Application of a battery of biomarkers in mussel digestive gland to assess long-term effects of the Prestige oil spill in Galicia and Bay of Biscay: tissue-level biomarkers and histopathology

Polycyclic aromatic hydrocarbon body residues and lysosomal membrane destabilization in mussels exposed to the Dubai Star bunker fuel oil (intermediate fuel oil 380) spill in San Francisco Bay

Following the spill of bunker fuel oil (intermediate fuel oil 380, approximately 1500-3000 L) into San Francisco Bay in October 2009, polycyclic aromatic hydrocarbon (PAH) concentrations in mussels from moderately oiled areas increased up to 87 554 ng/g (dry wt) and, 3 mo later, decreased to concentrations found in mussels collected prior to oiling, with a biological half-life of approximately 16 d. Lysosomal membrane destabilization increased in mussels with higher PAH body burdens.

Combined effects of thermal stress and Cd on lysosomal biomarkers and transcription of genes encoding lysosomal enzymes and HSP70 in mussels, Mytilus galloprovincialis

In estuaries and coastal areas, intertidal organisms may be subject to thermal stress resulting from global warming, together with pollution. In the present study, the combined effects of thermal stress and exposure to Cd were investigated in the endo-lysosomal system of digestive cells in mussels, Mytilus galloprovincialis. Mussels were maintained for 24h at 18°C and 26°C seawater temperature in absence and presence of 50 μg Cd/L seawater. Cadmium accumulation in digestive gland tissue, lysosomal structural changes and membrane stability were determined. Semi-quantitative PCR was applied to reveal the changes elicited by the different experimental conditions in hexosaminidase (hex), β-glucuronidase (gusb), cathepsin L (ctsl) and heat shock protein 70 (hsp70) gene transcription levels. Thermal stress provoked lysosomal enlargement whilst Cd-exposure led to fusion of lysosomes. Both thermal stress and Cd-exposure caused lysosomal membrane destabilisation. hex, gusb and ctsl genes but not hsp70 gene were transcriptionally up-regulated as a result of thermal stress. In contrast, all the studied genes were transcriptionally down-regulated in response to Cd-exposure. Cd bioaccumulation was comparable at 18°C and 26°C seawater temperatures but interactions between thermal stress and Cd-exposure were remarkable both in lysosomal biomarkers and in gene transcription. hex, gusb and ctsl genes, reacted to elevated temperature in absence of Cd but not in Cd-exposed mussels. Therefore, thermal stress resulting from global warming might influence the use and interpretation of lysosomal biomarkers in marine pollution monitoring programmes and, vice versa, the presence of pollutants may condition the capacity of mussels to respond against thermal stress in a climate change scenario.

Lysosomal and tissue-level biomarkers in mussels cross-transplanted among four estuaries with different pollution levels

A 3-4 wk cross-transplantation experiment was carried out in order to investigate the sensitivity, rapidity, durability and reversibility of lysosomal and tissue-level biomarkers in the digestive gland of mussels. Four localities in the Basque coast with different levels of chemical pollution and environmental stress were selected. Lysosomal membrane stability (LP) and lysosomal structural changes (VvL; S/VL; NvL) and changes in cell-type composition in digestive gland epithelium (VvBAS) were investigated to determine short (2d) and mid-term (3-4 wk) responses after cross-transplantation. Mussels from Txatxarramendi presented VvBAS<0.1 μm(3)/μm(3) (unstressed) whilst VvBAS>0.12 μm(3)/μm(3) was recorded in mussels from Plentzia (moderate stress) and VvBAS>0.2 μm(3)/μm(3) in Arriluze and Muskiz (high stress). Accordingly, LP<10 min (high stress) was recorded in mussels from Muskiz and Arriluze and LP~15 min (low-to-moderate stress) in those from Plentzia and Txatxarramendi. According to the VvL, S/VL and NvL data, a certain lysosomal enlargement was envisaged in mussels from Arriluze in comparison with those from Txatxarramendi and Plentzia. Mussels from Muskiz exhibited a peculiar endo-lysosomal system made of abundant tiny lysosomes (low VvL and high S/VL and NvL values). Lysosomal and tissue-level biomarkers were responsive after 2d cross-transplantation between the reference and the polluted localities, which indicated that these biomarkers were quickly induced and, to a large extent, reversible. Moreover, the tissue-level biomarker values were maintained during the entire period (3-4 wk) of cross-transplantation, which evidenced the durability of the responsiveness. In contrast, comparisons in the mid-term were unfeasible for lysosomal biomarkers as these exhibited a seasonal winter attenuation resulting from low food availability and low temperatures. In conclusion, lysosomal enlargement and membrane stability and changes in cell-type composition were sensitive, rapid and reversible responses to changes in environmental stress whilst durability of the response could not be demonstrated for lysosomal responses by interferences with the seasonal variability.

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.

