Impact of treated sewage on meiobenthic nematodes: a case study from the Tunisian Refining Industries Company / Impacto de esgoto tratado em nematoides meiobentônicos: um estudo de caso da Tunisian Refining Industries Company

The main objective of the current study was to assess the impact of the water taken from the 'Tunisian Refining Industries Company' on meiobenthic nematodes, before and after a series of treatments in decantation basins followed by its discharge in Bizerte bay, Tunisia. The comparison of environmental parameters of the two types of water was clearly indicative of an improvement in the quality of treated waters after a significant reduction in their loads in hydrocarbons. Overall, the water retained a good quality after being treated by 'Tunisian Refining Industries Company' before discharge in the sea. At the end of the experiment, differential responses were observed according to the richness of sediment in organic matter and hydrocarbons. Thus, it was apparent that the nematode assemblage exposed to the treated waters was closer to controls and associated to higher values of abundance, than that under untreated ones. It was also assumed that the species Microlaimus honestus De Man, 1922, Paramonohystera proteus Wieser, 1956 and Cyartonema germanicum Juario, 1972 are sensitive bioindicators of bad environmental statues and of hydrocarbon presence in the environment. On the other hand, Metoncholaimus pristiurus (Zur Strassen, 1894) Filipjev, 1918 would rather be classified as a positive bioindicative species of this type of pollutants.

O principal objetivo do presente estudo foi avaliar o impacto da água retirada da "Tunisian Refining Industries Company" sobre os nematoides meiobentônicos, antes e depois de uma série de tratamentos em bacias de decantação seguidos de seu descarte na baía de Bizerte, Tunísia. A comparação dos parâmetros ambientais dos dois tipos de água foi claramente indicativa de uma melhoria na qualidade das águas tratadas após uma redução significativa das suas cargas em hidrocarbonetos. No geral, a água reteve uma boa qualidade após ser tratada pela "Tunisian Refining Industries Company" antes da descarga no mar. Ao final do experimento, foram observadas respostas diferenciais de acordo com a riqueza de sedimentos em matéria orgânica e hidrocarbonetos. Assim, ficou claro que a assembleia de nematoides exposta às águas tratadas estava mais próxima dos controles e associada a maiores valores de abundância do que nas não tratadas. Também foi assumido que as espécies Microlaimus honestus De Man, 1922, Paramonohystera proteus Wieser, 1956 e Cyartonema germanicum Juario, 1972 são bioindicadores sensíveis de más estátuas ambientais e da presença de hidrocarbonetos no meio ambiente. Por outro lado, Metoncholaimus pristiurus (Zur Strassen, 1894) Filipjev, 1918 preferiria ser classificado como uma espécie bioindicativa positiva deste tipo de poluentes.

Assessment of carbamazepine acute toxicity in the cockle Cerastoderma edule through chemical, physiological and biochemical tools / Avaliação da toxicidade aguda da carbamazepina no berbigão Cerastoderma edule por meio de ferramentas químicas, fisiológicas e bioquímicas

The cockle Cerastoderma edule was exposed to four concentrations (5, 10, 20 and 70 μg L-¹) of carbamazepine (CBZ). This anticonvulsant was found to alter the mussel behavior of by reducing its clearance rate (CR). Analysis of CBZ accumulation in tissues of C. edule was carried out using HPLC-UV after 48 or 96 hours of exposure. In addition, an overproduction of H2O2 by the bivalves was detected following exposure to CBZ but nitrite levels remained unchanged. Moreover, superoxide dismutase and catalase activities showed a significant increase in relation to their contact with CBZ. The activity of the biotransformation enzyme gluthatione-S-transferase did not change during exposure. Malondialdehyde (MDA) levels indicating cellular damage, increased when bivalves were exposed to 20 and 70 μg l-¹ of carbamazepine for 96 h CBZ. The results also indicate that acetylcholinesterase activity (AChE) was inhibited in all CBZ concentrations during the 48 h exposure period. However, during the 96 h exposure period, AChE was only inhibited at the highest concentration. Further studies are needed now for more exploration of the toxicity of CBZ since it could be bioaccumulable throughout the food web and may affect non-target organisms.

O berbigão Cerastoderma edule foi exposto a quatro concentrações (5, 10, 20 e 70 μg L-¹) de carbamazepina (CBZ). Este anticonvulsivante alterou o comportamento do mexilhão, reduzindo sua taxa de depuração (CR). A análise do acúmulo de CBZ nos tecidos de C. edule foi realizada por HPLC-UV após 48 ou 96 horas de exposição. Além disso, uma superprodução de H2O2 pelos bivalves foi detectada após a exposição à CBZ, mas os níveis de nitrito permaneceram inalterados. Além disso, as atividades de superóxido dismutase e catalase apresentaram aumento significativo em relação ao contato com CBZ. A atividade da enzima de biotransformação glutationa-S-transferase não se alterou durante a exposição. Os níveis de malondialdeído (MDA), indicando dano celular, aumentaram quando os bivalves foram expostos a 20 e 70 μg l-1 de carbamazepina por 96 h CBZ. Os resultados também indicam que a atividade da acetilcolinesterase (AChE) foi inibida em todas as concentrações de CBZ durante o período de exposição de 48 horas. No entanto, durante o período de exposição de 96 horas, a AChE foi inibida apenas na concentração mais alta. Mais estudos são necessários agora para uma maior exploração da toxicidade da CBZ, uma vez que pode ser bioacumulável em toda a cadeia alimentar e pode afetar organismos não alvo.

