Fish biological alterations induced by the Aveiro Lagoon contaminants

Mestrado em Toxicologia e EcotoxicologiaThe present research work has been focused on the importance and complementarity of field and laboratory in vivo and in vitro studies. Fish are often used as bioindicator organisms in biomonitorization studies because they play a major role in the aquatic food-webs. Thus, two representative species of Aveiro Lagoon ichthyofauna were adopted in the present work: the sea bass (Dicentrarchus labrax L.) and the european eel (Anguilla anguilla L.). The field study (Chapter I) concerned the seasonal genotoxic assessment of a polluted lagoon (Ria de Aveiro), using erythrocytic nuclear abnormalaties (ENAs) of D. labrax specimens, collected at six stations of Aveiro lagoon. ENA results demonstrated the existence of a serious risk to fish populations almost at all the sites (except at GAF in spring, RIO in autumn and LAR in winter). Thus, at all the critical sites (BAR, GAF, RIO, LAR and VAG) identified, the results reflected the presence of genotoxic contaminants in the water. In this context, the ENA assay revealed to be a relatively rapid, easy to perform and sensitive genotoxicity test. The laboratory in vivo and in vitro components of the present Master thesis (Chapters II, III, IV and V) was carried out using A. anguilla L. as a biological model. Anguilla anguilla L. was intraperitoneally injected with β-naphthoflavone, (4mg/kg) which is a synthetic flavonoid compound known as a strong hepatic monooxigenases inducer such as ethoxyresourfin-O-deethylase (EROD). A. anguilla L. hepatic microsomes were then isolated and used in EROD activity in vitro studies. The in vitro effects of (i) PAHs - Naphthalene (Naph) and Phenanthrene (Phe); (ii) Resin acid (RAs) – abietic acid (AA) and its derivatives- Retene (Re) on liver microsomal EROD activity were assessed. A consistent dose dependent liver microsomal EROD activity increase in vitro was demonstrated for both Naph and Phe exposure, confirming their strong liver EROD activity in vitro inducer A. anguilla L. (Chapter II). Since the endocrine system plays a major role in fish stress mechanism, the in vitro effect of a steroid hormone such as cortisol – on liver microsomal EROD activity was also studied, individually and in combination with AA and Re. The cortisol concentration adopted for our studies was 6.9nM, based on previous trials (Chapter III). AA (Chapter IV) and Re (Chapter V) in vitro exposure on hepatic microsome showed a significant inhibition of EROD activity at all the concentrations. In vitro EROD activity inhibition caused by AA was inversely proportional to the increased concentration of AA whereas the inhibition caused by Re was proportional to its increased concentrations. The EROD activity inhibition induced in liver microsome by AA and Re in vitro exposure was significantly decreased by the addition of cortisol, (except at 0.3μM concentration of Re). The cortisol exerted a protective effect in liver EROD activity, since a significant reduction of the inhibitory effects caused by AA and Re, was observed in its presence. The data concerning the assessment of in vitro hepatic EROD activity under the above conditions confirm the importance of PAHs and RAs structure and molar concentration as well as the organism’s physiological conditions such as different hormonal status related with EROD activity in vivo induction i.e. either laboratory or field survey. ABSTRACT: O trabalho de investigação que se apresenta foi direccionado para a importância da complementaridade dos trabalhos de campo e laboratoriais in vivo e in vitro. Os peixes são frequentemente utilizados como organismos bioindicadores