The growth of Monoraphidium sp. and Scenedesmus sp. cells in the presence of thorium.
Toxicity of thorium by Monoraphidium sp. and Scenedesmus sp. was studied. Microalgal cultures were inoculated in ASM-1 medium in presence and absence of thorium. Its effect was monitored by direct counting on Fuchs-Rosenthal chamber and with software. The toxicity of thorium over the species was observed for concentrations over 50.0 mg/L. After 30 days, Monoraphidium cells decreased their concentration from 4.23 × 10(6) to 4.27 × 10(5) and 8.57 × 10(5) cells/mL, in the presence of 50.0 and 100.0 mg/L of thorium, respectively. Scenedesmus sp. cells were more resistant to thorium: for an initial cell concentration of 7.65 × 10(4) cells/mL it was observed a change to 5.25 × 10(5) and 5.12 × 10(5) cells/mL, in the presence of thorium at 50.0 and 100.0 mg/L, respectively. This is an indication that low concentrations of the radionuclide favored the growth, and that Scenedesmus cells are more resistant to thorium than Monoraphidium cells. The software used for comparison with direct count method proved to be useful for the improvement of accuracy of the results obtained, a decrease in the uncertainty and allowed recording of the data. The presence of thorium suggests that low concentrations have a positive effect on the growth, due to the presence of the nitrate, indicating its potential for ecotoxicological studies.
Instituto de Radioproteção e Dosimetria, SEANA, Jacarepaguá, 22780-160 Rio de Janeiro, Brazil.
Juliana Cristina
JC
de Queiroz
Ana Cristina de Melo
AC
Ferreira
Antonio Carlos Augusto
AC
da Costa
D002452:Cell Count / Q000379:methods; D000460:Chlorophyta / Q000187:drug effects / Q000254:growth & development*; D058086:Microalgae / Q000254:growth & development; D044444:Scenedesmus / Q000187:drug effects / Q000254:growth & development*; D013910:Thorium / Q000494:pharmacology* / Q000633:toxicity
D013910:Thorium