Accumulation, assimilation and growth inhibition of copper on freshwater alga (Scenedesmus subspicatus 86.81 SAG) in the presence of EDTA and fulvic acid

Abstract

Accumulation and growth inhibition of Cu to fresh water alga (Scenedesmus subspicatus 86.81 SAG) and the influences of ethylenediaminetetraacetic acid (EDTA) and fulvic acid (FA) were examined. These results demonstrated that both EDTA and FA could reduce toxicity of Cu to alga by the way of preventing Cu from being adsorbed by cell wall of alga. When dissolved Cu (Cu dissolved ), extracellular Cu (Cu extracellular ), and intracellular Cu (Cu intracellular ) were differentiated, our results showed that the concentration level of extracellular Cu ([Cu extracellular ]) was a good indicator for measuring the toxic effects of Cu on alga growth in complex matrix. Either in the absence or in the presence of EDTA and FA, the concentration of intracellular Cu increased to 0.6 Á/1.5 )/10 (8 mM per cell when the growth inhibition reached to about 50%. We found that the acute toxicity of copper on unicellular alga could be interpreted by its accumulation at a discrete site or biotic ligand at alga cell wall and critical accumulation of Cu associated with EC 50 was determined to be 1 )/10 (8 mM per cell. Therefore, the Biotic Ligand Model (BML) could be extended to predict the influence of copper on growth inhibition of alga. #

Biosorption of zinc and copper from aqueous solutions by two freshwater green microalgae Chlorella pyrenoidosa and Scenedesmus obliquus

“…This indicates that the promotion and inhibition on growth and photosynthetic pigment of both algae depended on the binding of metals on algal cell wall, not by the binding at intracellular active sites. A similar viewpoint was once mentioned by Ma et al (2003). Thus, extracellular metal concentration is a good indicator of metal toxicity to the both algae.…”

“…Light was provided by continuous cool white fluorescent lamps at 3,000 lx with a dark/light cycle of 12 h:12 h. The experiments were conducted for 8 days, and all tests were carried out in triplicate. The concentrations of zinc and copper were measured by the procedure described by Franklin et al (2000) and Ma et al (2003) with minor modifications. Dissolved zinc and copper concentrations in the samples were monitored daily.…”

Algas como bioindicadores da qualidade da água

“…A P. subcapitata apresentou efeitos de toxidade e genotoxidade, a uma dose de 20 µg/mL, quantidade extremamente superior ao que pode ser encontrado disponível no meio ambiente. Ma et al (2003), escolheram como contaminante em seu estudo o cobre, devido ao fato de que o cobre é um elemento onipresente na natureza, por ser essencial no sustento de plantas e animais, incluindo a vida aquática. E, em contrapartida, a elevados níveis, esse elemento torna-se tóxico.…”

“…No estudo desenvolvido, Ma et al (2003) escolheram a alga unicelular de água doce Scenedesmus subspicatus para avaliar a toxicidade do Cu na presença do ácido etilenodiaminetetracético (EDTA), um ligante orgânico sintético, e do ácido fúlvico (FA), um ligante orgânico tipicamente natural. Como parâmetros de avaliação, os autores consideraram o acumulo, a assimilação e a inibição do crescimento do cobre nas algas.…”

“…Como parâmetros de avaliação, os autores consideraram o acumulo, a assimilação e a inibição do crescimento do cobre nas algas. O resultado encontrado indicou que toxicidade aguda a cobre em algas unicelulares ocorre em decorrência do acúmulo em local discreto ou ligante biótico na parede celular destas algas, e um acúmulo crítico de Cu associado com CE 50 (concentração de exposição) foi determinado como sendo na ordem de 1 x 10 -8 μM por célula (MA et al, 2003). …”