[pt] Neste estudo foram determinadas as concentrações de selênio total (TSe) no músculo, fígado e gônada de três espécies de peixe (Mugil liza - tainha, peixe planctívoro; Bagre spp. - bagre, peixe onívoro e Micropogoni as furnieri - corvina, peixe carnívoro) e também, nos tecidos moles de uma espécie de mexilhão (Perna perna) coletados na Baía de Guanabara. TSe foi determinado por GF-AAS equipado com corretor Zeeman. O modificador químico foi o Pd. A metodologia analítica apresentou ótima precisão e exatidão quando comparada com amostras certificadas, DORM-2 e NIST 2976 e também, através de uma intercalibração laboratorial com amostras de peixe realizada entre dois laboratórios: Radioisótopos na UFRJ e um de referência na Finlândia. Dentre todos os tecidos, o fígado foi o que apresentou as maiores TSe em todas as espécies de peixe. Os peixes carnívoros e planctívoros apresentaram concentrações similares no fígado. O peixe carnívoro foi a espécie que apresentou as maiores TSe no músculo. O músculo parece ser o único tecido que sofreu influência direta do hábito alimentar. Nos peixes, TSe no músculo apresentou uma correlação significativa e positiva com o comprimento total, idade e conseqüentemente, com o tempo de exposição ao meio ambiente. Os mexilhões apresentaram uma correlação significativa entre TSe nos tecidos moles e o índice de condição (IC). Segundo a literatura científica, este trabalho é o segundo do gênero a ser realizado no Brasil. Sendo que este correspondeu ao primeiro trabalho em que se comparou TSe entre os diversos órgãos e tecidos da biota aquática com diferentes hábitos alimentares. / [en] This study assessed total selenium concentrations (TSe) in the muscle tissues, liver and gonads samples of three fish species (Mugil liza - mullet, planktivorous fish; Bagre spp. - catfish, omnivorous fish and Micropogonias furnieri - Atlantic croaker, carnivorous fish) and also in the soft tissues of a mussel (Perna perna) from Guanabara Bay. TSe in the digested samples was analyzed by GF-AAS using Zeeman background correction. Pd was the chemical modifier. The analytical methodology presented high precision and accuracy when tested with certified reference materials, DORM-2 and NIST 2976, and also through intercomparison between two laboratories, Laboratório de Radioisótopos (UFRJ) and a reference laboratory from a Finish National Public Health Institute, using fish samples. The liver samples of all studied fish species presented the highest TSe. Carnivorous and planktivorous fishes presented similar TSe in their liver. Carnivorous fish showed the highest TSe in the muscle. The muscle was the only tissue that presented a direct influence of the feeding habits. Carnivorous and planktivorous fishes showed high positive correlations between TSe in the muscle and their total length, age and consequently, with the exposure time at environment. A significant correlation was observed between the selenium concentration in the mussel soft tissues and the condition index (IC). We verified in the scientific literature that our study was the second one conducted in Brazil. Furthermore it was the first one that compared the total selenium concentrations in organs and tissues of several aquatic organisms with different feeding habits.

Les thiols et le sélénium peuvent jouer un rôle important dans la méthylation du mercure des environnements aquatiques. Pour démontrer la présence des thiols et du sélénium et leur relation avec le mercure dans certains écosystèmes d'eau douce québécois, une campagne d’échantillonnage fut réalisée durant l’été 2010, dans le parc national du Mont-Tremblant (Laurentides, Québec). Il existe une corrélation significative entre le sélénium et le mercure total dans l’eau des lacs du parc. Cependant, les concentrations de sélénium sont très faibles dans les lacs, les étangs de castor et les ruisseaux. Par ailleurs, les lacs du parc national du Mont-Tremblant ont des concentrations relativement élevées de méthylmercure avec une moyenne de 0,33 ng L-1 et des maximums allant jusqu’à 3,29 ng L-1. Les étangs de castor peuvent aussi être considérés comme des lieux de contamination au méthylmercure, avec une concentration moyenne de 0,95 ng L-1. Toutefois, la présence d’une colonie de castors sur le bassin versant d’un lac ne semble pas influencer les concentrations de mercure que l’on y retrouve. Deux thiols sont détectables dans l’eau de surface des Laurentides, soit le glutathion et l’acide thioglycolique. La concentration de ce dernier thiol est corrélée significativement avec celle du mercure total et du méthylmercure. Les thiols peuvent jouer un rôle important dans les processus de méthylation en favorisant le transport du mercure inorganique à l’intérieur des bactéries sulfato-réductrices. Afin de mieux comprendre l’action antagoniste entre le sélénium et le mercure, des études devraient être réalisées au niveau des tissus des organismes vivants dans ces zones pauvres en sélénium. / Thiols and selenium may influence mercury methylation in aquatic environments. To demonstrate the occurrence of both elements with mercury in selected aquatic systems of Quebec, a sampling campaign was conducted during the summer of 2010 in Mont-Temblant national park (Laurentians, Quebec). There is a significant correlation between selenium and total mercury in surface water. However, concentrations of selenium are very low in lakes and beavers ponds. In addition, the park’s lakes have a relatively high concentrations of methyl mercury with an average of 0,33 ng L-1 and maximum values up to 3,29 ng L-1. Beaver ponds can also be considered hotspots of methylmercury contamination, with an average concentration of 0,95 ng L-1. However, the presence of a colony of beavers in the watershed of a lake does not appear to influence the levels of mercury in that lake. Two species of thiols are present in the surface water of the Laurentian ecosystems: glutathione and thioglycolic acid. The latter is significantly correlated with total mercury and methyl mercury. Thiols may play an important role in the methylation process by promoting the transport of inorganic mercury within the sulfate-reducing bacteria. To better undestand the antagonistic action between selenium and mercury, more research should be conducted in the tissue of organisms living in areas of low concentration of selenium to know if they are protected against mercury toxicity.

