Camara, E.M.; Caramaschi, É.P.; Di Dario, F., and Petry, A.C., 2018. Short-term changes in two tropical coastal lagoons: Effects of sandbar openings on fish assemblages.

Sandbar openings (SBOs) are among the largest possible disturbances in coastal lagoons. This study investigated the mechanisms of the responses of fish assemblages to short-term environmental changes resulting from several SBOs during 1 year in two coastal lagoons in southeastern Brazil. Lagoons were sampled monthly in sites closer to, and more distant from, the sandbars. A principal component analysis summarized limnological differences between periods of contact and isolation from the sea, and site- and lagoon-based variation partitioning and independent redundancy analyses (RDAs) quantified the unique and shared effects of limnology, space, and period on species and groups of species (marine, estuarine, and freshwater). Limnological differences between periods were associated with a higher marine influence during SBOs and an increasingly eutrophic state influenced by the lagoon and days of isolation. Limnology explained most of the variance in composition and abundance of species, and large fractions were shared with, or explained exclusively by, lagoons and distance of sites from the sandbar. The responses of groups of species were less evident in lagoon-based analyses and more associated with trophic state, most likely because of the short intervals between SBOs, which reduced temporal differences in the marine influence. Responses at the group level were more relevant in site-based analyses, given the predominance of species based on their tolerances or affinities in sites with different salinities. Therefore, the responses of groups of species to limnological changes associated with the features of lagoons and sites (e.g., morphometry, human impacts, and freshwater inflow) determined the effects of SBOs on the fish assemblages.