Mangroves as phytoremediation agents: a case study of young plant responses to cadmium toxicity

Abstract

Mangroves are transitional ecosystems between land and sea, common in tropical and subtropical regions. They play a significant role in maintaining the ecological balance of the coast, besides offering several other important ecosystem services, such as protecting the coastline and promoting the sequestration of carbon dioxide (CO2) and contaminants. In the first part of this work, some examples will be presented of how it is possible to use mangrove plants, with or without association with other elements or microorganisms to remedy contaminated soils and waters. Then, a study of the morphophysiological response of young plants of three mangrove species - Avicennia schaueriana, Laguncularia racemosa, and Rhizophora mangle - exposed to the heavy metal cadmium (Cd), which is highly toxic and has no biological function in plants. It was observed that the species A. schaueriana, besides having the highest tolerance to salinity, was also the most tolerant to Cadmium. On the other hand, the species L. racemosa, the least tolerant to salt, was also the most susceptible to the metal. In the last chapter, however, when we presented the association of cadmium and silicon (Si), it was possible to observe a positive response in the development of L. racemosa propagules and plants. Silicon has been considered an attenuator of abiotic stresses in different plant species. It is considered of great importance to know the morphophysiological responses of young mangrove plants to stress induced by toxic metals, since these plants may be selected for restoration and decontamination strategies, as well as for the management of this ecosystem.