Growth Response of Freshwater Algae to Continuous Flow of Terbutryn

Abstract

The single species approach, although advantageous in comparability of results, has its limitations. The most important one is that the standard test species may not be the dominant species in natural water environment, so the algal assay test result may be irrelevant to that particular in the environment. Furthermore, phytoplankton in the aquatic environment is a mixed and balanced community. Algal species composition and interactions in the community during algal assay are important parameters for observing the algal response to the environmental stress (Del Giorgio et al 1991).Toxicant effects on aquatic microorganisms have been emphasized. Much of this research has dealt with phototrophic algae and cyanobacteria, which are the main primary producers in the hydrosphere (El-Dib et al 1989). A common contaminant of surface water of agricultural regions are triazine herbicides (Morris and Ron 1981). The volume of herbicide used and introduced into the aquatic environment as a final reservoir has grown markedly. Although research concerning the effects of herbicides on algae has been extensive, few studies have examined the impact on algal productivity. Long-term bioassay effects, using continuous system, is a relatively new approach in the screening of complex environmental compounds.The purpose of this study was to determine the changes in both growth and population of fresh water algae under stress of continuous flow of terbutryn concentrations and the rate of accumulated terbutryn algal cells. MATERIALS AND METHODSA laboratory-scale unit (continuous flow system) was designed to study the effect of triazine herbicide terbutryn (2,4-diamine-N-dimethylethyl) N-ethyl-6(methylthio)-5 triazine) (99.9% purity) obtained from CIBA Geigy (Swizerland) on the algal growth under continuous flow rate.

A new cell primo-culture method for freshwater benthic diatom communities

“…Moreover, transfer of a species to culture induces genetic selection of individuals and alters their sensitivity to chemicals (Peterson et al 1997). For these reasons, classic mono-specific tests do not predict the effects of perturbations at the community level, especially under natural conditions (Badr et al 1997).…”