Assessment of toxic effects of pesticide extracts on different green algal species by using chlorophyll a fluorescence

Abstract

In this study, the toxicity of pesticides extracted from the Yamaska River watershed surface waters were tested on three species of green algae (Chlorella vulgaris, Scenedesmus obliquus and Pseudokirchneriella subcapitata) by using slow and fast fluorescence kinetics (Maxi-Imaging-Pulse-Amplitude-Modulated and Plant Efficiency Analysis). Two types of extractions for a variety of herbicides and insecticides (organosphosphorous-type (OP) and phenoxyacid-type (PA)) were conducted on the water samples of three sites having different pesticide concentrations (‘Deborah Stairs’, ‘Rivière Noire’ and ‘Rivière à la Barbue’). Our results showed that of the three species of green algae studied, S. obliquus was the most sensitive to both pesticide extracts. Moreover, PA pesticide extracts from ‘Rivière à la Barbue’ were the most toxic since the algae exposed to those extracts had the lowest photosynthetic activity when evaluated by the PSII quantum yields (ΦM and ), the photochemical quenching (qP(REL)) and the electron transport rate per reaction center (ET0/RC). The fast fluorescence kinetic data also indicate that the site of action of the different extracts was at the level of the primary photochemical events, probably electron flow blockage at the Q B binding site. This study demonstrated the advantages of using chlorophyll fluorometry in assessing toxic effect of pesticide mixtures.