Characterizing aquatic ecological risks from pesticides using a diquat dibromide case study III. Ecological process models

The purpose of this study was to add to the set of risk characterization ap proaches developed in an earlier study beyond simple comparisons of exposur e and effects (e.g., quotients, overlapping frequency distributions) throug h use of ecological models. These models were used to evaluate the ecologic al risks from diquat dibromide for individual Daphnia using an individual-o riented model, a population of bluegill sunfish (Lepomis macrochirus) using a demographic model, and ecological communities within a generic lake in C entral Florida, USA, using the Comprehensive Aquatic Systems Model. The eco logical models presented in this study more realistically address the poten tial risks posed by pesticides to individual organisms, populations, commun ities, and ecosystems than risk assessment methods based on simple comparis ons of exposure and effects. The ecological impacts calculated by these mod els support the inference of minimal risks being posed by diquat dibromide to aquatic systems as concluded from previous empirical comparisons of expo sure and toxicity data.