Spatio-temporal distribution patterns of Chironomidae communities in the wadis of Northern Tunisia / Padrões de distribuição espaço-temporal de comunidades Chironomidae nos wadis do norte da Tunísia

In Northern Tunisia, seasonal streams, called wadi, are characterized by extreme hydrological and thermal conditions. These freshwater systems have very particular features as a result of their strong irregularity of flow due to limited precipitation runoff regime, leading to strong seasonal hydrologic fluctuations. The current study focused on the spatio-temporal distribution of chironomids in 28 sampling sites spread across the Northern Tunisia. By emplying PERMANOVA, the results indicated a significant spatio-temporal variation along various environmental gradients. The main abiotic factors responsible for noted differences in the spatial distribution of chironomids in wadi were the conductivity and temperature, closely followed by altitude, pH, salinity, talweg slope and dissolved oxygen, identified as such by employing distance-based linear models' procedure. The Distance-based redundancy analysis ordination showed two main groups: the first clustered the Bizerte sites, which were characterized by high water conductivity, sodium concentration and salinity. The second main group comprised sites from the Tell zone and was characterized by low temperatures, neutral pH, low conductivity and nutrients content. The subfamily TANYPODIINAE (e.g., Prochladius sp., Prochladius choerus (Meigen, 1804) and Macropelopia sp.) was the dominant group at Tell zone, whereas species such as Diamesa starmachi (Kownacki et Kownacha, 1970) and Potthastia gaedii (Meigen, 1838) were found only in Tell Wadis. In contrast, chironomid species such as Diamesa starmachi (Kownacki et Kownacha, 1970), Potthastia gaedii (Meigen, 1838), Procladius choreus (Meigen, 1804) were specific for Tell Mountain. Cap Bon wadis region was dominated by genus Cladotanytarsus sp. The results of this survey liked the taxonomic composition of chironomid assemblages to the variation of hydromorphological and physic-chemical gradients across the northern Tunisia wadis.

No norte da Tunísia, riachos sazonais chamados wadi são caracterizados por condições hidrológicas e térmicas extremas. Esses sistemas de água doce têm características muito particulares como resultado de sua forte irregularidade de fluxo devido ao regime de escoamento de precipitação limitado, levando a fortes flutuações hidrológicas sazonais. O estudo atual enfocou a distribuição espaço-temporal dos quironomídeos em 28 locais de amostragem espalhados pelo norte da Tunísia. Ao aplicar PERMANOVA, os resultados indicaram uma variação espaço-temporal significativa ao longo de vários gradientes ambientais. Os principais fatores abióticos responsáveis pelas diferenças observadas na distribuição espacial dos quironomídeos no wadi foram a condutividade e a temperatura, seguidos de perto por altitude, pH, salinidade, declive do talvegue e oxigênio dissolvido, identificados como tais empregando o procedimento de modelos lineares baseados na distância. A ordenação da análise de redundância baseada em distância mostrou dois grupos principais: o primeiro agrupou os sítios Bizerte, que foram caracterizados por alta condutividade da água, concentração de sódio e salinidade. O segundo grupo principal compreendia locais da zona de Tell e era caracterizado por baixas temperaturas, pH neutro, baixa condutividade e conteúdo de nutrientes. A subfamília Tanypodiinae (por exemplo, Prochladius sp., Prochladius choerus [Meigen, 1804] e Macropelopia sp.) era o grupo dominante na zona de Tell, enquanto espécies como Diamesa starmachi (Kownacki et Kownacha, 1970) e Potthastia gaedii (Meigen, 1838) foram encontradas apenas em Tell Wadis. Em contraste, espécies de quironomídeos, como Diamesa starmachi (Kownacki et Kownacha, 1970), Potthastia gaedii (Meigen, 1838), Procladius choreus (Meigen, 1804), eram específicas para Tell Mountain. A região de Cap Bon wadis [...].

