Impactos da variabilidade hidroclimática na estrutura de uma assembleia de peixes em um lago de várzea amazônico

Abstract

We investigated how the dominance at different scales and the diversity of a fish assemblage in a floodplain at the confluence of the Negro and Solimões rivers respond to hydroclimatic variations. The study used species abundance data obtained during the dry periods between 1999 and 2020 in the Catalão floodplain, in addition to the historical record of the level of the Negro River in the port of Manaus and satellite images of the area, available on freely accessible websites. Regression analyzes indicated variation in dominance and diversity indices not directly associated with hydrometric variables, relationship between dominance classes grouped based on principal components and drought severity, and relationship between the abundance of two dominant species with hydrometric variables linked to dry. The results show a growing biotic homogenization over the years, by increasing dominance and reducing diversity. Despite the recession of the waters and the establishment of intense droughts representing a stressful condition for many species, its effect was notable only in the less comprehensive scales, with the increase in the number of species classified as subrare, and among the dominant ones, by the identification of the greater sensitivity from Hemiodus sp. in relation to the others. Unusual hydroclimatic events indirectly influence the structure of fish assemblages in floodplains. The results indicate that the frequency of irregular drought events enhances the fragility of isolated assemblages in the floodplain environment, undermining their role as refuge zones.