Browsing by Author "Martins, M."
Now showing 1 - 4 of 4
Results Per Page
Sort Options
- Assessment of sediment contamination in an impacted estuary: differential effects and adaptations of sentinel organisms and implications for biomonitoringPublication . Costa, Pedro M.; Gonçalves, C.; Martins, M.; Rodrigo, Ana; Carreira, S.; Costa, Maria Helena; Caeiro, SandraEstuarine pollution is reflected in the concentration of toxicants in sediments, depending on their geochemical properties, since sediments trap substances from the water column, either dissolved or bound to suspended matter. However, determining risk of sediment contaminants to biota has many constraints. For such reason, integrative approaches are keystone. Taking the Sado estuary (SW Portugal) as a case study, contrasted to a reference estuary (the Mira) within the same geographical location, the present study aimed at integrating sediment contamination with the effects and responses to pollutants in distinct benthic organisms with commercial and ecological value.
- Ecological risk assessment of impacted estuarine areas: integratingPublication . Gonçalves, Cátia; Martins, M.; Costa, Maria Helena; Caeiro, Sandra; Costa, Pedro M.The analysis of multiple biomarker responses is nowadays recognized as a valuable tool to circumvent potential confounding factors affecting biomonitoring studies and allows a better understanding of the mechanisms underlying exposure to natural mixtures of toxicants. For the purpose of an environmental risk assessment (ERA) in an impacted estuary in SW Europe (the Sado, Portugal), juvenile Solea senegalensis from commercial fishing areas were surveyed for histopathological liver alterations and biochemical biomarkers. Although the findings revealed moderate differences in the patterns of histopathological traits between urban/industrial- and agricultural-influenced areas within the same estuary, no significant distinction was found between the cumulative alterations in animals from the two sites. The overall level of histopathological injury was low and severe traits like neoplasms or preneoplastic foci were absent. While metallothionein induction and lipid peroxidation could relate to histopathological condition indices, the activity of anti-oxidant enzymes appeared to be impaired in animals collected off the estuary's heavy-industry belt (the most contaminated site), which may partially explain some degree of hepatic integrity loss. Overall, the results are consistent with low-moderate contamination of the estuary and indicate that oxidative stress is the most important factor accounting for differences between sites. The study highlights the need of integrating multiple biomarkers when multiple environmental stressors are involved and the advantages of surveying toxicity effects in fieldcollected, foraging, organisms.
- Ecotoxicological heterogeneity in transitional coastal habitatsPublication . Carreira, S.; Costa, Pedro M.; Martins, M.; Lobo, J.; Costa, Maria Helena; Caeiro, SandraTransitional waterbodies, such as estuaries, are highly diversified environments with respect to ecology, geophysics, and nature of anthropogenic impacts. This spatial heterogeneity may pose important constraints when developing monitoring programmes for aquatic pollution. The present study compared three distinct coastal ecosystems located in Southern Portugal (subjected to different anthropogenic stressors), namely, two estuaries and a coastal lagoon, through the characterisation of sediment contamination and a biomarker approach to an important commercial clam (Ruditapes decussatus) obtained from local fishing grounds. The results showed high heterogeneity of sediment contamination for both estuaries and a marked distinction between industrially and agriculturally influenced areas as well as between natural and artificialized sites. Hydrodynamics and oceanic influence (in essence dictating sediment type) play a major role in environmental quality. Environmental heterogeneity constituted an important confounding factor for biomarker analysis in the clams’ digestive glands since the animals appeared to respond to their immediate surroundings’ characteristics rather than the geographical area where they were collected from, despite the relative distance to pollution hot spots. Still, oxidative stress biomarkers (lipid peroxidation and catalase activity) could correlate with each other and to both organic and metallic contamination, whereas metallothionein- like protein induction failed to correlate to any class of sediment toxicants (albeit metals being the most representative pollutants) and appeared to be strongly affected (unlike the previous) by clam size and probably other unknown internal and external variables, among which contaminant interactions should play a major role.
- Estuarine ecological risk based on hepatic histopathological indices from laboratory and in situ tested fishPublication . Costa, P. M.; Caeiro, Sandra; Lobo, J.; Martins, M.; Ferreira, A. M.; Caetano, Miguel; Vale, C.; DelValls, T. Ángel; Costa, Maria HelenaJuvenile Senegalese soles were exposed through 28-day laboratory and field (in situ) bioassays to sediments from three sites of the Sado estuary (W Portugal): a reference and two contaminated by metallic and organic contaminants. Fish were surveyed for ten hepatic histopathological alterations divided by four distinct reaction patterns and integrated through the estimation of individual histopathological condition indices. Fish exposed to contaminated sediments sustained more damage, with especial respect to regressive changes like necrosis. However, differences were observed between laboratory- and fieldexposed animals, with the latest, for instance, exhibiting more pronounced fatty degeneration and hepatocellular eosinophilic alteration. Also, some lesions in fish exposed to the reference sediment indicate that in both assays unaccounted variables produced experimental background noise, such as hyaline degeneration in laboratory-exposed fish. Still, the field assays yielded results that were found to better reflect the overall levels of contaminants and physico-chemical characteristics of the tested sediments.