Impact of treated sewage on meiobenthic nematodes: a case study from the Tunisian Refining Industries Company

Abstract The main objective of the current study was to assess the impact of the water taken from the Tunisian Refining Industries Company on meiobenthic nematodes, before and after a series of treatments in decantation basins followed by its discharge in Bizerte bay, Tunisia. The comparison of environmental parameters of the two types of water was clearly indicative of an improvement in the quality of treated waters after a significant reduction in their loads in hydrocarbons. Overall, the water retained a good quality after being treated by Tunisian Refining Industries Company before discharge in the sea. At the end of the experiment, differential responses were observed according to the richness of sediment in organic matter and hydrocarbons. Thus, it was apparent that the nematode assemblage exposed to the treated waters was closer to controls and associated to higher values of abundance, than that under untreated ones. It was also assumed that the species Microlaimus honestus De Man, 1922, Paramonohystera proteus Wieser, 1956 and Cyartonema germanicum Juario, 1972 are sensitive bioindicators of bad environmental statues and of hydrocarbon presence in the environment. On the other hand, Metoncholaimus pristiurus (Zur Strassen, 1894) Filipjev, 1918 would rather be classified as a positive bioindicative species of this type of pollutants.

Resumo O principal objetivo do presente estudo foi avaliar o impacto da água retirada da Tunisian Refining Industries Company sobre os nematoides meiobentônicos, antes e depois de uma série de tratamentos em bacias de decantação seguidos de seu descarte na baía de Bizerte, Tunísia. A comparação dos parâmetros ambientais dos dois tipos de água foi claramente indicativa de uma melhoria na qualidade das águas tratadas após uma redução significativa das suas cargas em hidrocarbonetos. No geral, a água reteve uma boa qualidade após ser tratada pela Tunisian Refining Industries Company antes da descarga no mar. Ao final do experimento, foram observadas respostas diferenciais de acordo com a riqueza de sedimentos em matéria orgânica e hidrocarbonetos. Assim, ficou claro que a assembleia de nematoides exposta às águas tratadas estava mais próxima dos controles e associada a maiores valores de abundância do que nas não tratadas. Também foi assumido que as espécies Microlaimus honestus De Man, 1922, Paramonohystera proteus Wieser, 1956 e Cyartonema germanicum Juario, 1972 são bioindicadores sensíveis de más estátuas ambientais e da presença de hidrocarbonetos no meio ambiente. Por outro lado, Metoncholaimus pristiurus (Zur Strassen, 1894) Filipjev, 1918 preferiria ser classificado como uma espécie bioindicativa positiva deste tipo de poluentes.

Assessment of carbamazepine acute toxicity in the cockle Cerastoderma edule through chemical, physiological and biochemical tools

Abstract The cockle Cerastoderma edule was exposed to four concentrations (5, 10, 20 and 70 g L-1) of carbamazepine (CBZ). This anticonvulsant was found to alter the mussel behavior of by reducing its clearance rate (CR). Analysis of CBZ accumulation in tissues of C. edule was carried out using HPLC-UV after 48 or 96 hours of exposure. In addition, an overproduction of H2O2 by the bivalves was detected following exposure to CBZ but nitrite levels remained unchanged. Moreover, superoxide dismutase and catalase activities showed a significant increase in relation to their contact with CBZ. The activity of the biotransformation enzyme gluthatione-S-transferase did not change during exposure. Malondialdehyde (MDA) levels indicating cellular damage, increased when bivalves were exposed to 20 and 70 g l-1 of carbamazepine for 96 h CBZ. The results also indicate that acetylcholinesterase activity (AChE) was inhibited in all CBZ concentrations during the 48 h exposure period. However, during the 96 h exposure period, AChE was only inhibited at the highest concentration. Further studies are needed now for more exploration of the toxicity of CBZ since it could be bioaccumulable throughout the food web and may affect non-target organisms.

Resumo O berbigão Cerastoderma edule foi exposto a quatro concentrações (5, 10, 20 e 70 g L-1) de carbamazepina (CBZ). Este anticonvulsivante alterou o comportamento do mexilhão, reduzindo sua taxa de depuração (CR). A análise do acúmulo de CBZ nos tecidos de C. edule foi realizada por HPLC-UV após 48 ou 96 horas de exposição. Além disso, uma superprodução de H2O2 pelos bivalves foi detectada após a exposição à CBZ, mas os níveis de nitrito permaneceram inalterados. Além disso, as atividades de superóxido dismutase e catalase apresentaram aumento significativo em relação ao contato com CBZ. A atividade da enzima de biotransformação glutationa-S-transferase não se alterou durante a exposição. Os níveis de malondialdeído (MDA), indicando dano celular, aumentaram quando os bivalves foram expostos a 20 e 70 g l-1 de carbamazepina por 96 h CBZ. Os resultados também indicam que a atividade da acetilcolinesterase (AChE) foi inibida em todas as concentrações de CBZ durante o período de exposição de 48 horas. No entanto, durante o período de exposição de 96 horas, a AChE foi inibida apenas na concentração mais alta. Mais estudos são necessários agora para uma maior exploração da toxicidade da CBZ, uma vez que pode ser bioacumulável em toda a cadeia alimentar e pode afetar organismos não alvo.