nos estudos de biomonitorização devido ao facto de desempenharem um papel fundamental na cadeia alimentar aquática. Deste modo, no presente trabalho foram seleccionadas duas espécies representativas da ictiofauna da Ria de Aveiro: o robalo (Dicentrarchus labrax L.) e a enguia europeia (Anguilla anguilla L.). O trabalho de campo (Capítulo I) diz respeito ao estudo da variação sazonal da genotoxicidade, numa Ria poluída tal como a Ria de Aveiro, utilizando o estudo da frequência das anomalias nucleares eritrocíticas (ANEs) em especímens de D. labrax, capturados em seis estações da Ria (de Aveiro). Os resultados referentes aos As demonstraram a existência de um sério risco para esta população de peixes, em quase todos os seis locais da Ria, (exceptuando a GAF na primavera, o Rio no outono e o LAR no inverno). Assim, em todos os locais identificados como críticos (BAR, GAF, RIO, LAR and VAG) os resultados reflectem a presença de contaminantes genotóxicos na água. Neste contexto, o método das ANEs revelou ser um ensaio de genotoxicidade relativamente rápido, fácil de realizar e sensível. A componente laboratorial in vivo e in vitro da presente Tese de Mestrado, correspondente aos Capítulos II, III, IV and V, foi executada utilizando A. anguilla L. como um modelo biológico. A. anguilla L. foi injectada intraperitonealmente com β-naftoflavona (BNF) (4mg/kg), um composto flavonóide sintético, conhecido pela sua capacidade como forte indutor das monooxigenases hepáticas tal como a -O-desetilase etoxiresourfina (EROD). Os microsomas hepáticos foram isolados, após 24 horas de exposição da enguia ao BNF, e a sua actividade EROD utilizada nos estudos in vitro. Os efeitos in vitro dos (i) HAPs – Naftaleno (Naph) e Fenantreno (Phe); ácidos resínicos (RAs) – Abietic acid (AA) e seus derivados Reteno (Re) sobre a actividade EROD microsomal hepática foram estudados e analisados. O aumento da actividade da EROD microsomal hepática, após exposição in vitro ao Naph ou Phe, revelou de uma forma consistente ser dependente da respectiva dose, confirmando a sua elevada capacidade de indução da actividade EROD in vitro (Capítulo II). Uma vez que o Sistema endócrino nos peixes desempenha um papel importante nos mecanismo de stress, o efeito in vitro de uma hormona esteróide tal como o cortisol sobre a actividade EROD microsomal hepática foi também estudada, individualmente e em combinação com o AA e o Re. A concentração de cortisol seleccionada foi de 6.9 nM, baseada em experiências realizadas para o efeito (Capítulo III). A exposição in vitro dos microsomas hepáticos ao AA (Capítulo IV) e ao Re (Capítulo V) demonstrou a sua capacidade de inibição da actividade EROD para todas as concentrações estudadas. In vitro, a inibição da actividade EROD induzida pelo AA, é inversamente proporcional ao aumento de concentração do mesmo, enquanto que a inibição provocada pelo Re foi proporcional ao aumento da sua concentração. A exposição prévia dos microsomas hepáticos ao cortisol 6.9 nM diminuiu significativamente a inibição in vitro da actividade EROD induzida em pelo AA e Re, (com excepção da concentração 0.3μM de Re). A exposição prévia ao cortisol exerceu uma acção protectora sobre a actividade EROD dos microsomas hepáticos, uma vez que se observou uma redução significativa dos efeitos inibitórios provocados pelo AA e Re. Os resultados obtidos relativos ao estudo in vitro da actividade EROD nos microsomas hepáticos, sob as condições acima referidas, confirmam a importância da estrutura e concentrações molares dos PAHs e RAs, assim como do estado fisiológico do organismo tal como o estado hormonal relacionado com a indução da actividade EROD in vivo, tanto no campo como no laboratório

