ABSTRACT
The toxicity of cadmium and chromium to Pseudokirchneriella subcapitata and Microcystis aeruginosa was evaluated through algal growth rate during 96h exposure bioassays. Free metal ion concentrations were obtained using MINEQL+ 4.61 and used for IC50 determination. Metal accumulations by the microorganisms were determined and they were found to be dependent on the concentration of Cd2+ and Cr6+. IC50 for P. subcapitata were 0.60 µmol L-1 free Cd2+ and 20 µmol L-1 free Cr6+, while the IC50 values for M. aeruginosa were 0.01 µmol L-1 Cd2+ and 11.07 µmol L-1 Cr6+ . P. subcapitata accumulated higher metal concentrations (0.001 -0.05 µmol Cd mg-1 dry wt. and 0.001 -0.04 µmol Cr mg-1 dry wt) than the cyanobacteria (0.001 -0.01 µmol Cd mg-1 dry wt and 0.001 -0.02 µmol Cr mg-1 dry wt). Cadmium was more toxic than chromium to both the microorganisms.
ABSTRACT
The objective of this work was to evaluate the toxicity of the sediments of the Monjolinho River (São Carlos - São Paulo/Brazil), through partial chronic toxicity bioassays with juveniles of D. rerio and P. reticulata. Histological analyses of the gills and biometric measurements were conducted to detect the possible deleterious effects that caused the death. In all points the sampled the alterations were found in the gills (hyperplasia, fusion of secondary lamellas and dilation of blood vessels), with the most intense lesions (second stage) occurring at the point two. The biometric analysis pointed to inadequate conditions for the growth of the test-organisms when exposed to the sediment samples. These results showed that the conditions of these environments were not suitable for the survival and growth of these fishes.
Este trabalho teve como objetivo avaliar a toxicidade dos sedimentos do rio Monjolinho (São Carlos - São Paulo/Brasil), por meio de bioensaios de toxicidade crônicos parciais com juvenis de D. rerio e P. reticulata. Foram realizadas análises histológicas das brânquias dos organismos para detectar possíveis efeitos deletérios que antecedam a mortalidade. Em todos os pontos amostrados, foram verificadas alterações nas brânquias (hiperplasia, fusão de lamelas secundárias e dilatação de vasos sanguíneos), sendo no ponto dois foram encontradas lesões mais acentuadas (segundo estágio). A análise biométrica dos indivíduos expostos em amostras de sedimento demonstrou condições inadequadas para o crescimento e desenvolvimentos dos organismos-teste em todo o ambiente estudado. Os sedimentos apresentaram maior toxicidade no período chuvoso, sendo estes resultados confirmados por meio das análises histológicas das brânquias dos organismos expostos, as quais demonstraram lesões mais acentuadas no mesmo período. Tal situação possivelmente decorre dos impactos antrópicos os quais o sistema está suscetível (efluentes domésticos, industriais e agrícolas), que foram constatados pelas análises físicas e químicas dos sedimentos.
ABSTRACT
O objetivo deste estudo foi analisar as variáveis limnológicas em sistema semi-intensivo de criação Leporinus macrocephalus, piauçu, na Fazenda Experimental da Universidade do Estado de Minas Gerais-Campus de Ituiutaba-MG. Foi realizado o monitoramento de variáveis físicas e químicas e clorofila a na água da canaleta de abastecimento, no meio e na saída de água de viveiros com peixes e sem peixes, a cada três dias, durante 104 dias. Os valores de oxigênio dissolvido, condutividade elétrica, amônia, fósforo total e clorofila a obtidos na canaleta diferiram significativamente dos valores obtidos nos viveiros. As concentrações de amônia, fósforo total e clorfila a sofreram influência da adubação resultando em grande amplitude de variação. A presença dos peixes não afetou as características limnológicas, pois não houve diferença significativa entre os viveiros, exceto para os valores de transparência. Os valores das variáveis limnológicas obtidas apresentaram-se adequados à criação do piauçu.
The aim of this research was to analyze limnological characteristics in a semi-intensive system of fish culture in the Experimental Farm of the University of the State of Minas Gerais-Campus de Ituiutaba-MG. We done limnological monitoramento f physical, chemical and chlorophyll a characteristics in the gurret of provisioning, middle and exit of pond 1 (with fish) and pond 2 (without fish) each three days during 104 days. The values of the dissolved oxygen, eletric conductivity, ammonia, total phosphorus and chlorophyll a obtained in the gurret differed significatively from the ponds. The ammonia concentrations, total phosphorus presented direct influence of the fertilization resulting in a big amplitude of variation. The presen of fish didnt affect the mimnological caracteristcis because it didnt have a significative difference among the ponds, exept for the of transparency values in that the pond without fish differed significatively from the pond with fish. The values from the limnological caracteristics obtained in the ponds showed adequated to the fish cultive.
Subject(s)
Animals , Fisheries , Fishes , LimnologyABSTRACT
The objective of this work was to assess the toxicity of sediment samples from six cascade reservoirs in Tietê river system, in Säo Paulo State, Brazil, through chronic-partial toxicity bioassays with Danio rerio larvae as test-organisms. Histology of gills and biometric measurements were used to determine the existence of toxicity problems. The alterations on gill morphology here detected were considered of first stage (hyperplasia, lamellar junction and excess of mucous cells) in the first reservoirs and very slight in the last ones. The biometric analysis pointed to inadequate conditions for the growth of the test-organisms when exposed to the sediment of the rivers and upstream reservoirs and also indicated an improvement of environmental conditions along the system