Abstract
The inherent nature of coastal ponds and their small size make them highly dynamic ecosystems, with great variations in their environmental conditions, such as changes in conductivity (due to sea storms or freshwater inputs), water level, or dissolved oxygen (DO) concentration. Because of these frequent fluctuations, aquatic communities are generally adapted to them, which often hinders the detection of the effects of disturbances on aquatic assemblages (“the Estuarine Quality Paradox”). Using high-frequency sondes, daily fluctuations in conductivity and water level, and hypoxia episodes were detected over more than one year in four coastal ponds showing differences in their degree of water circulation. The effects of these fluctuations on monthly zooplankton community attributes (abundance, biomass, richness, diversity, and size diversity and evenness) were analysed. The results showed that the environmental fluctuations had a limited influence on zooplankton community attributes, highlighting the adaptation of species to environmental variations in coastal habitats. These fluctuations did not produce major changes in assemblage composition nor community homogenization. In addition, the degree of water circulation rate influenced the occurrence and number of fluctuations, with a seasonal and predictable pattern of fluctuations in confined ponds, while in the ponds with higher circulation, environmental variations were more unpredictable.