*Appendix A.4. Hydrogeological Characteristics*

La Carbonera is part of the karst system of the Peninsula of Yucatan (Batllori-Sampedro et al., 2006). In the lagoon, three types of sediment lie on top of the karst strata: sand, rocky sediment, and mud [24]. The orientation of the sandy beaches on the coast is predominantly north–northwest. The mean grain diameter is 0.2–0.5 mm [84,85].

The main hydrological feature of the coastal systems of the peninsula es that freshwater emerges from underground springs or seeps into lagoons and wetlands [86]. Once in the lagoon systems, it begins to mix and patterns of salinity and temperature develop between the fresh water and the water of the lagoon, producing a complex thermohaline circulation system [27]. Such is the case with the inflow in the southwest of the lagoon, where an estuarine gradient is produced.

#### *Appendix A.5. Hydrodynamics*

The main hydrodynamic drivers are the tides, the predominant winds of the region (Trade Winds, sea breezes, and Nortes). The study in [33] reported that inside the system, the residual currents are around 0.05 m/s, both when influenced by the local breezes as well as the winds (Figures A3 and A4). As can be seen, the tides entering through the inlet spread east, west, and southwards in the lagoon system (Figure A3). In the centre, south, and east of the lagoon, there are mixing zones, with higher values (close to 0.2 m/s) which are greater during 'Nortes' (Figure A4).

**Figure A3.** Example of the residual circulation pattern (m/s) during a spring tide with sea breeze forcing [33].

**Figure A4.** Example of the residual circulation pattern (m/s) during a spring tide with forcing from NE winds [33].
