ABSTRACT. – Coastal lagoons are high productivity ecosystems with high biodiversity, but very unstable systems. When assessing the ecological status of these ecosystems it is necessary to consider the influence of natural variations. In order to understand the community variation of coastal lagoons we studied spatial (among-lagoons) and temporal (among-years) changes in aquatic insect assemblages and variations in 23 measures potentially useful for bioindication purposes. Two series of data were examined: (a) aquatic insect families and (b) Coleoptera and Hemiptera species. Coefficients of variation were used to quantify the effect of among-lagoon and interannual variability on the selected metrics. Data analyses showed that within-lagoon variation (temporal) was higher than among-lagoon variation (spatial). Both aquatic insect families and Coleoptera and Hemiptera species provided similar information about among-lagoon similarity. According to the results, taxa richness, rarefied richness (ES200), species richness of Coleoptera and Hemiptera (%S CH), the Margalef diversity index (d), and richness and abundance of predators could be the most useful metrics when assessing ecological status in these coastal lagoons. Diversity metrics and fauna composition may be used together for a better understanding of the diversity patterns in these ecosystems.