Laboratory Studies with Microbiotests to Evaluate the Acute Toxicity to Aquatic Biota of Herbicides used in Portugese Paddy Fields
Abstract : Rice crops constitute a potential risk of contamination of aquatic ecosystem since the water from paddy fields (which may still contain certain amounts of herbicides used to combat plant pests) is in most cases, discharged directly or indirectly into the surrounding water bodies. In order to evaluate the possible effects of this contamination, laboratory and field work is performed in the Sado Valley in Portugal. In the present study, laboratory results are presented on the effects of the main herbicides used in paddy fields to aquatic biota. Mcrobiotests have been performed with bacteria (Vibrio fischeri), micro-algae (Selenastrum capricornutum, renamedRaphidocelis subcapitata) and crustaceans (Daphnia magna,Thamnocephalus platyurusandArtemia franciscana). The experiments were performed with different dosages of the most used commercial products based on MCPA, molinate, propanil and quinclorac as active ingredients. The concentration ranges used in the laboratory are the same as those applied by the farmers in real field conditions.