Effects of five insecticides on zygospore germination and growth of the green alga Chlamydomonas moewusii.

Abstract

The toxic effects of various pesticides on algae have been studied extensively, and several review articles containing information about algae and pesticides have been written (Ware and Roan 1970; Hurlbert 1975; Tu and Miles 1976; Butler 1977; McCann and Cullimore 1979; Lal and Saxena 1980). However, an examination of previous pesticide-algae studies reveals that toxic effects have been demonstrated chiefly with the vegetative phases of algal life histories~ This is perhaps unfortunate since many algae, in addition to vegetative phases, produce reproductive stages such as gametes and spores as part of their sexual and/or asexual life cycles. For example, Chlamydomonas moewusii, a common alga in both freshwater aquatic and soil habitats, produces a thickwalled zygospore as a result of sexual reproduction. Therefore, this organism possesses in its sexual life cycle two different morphological entities, both of which could theoretically experience toxic effects from pesticides. The only study of which we are aware which has examined toxic effects of pesticides on an algal reproductive stage is our own recent work (Cain and Cain 1983). The results of this latter study, which examined the effects of 20 different herbicides on zygospore germination and growth of C. moewusii, demonstrated that zygospore germination can be inhibited by herbicide presence, and that zygospores are more resistant than vegetative cells to some but not all herbicides. In view of these results, we felt it important to conduct a similar study with 5 insecticides, to examine and compare possible toxic effects of these compounds on both morphological stages of the C. moewusii sexual cycle.