Wetlands are one of the most altered natural systems due to the creation and development of agricultural landscapes. Some of agriculture’s impacts are in relation to water quality decreases, due to the use of potentially toxic herbicides or pesticides, and they are responsible of ecological alterations. This study shows the negative effect that two pesticides generate in a population of the copepod Arctodiaptomus salinus in an aquatic ecosystem that is surrounded by intensive olive tree cultivation. Adult females and egg sacs of that calanoid copepod were exposed to different concentrations of copper sulphate and the pesticide dimethoate, to examine their tolerance response. The adult lethal concentration obtained was lower than the regular dose of pesticide used in olive agriculture. These results also reflect the negative effect over A. salinus secondary production as a consequence of the increase in females and nauplii mortality and by the hatching rate reduction.