Efeitos da seca prolongada sobre a ictiofauna marinha-migrante em um estuário da costa semiárida brasileira e sua contribuição para o fornecimento de serviços ecossistêmicos

Abstract

Estuaries play a fundamental role as nursery areas, connecting continental and marine environments and supporting important ecosystem services, such as the provision of fishery resources and the regulation of matter and energy flows. On the semi-arid coast of Brazil, these environments are strongly influenced by extreme climatic variations, especially prolonged drought events, which intensify marine intrusion and alter the structure of fish communities. This study aimed to describe variations on biomass and composition patterns of migratory marine fish (guild that represents 50% of the ichtyofauna in estuaries from Brazilian semiarid region) during periods of prolonged drought and regular rainfall, and to evaluate their implications for the ecosystem services of provision and regulation in the Curu River estuary (CE). Data collected during campaigns conducted during the prolonged drought (2014–2015) and in two periods with regular rainfall (2021–2022 and 2023–2024) were analyzed, considering only migratory marine species, classified into trophic guilds. Analyses indicated that the total biomass of this guild was significantly higher during the prolonged drought, being at least eight times greater than during periods of regular rainfall. There were significant differences in species composition and trophic guilds between the periods, with greater dominance of detritivorous and omnivorous species during the drought. Species of high ecological and fisheries importance, such as Mugil curema, Eugerres brasilianus, and Eucinostomus argenteus, showed greater abundance on years of prolonged drought. These results suggest that, under the observed conditions, the prolonged drought enhanced the estuary's nursery function and increased the availability of fishery resources, in addition to reinforcing the role of fish in nutrient recycling and estuary-sea connectivity. However, changes resulting from climate changes and the intensification of extreme events may lead these systems to an environmental threshold, from which the increase in salinity may compromise the diversity and maintenance of ecosystem services provided by estuarine ichthyofauna.