Variações espaço-temporais de um ecossistema praial: morfodinâmica e comunidades macrobentônicas da praia do Canto Verde, Beberibe-Ce (2015-2024)

Abstract

Sandy beaches are highly dynamic coastal ecosystems, whose physical and biological characteristics vary in response to climatic seasonality and the interaction of hydrodynamic and sedimentary processes. On the coast of Ceará, these variations are still poorly understood, especially in protected areas such as the Extractive Reserve of Prainha do Canto Verde. This study aimed to analyze the spatiotemporal variations of benthic macrofauna and of the morphodynamics of the intertidal zone of Canto Verde beach (Beberibe–CE), over a nine-year interannual series (2015 to 2024), relating these patterns to the regional climatic seasonality. Sampling was carried out semiannually, following the protocol of the Coastal Benthic Habitat Monitoring Network (ReBentos), and included the characterization of environmental variables (precipitation, temperature and salinity of the sediment, grain size, wind speed), topographic survey of the beach, and macrofauna sampling in transects perpendicular to the waterline. The results indicated a trend of sediment accretion in the intertidal zone, with an increase in the linear volume of sediments and predominance of medium to fine sand, especially during the rainy periods. The beach showed interannual morphodynamic variations, with a predominance of the intermediate state with low-tide bars and currents. The benthic macrofauna totaled 3,284 individuals belonging to 40 taxa, with emphasis on Donax striatus, Excirolana braziliensis and Hesionura sp., which together accounted for more than 75% of total abundance. Community structure varied significantly seasonally (RGlobal = 0.664; p = 0.001), with greater richness, density, and diversity during the rainy months. These changes reflected the influence of variations in salinity, particle size, and precipitation. During the rainy season, there was a statistically significant difference in taxon richness (Kruskal-Wallis, p = 0.0048) and mean density (Kruskal-Wallis, p = 0.0004) between collection points. In contrast, no significant differences in richness (Kruskal-Wallis, p = 0.3154) or mean density (Kruskal-Wallis, p = 0.0598) were detected during the dry season. Thus, it is concluded that the benthic macrofauna of Canto Verde beach presents significant responses to seasonal climate oscillations and morphodynamic changes in the intertidal environment. The observed pattern reinforces the importance of long-term ecological monitoring as a tool for detecting changes in biodiversity and guiding conservation strategies.