Knowing the mercury levels of an environment allows a diverse array of biogeochemical studies into the mercury cycle on a local or global scale. Among matrices commonly evaluated, water remains a challenge for research because its mercury levels can be very low, requiring development of complex analytical protocols. Currently, sample preservation methods, protocols that avoid contamination, and analytical techniques with low detection limits allow analysis of mercury in pristine waters. However, different protocols suggest different methods depending on a range of factors such as the characteristics of water sampled and storage time. In remote areas, such as oceanic and Amazonian regions, sample preservation and transport to a laboratory can be difficult, requiring processing of the water during the sampling expedition and the establishment of a field laboratory. Brazilian research on mercury in water can be limited due to difficulty obtaining reagents, lack of laboratory structure, qualified personnel, and financial support. Considering this complexity for analyzing water, we reviewed methodologies for sampling, preservation, and storage of water samples for analysis of the most commonly evaluated mercury species (dissolved gaseous mercury, reactive mercury, methylmercury and total mercury).

A pesca esportiva de tucunarés Cichla spp., na Amazônia brasileira, aumentou em popularidade nos últimos anos e tem atraído pescadores esportivos que geram benefícios econômicos para essa região. Entretanto, a sustentabilidade dessa pescaria depende em parte da sobrevivência dos peixes capturados por meio da prática do pesque e solte. O objetivo deste trabalho foi avaliar a mortalidade de Cichla spp., incluindo o tucunaré paca (C. temensis Humbolt), o borboleta (C. orinocensis Humbolt) e o popoca (C. monoculus Agassiz) em dois locais na bacia do rio Negro, o maior tributário do rio Amazonas. Os peixes foram capturados por variados tipos de iscas artificiais e posteriormente monitorados em viveiros construídos no próprio rio por 72 horas. Um total de 162 tucunarés foi capturado, e as mortalidades (% ± intervalo de confiança 95%) foram calculadas. A mortalidade foi 3,5% (± 5,0), 2,3% (± 3,2) e 5,2% (±10,2) para o paca, o borboleta e o popoca, respectivamente. O comprimento padrão dos peixes capturados variou de 26 a 79 cm, mas apenas os peixes menores até 42 cm morreram. A pesquisa sugere que a pesca esportiva não causou substancial mortalidade na população de Cichla spp. na bacia do rio Negro.

Sport fishing for peacock bass Cichla spp. in the Brazilian Amazon has increased in popularity and attracts anglers who generate significant economic benefits in rural regions. The sustainability of this fishery is partly dependent on the survival of fish caught through catch-and-release fishing. The objective of this work was to investigate, hooking mortality of Cichla spp., including speckled peacock bass (C. temensis Humbolt), butterfly peacock bass (C. orinocensis Humbolt), and popoca peacock bass (C. monoculus Agassiz) in the basin of the Negro River, the largest tributary of the Amazon River. Fish were caught at two different sites using artificial lures, transported to pens anchored in the river and monitored for 72 hours. A total of 162 individual peacock bass were captured and hooking mortality (mean % ± 95% confidence intervals) was calculated. Mean mortality was 3.5% (± 5.0), 2.3% (± 3.5) and 5.2% (± 10.2) for speckled peacock bass, butterfly peacock bass, and popoca peacock bass, respectively. Lengths of captured fish ranged from 26 to 79 cm (standard length), however, only fish under 42 cm died. This research suggests that catch-and-release sport fishing of peacock bass does not result in substantial mortality in the Negro River basin.

Con el propósito de evaluar la participación de bacterias heterotróficas en el flujo de carbono en la cadena trófica de un lago de inundación amazónico, recolectas mensuales de estos microorganismos fueron realizadas durante el año hidrológico de diciembre de 2007 hasta noviembre de 2008, en las regiones litoral, pelágica y de macrófitas acuáticas del lago Catalão, en la Amazonia central brasilera. Las bacterias fueron multiplicadas in vitro, usando como sustrato carbono orgánico disuelto (COD) del lago en cada una de las regiones estudiadas, para posterior análisis de la abundancia de isotopos estables de carbono y nitrógeno. Estos datos fueron confrontados con los valores de COD de los cuatro periodos limnológicos del lago (seca, inundación, llena y bajada de aguas). En general se encontró que la fuente principal de carbono de las bacterias heterotróficas fue aquella de origen C4, que presentó un aporte mínimo de 75%, en la medida en que el d13C de las bacterias presentó valor medio de -17,72‰ ± 2,25. Confrontando ese valor, con el d13C del zooplancton en el mismo período (- 33,04‰ ± 3,81) se concluye que el aporte de las bacterias heterotróficas al flujo de carbono hacia niveles tróficos superiores en el lago estudiado es mínimo.

