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

In order to assess the biological effects of the Prestige oil spill (POS), mussels, Mytilus galloprovincialis, were collected in 22 localities along the North coast of the Iberian Peninsula over 3 years (April 2003-April 2006). Different tissue-level biomarkers including cell type composition (volume density of basophilic cells, Vv(BAS)) in digestive gland epithelium, structural changes of digestive alveoli (mean luminal radius to mean epithelial thickness, MLR/MET) and histopathological alterations (prevalence and intensity) of the digestive gland were analysed. Severe alterations in the general condition of the digestive gland tissue were observed all over the study area up to 2004-2005. High Vv(BAS) values were recorded mainly in Galicia but also to a lesser extent in the Bay of Biscay in 2003-2004. Atrophy of the digestive alveoli, measured in terms of MLR/MET, was detected all along the studied area up to 2006. Inflammatory responses cannot be related to pollution due to the POS: (a) prevalence and intensity of focal hemocytic infiltration were higher in the Bay of Biscay than in Galicia but they did not show a clear temporal trend; (b) high intensities of brown cell aggregates were only sporadically recorded; and (c) granulocytomas were more frequently recorded in the Bay of Biscay than in Galicia and especially in localities (i.e. Arrigunaga) subjected to chronic pollution. Likewise, Marteilia, trematodes, intracellular ciliates, unidentified eosinophilic bodies, R/CLO and Mytilicola did not follow any recognisable pattern that could be associated to the POS. In contrast, high Nematopsis intensities recorded in several localities in 2003 might suggest some response of local interest after the POS (i.e., in combination with particular factors/conditions). More data at a regional scale are needed before histopathology may provide a reliable ecosystem health assessment but the present results suggest that the approach is worthwhile. Overall, although Vv(BAS) returned to reference values by 2004-2005, MLR/MET values indicated that the mussel health condition was affected during the whole study period up to April 2006.     

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.     

Effects of the fuel oil spilled by the Prestige tanker on reproduction parameters of wild mussel populations

The aim of this work was to assess possible effects of the Prestige oil spill on reproduction parameters of mussels along the Galician and Bay of Biscay coast. Studied endpoints included sex ratio, gonad histology and vitellogenin-like proteins using the alkali-labile phosphate (ALP) method. A high prevalence of haemocytic infiltration of follicles and severe oocyte atresia was found in most localities in April 2003. Spawning gonads were observed in most impacted populations in the same sampling. In April 2004 mature small sized follicles were observed. No histopathological changes were observed in April 2005 and 2006, except a high prevalence of necrotic gametes in 6 out of 22 localities in April 2006. Female ALP levels showed high interindividual variability in April 2004, which was reduced in April 2005 and 2006. No xenoestrogenic effects were observed in male mussels. Overall, gamete alterations were detected during 2003-2004 and a recovery trend was observed afterwards.     

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: correlation and multivariate analysis

According to published reports, selected cell and tissue-level biomarkers revealed alterations in the health status of mussels collected after the Prestige oil spill (POS) in Galicia and the Bay of Biscay (2003-2006). Presently, univariate and multivariate analysis provides a comprehensive view of the whole data set. Correlation and principal component analysis (PCA) were performed using biomarkers corresponding to or derived from those data, say: induction, AOX(exp), and inhibition, AOX(eff), of Acyl-CoA oxidase enzyme activity; membrane labilisation period, LP, volume density, Vv(LYS), and surface-to-volume ratio, S/V(LYS), of digestive cell lysosomes; volume density of neutral lipids, Vv(NL); volume density of basophilic cells, Vv(BAS), mean luminal radius to mean epithelial thickness in digestive gland epithelium, MLR/MET; gonad index, GI; cumulative intensity of inflammatory responses, CI(IR) and parasitic infestation, CI(PI). The PCA results were used to classify sampling times and localities by means of hierarchical cluster analysis. Biomarkers were more frequently correlated with naphthalene than with total PAH concentration in mussel tissues. Many biological parameters were correlated with each other in agreement with their involvement in toxic processes or their role in the mussels' response against environmental insult. Naphthalene appears to be the most effective toxic herein, which supports that the reported effects may be mainly due to POS. According to the PCA, 4 groups of biomarkers explained 67.37% variability and the factors that most strongly contributed were S/V(LYS), CI(IR), Vv(BAS) and MLR/MET. These factors were used in the hierarchical cluster analyses carried out. The cluster analysis performed to classify sampling times discriminated 3 significantly different periods after POS: (a) a high affection period (until April-04); (b) the beginning of the recovery; and (c) an advanced recovery status in which geographical variability increased (from April-05 onwards). As regards the clustering of localities, major geographical differences were not detected but three outliers were identified: (a) early and highly impacted localities in Galicia and Bay of Biscay; (b) Agui?o that was characterised by extremely high Vv(BAS) during 2003; and (c) localities that were subjected to persistent chronic pollution.