Crustacean zooplankton plays a pivotal role in the functioning of lakes and reservoirs. They are important in food web linkage and as food source for young and adult planktivorous fish and aquatic insect larvae (e.g Chaoboridae) As grazers, they influence and are influenced by phytoplankton, bacterioplankton and protozoan assemblages. Nutrient and detritus flow processes are modulated by zooplankton through their interactions with higher and lower trophic levels . Their role in the ecosystem functioning together with their highly sensitiveness and quick response to environmental variation can make them good tools for evaluate the impacts of human activities. Therefore the target of the present work is to monitor zooplankton assemblage in order to identify and assess the impacts of the installation of the Resort & SPA MonteBelo Aguieira harbour on the water quality and reservoir ecological integrity.