Indicators of influence of salinity in the resistance and resilience of fish community in a tropical coastal lagoon (southeastern Brazil)

Abstract

The effects of a disturbance by sandbank opening on the fish fauna community were evaluated through a long-term study in the Imboassica coastal lagoon, Rio de Janeiro State, Brazil. The fish and salinity samples were conducted between 1993 and 2004, with the goal of characterizing the structure and effects of four sandbank openings on this community, such as resilience and resistance measurements. During three sandbank openings, between the years of 1993 and 1996, the resilience time of the fish community could not be identified due to the short time period between openings, their magnitude and the discontinuity of the fish sampling. Monitoring studies previously conducted between 1993 and 2004, indicated that factors structuring the fish fauna of Imboassica lagoon are due to salinity fluctuations, influenced by the sandbank openings to which this environment is subjected. These events were indicated by the recolonization of primary freshwater species, oligohaline salinity values, and small variations in the composition and abundance on the fish community. Due to the magnitude and frequency of the disturbance, the ichthyic populations available that enter the lagoon from the adjacent ocean plus the resistance of this environment to salinity variations, determined the resilience and resistance of the fish fauna in the Imboassica lagoon. Thus, the resilience of the fish fauna in this lagoon was indicated in groupings of: a) Spearman probability values lower than 0.05 between the pairs of communities pre and post-disturbance; b) presence of freshwater species that indicate resilience; c) salinity values varying between 0 and 5; and d) small alterations in the abundance of fish populations