Contaminação da água com elementos potencialmente tóxicos: processo de remediação com nanopartículas e avaliação da ecotoxicidade

Mercury is a well-known hazardous element. Its toxicity and non-degradability in the environment has led to the necessity of its removal from the environmental compartments. Regarding the aquatic compartment, where its toxicity causes serious concerns due to bioaccumulation and biomagnification processes, several new techniques have been development for mercury removal. So far, most of the water treatment methodologies are intended to fresh water. Nevertheless, salt waters are often the last receptor of pollutants, which may constitute a risk, both to the environment and human health. In this perspective, the current study was executed with the following aims to: (a) assess the efficiency of dithiocarbamate functionalized silica coated magnetite nanoparticles (NPs) for mercury (Hg) decontamination, in the presence and absence of other hazardous chemicals (arsenic, As; and cadmium, Cd), in seawater; (b) assess the influence of increased water temperature on the NPs’ efficiency in the toxicity removal or decrease of Hg-contaminated seawater in the absence and presence of As and Cd; and (c) evaluate the toxic effects caused by the NPs used in the removal of Hg. To address the objective (a), the residual levels of Hg in spiked seawater were assessed and the toxicity of seawater to aquatic biota contaminated with Hg or with Hg, As and Cd, before (non-remediated solutions) and after (remediated solutions with and without NPs) the sorption process, were compared. To address the objective (b), Anguilla anguilla L. gill ex vivo approach was considered taking into account a scenario of increased temperature and its comparison with temperature 20 ºC. The influence of temperature was assessed using biochemical endpoints (lipid peroxidation, LPO; protein carbonyl oxidation, PC; 8--Hydroxy-2’-deoxyguanosine, 8-OHdG; and antioxidants protection: catalase; glutathione peroxidise; glutathione reductase; glutathione S-transferase; non-protein thiol; total glutathione) before and after the remediation process adopted, and for the different degree of contamination. To address the objective (c), the eco-friendly nature of NPs was assessed conducting short-term exposure (2 to 72 h) of A. anguilla to NPs either alone or in combination with Hg under in vitro conditions profiling the responses of A. anguilla genotoxicity (LPO; 8-OHdG; erythrocytic nuclear abnormalities, ENA) and immunotoxicity (viability; phagocytosis; oxidative burst activity, OBA; LPO). The observations pertaining to objective (a) revealed that the NPs used in the current study were efficient to remove Hg from single- and multi-contaminated seawater. However, the removal of Hg by the NPs was faster for the lowest contamination scenario (50 μg/L). The presence of other contaminants displayed no interference on the rate of removal of Hg by the NPs. Concerning ecotoxicological profile, the non-remediated solutions caused higher toxicity than the remediated ones, highlighting the effectiveness of the magnetic NPs on the remediation of Hg-contaminated seawater. The observations related to objective (b) revealed that an increase in the water temperature results in higher Hg absorption and increased damage to lipid, protein and DNA in A. anguilla gill. Moreover, the increase of temperature, decreased the benefits of the remediation process as the damage observed in remediated solutions was higher at the highest temperature. Regarding antioxidants protection, in general, the antioxidant defences were likely overwhelmed in fish gill, leading to increased Hg accumulation and exaggerated Hg toxicity when the temperature was increased. Despite the modulation of antioxidants protection in response to the exposure of Hg or its co-exposure with other hazardous contaminants, their