Mercury (Hg) is a potent neurotoxicant known to induce important adverse effects on fish, but a deeper understanding is lacking regarding how environmental exposure affects the brain morphology and neural plasticity of specific brain regions in wild specimens. In this work, it was evaluated the relative volume and cell density of the lateral pallium, hypothalamus, optic tectum and molecular layer of the cerebellum on wild Liza aurata captured in Hg-contaminated (LAR) and non-contaminated (SJ) sites of a coastal system (Ria de Aveiro, Portugal). Given the season-related variations in the environment that fish are naturally exposed, this assessment was performed in the winter and summer. Hg triggered a deficit in cell density of hypothalamus during the winter that could lead to hormonal dysfunctions, while in the summer Hg promoted larger volumes of the optic tectum and cerebellum, indicating the warm period as the most critical for the manifestation of putative changes in visual acuity and motor-dependent tasks. Moreover, in fish from the SJ site, the lateral pallium relative volume and the cell density of the hypothalamus and optic tectum were higher in the winter than in summer. Thus, season-related stimuli strongly influence the size and/or cell density of specific brain regions in the non-contaminated area, pointing out the ability of fish to adapt to environmental and physiological demands. Conversely, fish from the Hg-contaminated site showed a distinct seasonal profile of brain morphology, presenting a larger optic tectum in the summer, as well as a larger molecular layer of the cerebellum with higher cell density. Moreover, Hg exposure impaired the winter-summer variation of the lateral pallium relative size (as observed at SJ). Altogether, seasonal variations in fish neural morphology and physiology should be considered when performing ecotoxicological studies in order to better discriminate the Hg neurotoxicity.

This work characterizes levels of polycyclic aromatic hydrocarbons (PAHs) in indoor and outdoor air of preschool environments, and assesses the respective risks for 3–5-years old children. Eighteen gaseous and particulate (PM1 and PM2.5) PAHs were collected indoors and outdoors during 63 days at preschools in Portugal. Gaseous PAHs accounted for 94–98% of total concentration (ΣPAHs). PAHs with 5–6 rings were predominantly found in PM1 (54–74% particulate ΣPAHs). Lighter PAHs originated mainly from indoor sources whereas congeners with 4–6 rings resulted mostly from outdoor emissions penetration (motor vehicle, fuel burning). Total cancer risks of children were negligible according to USEPA, but exceeded (8–13 times) WHO health-based guideline. Carcinogenic risks due to indoor exposure were higher than for outdoors (4–18 times).

Carbon dioxide is one of the main soil gases released silently and permanently in diffuse degassing areas, both in volcanic and non-volcanic zones. In the volcanic islands of the Azores (Portugal) several villages are located over diffuse degassing areas. Lethal indoor CO2 concentrations (higher than 10 vol %) were measured in a shelter located at Furnas village, inside the caldera of the quiescent Furnas Volcano (S. Miguel Island). Hazardous CO2 concentrations were detected not only underground, but also at the ground floor level. Multivariate regression analysis was applied to the CO2 and environmental time series recorded between April 2008 and March 2010 at Furnas village. The results show that about 30% of the indoor CO2 variation is explained by environmental variables, namely barometric pressure, soil water content and wind speed. The highest indoor CO2 concentrations were recorded during bad weather conditions, characterized by low barometric pressure together with rainfall periods and high wind speed. In addition to the spike-like changes observed on the CO2 time series, long-term oscillations were also identified and appeared to represent seasonal variations. In fact, indoor CO2 concentrations were higher during winter period when compared to the dry summer months. Considering the permanent emission of CO2 in various volcanic regions of the world, CO2 hazard maps are crucial and need to be accounted by the land-use planners and authorities.

Mercury (Hg) is recognized as a dangerous contaminant due to its bioaccumulation and biomagnification within trophic levels, leading to serious health risks to aquatic biota. Therefore, there is an urgent need to unravel the mechanisms underlying the toxicity of Hg. To this aim, a metabolomics approach based on protonic nuclear magnetic resonance (1H NMR), coupled with chemometrics, was performed on the gills of wild golden grey mullets L. aurata living in an Hg-polluted area in Ria de Aveiro (Portugal). Gills were selected as target organ due to their direct and continuous interaction with the surrounding environment. As a consequence of accumulated inorganic Hg and methylmercury, severe changes in the gill metabolome were observed, indicating a compromised health status of mullets. Numerous metabolites, i.e. amino acids, osmolytes, carbohydrates, and nucleotides, were identified as potential biomarkers of Hg toxicity in fish gills. Specifically, decrease of taurine and glycerophosphocholine, along with increased creatine level, suggested Hg interference with the ion-osmoregulatory processes. The rise of lactate indicated anaerobic metabolism enhancement. Moreover, the increased levels of amino acids suggested the occurrence of protein catabolism, further supported by the augmented alanine, involved in nitrogenous waste excretion. Increased level of isobutyrate, a marker of anoxia, was suggestive of onset of hypoxic stress at the Hg contaminated site. Moreover, the concomitant reduction in glycerophosphocholine and phosphocholine reflected the occurrence of membrane repair processes. Finally, perturbation in antioxidant defence system was revealed by the depletion in glutathione and its constituent amino acids. All these data were also compared to the differential Hg-induced metabolic responses previously observed in liver of the same mullets (Brandão et al., 2015). Overall, the environmental metabolomics approach demonstrated its effectiveness in the evaluation of Hg toxicity mechanisms in wild fish under realistic environmental conditions, uncovering tissue-specificities regarding Hg toxic effects namely in gills and liver.