[pt] Neste estudo foram determinadas as concentrações de Se e Hg, no tecido hepático, muscular e renal, de 70 golfinhos de cinco espécies diferentes (Tursiops truncatus, Stenella frontalis, Steno bredanensis, Sotalia guianensis e Pontoporia blainvillei) e uma espécie de ave marinha (Sula leucogaster), encontrados mortos, durante os anos de 2001 e 2013, na Costa Centro-Norte fluminense. A fim de identificar o processo de bioacumulação e biomagnificação, foram determinadas as concentrações de Se e Hg no fígado e no músculo de cinco espécies de peixe (Trichiurus lepturus, Micropogonias furnieri, Mugil liza, Sardinella brasiliensis, Scomber japonicus) e um cefalópode (Loligo plei). Para auxiliar no estudo dos níveis de Se e Hg, também foram avaliados os valores dos isótopos estáveis Delta 13C e Delta 15N no músculo de todas as espécies envolvidas. As concentrações mais elevadas de mercúrio e selênio foram observadas no fígado dos golfinhos, que apresentaram valores entre 11,2 e 684 mg kg elevado a potência negativa 1 para o Hg e entre 10,2 e 111 mg kg elevado a potência negativa 1 para Se. No músculo foram observadas concentrações mais baixas de Se e Hg nos golfinhos, apresentando concentrações de Hg que variaram entre 1,8 a 9,8 mg kg elevado a potência negativa 1, e de Se que variaram entre 1,9 a 2,3 mg kg elevado a potência negativa 1. A concentração de Hg no rim variou de 1,5 a 22 mg kg elevado a potência negativa 1 e de Se entre 7,6 a 12 mg kg elevado a potência negativa 1 nos golfinhos. Entre as presas, as concentrações mais elevadas de Hg e Se foram observadas no fígado, o mercúrio variou entre 0,3 e 1,6 mg kg elevado a potência negativa 1 e o selênio entre 6,6 e 40,4 mg elevado a potência negativa 1. As concentrações de Hg muscular ficaram entre 0,45 e 0,046 mg kg elevado a potência negativa 1 e de Se muscular entre 2,3 e 1,4 mg kg elevado a potência negativa 1 nas presas. Os golfinhos apresentaram maior enriquecimento de nitrogênio com valores médios entre 14,0 e 17,5 por mil. Para os isótopos estáveis de carbono, os valores médios variaram entre menos 16,8 e menos 15,5 por mil nos cetáceos. A razão isotópica entre as presas varou entre 8,3 e 13,5 por mil para o Delta 15N e entre menos 18,3 a menos 11,9 para o Delta 13C. Foi observado poder de biomagnificação positivo para o mercúrio nas espécies S. guianenis (log [Hg] = menos 0,031 mais 0,195 asterisco Delta 15 N; r igual a 0,719; p menor 0,001) e S. frontalis (log [Hg] igual a menos 0,15 mais 0,21 asterisco Delta 15 N; r igual 0,68; p menor que 0,0001), sendo possível concluir que a biomagnificação do Hg é efetiva na região estudada. / [en] This study determined the concentrations of Se and Hg in the liver, muscle and kidney tissue, of 70 dolphins from five different species (Tursiops truncatus, Stenella frontalis, Steno bredanensis, Sotalia guianensis and Pontoporia blainvillei) and a species of seabird (Sula leucogaster), found dead during 2001 and 2013 on the North-Central Coast of the State of Rio de Janeiro. In order to identify the bioaccumulation and biomagnification processes, the concentrations of Se and Hg in the liver and muscle of five species of fish (Trichiurus lepturus, Micropogonias furnieri, Mugil liza, Sardinella brasiliensis, Scomber japonicus) and a cephalopods (Loligo plei) were determined. To assist in the study of Se and Hg, Delta 13 C and Delta 15 N stable isotopes in the muscle of all investigated were also evaluated species involved. The highest concentrations of mercury and selenium were observed in dolphin liver, which presented values between 11.2 and 684 mg kg elevated to negative power 1 for Hg and between 10.2 and 111.3 mg kg elevated to negative power 1 for Se. In muscle lower concentrations of Se and Hg were observed for these species, showing Hg concentrations ranging from 1.8 to 9.8 mg Kg elevated to negative power 1, while Se ranged from 1.9 to 2.3 mg kg elevated to negative power 1. Hg concentrations in the kidney varied from 1.5 to 22.0 mg kg elevated to negative power 1 and Se between 7.6 to 12.2 mg kg elevated to negative power 1 in dolphins. Among the prey, higher concentrations of Hg and Se were observed in