insufficiency to abolish damage as observed by increase in LPO, 8-OHdG and PC oxidation. On the aspect of the objective (c), the results concluded that NP-Hg complex formation is efficient to eliminate the DNA damage-induced by individual exposure to NPs or Hg at early hour, whereas plasma exposure to NPs alone displayed a significant increase in 8-OHdG levels at both 2 and 48-hour of exposure. Nevertheless, NPs in combination with Hg co-exposure revealed an increase in 8-OHdG levels at all the exposure length (except 16 hours), suggesting that both NPs and Hg independently oxidized DNA. At the aspect of immune responses, A. anguilla phagocytes isolated from peritoneum (P-phagocytes), gill (G-phagocytes), head-kidney (HK-phagocytes) and spleen (S-phagocytes) revealed overactivation and reactive oxygen species (ROS) production as an indirect mechanism of immunotoxicity. The phagocytes responded in the following manner: P- > S- > HK- = G-phagocytes for NP exposure alone; S- > HK- > P- = G-phagocytes for Hg exposure alone; and HK- > G- = S- > P-phagocytes for NPs-Hg exposure. Overall, the efficiency of NPs (high Hg removal percentage and decrease of water toxicity) combined with its magnetic property proved this material a very promissory adsorbent and can be applied for both insitu and/or exsitu treatment applications in systems like coastal lagoons, harbours, estuaries, or even aquacultures. Considering Hg and its association with NPs, as well as the likelihood that it could pose a serious threat to aquatic organisms, current results suggest that the step of NPs-Hg complex removal must not be underrated and should be processed without any more ado.O mercúrio é reconhecido como um elemento de elevada perigosidade. Devido à sua toxicidade e persistência no ambiente existe a necessidade de removê-lo dos diversos compartimentos ambientais e de promover o desenvolvimento de novos métodos para a sua remoção, nomeadamente para um dos compartimentos onde a sua presença causa maior preocupação, a água. Uma das lacunas neste campo, é que a grande maioria das metodologias de tratamento são especificas para água doce. No entanto, águas com salinidade são muitas vezes o último recetor dos poluentes, constituindo assim um risco para o ambiente e para a Saúde Humana. Neste contexto, o presente trabalho de investigação tem como principais objetivos: (a) avaliar a eficiência de nanopartículas (NPs) de magnetite revestidas com sílica e funcionalizadas com grupos ditiocarbamato para a descontaminação de mercúrio em água do mar, na ausência e presença de outros contaminantes (arsénio, As; e cádmio, Cd); (b) avaliar a influência de um aumento da temperatura da água na eficiência das NPs na remoção ou diminuição da toxicidade da água do mar contaminada com Hg, na ausência e presença de As e Cd; e (c) avaliar a possível toxicidade das NPs utilizadas para a remoção de Hg. Para responder ao objetivo (a), os níveis de Hg em água do mar fortificada antes (solução não-remediada) e depois do processo de remediação (solução remediada) foram determinados; foi também avaliada a toxicidade de água do mar contaminada com Hg e com Hg, As e Cd, antes (solução não-remediada) e depois (solução remediada sem e com NPs) do processo de remediação, para diferentes espécies aquáticas. Para responder ao objetivo (b), simulou-se um cenário de aumento da temperatura da água e realizou-se uma análise toxicológica ex-vivo utilizando guelras de Anguilla anguilla L. para diferentes temperaturas (20 ºC foi a temperatura escolhida para comparação de resultados). A influência da temperatura foi avaliada através de marcadores bioquímicos (peroxidação lipídica, LPO; oxidação da proteína carbonilo, PC; 8-hidroxi-2'-desoxiguanosina, 8-OHdG; e da proteção antioxidante: catálase; glutationa peroxidase; glutationa redutase; glutationa S-transferase; tiol não proteico; glutationa total) antes e depois do