MA3 Aquatic Ecotoxicology
254 Portland Ballroom
8:00 AM - 12:00 PM, Monday
() In vitro toxicity testing using the coenobia of Volvox aureus Ehrenb. (Chlorophyceae).
Abdel-Hamid, Mohammad I.1, Skulberg, Olav M.2, 1 Botany Department, Faculty of Science, University of Mansoura, Mansoura, Egypt2 Norwegian Institute for Water Research, P.O.Box 173 Kjelsås, N-0411, Oslo, Norway
ABSTRACT- A simple microplate technique was adopted to assess the acute toxicity of a number of toxicants. The alga Volvox aureus was used as test organism. Parallel tests were carried out, for comparison, using the standard test alga Pseudokirchneriella subcapitata. Both biotests were performed under favourable growth conditions. Motility of Volvox and growth of Pseudokirchneriella were employed as toxicity-response parameters for the calculation of LC50 and EC50, respectively. Toxicity values were obtained from dose-response curves. The tested toxicants include 6 herbicides (atrazine, chlorsulfuron, dichloroprop, glyphosate, MCPA, simazine), a fungicide (propiconazole), an insecticide (dimethoate), 12 metals (Al, As, Cd, Co,Cr, Cu, Hg, Ni, Pb, Se, Sr, Zn), three toxic compounds (potassium dichromate, potassium cyanide, phenol), a toxic industrial effluent, and a crude water extract of a toxic isolate of Microcystis aeruginosa. Responses of Volvox and Pseudokirchneriella to the tested toxicants were compared in quantitative terms of LC50 and EC50 respectively. The t-test was used to examine for significant differences (p≤0.05) between the mean values of LC50 and EC50. The relationship between LC50 and EC50 was evaluated through correlation analysis and by examining their distribution fitting and goodness of fit. For most toxicants, the coenobia immotility took place immediately after adding the toxicant. Volvox was more sensitive to pesticides and to the metals Hg, Cu, Cr, Al, and Sr. Pseudokirchneriella was more sensitive to the rest of metals tested in addition to KCN and phenol. Both algae maintained similar responses towards the industrial effluent. Water extract of Microcystis was more toxic to Volvox. LC50 and EC50 maintained strong positive linear correlation (r = 0.85). Analysis of distribution fitting and goodness of fit showed that values of LC50 and EC50 came from very close distributions (DN = 0.13). These findings may indicate that both Volvox and Pseudokirchneriella maintained, more or less, comparable responses to the tested toxicants. The Volvox test highlights the possible use of algal bioassays for measuring the lethal concentrations of a given toxicant. The sensitive responses of Volvox pointed out the advantages of the present biotest for more realistic assessment of acute toxicity.
Key words: Pseudokirchneriella, Volvox aureus, Toxicity Assesment, Algal Bioassays