Spatio-temporal distribution patterns of Chironomidae communities in the wadis of Northern Tunisia

Abstract In Northern Tunisia, seasonal streams, called wadi, are characterized by extreme hydrological and thermal conditions. These freshwater systems have very particular features as a result of their strong irregularity of flow due to limited precipitation runoff regime, leading to strong seasonal hydrologic fluctuations. The current study focused on the spatio-temporal distribution of chironomids in 28 sampling sites spread across the Northern Tunisia. By emplying PERMANOVA, the results indicated a significant spatio-temporal variation along various environmental gradients. The main abiotic factors responsible for noted differences in the spatial distribution of chironomids in wadi were the conductivity and temperature, closely followed by altitude, pH, salinity, talweg slope and dissolved oxygen, identified as such by employing distance-based linear models procedure. The Distance-based redundancy analysis ordination showed two main groups: the first clustered the Bizerte sites, which were characterized by high water conductivity, sodium concentration and salinity. The second main group comprised sites from the Tell zone and was characterized by low temperatures, neutral pH, low conductivity and nutrients content. The subfamily TANYPODIINAE (e.g., Prochladius sp., Prochladius choerus (Meigen, 1804) and Macropelopia sp.) was the dominant group at Tell zone, whereas species such as Diamesa starmachi (Kownacki et Kownacha, 1970) and Potthastia gaedii (Meigen, 1838) were found only in Tell Wadis. In contrast, chironomid species such as Diamesa starmachi (Kownacki et Kownacha, 1970), Potthastia gaedii (Meigen, 1838), Procladius choreus (Meigen, 1804) were specific for Tell Mountain. Cap Bon wadis region was dominated by genus Cladotanytarsus sp. The results of this survey liked the taxonomic composition of chironomid assemblages to the variation of hydromorphological and physic-chemical gradients across the northern Tunisia wadis.

Resumo No norte da Tunísia, riachos sazonais chamados wadi são caracterizados por condições hidrológicas e térmicas extremas. Esses sistemas de água doce têm características muito particulares como resultado de sua forte irregularidade de fluxo devido ao regime de escoamento de precipitação limitado, levando a fortes flutuações hidrológicas sazonais. O estudo atual enfocou a distribuição espaço-temporal dos quironomídeos em 28 locais de amostragem espalhados pelo norte da Tunísia. Ao aplicar PERMANOVA, os resultados indicaram uma variação espaço-temporal significativa ao longo de vários gradientes ambientais. Os principais fatores abióticos responsáveis pelas diferenças observadas na distribuição espacial dos quironomídeos no wadi foram a condutividade e a temperatura, seguidos de perto por altitude, pH, salinidade, declive do talvegue e oxigênio dissolvido, identificados como tais empregando o procedimento de modelos lineares baseados na distância. A ordenação da análise de redundância baseada em distância mostrou dois grupos principais: o primeiro agrupou os sítios Bizerte, que foram caracterizados por alta condutividade da água, concentração de sódio e salinidade. O segundo grupo principal compreendia locais da zona de Tell e era caracterizado por baixas temperaturas, pH neutro, baixa condutividade e conteúdo de nutrientes. A subfamília Tanypodiinae (por exemplo, Prochladius sp., Prochladius choerus [Meigen, 1804] e Macropelopia sp.) era o grupo dominante na zona de Tell, enquanto espécies como Diamesa starmachi (Kownacki et Kownacha, 1970) e Potthastia gaedii (Meigen, 1838) foram encontradas apenas em Tell Wadis. Em contraste, espécies de quironomídeos, como Diamesa starmachi (Kownacki et Kownacha, 1970), Potthastia gaedii (Meigen, 1838), Procladius choreus (Meigen, 1804), eram específicas para Tell Mountain. A região de Cap Bon wadis foi dominada pelo gênero Cladotanytarsus sp. Os resultados desta pesquisa gostaram da composição taxonômica das assembleias de quironomídeos com a variação dos gradientes hidromorfológicos e físico-químicos nos wadis do norte da Tunísia.

Impact of treated sewage on meiobenthic nematodes: a case study from the Tunisian Refining Industries Company / Impacto de esgoto tratado em nematoides meiobentônicos: um estudo de caso da Tunisian Refining Industries Company

The organization of the roots, ganglia and the peripheral distribution of the cranial nerves of the fully formed embryos of Oreochromis niloticus are examined in the transverse serial sections. These nerves carry fibers, which were also analyzed. The results of this study demonstrated that the glossopharyngeal nerve originates by means of only one root, which leaves the cranium through the glossopharyngeal foramen. This nerve gives fibers (visceromotor) to the first internal and external levator arcus branchialis muscles. There is a single epibranchial (petrosal) ganglion located extracranially. Nervus glossopharyngeus has three rami; pharyngeus, pretramticus and posttrematicus. The ramus pharyngeus carries only viscerosensory fibers; general for the pharyngeal epithelium and special ones for the pseudobranch. General viscerosensory fibers are also carried by rami pretrematicus and posttrematicus for the pharyngeal epithelial lining. The special sensory fibers are carried by the ramus pretrematicus for the taste buds and by ramus posttrematicus for the gill filaments. The ramus pretrematicus also carries visceromotor fibers for the first adductor arcus branchialis and to the first obliquus ventralis muscles.

