Fertilizers and pest control are used in agricultural intensification to enhance agricultural production and economic returns. The need to improve food production and commercial benefits from agriculture has seen the demand for fertilizers and pesticides increase. Subsequently, risks associated with contamination by nutrients from fertilizers and pesticides from pest control have been elevated for recipient aquatic ecosystems. Moreover, the interaction between nutrients and pesticides in aquatic ecosystems potentially amplifies the contamination risk, but has attracted limited attention. This study aims to determine the response of aquatic ecosystems to combined contamination from nutrient and pesticide residues.

To achieve the aim, this study will carry out an environmental exposure survey to determine the concentrations of nutrients (nitrogen and phosphorus) and pesticides (cyfluthrin, cypermethrin, dichlorodiphenyltrichloroethane and lindane) in the aquatic ecosystem. It will measure the response of: (a) aquatic macroinvertebrate and phytoplankton/periphyton taxa and communities; and (b) ecological processes comprising primary production, respiration, reproduction and decomposition, to nutrients and pesticides contamination. The study will employ laboratory and in-situ experiments, and field surveys to determine the effect environmental exposure of a nutrients-pesticide combination to aquatic functional groups and ecological processes.

The research will: investigate the potential of a trait-based indicator for monitoring nutrient-pesticides combined effects and toxicity; produce a spatiotemporal water quality map indicating the pollution with reference to nutrients and pesticides contamination in an agricultural catchment of Lake Naivasha, Kenya; and document an ecotoxicological dose-response relationship profile for potential effects of a nutrient-pesticide combined contamination.