Evaluation of different algal species sensitivity to mercury and metolachlor by PAM-fluorometry

In this study, the pulse-amplitude-modulation (PAM)-fluorometric method was used to evaluate the difference in the sensitivity to mercury (Hg) and met olachlor of six algal species: Ankistrodesmus falcatus, Selenastrum caprico rnutum, Chlorella vulgaris, Nannoplankton (PLS), Microcystis aeruginosa and Pediastrum biwae. We found that the fluorescence parameters (phi (M), the maximal photosystem II (PSII) quantum yield, phi'(M), the operational PSII quantum yield at steady state of electron transport, Q(P), the photochemica l quenching value, and Q(N), the non-photochemical quenching value) were ap propriate indicators for inhibitory effects of mercury but only phi'(M) and Q(N) were useful for metolachlor. The examined algal species showed very d ifferent levels of sensitivity to the effect of Hg and of metolachlor. The most sensitive species to Hg and metolachlor were respectively M. aeruginos a and A. falcatus, while the least sensitive were C. vulgaris and P. biwae. We interpreted these differences by the action mode of pollutants and by t he different metabolism properties and morphological characteristics betwee n algal species. These results related to fluorescence parameters may offer useful tool to be used in bioassay for different pollutants. Heterogeneous algal sensitivity to the same pollutant suggests the need to use a battery of species to evaluate the effects of mixtures of pollutants in aquatic sy stems. Crown Copyright (C) 2001 Published by Elsevier Science Ltd. All righ ts reserved.