Numerous hazardous chemicals released into freshwater ecosystems threaten ecological structure and function. My study will focus on the explanation and prediction of the short-and long-term effects of chemicals at the individual, population and ecosystem level in the tropics. A set of endpoints will be observed to assess the effects in terms of direct toxicity and how they propagate through the food web, and to unravel the differences in sensitivities to chemical toxicants between temperate and (sub)-tropical aquatic ecosystems and to incorporate the differences in sensitivities into ecological risk assessment.