Limnological and ecotoxicological studies in the cascade of reservoirs in the Tietê river (São Paulo, Brazil)

Abstract

An evaluation was made of the quality of samples of water and sediment collected from a series of reservoirs in the Tietê River (SP), based on limnological and ecotoxicological analyses. The samples were collected during two periods (Feb and Jul 2000) from 15 sampling stations. Acute toxicity bioassays were performed using the test organism Daphnia similis, while chronic bioassays were carried out with Ceriodaphnia dubia and Danio rerio larvae. The water samples were analyzed for total nutrients, total suspended matter and total cadmium, chromium, copper and zinc concentrations, while the sediment samples were examined for organic matter, granulometry and potentially bioavailable metals (cadmium, chromium, copper and zinc). The results obtained for the limnological variable, revealed differences in the water quality, with high contribution of nutrients and metals for Tietê and Piracicaba rivers, besides the incorporation and sedimentation, consequently causing a reduction of materials in Barra Bonita reservoir, thus promoting the improvement of the water quality in the other reservoirs. The toxicity bioassays revealed acute toxicity for Daphnia similis only in the reservoirs located below Barra Bonita dam. On the other hand, chronic toxicity for Ceriodaphnia dubia and acute for Danio rerio showed a different pattern, decreasing in magnitude from Barra Bonita to Três Irmãos, demonstrating an environmental degradation gradient in the reservoirs.Keywords: reservoirs ecology, limnology, ecotoxicology, Tietê River. RESUMO Estudos limnológicos e ecotoxicológicos na cascata de reservatórios do rio Tietê (São Paulo, Brasil)O presente trabalho visou avaliar a qualidade de amostras de água e sedimento dos reservatórios em cascata do rio Tietê (SP) através de análises limnológicas e ecotoxicológicas. Foram realizadas coletas de água e sedimento em dois períodos (fevereiro e julho de 2000) e em 15 estações de amostragem. Foram realizados bioensaios de toxicidade aguda para Daphnia similis, de toxicidade crônica para Ceriodaphnia dubia e para larvas pós-eclodidas de Danio rerio. Análises de nutrientes totais, material em suspensão total e cádmio, cromo, cobre e zinco foram realizadas para as amostras de água e análises de matéria orgânica, granulometria e metais biodisponíveis (cádmio, cromo, cobre e zinco) para o sedimento. Os resultados obtidos para as variáveis limnológicas, revelaram diferenças na qualidade da água, com elevado aporte 698 RODGHER, S. et al.

Assessing Water Quality of Murum Reservoir Halfway Through Impoundment

“…At Murum Reservoir, the concentration of DO reduced to 0 mg/L as it went deeper indicating anoxia state as a result of intensive decomposition of organic matter and submerged vegetation leading to depletion of oxygen. This result is similar to that reported in Barra Bonita Reservoir in Brazil (Rodgher et al 2005) and Bakun Reservoir in Malaysia (Nyanti et al 2012). Figure 3 shows the profile of DO concentrations at all stations.…”

“…Temperature is a good indicator to determine thermocline (Dodson et al 2007), in the early stage of this study, thermocline occurrence was observed at 4 to 8 m depths. Table 2 shows the water temperature The dissolved oxygen concentration is a crucial environmental parameter in the dynamics and characterisation of aquatic ecosystems (Rodgher et al 2005). Figure 3 shows the profiles of dissolved oxygen at all stations.…”

Nitrogen and phosphorus in cascade multi-system tropical reservoirs: water and sediment

“…In another study concerning spatial variation in a cascade system of six reservoirs located along the Tietê River (São Paulo State, Brazil), Rodgher et al (2005) and Smith et al (2014) observed that TN and TP showed the same patterns of variation in water and sediment, as suggested by the CRCC (Barbosa et al 1999). The patterns were similar to those observed in the present study.…”

Formulation of sediments with characteristics of tropical lotic systems for use in ecotoxicological assays

“…The tested formulations were based on previous studies regarding the formation of natural sediments from 14 locations in the Tietê River system in four different periods (RODGHER et al, 2005). Tietê River is an important aquatic system impacted by a range of anthropogenic influences, and it is used for different purposes such as power generation, public water supply, and navigation.…”