Impacts of contaminants in freshwater macrophytes

• Autor(a) principal: Roque, Patrícia Alexandra Franco
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/26902
• topic: Herbicides; Contamination; Macrophytes; Freshwater ecosystem; Biochemical profiles; Ecotoxicology

In the last decades, the use of pesticides has been intensified mainly in European Mediterranean regions, and in some cases exceeding the limits of regular legislations established by the European Union. The intensive use of chemicals on agricultural fields surrounding aquatic systems may comport consequences to the ecosystems and communities. Primextra® Gold TZ is one of the most used herbicide in corn crop fields of the Mondego valley, according to the information from agricultural cooperatives. The main active ingredients of the herbicide are S-Metolachlor and Terbuthylazine. Moreover, copper based formulations, such as copper sulphate, are also quite used in agriculture practices being one of the main constituents of these products. Thus, this work pretended to evaluate the toxic and biochemical effects of these chemicals (S-Metolachlor, Terbuthylazine and copper) in the non-target species Lemna minor and Lemna gibba, two freshwater macrophytes, reported as standard species in ecotoxicological bioassays. In a first step, the organisms were exposed to the contaminants under laboratory conditions, after which the biochemical analysis to determine changes on the fatty acids, polysaccharides and free sugars profiles. The results showed L. minor is more sensitive than L. gibba to S-Metolachlor (EC50Lm = 43.10 μg/L (30.89-55.30) and EC50Lg 86.81 μg/L (40.51-133.12), respectively), and to Copper (EC50Lm =199.20 μg/L (149.28-249.13) and EC50Lg =504.31 μg/L (308.73- 699.90), respectively). However, the opposite trend was observed when macrophytes were exposed to Terbuthylazine, with L. minor (EC50=93.43 μg/L (75.35-111.51)) demonstrating less sensitivity to this chemical action than L. gibba (EC50=43.89 μg/L (38.63- 49.15). Furthermore, the composition on lipids decreased, especially polyunsaturated fatty acids (PUFA), and carbohydrates contents also changed with the exposure to all compounds for both species. Therefore, biochemical biomarkers revealed to be important tools and endpoints in ecotoxicological studies and may be used as early-warning indicators of the presence of contaminants at the ecosystems and on the determination of potential effects in aquatic communities.