Effect of organotin compounds on the growth of the freshwater alga Scenedesmus quadricauda.

Organotin compounds (OTCs) are extensively used in a variety of industrial processes and their increasing discharge into the environment is a topic of current concern. Many OTCs are toxic to various organisms and they are used to a limited but significant extent as biocidal agents in agriculture and technology. The concentration and form in which tin (Sn) is present in the environment determines its toxicological effects. The present study was conducted to determine the inhibitory effect of 12 OTCs [A, dibutyl tin bis-N,N-diethyldithiocarbamate; B, dimethyltin bis(N, N-diethyldithiocarbamate); C, triphenyltin chloride; D, triphenyltin acetate; E, triphenyltin N,N-diethyldithiocarbamate; F, tribenzyltin bis(N,N-diethyldithiocarbamate); G, tribenzyltin chloride; H, bis (tributyltin)-3,4,5,6-tetrachlor phthalate; I, tributyltin sulfaminate; J, tributyltin N,N-diethyldithiocarbamate; K, tributyltin naphthenate; and L, tributyltin oxide (TBTO)] in four concentrations (0.001, 0.01, 0.1, and 1.0 mg/liter) on the growth of freshwater alga Scenedesmus quadricauda under standardized conditions. The inhibitory effect of OTCs after 12 days cultivation in percentages for each concentration used was determined and individual growth curves of S. quadricauda for tested concentrations of OTCs and for control were plotted. On the basis of the percentage of control growth the rank order of inhibition after 12 days application of OTCs in concentration 1.0 mg/liter was made: L = H = F = C > E > D > J = K > I > G > A > B. From this rank order, it is evident that the least inhibitive effects on algal growth were from the diorganotin compounds A and B, especially compound B with a methyl group in the n-alkyl chain. The most toxic was compound L (TBTO) with a butyl group in side chain.