processo de remediação adotado, e para diferentes níveis de contaminação. Para dar resposta ao objetivo (c), os possíveis efeitos adversos provocados pelas NPs foram avaliados através de ensaios toxicológicos de curta exposição (2 - 72 h) de A. anguilla às NPs, e às NPs com Hg, em condições in vitro. Foram avaliados marcadores de genotoxicidade (LPO; 8-OHdG; anomalias nucleares eritrocíticas, ANE) e de imunotoxicidade (viabilidade; fagocitose; oxidação de neutrófilos, OBA; LPO). Os resultados obtidos referentes ao objetivo (a) indicam que as de nanopartículas de magnetite revestidas com sílica e funcionalizadas com grupos ditiocarbamato são eficientes na remoção de Hg(II) de soluções mono e multi elementares de água do mar. Os resultados indicam também que o processo de remoção de Hg(II) pelas NPs é mais rápido para concentrações de metal mais baixas (50 g/L), e a presença dos outros contaminantes não interfere na taxa de remoção de Hg(II) pelas NPs. Relativamente aos resultados ecotoxicológicos, as soluções não remediadas causaram maior toxicidade às espécies testadas, do que as soluções remediadas. Este resultado evidência a eficiência das NPs na descontaminação de água do mar com Hg. Os resultados obtidos referentes ao objetivo (b) permitem-nos concluir que um aumento da temperatura da água poderá resultar numa maior adsorção de Hg e no aumento de dano lipídico, proteico e no ADN, nas guelras de A. anguilla. Um possível aumento da temperatura da água, diminuirá também os benefícios do processo de remediação, uma vez que o dano observado nas soluções remediadas foi maior para a temperatura mais elevada testada. Relativamente, à proteção antioxidante, verificou-se que de um modo geral, as defesas antioxidantes existentes nas guelras de A. anguilla provavelmente foram suprimidas, levando ao aumento da acumulação de Hg e a uma maior toxicidade quando a temperatura foi aumentada. Para além disso, a modulação da proteção antioxidante em resposta à exposição de Hg ou à sua co-exposição com outros contaminantes, foi insuficiente para abolir o dano, como observado pelo aumento da LPO, 8-OHdG e oxidação da proteína carbonilo. Os resultados obtidos referentes ao objetivo (c) permitem-nos concluir que a formação do complexo NPs-Hg é eficiente para eliminar o dano de ADN induzido pela exposição individual às NPs ou Hg, durante o período inicial, mas os resultados da exposição de plasma apenas às NPs, evidenciaram um aumento relevante dos níveis de 8-OHdG após 2 e 48 horas de exposição. No entanto, os resultados da co-exposição de NPs e Hg revelaram um aumento nos níveis de 8-OHdG para todos os tempos de exposição (exceto 16 horas), sugerindo que tanto as NPs como o Hg oxidaram, independentemente o DNA. Em relação às respostas imunitárias, os fagócitos de A. anguilla isolados do peritónio (P-fagócitos), guelras (G-fagócitos), prónefros (HK-fagócitos) e baço (Fagocitos-S) revelaram sob ativação e produção de espécies reativas de oxigênio (ROS), como mecanismo indireto de imunotoxicidade. A resposta dos fagócitos seguiu a seguinte ordem: P-> S-> HK- = G-fagócitos G para a exposição apenas às NPs; S-> HK-> P- = Fagocitos G para exposição apenas a Hg; e HK-> G- = S-> P-fagócitos para a exposição a NPs-Hg. Em geral, a eficiência das NPs (elevada percentagem de remoção de Hg e diminuição da toxicidade da água) em conjunto com as suas propriedades magnéticas, evidenciam um conjunto de vantagens que fazem deste material, um adsorvente promissor para aplicações de tratamento in-situ e/ou ex-situ em sistemas como lagoas costeiras, portos, estuários ou mesmo aquacultura. Considerando a associação do Hg e às NPs, bem como a probabilidade de que ela possa representar uma séria ameaça para os organismos aquáticos, os resultados atuais sugerem que o passo da remoção desse complexo, NPs-Hg, não deve ser subestimado e deverá ser sempre realizado.Programa Doutoral em Químic

