Uso de espécies nativas em ensaios ecotoxicológicos para avaliar a qualidade de água e sedimento da Bacia Hidrográfica do Rio Doce, RN

Abstract

In the Rio Doce watershed (RDW), Brazilian Northeast, there is an unplanned occupation, pollution and high-water deficit. These factors were aggravated by the drought that started in 2012 and lasted for 5 years. Studies already carried out on this watershed showed high levels of anthropization on their reservoirs near the coast (Extremoz Lake and Doce river). However, there are few information pertaining to their spring areas, in the Mudo and Guajiru rivers. This research sought to describe the chemical and ecotoxicological characteristics of the water and sediment, of eight reservoirs of water, located in the sub basins of the Mute and Guajiru Rivers, in 2016. In addition, this work proposes the use of Cladocera occurring naturally in the watershed, in ecotoxicological studies. This information is divided into three chapters.The first titled "Using Indigenous Cladocera from Doce River Watershed, Northeast of Brazil, as alternatives to exotic organisms in Ecotoxicological Studies.", showing how we implemented cultures and described the life story of two native species (Moina micrura and Ceriodaphnia cornuta), and compared their performance other that of a species standardized and normally used in ecotoxicological studies (C. dubia). The species of Ceriodaphnia investigated exhibit similar life history parameters. In intraspecific comparison, records indicate better results for the cultivation methodology used in this study compared to data available in the literature. It was noticed that M. micrura is more tolerant to sodium chloride (NaCl) the reference substance, followed by C. cornuta and C. dubia. The increased tolerance to salinity of native species is a positive factor, with possibility of indication for their use in semi-arid climates, environments in which events of toxicity could be assigned with greater safety to other parameters besides natural salinity, common in reservoirs affected by prolonged droughts. In the second chapter "Surface water quality of temporary reservoirs located between the semi-arid region and the Brazilian northeast coast", the aim of the study was to analyze physical, chemical and ecotoxicological characteristicsof Doce River headwaters in relation to rainfall, soil occupancy and water quality criteria. It was found that among its two main subbasins electrical conductivity (EC), water hardness, and Cd, Ni and chloride concentrations were significantly. This is probably due the different lithologies. The Cd, Pb, Cu and Zn content, present disconformity to water quality criteria for the protection of aquatic life, for human consumption and animal breeding. The Pb and EC also showed values higher than those indicated for irrigation. Toxic effects were also observed for the reproduction of M. micrura and Ceriodaphnia silvestrii, which suggests the bioavailability of Pb, Cu and Zn. The third chapter, is entitled "Shallow surface water reservoir in the Brazilian semiarid: ecotoxicological and geochemical analysis of sediment.", here are presented the results of a study aiming to describe the behavior of metals (Fe, Cd, Ni, Cu, Mn Pb, Zn and Cr), organic matter (O.M.), carbonate and particle size in the sediments of both subbasins in relation to climate and lithology. Took into consideration possible toxic effects of these physical, chemical and biological variables to the Hyalella azteca e H. meinerti and its application as pollution indicatives. It was observed that the behavior of metal over most sampling stations was not significantly affected by anthropogenic activities. However, in the sampling stations with the highest population densities, toxic effects were verified, with mortality higher than the 20%, what indicates the domestic waste input in that area.