A organização das raízes, gânglios e a distribuição periférica dos nervos cranianos dos embriões totalmente formados de Oreochromis niloticus são examinados nas seções transversais seriais. Esses nervos carregam fibras, que também foram analisadas. Os resultados deste estudo demonstraram que o nervo glossofaríngeo se origina por meio de apenas uma raiz, que sai do crânio pelo forame glossofaríngeo. Este nervo fornece fibras (visceromotoras) para os primeiros músculos levantadores do arco branquial interno e externo. Existe um único gânglio epibranquial (petroso) localizado extracranialmente. Nervus glossopharyngeus tem três ramos; faríngeo, pretramticus e póstrematicus. O ramo faríngeo contém apenas fibras viscerossensoriais ­ gerais para o epitélio faríngeo e especiais para o pseudobrânquio. Fibras viscerossensoriais gerais também são transportadas por ramos pretrematicus e posttrematicus para o revestimento epitelial da faringe. As fibras sensoriais especiais são transportadas pelo ramus pretrematicus para as papilas gustativas e pelo ramus posttrematicus para os filamentos branquiais. O ramo pretrematicus também carrega fibras visceromotoras para o primeiro adutor arcus branchialis e para o primeiro músculo oblíquo ventral.

Spatio-temporal distribution patterns of Chironomidae communities in the wadis of Northern Tunisia / Padrões de distribuição espaço-temporal de comunidades Chironomidae nos wadis do norte da Tunísia

In Northern Tunisia, seasonal streams, called wadi, are characterized by extreme hydrological and thermal conditions. These freshwater systems have very particular features as a result of their strong irregularity of flow due to limited precipitation runoff regime, leading to strong seasonal hydrologic fluctuations. The current study focused on the spatio-temporal distribution of chironomids in 28 sampling sites spread across the Northern Tunisia. By emplying PERMANOVA, the results indicated a significant spatio-temporal variation along various environmental gradients. The main abiotic factors responsible for noted differences in the spatial distribution of chironomids in wadi were the conductivity and temperature, closely followed by altitude, pH, salinity, talweg slope and dissolved oxygen, identified as such by employing distance-based linear models' procedure. The Distance-based redundancy analysis ordination showed two main groups: the first clustered the Bizerte sites, which were characterized by high water conductivity, sodium concentration and salinity. The second main group comprised sites from the Tell zone and was characterized by low temperatures, neutral pH, low conductivity and nutrients content. The subfamily TANYPODIINAE (e.g., Prochladius sp., Prochladius choerus (Meigen, 1804) and Macropelopia sp.) was the dominant group at Tell zone, whereas species such as Diamesa starmachi (Kownacki et Kownacha, 1970) and Potthastia gaedii (Meigen, 1838) were found only in Tell Wadis. In contrast, chironomid species such as Diamesa starmachi (Kownacki et Kownacha, 1970), Potthastia gaedii (Meigen, 1838), Procladius choreus (Meigen, 1804) were specific for Tell Mountain. Cap Bon wadis region was dominated by genus Cladotanytarsus sp. The results of this survey liked the taxonomic composition of chironomid assemblages to the variation of hydromorphological and physic-chemical gradients across the northern Tunisia wadis.

No norte da Tunísia, riachos sazonais chamados wadi são caracterizados por condições hidrológicas e térmicas extremas. Esses sistemas de água doce têm características muito particulares como resultado de sua forte irregularidade de fluxo devido ao regime de escoamento de precipitação limitado, levando a fortes flutuações hidrológicas sazonais. O estudo atual enfocou a distribuição espaço-temporal dos quironomídeos em 28 locais de amostragem espalhados pelo norte da Tunísia. Ao aplicar PERMANOVA, os resultados indicaram uma variação espaço-temporal significativa ao longo de vários gradientes ambientais. Os principais fatores abióticos responsáveis pelas diferenças observadas na distribuição espacial dos quironomídeos no wadi foram a condutividade e a temperatura, seguidos de perto por altitude, pH, salinidade, declive do talvegue e oxigênio dissolvido, identificados como tais empregando o procedimento de modelos lineares baseados na distância. A ordenação da análise de redundância baseada em distância mostrou dois grupos principais: o primeiro agrupou os sítios Bizerte, que foram caracterizados por alta condutividade da água, concentração de sódio e salinidade. O segundo grupo principal compreendia locais da zona de Tell e era caracterizado por baixas temperaturas, pH neutro, baixa condutividade e conteúdo de nutrientes. A subfamília Tanypodiinae (por exemplo, Prochladius sp., Prochladius choerus [Meigen, 1804] e Macropelopia sp.) era o grupo dominante na zona de Tell, enquanto espécies como Diamesa starmachi (Kownacki et Kownacha, 1970) e Potthastia gaedii (Meigen, 1838) foram encontradas apenas em Tell Wadis. Em contraste, espécies de quironomídeos, como Diamesa starmachi (Kownacki et Kownacha, 1970), Potthastia gaedii (Meigen, 1838), Procladius choreus (Meigen, 1804), eram específicas para Tell Mountain. A região de Cap Bon wadis foi dominada pelo gênero Cladotanytarsus sp. Os resultados desta pesquisa gostaram da composição taxonômica das assembleias de quironomídeos com a variação dos gradientes hidromorfológicos e físico-químicos nos wadis do norte da Tunísia.

