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1. This work investigated the consumption of a microalgal (Anabaena spiroides) exopolysaccharide by the cladoceran Simocephalus serrulatus (Cladocera, Daphnidae) and its effect on copper toxicity. 2. Total organic carbon concentration was used to quantify the microalgal exopolysaccharide. Both copper-complexed exopolysaccharides and copper-free exopolysaccharides were taken up by S. serrulatus. 3. A reduction of free copper ions was obtained in the presence of A. spiroides exopolysaccharide. Copper toxicity (EC 50 ) and zooplankton concentrations were inversely correlated to exopolysaccharide concentration in experimental media.4. An increase of free copper ions in experimental media was obtained after exopolysaccharide consumption, suggesting that S. serrulatus excreted copper to the surrounding environment.

A nanotecnologia se desenvolveu rapidamente durante a última década, com aplicações em áreas estratégicas, incluindo saúde, energia, eletrônica, entre outras. Atualmente, a nanotecnologia possui um campo de atuação multidisciplinar, sendo o desenvolvimento e utilização de nanopartículas um dos mais importantes campos de aplicação. A alta demanda comercial das nanopartículas de prata (NPAg) e o aumento dos riscos desses compostos de alcançarem os diferentes ecossistemas e, assim, causarem impacto nesses ambientes e na saúde humana têm provocado amplo debate na comunidade científica. A presente revisão faz um breve levantamento do impacto ambiental das NPAg, como transformação, biodisponibilidade e toxicidade e suas consequências para saúde pública, além de uma descrição sobre a atual legislação internacional.

This study aimed to investigate the influence of natural dissolved organic materials (DOM) on copper speciation (total dissolved, particulate, and free Cu2+ ions) and bioavailability during a two-level experimental microbial food chain. Bacteria were used as the first trophic level, and Paramecium caudatum (protozoan) as the second. The organisms were obtained from a freshwater reservoir and kept under controlled laboratory conditions. Three experimental treatments were performed: exposure of the organisms to copper in the absence of DOM, exposure to DOM in the absence of copper, and exposure to both copper and DOM. Freshwater medium containing natural DOM and copper at a total dissolved concentration of 1.8 x 10(-6) mol L(-1) was furnished to bacteria, which was further used as food to the protozoan. The results showed that after bacterial growth, DOM concentration decreased as quantified by total organic carbon determinations. At the same time, free Cu2+ ions concentration increased in the medium. A lower copper concentration was detected in both microorganisms in the presence of DOM. We conclude that natural DOM reduced copper accumulation in the organisms on the first and second trophic levels, thus reducing the entrance of copper into the aquatic microbial food chain.

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