Biomarkers and transcription levels of cancer-related genes in cockles Cerastoderma edule from Galicia (NW Spain) with disseminated neoplasia

Disseminated neoplasia (DN) is a pathological condition reported for several species of marine bivalves throughout the world, but its aetiology has not yet been satisfactorily explained. It has been suggested that chemical contamination could be a factor contributing to neoplasia. The aim of the present study was to compare cell and tissue biomarkers and the transcription level of cancer-related genes in cockles (Cerastoderma edule) affected by DN with those of healthy cockles in relation to chemical contaminant burdens. For this, cockles were collected from a natural bed in Cambados (Ria de Arousa, Galicia) in May 2009. The prevalence of DN was 12.36% and 3 degrees of DN severity were distinguished. No significant differences in metal accumulation, non-specific inflammatory responses and parasites were observed between healthy and DN-affected cockles. Lysosomal membrane stability was significantly reduced in cockles affected by DN, which indicates a poorer health condition. Very low frequencies of micronuclei were recorded and no significant differences were detected between DN severity groups. Haemolymph analyses showed a higher frequency of mitotic figures and binucleated cells in cockles affected by moderate and heavy DN than in healthy ones. Neoplastic animals showed significantly higher transcription levels of p53 and ras than healthy cockles and mutational alterations in ras gene sequence were detected. Low concentrations of metals, polycyclic aromatic hydrocarbons, polychlorinated biphenyls and phthalate esters were measured in cockles from Cambados. In conclusion, cockles affected by DN suffer a general stress situation and have altered patterns of cancer-related gene transcription. Further studies are in progress to elucidate mechanisms of carcinogenesis in this species.

Combined use of native and caged mussels to assess biological effects of pollution through the integrative biomarker approach

Native and caged mussels were used in combination for the monitoring of pollution biological effects through an integrative biomarker approach. Mussels (Mytilus galloprovincialis) were deployed in cages in two well-known model localities with different pollution levels in the Basque coast. After 3 weeks caged and native mussels were collected from each site and a suite of effect and exposure biomarkers (from molecular/cellular to organism level) was applied and chemical contaminants (metals, PAHs, PCBs, phthalates and nonylphenol ethoxylates) were analytically determined. Integrative biomarker indices and pollutant indices of tissues were calculated. Several biomarkers used herein responded similarly in native and caged mussels, whereas others exhibited significant differences. Overall, biomarkers in-a-suite depicted site-specific profiles useful for the diagnostic of mussel health status and therefore for ecosystem health assessment in marine pollution biomonitoring. On the other hand, biomarkers and bioaccumulation exhibited different response times, which was especially evident when comparing biomarker and pollutant indices of tissues. The suite of biomarkers was more sensitive after caging (short-term response), whereas tissue pollutant concentrations were more sensitive in native mussels (long-term response). Thus, the combination of native and caged mussels is highly recommended to monitor biological effects of pollution in mussels through the integrative biomarker approach, especially in chronically polluted sites.

Occurrence of zebra mussel parasites: modelling according to contamination in France and the USA

Parasites can be reliable tool in assessing the effects of ecosystem disturbances. However, they can respond in different ways and any changes in assemblages are not easily predictable. Descriptive modelling could be a first step since providing information on the relative importance of a pollutant on parasite occurrence. We chose the zebra mussel, as test organism and twelve sites in France and the United States. Contaminants had not the same impact on microparasite occurrence. Metals enhanced the infection, except zinc associated only with higher prevalence of the commensal ciliate Conchophthirus acuminatus. We should note that Rickettsiales-like organism infection is higher at higher Ni and Cr concentrations. Models indicated also that the most polluted sites were also those with higher rates of co-infections. Therefore, the continuous contamination of freshwater ecosystems implies a significant risk promoting the development of parasites that may affect bivalve populations and other species belonging to their life-cycle.

Marine ecosystem health status assessment through integrative biomarker indices: a comparative study after the Prestige oil spill "Mussel Watch"

Five integrative biomarker indices are compared: Bioeffects Assessment Index (BAI), Health Status Index (HSI), integrated biological response (IBR), ecosystem health condition chart (EHCC) and Integrative Biomarker Index (IBI). They were calculated on the basis of selected biomarker data collected in the framework of the Prestige oil spill (POS) Mussel Watch monitoring (2003-2006) carried out in Galicia and the Bay of Biscay. According to the BAI, the health status of mussels was severely affected by POS and signals of recovery were evidenced in Galicia after April-04 and in Biscay Bay after April-05. The HSI (computed by an expert system) revealed high levels of environmental stress in 2003 and a recovery trend from April-04 to April-05. In July-05, the health status of mussels worsened but in October-05 and April-06 healthy condition was again recorded in almost all localities. IBR/n and IBI indicated that mussel health was severely affected in 2003 and improved from 2004 onwards. EHCC reflected a deleterious environmental condition in 2003 and a recovery trend after April-04, although a healthy ecosystem condition was not achieved in April-06 yet. Whereas BAI and HSI provide a basic indication of the ecosystem health status, star plots accompanying IBR/n and IBI provide complementary information concerning the mechanisms of biological response to environmental insult. Overall, although the integrative indices based on biomarkers show different sensitivity, resolution and informative output, all of them provide coherent information, useful to simplify the interpretation of biological effects of pollution in marine pollution monitoring. Each others' advantages, disadvantages and applicability for ecosystem health assessment are discussed.