Assessment of carbamazepine acute toxicity in the cockle Cerastoderma edule through chemical, physiological and biochemical tools / Avaliação da toxicidade aguda da carbamazepina no berbigão Cerastoderma edule por meio de ferramentas químicas, fisiológicas e bioquímicas

The cockle Cerastoderma edule was exposed to four concentrations (5, 10, 20 and 70 µg L-1) of carbamazepine (CBZ). This anticonvulsant was found to alter the mussel behavior of by reducing its clearance rate (CR). Analysis of CBZ accumulation in tissues of C. edule was carried out using HPLC-UV after 48 or 96 hours of exposure. In addition, an overproduction of H2O2 by the bivalves was detected following exposure to CBZ but nitrite levels remained unchanged. Moreover, superoxide dismutase and catalase activities showed a significant increase in relation to their contact with CBZ. The activity of the biotransformation enzyme gluthatione-S-transferase did not change during exposure. Malondialdehyde (MDA) levels indicating cellular damage, increased when bivalves were exposed to 20 and 70 µg l-1 of carbamazepine for 96 h CBZ. The results also indicate that acetylcholinesterase activity (AChE) was inhibited in all CBZ concentrations during the 48 h exposure period. However, during the 96 h exposure period, AChE was only inhibited at the highest concentration. Further studies are needed now for more exploration of the toxicity of CBZ since it could be bioaccumulable throughout the food web and may affect non-target organisms.

O berbigão Cerastoderma edule foi exposto a quatro concentrações (5, 10, 20 e 70 µg L-1) de carbamazepina (CBZ). Este anticonvulsivante alterou o comportamento do mexilhão, reduzindo sua taxa de depuração (CR). A análise do acúmulo de CBZ nos tecidos de C. edule foi realizada por HPLC-UV após 48 ou 96 horas de exposição. Além disso, uma superprodução de H2O2 pelos bivalves foi detectada após a exposição à CBZ, mas os níveis de nitrito permaneceram inalterados. Além disso, as atividades de superóxido dismutase e catalase apresentaram aumento significativo em relação ao contato com CBZ. A atividade da enzima de biotransformação glutationa-S-transferase não se alterou durante a exposição. Os níveis de malondialdeído (MDA), indicando dano celular, aumentaram quando os bivalves foram expostos a 20 e 70 µg l-1 de carbamazepina por 96 h CBZ. Os resultados também indicam que a atividade da acetilcolinesterase (AChE) foi inibida em todas as concentrações de CBZ durante o período de exposição de 48 horas. No entanto, durante o período de exposição de 96 horas, a AChE foi inibida apenas na concentração mais alta. Mais estudos são necessários agora para uma maior exploração da toxicidade da CBZ, uma vez que pode ser bioacumulável em toda a cadeia alimentar e pode afetar organismos não alvo.

Impact of treated sewage on meiobenthic nematodes: a case study from the Tunisian Refining Industries Company.

The main objective of the current study was to assess the impact of the water taken from the 'Tunisian Refining Industries Company' on meiobenthic nematodes, before and after a series of treatments in decantation basins followed by its discharge in Bizerte bay, Tunisia. The comparison of environmental parameters of the two types of water was clearly indicative of an improvement in the quality of treated waters after a significant reduction in their loads in hydrocarbons. Overall, the water retained a good quality after being treated by 'Tunisian Refining Industries Company' before discharge in the sea. At the end of the experiment, differential responses were observed according to the richness of sediment in organic matter and hydrocarbons. Thus, it was apparent that the nematode assemblage exposed to the treated waters was closer to controls and associated to higher values of abundance, than that under untreated ones. It was also assumed that the species Microlaimus honestus De Man, 1922, Paramonohystera proteus Wieser, 1956 and Cyartonema germanicum Juario, 1972 are sensitive bioindicators of bad environmental statues and of hydrocarbon presence in the environment. On the other hand, Metoncholaimus pristiurus (Zur Strassen, 1894) Filipjev, 1918 would rather be classified as a positive bioindicative species of this type of pollutants.