Nanoscale materials and their use in water contaminants removal-a review

Water scarcity is being recognized as a present and future threat to human activity and as a consequence water purification technologies are gaining major attention worldwide. Nanotechnology has many successful applications in different fields but recently its application for water and wastewater treatment has emerged as a fast-developing, promising area. This review highlights the recent advances on the development of nanoscale materials and processes for treatment of surface water, groundwater and industrial wastewater that are contaminated by toxic metals, organic and inorganic compounds, bacteria and viruses. In addition, the toxic potential of engineered nanomaterials for human health and the environment will also be discussed.Iram Mohmood (SFRH/BD/74410/2010), Claúdia Batista Lopes (SFRH/BPD/45156/2008), Isabel Lopes, Iqbal Ahmad, Armando Duarte and Eduarda Pereira are grateful to the Portuguese Foundation for Science and Technology (FCT), FSE and POPH funds (Programa Ciência 2007) and the Aveiro University Research Institute/Centre for Environmental and Marine Studies (CESAM) for partial financial supports.publishe

Mercury's mitochondrial targeting with increasing age in Scrobicularia plana inhabiting a contaminated lagoon: damage-protection dichotomy and organ specificities

This study aimed to understand bivalves' (Scrobicularia plana) adaptive strategies, with emphasis on mitochondria as a target organelle, in response to mercury-contaminated environment. Inter-age and organ-specific approaches were applied using different annual size classes (2+, 3+, 4+and 5+years old) and assessing specific organs (gill, digestive gland), respectively. Bivalves were collected from moderately (M) and highly (H) contaminated sites at Laranjo basin - Ria de Aveiro (Portugal), where a mercury gradient was identified, and compared with those from a reference (R) site. Total antioxidants capacity (TAC) was measured in mitochondria, whereas the lipid peroxidation was assessed as a marker of damage. S. plana age determined the clams' vulnerability towards mercury induced mitochondrial peroxidative damage depending upon the mercury accumulation: younger animals were more vulnerable than older. Clams showed a decreasing trend of TAC with increasing age. This decrease was found to be statistically significant in 4+and 5+years at M; whereas, at H, with depleted TAC, remained same until they have grown 5+years. The organ specificity was evident for antioxidant response and peroxidative damage. A clear pattern of overall TAC increase in digestive gland (at M) and decrease in gill (at H) was observed, while only gills were found to be susceptible to peroxidative damage. Overall, mitochondria proved to be a sensitive fraction for the effects of mercury in S. plana inhabiting mercury contaminated area.Financial support provided by the Portuguese FCT (Foundation for Science and Technology) to CESAM (Centre for Environmental and Marine Studies) is gratefully acknowledged. The authors are thankful to J.P. Coelho, Department of Chemistry, University of Aveiro for his valuable help during field campaign.publishe

Interference of the co-exposure of mercury with silica-coated iron oxide nanoparticles can modulate genotoxicity induced by their individual exposures: a paradox depicted in fish under in vitro conditions

The study aimed to assess the genotoxic potential of silica-coated iron oxide nanoparticle functionalized with dithiocarbamate groups (IONP, 100 nm) in vitro exposure alone or its interference with mercury (Hg) co-exposure in the blood of European eel (Anguilla anguilla L.) by evaluating 8-hydroxy-2′-deoxyguanosine (8-OHdG), lipid peroxidation (LPO), and erythrocytic nuclear abnormalities (ENA). Four groups were made: (i) 2×106 erythrocytes+Roswell Park Memorial Institute-1640 (RPMI-1640) (control), (ii) 2×106 erythrocytes+IONP (2.5 mg L−1), (iii) 2×106 erythrocytes+ Hg (50 μg L−1), and (iv) 2×106 erythrocytes+IONP+Hg. Blood plasma was also processed following the previous exposure conditions. Samplings were performed at 0, 2, 4, 8, 16, 24, 48, and 72 h of exposure. The results revealed significant ENA increases at both early (2, 4, 8) and late (16, 24, 48, 72) hours of exposure to IONP alone. However, IONP exposure combined with Hg co-exposure revealed no ENA increase at 2 h, suggesting that IONP-Hg complex formation is efficient to eliminate the DNA damage induced by individual exposure to IONP or Hg at early hours. Hence, the initial occurrence of antagonism between IONP and Hg was perceptible; however, at late hours of exposure, IONP was unable to mitigate the mercury-accrued negative impacts. Plasma exposure to IONP alone displayed a significant increase in 8- OHdG levels at 2 and 48 h of exposure. However, IONP in combination with Hg co-exposure revealed an increase in 8- OHdG levels at all the exposure length (except 16 h), suggesting that both IONP and Hg independently oxidized DNA. In addition, an additive effect on 8-OHdG levels at both early and late hours, and on LPO only at late hours (except 24 h), suggested that DNA is more susceptible to peroxidative damage than lipid

Modulation of glutathione and its related enzymes in plants’ responses to toxic metals and metalloids—a review

The rapid increase in the contamination of the environment by toxic metals (TMs) and metalloids is posing serious threats to biotic communities. Plants are among the organisms most vulnerable to TMs and metalloids due to their sedentary and stationary existence under changing environmental conditions. Toxic metals- and metalloids-stress-impacts cause either directly or indirectly excessive generation of reactive oxygen species (ROS) leading to oxidative stress in plants. Being a significant component of ascorbate-glutathione (AsA-GSH) pathway, tripeptide glutathione (GSH, γ-Glu-Cys-Gly) is involved in both direct and indirect control of ROS and their reaction products concentrations in cells and thus, protects plants against TMs- and metalloids-mediated oxidative stress. Additionally, several GSH-related enzymes such as GSH reductase (GR, EC 1.6.4.2), GSH peroxidases (GPXs, EC 1.11.1.9) and GSH sulfo-transferases (GSTs, EC 2.5.1.18) cumulatively form an efficient defense system to protect plants against ROS-induced effects in addition to their significance for the detoxification, chelation and compartmentalization of major TMs and metalloids in plants. The present review critically evaluates the recent studies on the modulation of total reduced GSH, GSH/GSSG redox couple, the major GSH-related enzymes and their cumulative significance in plants’ adaptation and/or tolerance to TMs and metalloids in detail.publishe

