Assessment of the effects of pesticides used on floricultural farms on water quality and \water bird numbers in lake Naivasha,Kenya

Abstract

Lake Naivasha and its environs experienced increased levels of pesticideapplication due to the direct flow of agrochemicals pollution into water bodies from rapid expanding floricultural farms. The situation had recently raised speculation having attracted public attention following thousands of fish deaths earlier reported. The Lake is under threat of losing its water birds a phenomenon linked to water quality degradation. However, there is no specific research which has been done on the effects of pesticide residue on water physico-chemical parameters and water bird numbers within the shores of Lake Naivasha. The Organochlorine pesticide residues previously detected is persistent in the environment and bio-accumulates in the body tissue of water birds while, the Organophosphate pesticides which had been adopted as an alternative to Organochlorine pesticides are highly toxic to water birds. The occurrences of pesticide residue in water provide a dietary pathway to the aquatic ecosystem which contributes to reduction of water bird numbers. The study investigated the effects of Organochlorine and Organophosphate pesticide residues on water quality and how they affect water bird numbers. The specific objectives of the study were: to determine water physico-chemical parameters, to determine the concentration of Organophosphate and Organochlorine pesticides and lastly, investigate the effects of water quality on water bird numbers within the shores of Lake Naivasha. Longitudinal study design was adopted between February to July, 2011 (6 months). The sampling sites were selected on the basis of their relevance as point sources of pesticide contamination and uniqueness in the nature of discharge released into the Lake. Three replicates of water samples were collected giving 18 water samples per site, totalling to 90 samples. These samples were subjected to water quality analysis and Gas Liquid Chromatography technique while, the ecological study of water birds focussed on their numbers. The study targeted bird's beak since this feature was conspicuous while the counts were based on standardised belt transects method. The data generated were recorded on Microsoft excel spread sheets and subjected to analysis while applying Statistical Package of Social Science using one way ANOV A at p<0.05. The results revealed that the water samples tested were in compliance with World Health Organisation and Kenya Bureau of Standards recommended guidelines in regard to physicochemical parameters standards while, Organochlorine and Organophosphate pesticide residues were not detected. The results also revealed an increase in the water bird abundance. It was concluded that lack of these pesticide residues and an increase in water bird abundance was due the current conservation measures preventing water pollution in the Lake. The study further, recommended continuous monitoring and conservation measures to be maintained.