PARENT SESSION
19 - Pesticide Ecotoxicology
8:00 AM to 6:30 PM, Monday, 13 May 2002
Exhibition Area

(19-23) Effect of glyphosate and diflufenican in two species of freshwater algae.

Pereira, M.J.^*,1, Resende, P.¹, Almeida, P.¹, C. Augusto, C. Pina¹, Gonçalves, F.¹, Soares, A.M.V.M.¹, ¹ Departamento de Biologia, Universidade de Aveiro, Aveiro, Portugal

ABSTRACT- Glyphosate is a systemic herbicide used against perennial species. Sub-cellular effects of these herbicides have been described on aromatic aminoacid synthesis, amount of chlorophyll, photosynthesis and the respiratory processes. Chronic assays with a commercial mixture of two herbicides (glyphosate (N-(phosphonomethyl)glycine), 40 g/l and diflufenican (2',4'-difluoro-2-(,,-trifluoro-m-toxyloxy)nicotinanilide) 160 g/l), with Pseudokirchneriella subcapitata (Korshikov) Hindak and Gonium pectorale Müller revealed a high toxicity at levels lower to those that were used for agricultural purposes. Static assays showed sub-cellular alterations in chloroplasts, nucleus, vacuolisation, less intense and brownish coloration, on Gonium pectorale cells, for values higher than the EC50-96h (1-10 g/l) value. A pronounced reduction of cellular division and an increase of the adaptation period for lower concentrations was also observed. Assays with Daphnia magna Strauss and with Vibrio fischeri showed values of LC50-48h and EC50 of, respectively, 100-200 g/l and 28.9 g/l. This work demonstrated a pernicious effect of these mixtures in phytoplankton and cladocerans, suggesting the need for a reduction of the application of commercial mixtures of this herbicide in agricultural areas.

Key words: Gonium, Pseudokirchneriella, glyphosate, diflufenican