liver, mercury varied from 0.28 to 1.6 mg kg elevated to negative power 1 and selenium between 6.6 and 40.4 mg kg elevated to negative power 1. Hg muscle concentrations were between 0.45 and 0.046 mg kg elevated to negative power 1 and muscle Se between 2.3 and 1.4 mg kg elevated to negative power 1 in the prey. Dolphins show higher nitrogen enrichment with mean values between 14.0 and 17.5 per thousand. For the stable carbon isotopes, the mean values ranged between less 16.8 and less 15.5 per thousand in cetaceans. The isotopic ratio of the prey ranged between 8.3 and 13.5 per thousand for Delta 15N and between less 18.3 and less 11.9 for Delta 13C. Positive biomagnification power was observed for mercury to species S. guianenis (log [Hg] equal less 0.031 more 0.195 asterisk Delta 15N; r equal 0.719; p less than 0.001) and S. frontalis (log [Hg] equal less 0.15 more 0.21 asterisk Delta 15N; r 10 equal 0.68; p less than 0.0001), and indicating that the biomagnification of Hg is effective in the region studied.

Les thiols et le sélénium peuvent jouer un rôle important dans la méthylation du mercure des environnements aquatiques. Pour démontrer la présence des thiols et du sélénium et leur relation avec le mercure dans certains écosystèmes d'eau douce québécois, une campagne d’échantillonnage fut réalisée durant l’été 2010, dans le parc national du Mont-Tremblant (Laurentides, Québec). Il existe une corrélation significative entre le sélénium et le mercure total dans l’eau des lacs du parc. Cependant, les concentrations de sélénium sont très faibles dans les lacs, les étangs de castor et les ruisseaux. Par ailleurs, les lacs du parc national du Mont-Tremblant ont des concentrations relativement élevées de méthylmercure avec une moyenne de 0,33 ng L-1 et des maximums allant jusqu’à 3,29 ng L-1. Les étangs de castor peuvent aussi être considérés comme des lieux de contamination au méthylmercure, avec une concentration moyenne de 0,95 ng L-1. Toutefois, la présence d’une colonie de castors sur le bassin versant d’un lac ne semble pas influencer les concentrations de mercure que l’on y retrouve. Deux thiols sont détectables dans l’eau de surface des Laurentides, soit le glutathion et l’acide thioglycolique. La concentration de ce dernier thiol est corrélée significativement avec celle du mercure total et du méthylmercure. Les thiols peuvent jouer un rôle important dans les processus de méthylation en favorisant le transport du mercure inorganique à l’intérieur des bactéries sulfato-réductrices. Afin de mieux comprendre l’action antagoniste entre le sélénium et le mercure, des études devraient être réalisées au niveau des tissus des organismes vivants dans ces zones pauvres en sélénium. / Thiols and selenium may influence mercury methylation in aquatic environments. To demonstrate the occurrence of both elements with mercury in selected aquatic systems of Quebec, a sampling campaign was conducted during the summer of 2010 in Mont-Temblant national park (Laurentians, Quebec). There is a significant correlation between selenium and total mercury in surface water. However, concentrations of selenium are very low in lakes and beavers ponds. In addition, the park’s lakes have a relatively high concentrations of methyl mercury with an average of 0,33 ng L-1 and maximum values up to 3,29 ng L-1. Beaver ponds can also be considered hotspots of methylmercury contamination, with an average concentration of 0,95 ng L-1. However, the presence of a colony of beavers in the watershed of a lake does not appear to influence the levels of mercury in that lake. Two species of thiols are present in the surface water of the Laurentian ecosystems: glutathione and thioglycolic acid. The latter is significantly correlated with total mercury and methyl mercury. Thiols may play an important role in the methylation process by promoting the transport of inorganic mercury within the sulfate-reducing bacteria. To better undestand the antagonistic action between selenium and mercury, more research should be conducted in the tissue of organisms living in areas of low concentration of selenium to know if they are protected against mercury toxicity.