Effectiveness of hydrological restoration in the mangrove of a coastal lagoon in the Gulf of Mexico

Mangroves rely on hydrological connectivity driven by tidal dynamics. This connectivity is diminished in degraded mangroves, resulting in physiologically stressful conditions for mangrove vegetation, characterized by high salinity and water stagnation. We evaluated the flooding dynamics of a mangrove associated with a coastal lagoon in the central Gulf of Mexico, using Fourier and continuous wavelet analyses of water level time series during three restoration phases, in degraded, and preserved mangroves. Mangrove degradation was caused by three embankments that obstructed surface water flow, increased interstitial salinity (up to 140 psu), resulted in extensive tree mortality (30 ha), and led to a collapsed soil level (−0.15 m). The first phase (2016 2018) involved the opening and widening of embankment breaches to allow higher surface water flow through the mangrove; however, the salinity remained high (74.5 ± 17.9 psu), and water flow was limited. In the second phase (2019), microtopography was enhanced by digging canals to create preferential flow paths connecting the mudflat (dead mangrove area) with the lagoon, and 750 artificial islets were constructed. Monitoring the restoration outcomes occurred at the third phase (20202021). We observed daily surface water renewal in all three mangrove conditions, driven by diurnal and semidiurnal tides, as well as biweekly renewal associated with spring and neap tides. Additionally, salinity levels were significantly reduced to 36.7 ± 7.06 psu. Another effect of hydrological restoration was the vigorous natural regeneration, high seedling survival, and growth. By the end of 2021, saplings entirely covered the islet surfaces and canal edges.