Metabolomic investigation of Mytilus galloprovincialis (Lamarck 1819) caged in aquatic environments

Environmental metabolomics was applied to assess the metabolic responses in transplanted mussels to environmental pollution. Specimens of Mytilus galloprovincialis, sedentary filter-feeders, were caged in anthropogenic-impacted and reference sites along the Augusta coastline (Sicily, Italy). Chemical analysis revealed increased levels of PAHs in the digestive gland of mussels from the industrial area compared with control, and marked morphological changes were also observed. Digestive gland metabolic profiles, obtained by 1H NMR spectroscopy and analyzed by multivariate statistics, showed changes in metabolites involved in energy metabolism. Specifically, changes in lactate and acetoacetate could indicate increased anaerobic fermentation and alteration in lipid metabolism, respectively, suggesting that the mussels transplanted to the contaminated field site were suffering from adverse environmental condition. The NMR-based environmental metabolomics applied in this study results thus in it being a useful and effective tool for assessing environmental influences on the health status of aquatic organisms.

Integrated coastal monitoring of a gas processing plant using native and caged mussels

The biological effects of a coastal process water (PW) discharge on native and caged mussels (Mytilus edulis) were assessed. Chemical analyses of mussel tissues and semi permeable membrane devices, along with a suite of biomarkers of different levels of biological complexity were measured. These were lysosomal membrane stability in haemocytes and digestive cells; micronuclei formation in haemocytes; changes in cell-type composition in the digestive gland epithelium; integrity of digestive gland tissue; peroxisome proliferation; and oxidative stress. Additionally the Integrative Biological Response (IBR/n) index was calculated. This integrative biomarker approach distinguished mussels, both native and caged, exhibiting different stress conditions not identified from the contaminant exposure. Mussels exhibiting higher stress responses were found with increased proximity to the PW discharge outlet. However, the biological effects reported could not be entirely attributed to the PW discharge based on the chemicals measured, but were likely due to either other chemicals in the discharge that were not measured, the general impact of the processing plant and or other activities in the local vicinity.

Monitoring the biochemical and cellular responses of marine bivalves during thermal stress by using biomarkers

The present work aimed to study the cellular, biochemical and molecular biomarkers in the digestive glands and hemocytes of Modiolus barbatus and whether there is a hierarchy in their response to thermal stress. We determined a) the neutral red retention assay (NRR) in heamotocytes and b) the lysosomal membrane stability (LMS), the levels of second messenger cAMP, the activity of acetylcholinesterase (AChE) in the digestive glands of Modiolus barbatus after acclimation to 18 °C, 24 °C, 28 °C or 30 °C for 30 days. Moreover, in order to estimate the threshold of temperature inducing expression of stress proteins we determined the levels of Hsp70 and Hsp90 in the digestive glands. Hsps are expressed at lower temperature than those causing reduction in the LMS and NNR times. The reduction in the LMS and NNR times at high temperatures of acclimation might be related to inability of Modiolus barbatus to gain energy from the ingested food.

Application of a battery of biomarkers in mussel digestive gland to assess long-term effects of the Prestige oil spill in Galicia and the Bay of Biscay: lysosomal responses

In order to assess the long-term lysosomal responses to the Prestige oil spill (POS), mussels, Mytilus galloprovincialis, were collected in 22 localities from Galicia and the Bay of Biscay (North Iberian peninsula) in July, and September 2003, April, July, and October 2004-2005 and April 2006. Lysosomal membrane stability (labilisation period, LP) and lysosomal structural changes (lysosomal volume density, Vv(L) and lysosomal surface-to-volume ratio, S/V(L)) were measured as general stress biomarkers. The most remarkable long-term effects after the POS were drastic changes in lysosomal size (lysosomal enlargement) and membrane stability (extremely low LP values) up to April-04. Later on, a recovery trend was envisaged all along the studied area after July-04, albeit membrane stability continued to be below 20 min throughout the studied period up to April-06, which indicates a "distress-to-moderate-stress" condition. Lysosomal Response Index (LRI) revealed that environmental stress was more marked in Galicia than in the Bay of Biscay, mainly in the first sampling year, although a "moderate-to-high-stress" condition persisted until July-05. Overall, although lysosomal size returned to reference values, membrane stability was not fully recovered indicating a stress situation throughout the studied period.