Distribuição de mercúrio e fenologia de espécies de mangue no litoral do Nordeste brasileiro

Abstract

Mangroves constitute vital coastal ecosystems, yet they are under increasing anthropogenic pressure, including mercury (Hg) contamination, a highly toxic metal with bioaccumulation capacity. The cycling of Hg in these environments is complex, influenced by the physiology of plant species and local environmental factors. Although leaf phenology is a known factor influencing nutrient cycling, the correlation between phenological stages and the dynamics of Hg accumulation in different mangrove species in the Brazilian Northeast remains a critical gap in ecotoxicological knowledge. In this context, the main objective of this study was to evaluate the variability of Hg accumulation and distribution in the leaves of four mangrove species across their different leaf phenological stages, investigating the species' response strategies to Hg and their implications for environmental management. Leaf samples were collected from Avicennia schaueriana, A. germinans, Rhizophora mangle, and Laguncularia racemosa, classified into four phenological stages (bud, young, mature, and senescent). Sampling was conducted in three coastal areas of the Brazilian Northeast with distinct environmental contexts and Hg concentrations were quantified and accumulation patterns among species and phenophases were compared. The results demonstrated that the concentration of Hg in the leaves progressively increases with the phenological stage, culminating in senescent phenophase, which establishes leaf senescence as an important detoxification pathway. A division based on physiology was observed: the Avicennia genus (salt secretor) accumulated significantly higher Hg concentrations than R. mangle and L. racemosa (salt excluders), indicating that the salt management strategy is the main ecotoxicological filter. Mangrove species show potential for remediation use: R. mangle and L. racemosa are candidates for phytostabilization, while Avicennia spp. demonstrate potential for phytoextraction via litter management.