Remediation of mercury contaminated saltwater with functionalized silica coated magnetite nanoparticles

The study aimed to evaluate the efficiency of dithiocarbamate functionalized silica coated magnetite nanoparticles (NPs) for Hg decontamination of saltwater either contaminated with Hg alone or with As and Cd. For this, the residual levels of Hg in seawater were assessed and Hg-contaminated or Hg+ As+ Cd-contaminated seawater toxicity to aquatic biota, before and after the sorption process, was compared. The results showed that under highly competitive conditions (water salts, Cd and As), the removal of Hg from seawater, by using these magnetic NPs, for the lowest concentration (50 mu g/L) was superior to 98% and for the highest concentration (500 mu g/L) ranged between 61% to 67%. Despite the great affinity of the magnetic NPs for Hg, they were not effective at removing As and Cd from seawater. In relation to the ecotoxicity endpoints after remediation, the mixture with lower Hg concentration exhibited no toxicity to rotifer Brachionus plicatilis and bacteria Vibrio fischeri; however, the mixture with higher concentration revealed toxicity. In addition, the toxicity of bacteria V. fischeri, rotifer B. plicatilis and algae Phaeodactylum tricornutum, whose responses where inhibited during its exposure to the non-remediate sample was considerably reduced after treatment with NPs. Furthermore, microalgae P. tricornutum appears to be most sensitive species while Artemia franciscana showed no toxic effects to the tested solutions. Both chemical and ecotoxicological approaches revealed a high efficiency for the remediation of Hg-contaminated saltwater. (C) 2016 Elsevier B.V. All rights reserved

Phagocytic cell responses to silica-coated dithiocarbamate-functionalized iron oxide nanoparticles and mercury co-exposures in Anguilla anguilla L.

Immune system responses in fish are considered as suitable and sensitive biomarkers for monitoring aquatic pollution. However, a clear knowledge gap persists in the literture on the immunotoxic potential of engineered nanoparticles toward aquatic organisms such as fish. Employing major enzymatic- (glutathione reductase, GR; glutathione peroxidase, GPX; glutathione sulfo-transferase, GST; catalase, CAT) and thiol- (non-protein thiols, NP-SH; total glutathione, TGSH)-based defense biomarkers, this study assessed the response of phagocytes isolated from peritoneum (P-phagocytes), gill (G-phagocytes), head kidney (HK-phagocytes), and spleen (S-phagocytes) of European eel (Anguilla anguilla L.) to silica-coated magnetite particles (Fe3O4@SiO2/SiDTC, hereafter called IONP; size range: 82 +/- 21 to 100 +/- 30 nm; 2.5 mg L-1) alone and IONP and mercury (Hg; 50 mu g L-1) concomitant exposures. Responses of previous biomarkers were studied in P-phagocytes, G-phagocytes, HK-phagocytes, and S-phagocytes collected during 0, 2, 4, 8, 16, 24, 48, and 72 h of exposures. Contingent to hour of exposure to IONP, Hg, and IONP + Hg GST, GPX, CAT, NP-SH, and TGSH exhibited their differential responses in all the phagocytic cells considered. In particular, under IONP exposure, the potential occurrence of the GSH-independent antioxidant defense was indicated by the observed herein inhibition in the enzymatic- and thiol-based defense in A. anguilla phagocytes. In contrast, the response of P-, G-, HK-, and S-phagocytes to the increasing Hg exposure period reflected an increased detoxification activity. Notably, the occurrence of an antagonism between IONP and Hg was depicted during late hours (72 h) under IONP + Hg concomitant exposure, where elevations in the defense biomarkers were depicted. Overall, the P-, G-, HK-, and S-phagocytic cells exhibited a differential induction in the studied enzymes and thiols to counteract impacts of IONP, Hg, and IONP + Hg concomitant exposures. Future studies on the fish immunotoxicity responses to IONP exposure in multi-pollution conditions can be benefited with the major outcomes of the present study

