay to caged clams (Ruditapes decussatus) and crabs (Carcinus maenas) in the assessment of dredged material

Dredged material management is a key issue for the protection of aquatic environments. The in situ approach using caged bioindicator species has been chosen lately as a new methodology for the assessment of dredged material. In a tier testing approach, neutral red retention (NRR) assay has been applied as a screening tool to detect adverse changes in health status associated with contamination. Nevertheless, to authors' knowledge, little is known about the application and validation of this technique in sediment bioindicator species and under field conditions. Caged Ruditapes decussatus and Carcinus maenas were exposed during 28 days to potentially contaminated sediments at three sites in Algeciras Bay (SW Spain) and one site in Cádiz Bay (SW Spain). Lysosomal membrane stability was measured over time in haemolymph samples of exposed clams and crabs using the NRR assay. Sediment characterization of the study sites was performed in parallel. NRR time did not vary significantly (p > 0.05) over time in organisms from Cádiz Bay. Conversely, significant differences (p < 0.05) in NRR time were found in clams and crabs exposed to sediments from Algeciras Bay, which exhibited a 30-70% decrease in haemocyte lysosome membrane stability compared to day 0. Statistical analysis showed a strong correlation between the drop of haemocyte lysosome membrane stability, in both crabs and clams, and the presence of metals (p < 0.05) and PAHs (p < 0.01) in the studied sediments. The results obtained confirmed the use of NRR assay as a suitable and sensitive method to be used in the assessment of sediment quality using as bioindicator species the clam R. philippinarum and the crab C. maenas.

In situ biomonitoring of caged, juvenile Chinook salmon (Oncorhynchus tshawytscha) in the Lower Duwamish Waterway

Contaminated sediments may have wide-ranging impacts on human and ecological health. A series of in situ caged exposure studies using juvenile Chinook salmon was conducted in the Lower Duwamish Waterway (LDW). Chemical analysis of sediment, water, and fish tissue were completed. Additionally, in 2004, DNA adducts in hepatic and gill tissues were measured. Gills contained significantly higher DNA adducts at stations B2 and B4, prompting further analysis of gills in 2006 and 2007. Fluorescent aromatic compounds (FACs) in bile, and CYP1A1 in hepatic tissue were also measured during 2006 and 2007, respectively. FACs in field-caged fish were comparable or significantly higher than wild-caught fish LDW fish and significantly higher than lab fish after only 8-10 days, demonstrating the equivalency of exposure to that of migrating salmon. Furthermore, selected biomarkers appear to be capable of detecting spikes in contamination between sampling years, emphasizing the need for multiple year data collection.

Biological effects of marine contaminated sediments on Sparus aurata juveniles

Chemical analysis of the compounds present in sediment, although informative, often is not indicative of the downstream biological effects that these contaminants exert on resident aquatic organisms. More direct molecular methods are needed to determine if marine life is affected by exposure to sediments. In this study, we used an aquatic multi-species microarray and q-PCR to investigate the effects on gene expression in juvenile sea bream (Sparus aurata) of two contaminated sediments defined as sediment 1 and 2, respectively, from marine areas in Northern Italy. Both sediments affected gene expression as evidenced by aquatic multi-species microarray analysis and q-PCR. Exposure of S. aurata juveniles to sediment 1 and sediment 2 altered expression of genes that are biomarkers for endocrine disruption. There were differences between the effects of sediment 1 and sediment 2 on gene expression in S. aurata juveniles indicating that the chemicals in the two sediments had different physiological targets. These results suggest that the classification of sediment solely on the basis of specific chemical profiles is inadequate, and not a true indicator of its potential to cause harmful effects. Our data also indicate that integration of physiochemical analysis and bioassays for monitoring the downstream harmful effects on aquatic organisms are required to gain a complete understanding of the effects of sediment on aquatic life.

Assessing sediment hazard through a weight of evidence approach with bioindicator organisms: a practical model to elaborate data from sediment chemistry, bioavailability, biomarkers and ecotoxicological bioassays

Quality assessments are crucial to all activities related to removal and management of sediments. Following a multidisciplinary, weight of evidence approach, a new model is presented here for comprehensive assessment of hazards associated to polluted sediments. The lines of evidence considered were sediment chemistry, assessment of bioavailability, sub-lethal effects on biomarkers, and ecotoxicological bioassays. A conceptual and software-assisted model was developed with logical flow-charts elaborating results from each line of evidence on the basis of several chemical and biological parameters, normative guidelines or scientific evidence; the data are thus summarized into four specific synthetic indices, before their integration into an overall sediment hazard evaluation. This model was validated using European eels (Anguilla anguilla) as the bioindicator species, exposed under laboratory conditions to sediments from an industrial site, and caged under field conditions in two harbour areas. The concentrations of aliphatic hydrocarbons, polycyclic aromatic hydrocarbons and trace metals were much higher in the industrial compared to harbour sediments, and accordingly the bioaccumulation in liver and gills of exposed eels showed marked differences between conditions seen. Among biomarkers, significant variations were observed for cytochrome P450-related responses, oxidative stress biomarkers, lysosomal stability and genotoxic effects; the overall elaboration of these data, as those of standard ecotoxicological bioassays with bacteria, algae and copepods, confirmed a higher level of biological hazard for industrial sediments. Based on comparisons with expert judgment, the model presented efficiently discriminates between the various conditions, both as individual modules and as an integrated final evaluation, and it appears to be a powerful tool to support more complex processes of environmental risk assessment.