Assessment of carbamazepine acute toxicity in the cockle Cerastoderma edule through chemical, physiological and biochemical tools.

The cockle Cerastoderma edule was exposed to four concentrations (5, 10, 20 and 70 µg L-1) of carbamazepine (CBZ). This anticonvulsant was found to alter the mussel behavior of by reducing its clearance rate (CR). Analysis of CBZ accumulation in tissues of C. edule was carried out using HPLC-UV after 48 or 96 hours of exposure. In addition, an overproduction of H2O2 by the bivalves was detected following exposure to CBZ but nitrite levels remained unchanged. Moreover, superoxide dismutase and catalase activities showed a significant increase in relation to their contact with CBZ. The activity of the biotransformation enzyme gluthatione-S-transferase did not change during exposure. Malondialdehyde (MDA) levels indicating cellular damage, increased when bivalves were exposed to 20 and 70 µg l-1 of carbamazepine for 96 h CBZ. The results also indicate that acetylcholinesterase activity (AChE) was inhibited in all CBZ concentrations during the 48 h exposure period. However, during the 96 h exposure period, AChE was only inhibited at the highest concentration. Further studies are needed now for more exploration of the toxicity of CBZ since it could be bioaccumulable throughout the food web and may affect non-target organisms.

Spatio-temporal distribution patterns of Chironomidae communities in the wadis of Northern Tunisia.

In Northern Tunisia, seasonal streams, called wadi, are characterized by extreme hydrological and thermal conditions. These freshwater systems have very particular features as a result of their strong irregularity of flow due to limited precipitation runoff regime, leading to strong seasonal hydrologic fluctuations. The current study focused on the spatio-temporal distribution of chironomids in 28 sampling sites spread across the Northern Tunisia. By emplying PERMANOVA, the results indicated a significant spatio-temporal variation along various environmental gradients. The main abiotic factors responsible for noted differences in the spatial distribution of chironomids in wadi were the conductivity and temperature, closely followed by altitude, pH, salinity, talweg slope and dissolved oxygen, identified as such by employing distance-based linear models' procedure. The Distance-based redundancy analysis ordination showed two main groups: the first clustered the Bizerte sites, which were characterized by high water conductivity, sodium concentration and salinity. The second main group comprised sites from the Tell zone and was characterized by low temperatures, neutral pH, low conductivity and nutrients content. The subfamily TANYPODIINAE (e.g., Prochladius sp., Prochladius choerus (Meigen, 1804) and Macropelopia sp.) was the dominant group at Tell zone, whereas species such as Diamesa starmachi (Kownacki et Kownacha, 1970) and Potthastia gaedii (Meigen, 1838) were found only in Tell Wadis. In contrast, chironomid species such as Diamesa starmachi (Kownacki et Kownacha, 1970), Potthastia gaedii (Meigen, 1838), Procladius choreus (Meigen, 1804) were specific for Tell Mountain. Cap Bon wadis region was dominated by genus Cladotanytarsus sp. The results of this survey liked the taxonomic composition of chironomid assemblages to the variation of hydromorphological and physic-chemical gradients across the northern Tunisia wadis.

Effects of ferroelectric oxides of barium strontium titanate (Ba0.85Sr0.15TiO3) nanoparticles on Ruditapes decussatus assessed through chemical, physiological, and biochemical methods.

Here, the effects of a newly designed ferroelectric oxide synthesized by solid reaction, barium strontium titanate [BST (85/15)] (Ba0.85Sr0.15TiO3), on the carpet shell clam Ruditapes decussatus were investigated. These clams were exposed to four concentrations of BST (85/15) nanoparticles (0.001, 0.01, 0.1, and 1 mg.L-1), and BST (85/15) was absorbed by R. decussatus in an exposure intensity-dependent manner. Measurements of clearance rate and biomarkers confirmed that the nanoparticles significantly affected the health of clams in an organ-dependent manner. Interestingly, BST (85/15) nanoparticles stimulated acetylcholinesterase (AChE) activity in the clams, suggesting their usefulness as antagonists of AChE inhibiting pollutants. These findings demonstrate the suitability of R. decussatus as a test organism to provide a framework for understanding the toxicological effects of these newly designed ferroelectrics. Moreover, concentrations of BST (85/15) < 0.1 mg.L-1 could be good alternatives to lead-based ferroelectric oxides and could be sustainable tools for use in electronic applications.

Stress-induced selection of a single species from an entire meiobenthic nematode assemblage: is this possible using iron enrichment and does pre-exposure affect the ease of the process?

