Determining hydrological flow paths to enhance restoration in impaired mangrove wetlands

Abstract

The restoration of mangroves has gained prominence in recent decades. Hydrological rehabilitation has been undertaken to connect impaired mangroves with the sea, lagoons or estuaries. Because mangrove hydrodynamics occurs on the surface and interstitial spaces in the sediment, we propose to determine the hydrological flow paths to restore the hydrological regimes of the impaired mangroves. The hydrological flow paths were determined through a micro basin analysis based on microtopographic data to generate a digital elevation model. Applying this methodological approach, the hydrology of an impaired area on a barrier island in the Gulf of Mexico was restored by excavating, desilting or clearing the channels on the identified hydrological flow paths. This area was compared to one in which impaired mangroves were reconnected to the marine lagoon but disregarding the flow paths. Data collected in both areas were evaluated by flood level analysis, using two methods: (i) a simple linear regression model (SLRM) and (ii) spectral analysis (SA), also known as dominant frequency analysis. The results suggest that restoration based on the hydrological flow paths was more effective than the direct opening to the nearest main water body without accounting for the microtopography. In both areas, soil salinity and sulfides decreased after hydrological reconnection. However, a greater efficiency in the investment of time and human resources was achieved when preferential flow paths were identified and taken into account. The methodological procedures described in this study are of universal application to other mangrove restoration programs.

Challenges during the execution, results, and monitoring phases of ecological restoration: Learning from a country-wide assessment

“…Changes in hydrology have been identified as one of the main causes of mangrove degradation [ 79 ]. Therefore, to foster mangroves natural regeneration hydrological rehabilitation is implemented [ 80 ]. Mangroves can regenerate naturally if the tidal hydrology has not been disrupted and if there are sufficient mangrove propagules nearby [ 81 ].…”

The fish community in Gulf of Mexico mangroves, a response to hydrological restoration

“…According to GLMM, water depth, temperature, and salinity significantly affect the abundance of residents and overall species. A greater abundance is expected as water depth increases because, after the hydrological restoration, mangroves recuperate their natural hydrological flow and tidal influence (Zaldívar-Jiménez et al 2017, Pérez-Ceballos et al 2020). Natural and long-term restored mangroves have greater water depth and lower temperature (Adite et al 2013), as well tides that favor the entrance of visiting fishes to the restored mangrove (Salmo et al 2018).…”

“…In this study, the evaluation was carried out in two years, and perhaps it was little to show changes in the fish community. The recovery of function of the mangrove ecosystem will take time; major changes in the structure of fish communities exhibit mangroves with a longer resto-ration period (Arceo-Carranza et al 2016, Schaberg et al 2019) because mangrove restoration involves a natural regeneration process (Echeverría-Ávila et al 2019, Pérez-Ceballos et al 2020. As mangrove structure and function are restored, it is expected that more habitats and resources will be made available to fish, like invertebrates, and larger and commercially important species such as the snooks (Family Centropomidae) or the snappers (Family Lutjanidae) -will enter the site under restoration (Schaberg et al 2019).…”

“…A recent alternative is a hydrological restoration, which involves dredging and rehabilitation of tidal channels, aiming to restore the natural tide flow to reconstruct the structural characteristics of the ecosystem, such as improving soil and water conditions and promoting natural regeneration of mangrove. Hydrological restoration is considered a relevant factor for the health of the mangrove and the ecosystem as a whole (Turner & Lewis III 1997, Moreno-Mateos et al 2012, Echeverría-Ávila et al 2019, Pérez-Ceballos et al 2020.…”

“…Hydrological restoration projects for the mangrove ecosystem have resulted in recruitment and mangrove growth, hydrological reconnection with Terminos Lagoon, and lower-salinity soils (Zaldívar-Jiménez et al 2017, Pérez-Ceballos et al 2020. As for wildlife, bird communities were more diverse in the restored vs. natural sites (Canales-Delgadillo et al 2019), while ectoparasites of Yucatan gambusia Gambusia yucatana did not differ in diversity between restored vs. natural sites (Morales-Serna et al 2019).…”