This study aimed to investigate the role of non-enzymatic antioxidants on adaptive skills over time in the bivalve Scrobicularia plana environmentally exposed to mercury. Inter-age (2⁺, 3⁺, 4⁺, 5⁺ year old) and organ-specific (gills, digestive gland) approaches were applied in bivalves collected from moderately and highly contaminated sites at Ria de Aveiro (Portugal). S. plana's adaptive skills were dependent on the contamination extent; under moderate contamination scenario, the intervention of the different antioxidants took place harmoniously, evidencing an adjustment capacity increasing with the age. Under higher contamination degree, S. plana failed to cope with mercury threat, showing an age-dependent deterioration of the defense abilities. In organ-specific approach, the differences were particularly evident for thiol-compounds, since only gills displayed the potential to respond to moderate levels by increasing non-protein thiols and total glutathione. Under high contamination degree, both organs were unable to increase thiol-compounds, which were compensated by the ascorbic acid elevation.

Surveying toxicity of complex geochemical media as aquatic sediments often yields results that are either difficult to interpret or even contradictory to acknowledged theory. Multi-level biomarkers were investigated in a benthic fish exposed to estuarine sediments through laboratory and in situ bioassays, to evaluate their employment either in ecological risk assessment or in more mechanistic approaches to assess sediment-bound toxicity. Biomarkers reflecting lesions (such as genotoxicity or histopathology), regardless of their low or absent specificity to contaminants, are efficient in segregating exposure to contaminated from uncontaminated sediments even when classical biomarkers like CYP1A and metallothionein induction are inconclusive. Conversely, proteomics and gene transcription analyses provided information on the mechanics of toxicity and aided explaining response variation as a function of metabolic imbalance and impairment of defences against insult. In situ bioassays, although less expedite and more affected by confounding factors, produced data better correlated to overall sediment contamination.

In natural environments fish are exposed to endocrine disrupting compounds (EDCs) present at low concentrations and with different modes of actions. Here, adult zebrafish of both sexes were exposed for 21 days to an estrogenic mixture (Mix) of eleven EDCs previously quantified in Douro River estuary (Portugal) and to 100 ng/L 17α-ethinylestradiol (EE2) as positive control. Vitellogenin mRNA and HSI in males confirmed both exposure regimes as physiologically active. Potential candidates for estrogenic disturbance of steroidogenesis were identified (StAR, 17β-HSD1, cyp19a1), but Mix only affected cyp19a1 in females. Significant differences in the response of FSHβ, cypa19a2, 20β-HSD were observed between EE2 and Mix. Mtf-1 and tfap2c transcription factor binding sites were discovered in the putative promoter regions and corresponding transcription factors were found to be differentially expressed in response to Mix and EE2. The results suggest that “non-classical effects” of estrogenic EDC in fish are mediated via transcription factors.

Pools of Zn, Cu, Cd and Co in leaf, stem and root tissues of Sarcocornia fruticosa, Sarcocornia perennis, Halimione portulacoides and Spartina maritima were analyzed on a bimonthly basis, in a Tagus estuary salt marsh. All the major concentrations were found in the root tissues, being the concentrations in the aboveground organs neglectable for sediment budget proposes, as seen by the low root-aboveground translocation. Metal annual accumulation, root turnovers and cycling coefficients were also assessed. S. maritima showed the higher root turnovers and cycling coefficients for most of the analyzed metals, making this a phytostabilizer specie. By contrast the low root turnover, cycling coefficient and low root necromass generation makes S. perennis the most suitable specie for phytoremediation processes. Although the high amounts of metal return to the sediments, due to root senescence, salt marshes can still be considered sinks of heavy metals, cycling heavy metals mostly between sediment and root.

The São Domingos mine (Portugal) is, potentially, a good site for ecotoxicological studies, due to a pH and metal gradient of acid mine drainage. In this study, the toxicity of several mine sediments was evaluated using the aquatic oligochaete Lumbriculus variegatus as a test organism. Our hypothesis was that exposure to contaminated sediments would cause behavioural early warning responses in L. variegatus. Five sites, with pH ranging from 2.5 to 6.5, and with associated metals, were investigated. The results showed poor sediment quality in most of the collected sediments and Fe, S and As were the dominant elements in the samples. High mortalities were observed, ranging from 32.6 to 100%, indicating severe contamination. The collected sediments did not support good L. variegatus growth and significantly changed its behaviour. Early warning responses consisted of decreased locomotion and decreased peristaltic movements. A behaviour inhibition will affect the ecosystem balance by limiting the organisms' ability to avoid capture, which leads to a higher risk of predation. Behavioural responses of the aquatic oligochaeta Lumbriculus variegatus may be used to detect early warning responses.

Vertical profiles of C, N, δ15N and Pb were measured in the Mondego and Mira estuaries as markers that conveyed notions as to the relative influence of anthropogenic influence over the past decades. Recent carbon changes in both estuaries may reflect changes in estuarine productivity, probably as a consequence of sediment reworking and erosion, and also of losses in salt marsh area and dwarf eelgrass beds. δ15N values began to diverge considerably before the %C and %N and were higher in Mondego. δ15N signatures detected N enrichment at relatively low rates, and indicated that Mondego received more enriched N than Mira. Lead concentrations differed between estuaries, with higher concentrations in Mondego. The secular increase in %N, Pb, and δ15N signatures was significantly related to human density in the watersheds of the estuaries and were sensitive indicators of anthropogenic activity. The variables C, %N, δ15N, and Pb were reliable sediment sentinels that reflected the level of anthropogenic influence in the past decades in estuarine ecosystems.