The present work proposes a new experimental design using iron enrichment to select a single species from an entire meiobenthic nematode community. The high diversity of nematodes makes it impossible to study their responses to stressors in terms of chemical biomarkers, as this kind of research demands a single species as a form of biological material. Two assemblages, one from a control site (Canal) and one from an iron-contaminated site (Fouledh) in Bizerte Lagoon (Tunisia), were used to validate the protocol and to study whether pre-exposure to iron could affect the ease of the selection process. Analyses of variance suggested that the abundance and species number of nematodes from the Canal and Fouledh sites decreased discernibly with exposure to iron. Multivariate analyses performed on nematode abundances revealed that Oncholaimus campylocercoides, Sabatieria granifer, Sabatieria punctata and Theristus flevensis were the most tolerant species, probably due to their deposit-feeding behaviour. Species with a restricted feeding spectrum showed a low tolerance potential. At the end of the experiment, O. campylocercoides became the unique component of the nematode community from both sites. The complete alteration of the community was achieved with more difficulty for nematodes from Fouledh than for those from Canal. The identity of the selected species was confirmed at both the morphological levels and by sequencing the nuclear small subunit ribosomal DNA (18S rDNA).

Effects of permethrin on biomarkers in Mediterranean clams (Ruditapes decussatus).

The present study was focused on the assessment of Catalase (CAT) and Acetylcholinesterase (AChE) activities in Mediterranean clams (Ruditapes decussatus) exposed to 50, 100 and 150 µg/L of Permethrin for 5, 10, 15, 20 and 25 days. In water, the measured concentrations of Permethrin in the treated aquariums were respectively 16.66, 38.24 and 55.61 µg/L. Results showed that CAT activity was increased after 5 days of exposure to high concentration reaching maximum value of 10.14 µmol/min/mg proteins after 25 days. However, no significant changes in AChE activity after 5 days of exposure were detected in all treated groups. AChE activity was significantly inhibited after 10 days with 100 and 150 µg/L and still depending on concentration and time. Maximum inhibition of AChE activity was reached after 25 days with the highest concentration of Permethrin. Our data indicated that exposure to Permethrin modifies biomarker profiles inducing oxidative stress and reducing AChE activity in Mediterranean clams.

Effects of increasing levels of nickel contamination on structure of offshore nematode communities in experimental microcosms.

A microcosm experiment was used to examine the effects of nickel on offshore nematode communities of a Tunisian coastal zone (Southwestern Mediterranean Sea). Sediments were contaminated with three nickel concentrations [low (250 ppm), medium (550 ppm) and high (900 ppm)], and effects were examined after 30 days. Results showed significant differences between nematode assemblages from undisturbed controls and those from nickel treatments. Most univariates measures, including diversity and species richness, decreased significantly with increasing level of Ni contamination. Results from multivariate analyses of the species abundance data demonstrated that responses of nematode species to the nickel treatments were varied: Leptonemella aphanothecae was eliminated at all the nickel doses tested and seemed to be intolerant species to nickel contamination; Daptonema normandicum, Neochromadora trichophora and Odontophora armata which significantly increased at 550 ppm nickel concentration appeared to be "opportunistic" species at this dose whereas Oncholaimus campylocercoides and Bathylaimus capacosus which increased at all doses tested (250, 550 and 900 ppm) seemed to be "nickel-resistant" species.

Individual and combined effects of cadmium and diesel on a nematode community in a laboratory microcosm experiment.

A microcosm experiment was carried out to study the influence of cadmium and diesel, individually and in a mixture, on a free living nematode community of a Tunisian lagoon. Sediments were contaminated with cadmium that ranged in concentration from 0.54 to 1.40 mg Cd kg(-1) (dry weight (dw)), by diesel at 0.25 mg kg(-1) (dw), by a cadmium-diesel mixture (Cd at 1.40 mg kg(-1)+Diesel at 0.25 mg kg(-1)) and effects were examined after 90 days. Univariate analysis showed that all univariate indices did not change significantly neither at all the levels of cadmium contamination nor at 0.25 mg kg(-1) (dw) diesel concentration. But, at the cadmium-diesel mixture, significant differences were recorded between nematode assemblages from uncontaminated sediment control microcosm and those from cadmium-diesel mixture amended sediment treatments. Total nematode abundance (I), mean individual weight (bi), Shannon-Weaver index H', species richness (d), evenness (J') and number of species (S) decreased significantly in microcosms contaminated with both cadmium and diesel. Results from multivariate analyses of the species abundance data demonstrated that responses of nematode species to the cadmium-diesel treatments were varied: Marylynnia stekhoveni, Calomicrolaimus honestus and Oncholaimellus mediterraneus were significantly affected at the cadmium-diesel contamination but they were not eliminated. These species could be categorized as "cadmium-diesel sensitive". Enoploides sp. and Oncholaimus campylocercoides, characterized by increased abundances in cadmium-diesel amended sediment, seemed to be "cadmium-diesel resistant" species. All these species, "cadmium-diesel sensitive" or "cadmium-diesel resistant", were not affected by either cadmium or diesel alone.