How does pore water H2S affect mangrove restoration?

Abstract
Despite their critical importance and the numerous efforts to protect, conserve and restore mangrove forests, these ecosystems are still disappearing at worrying rates around the world. Alongside these losses, many restoration projects fail to achieve their target. This is often a consequence of ignoring why the natural recovery has not occurred in the first place. In this regard, hydrogen sulfide (H2S) and its typical rotten egg smell are omnipresent components in mangrove sediments. Nevertheless, too little attention has been given to its influence on the mangrove seedlings when transplanted to an area with a different sulfide concentration compared to their original habitat. Thus, this study aims to determine the sulfide tolerance of the red mangrove (Rhizophora mangle) and black mangrove (Avicennia germinans) using experimental nurseries in areas with high and low sulfides. The results reveal that high sulfide levels (> 20 mM) have serious effects on the growth of R. mangle, while having no significant effect on A. germinans, unveiling its ability to tolerate higher concentrations. Replanting A. germinans seedlings can facilitate success when restoring degraded and highly sulfidic areas. Additionally, this study provides a novel analysis of how microbial communities of the rhizosphere of A. germinans affect the survivability of mangrove seedlings in restoration projects.