Mathematical Assessments of Pesticides Toxicity to Aquatic Species

The use of ecological models to assess the effects of pesticides on the structure and function of aquatic ecosystems is of growing interest Of utmost concern are assessments of pesticides that have the potential to biodegrade into metabolites that areas toxic as the parent pesticide. A mathematical model to predict and evaluate the effect of two pesticides on the population of aquatic bio-species where both pesticides are bio-available in water and sediments with one of the pesticides capable of biodegrading into the other but not vice versa is formulated and analyzed. Conditions for nonlinear stability instability and Hopf-bifurcation are obtained. The model undergoes a Hopf-bifurcation when the rate of discharge of pesticides crosses a critical value so that the population of the aquatic species follows an oscillatory pattern. Four hypotheses involving the concentration of the pesticides and the population of the aquatic species where qualitatively investigated.