In this study, we investigate to what extent the differences in openness of coastal lagoons structure meiofauna communities. Meiofauna comprises a group of benthic organisms ranging from 0.5 mm to 0.05 mm . They are omnipresent in all types of marine habitats occurring in high abundances and number of species. Given their short life cycles and tight relationship with the sediment composition , meiofauna is an ideal tool to investigate short- to long-term changes in coastal lagoons. We assume that open and closed lagoons are two alternative states of equilibria, and that intermittent lagoons are the transition phase between them. Based on this assumption, we expect that the benthic system will respond accordingly showing two alternative stable states. Additionally, we expect that (1) open lagoons will have higher regional richness and abundance as resources and consumers move among adjacent habitats; (2) absence of barriers and fauna movements by outlets will increase similarity between open lagoons, while the isolation would increase dissimilarity (species turnover) between closed lagoons; (3) openness generates environmental gradients which will increase dissimilarities within lagoons.