Hydrological and environmental drivers of fringe red mangrove (Rhizophora mangle) distribution: implications for rehabilitation strategies in a degraded semiarid coastal lagoon

We evaluate the distribution, hydroperiod, and salinity tolerance of Rhizophora mangle (RM) across four distinct physiognomic conditions to elucidate the hydrological drivers influencing habitat suitability, thereby identifying potential sites for mangrove rehabilitation efforts. RM populations were categorized into four physiognomic conditions: healthy stands (IP), transitional zones (TR), degraded areas (DE), and marginal stands at distributional limits (LI). Over the course of one year, we measured various environmental parameters, including (1) water level, (2) water temperature, (3) rainfall, and (4) water salinity. Wavelet coherence analysis revealed a significant influence of the semi-diurnal tide across all four physiognomic condition locations. Salinity levels ranged from 18 to 80 PSU, exhibiting seasonal variability, with the highest concentrations recorded within the LI distribution zone. Hydroperiod assessments indicated a logarithmic relationship between flood duration and peak water levels, characterized by a notably steeper slope in the IP zone. Canonical discriminant analysis demonstrated substantial and statistically significant differentiation among the four zones, particularly when focusing exclusively on annual water salinity. Furthermore, our analysis uncovered a significant linear trend between water salinity and flood duration; however, no correlation was found between water salinity and peak water levels. These findings facilitate the identification of potential zones for future rehabilitation initiatives, based on data collected from 57 sampling stations along a 28-km coastal stretch.