In order to evaluate the role of heterotrophic bacteria on carbon flow in food chains of an Amazonian floodplain lake, monthly collections of these organisms were made during the hydrological year from December 2007 to November 2008. Littoral, pelagic, and aquatic macrophyte regions of the Catalão Lake in Central Amazonia were sampled and bacteria were multiplied in vitro, using dissolved organic carbon (COD) of each one of the regions studied as a substrate. The bacterial biomass obtained was used for stable isotope analyses of carbon and nitrogen. These data were confronted with COD values of the four hydrological periods of the lake (dry, rising, flood and fall). In general, it was found that the main source of carbon for heterotrophic bacteria was that of C4 origin, which presented a minimum contribution of 75% of bacterial biomass, to the extent that the bacteria d13C average value was -17.72‰ ± 2.25. Comparing this value with the d13C of zooplankton in the same period (-33.04‰ ± 3.81) permit concludes that the contribution of heterotrophic bacteria in the carbon flow to higher trophic levels in the Catalão lake is minimal.

Amostras de água foram coletadas no Rio Amazonas, no Rio Negro (Brasil) e em 17 afluentes do Rio Negro, na Amazônia Central. As análises consistiram em medidas de pH, condutividade, carbono orgânico (DOC) e espectrometria de massas com fonte de ICP. Através da análise multivariada as variáveis foram classificadas em três fatores, correspondentes a 94% da variância. O gráfico de escores de fatores mostrou que a maioria das amostras da Bacia do Rio Negro formam um grupo homogêneo. Testes de ultrafiltração confirmaram que o Rio Negro apresenta compostos orgânicos de massa molecular mais alta que o Rio Solimões, e que alguns metais encontram-se associados com estes compostos. Observou-se também que, nas águas da maioria dos rios da Bacia do Rio Negro, os elementos pesados das Terras Raras estão enriquecidos em relação aos elementos leves, enquanto o contrário ocorre no material particulado.

Water samples were collected in Middle Amazonia from the Amazon River, Rio Negro and 17 tributaries of Rio Negro. The analyses consisted of pH, conductivity, and dissolved organic (DOC) measurements, as well as plasma source mass spectrometry (ICP-MS). Factor analysis revealed three factors, which explained 94% of the total variance. A plot of factor scores presented a cluster containing mostly samples from the Rio Negro Basin. Ultrafiltration tests confirmed that organics from the Rio Negro have higher molecular mass than in the Amazon, and that some metals are associated with these compounds. Heavy rare-earth elements (REE) are enriched relative to light REE in the dissolved fraction of most rivers of the Negro Basin; the opposite occurred in suspended matter.

A concentração de mercúrio total foi determinada em onze espécies de peixes coletados de setembro a outubro de 1991, na área de garimpo de ouro da Cachoeira de Tcotônio e da área considerada controle em Guajará-Mirim, ambas no rio Madeira, Estado de Rondônia. Utilizou-se, para a análise, a técnica de espectrofotometria de absorção atômica com gerador de vapor frio de Hg. Quase todos os peixes predadores da área de garimpo tiveram concentrações de mercúrio acima do nível critico de 0,5 pg.g"1 permitido para consumo humano pelo Ministério da Saúde do Brasil e Organização Mundial de Saúde, sendo bem maiores que as concentrações de mercúrio nas espécies predadoras da área controle, evidenciando a influência do garimpo de ouro na contaminação dos peixes por mercúrio. As espécies não-predadoras tiveram concentrações de mercúrio abaixo daquelas das espécies predadoras para as duas áreas, indicando o efeito da biomagnificação do mercúrio na cadeia alimentar. Procurou-se estabelecer limites para o consumo de peixes pelas populações humanas da área de garimpo estudada, calculando-se a taxa de ingestão necessária para se desenvolver os primeiros sintomas de contaminação mercurial. Concluiu-se que espécies como o pacu podem ser consumidas sem restrição, já os peixes como matrinchã, curimatã, mandi e tucunaré, deveriam ser consumidos com moderação e que a maioria dos peixes predadores (em geral Siluriformes), deveriam ser consumidos apenas esporadicamente. Discutem-se alguns fatores que poderiam estar interagindo no processo de contaminação por mercúrio dos ribeirinhos dessa área de garimpo.

Samples of eleven fish species were collected during September and October of 1991 in the gold mining area of Cachoeira de Teotônio and in the control area Guajará-Mirim, along the Madeira River, (Rondônia, Brazil) and anaiized for total mercury by cold vapor atomic absorption spectrofotometry. Almost all fish predators from the gold mining area had mercury concentrations above the maximal level of 0.5 ug.g"1, permitted for human consumption by Brazilian Secretary of Health and the World Health Organization and much greater than those found in predatory fish species in the control area were all below this critical value (0.5 pg.g'X demonstrating the influence of anthropogenic contamination in the gold mining area. In both areas, non-predators fish species had lower mercury concentrations than predators fish species, indicating the effects of biomagnification of mercury in the food chain. Safety limits for fish consumption by the human populations in this gold mining area were estabilished considering the mercury levels encontred in fish and the critical intake rate associated with the signs of mercury poisoning. Pacu, could be consumed without restrictions, matrinchã, curimatã, mandi and tucunaré, could be consumed with moderation and large predatory fish species (mostly Siluriformes), could be consumed only sporadically. Some factors that could influence mercury contaminations in "ribeirinhos" are discussed.