Water persistence and influence of herbicides utilized in rice paddy about zooplankton community of Cladocers Copepods and Rotifers

In the rice paddy field it is used a large amount of agrochemical that, depending on their field persistence and toxicity, can contaminate water bodies and may affect living organism. With the objective of determining the effect of field concentrations of Clomazone, Quinclorac, Metsulfuron-methyl and Propanil herbicides on zooplankton community (Cladocers, Copepods and Rotifers), it was carried an experiment in aquaculture ponds, during March to May 2005, in autumn season. In the 1st, 2nd, 3rd, 7th, 10th, 18th, 31th and 51th days after the herbicides application, water samples were collected to evaluate the physical chemical water parameters, herbicides concentration and zooplankton community. The water physical chemical parameters means were: dissolved oxygen (3.5mg L-1), temperature (20.1°C), pH (6.0), total hardness (18mg L-1 CaCO3) and total alkalinity (9mg L-1 CaCO3). The decreasing of herbicides persistence in water was: Clomazone = Quinclorac > Propanil > Metsulfuron-methyl with average of 31, 31, 10 and 7 days, respectively. The results indicated that the herbicides provoke little alteration in density of Rotifers and, Copepods (Adults and Nauplii). The Cladocers group density remained low for the whole experiment period.

agrochemicals; Crustacea; non-target organism; water quality; Southern Brazil; aquaculture ponds

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