Salt marsh halophyte services to metal-metalloid remediation: assessment of the processes and underlying mechanisms

Salt marshes are widely distributed and most productive ecosystems in the temperate zones on the globe. These areas perform vital ecological functions and are populated mainly by halophytes—plants that are able to survive and reproduce in environments with exceptionally high salt concentrations. In salt marshes, in addition to tolerating high salt concentrations, salt marsh halophytes have to cope with damages caused by multiple anthropgenic pressures including metal and metalloid pollution. Extensive studies have been performed aiming at exploring naturally occurring endemic salt marsh halophytes with extraordinary potential for metals and metalloids remediation. However, a knowledge gap is perceptible on the basics of salt marsh halophyte adaptation/ tolerance to the joint action of damaging factors such as high concentration of salt and presence of metals–metalloids. In light of available literature, the current paper is critical in: (i) highlighting ecological significance of salt marsh halophytes and their use as bioindicators or biomonitors of metal–metalloid pollution; (ii) analyzing salt marsh halophyte significant contributions for metal- and metalloid-remediation processes; (iii) overviewing salt marsh halophytes–microbes interaction influence on metalphytoremediation processes; and (iv) cross-talking important physiological/ biochemical strategies adopted by salt marsh halophytes for salinity-, metal-, and metalloid-tolerance. Conclusively, the paper highlights important aspects so far less explored in the context of salt marsh halophyte services to metal–metalloid remediation and underlying mechanisms. The discussion will enable researchers and environmentalists to set further exhaustive studies aiming at efficient and sustainable management of rapidly mounting salt marshes metal–metalloid contamination issues

Rescheduling the process of nanoparticle removal used for water mercury remediation can increase the risk to aquatic organism: evidence of innate immune functions modulation in European eel (Anguilla anguilla L.)

This study aimed to assess the mechanisms of innate immune function responses to silica-coated iron oxide nanoparticle functionalized with dithiocarbamate groups (IONP) exposure alone and its associated mercury (Hg) in European eel (Anguilla anguilla L.) phagocytes isolated from peritoneum (P-phagocytes), gill (G-phagocytes), head kidney (HK-phagocytes) and spleen (S-phagocytes). The study evaluated viability, phagocytosis, oxidative burst activity (OBA) and lipid peroxidation (LPO). Four groups were made: (1) 2 x 10(6) phagocytes + RPMI-1640 (control), (2) 2 x 10(6) phagocytes + IONP (2.5 mg L-1), (3) 2 x 10(6) phagocytes + Hg (50 mu g L-1) and (4) 2 x 10(6) phagocytes + IONP + Hg. Samplings were performed at 0, 2, 4, 8, 16, 24, 48 and 72 h of exposure. A. anguilla P-, G-, HK- and S-phagocytes in vitro exposure to IONP alone revealed either increased (except HK-phagocytes at 16 h) or no change in viability, suggesting that the cells are metabolically active and resistant to IONP exposure alone. In terms of phagocytes overactivation and reactive oxygen species (ROS) production as an indirect mechanism of immunotoxicity, the phagocytes responded in the following manner: P->S->HK-=G-phagocytes for IONP exposure alone, S->HK->P-=G-phagocytes for Hg exposure alone and HK->G-=S->P-phagocytes for concomitant exposure. Overall, considering Hg as a surrogate for metals and its association with IONP, as well as the likelihood that it could pose a serious threat to aquatic organisms by modulating their immune defense mechanisms if accidentally discharged into the aquatic environment, current results suggest that the step of IONP-metal complex removal must not be underrated and should be processed without any more ado