Effects of pesticides on pure and mixed species cultures of salt marsh pool algae.

Abstract

A number of studies on the effects of pesticides and other toxicants in single species algal cultures have demonstrated that while some species show inhibition of growth and/or photosynthesis when exposed to levels as low as a few ppb (WURSTER 1968), other species are resistant to levels of several ppm or higher (UKELES 1962, MENZEL et al. 1970, DERBY & RUBER 1970). Because of differential algal sensitivity one might predict that toxicants would have no long-term inhibitory effect on biomass and production in mixed-species cultures of algae. Instead, a shift in community composition, with the more resistant species replacing the sensitive ones might be expected. There have been few studies using several species communities comprised only of algae. MOSSER et al. (1972) found that addition of DDT or PCB reversed the outcome of competition between two species and also that neither final biomass nor productivity were affected by the toxicants. In this study we report on the general sensitivity of five species of salt marsh pool algae to five pesticides and then proceed to examine more closely the effects of carbaryl on single species and on communities made up of three and five species in order to determine the effects on community sensitivity of varying the composition and numbers of species.