3.4.2. Lagoon and Mangroves

According to Psuty et al. [15], the variability of the water level and salinity has important effects on the species growing in the mangrove ecosystem. The opening and closing of the inlet are the determining factors in the behavior of this system; the closure of the bar, which prevents entry of seawater to the lagoon, produces a decrease in oxygen, salinity, pH and chlorophyll [18]. Some fish species in the lagoon change their balances depending on whether the inlet is open or closed, and the existence, or dominance, of many species varies depending on the quality of the lagoon water [15].

The mangrove species in the area provide shelter to native and endemic species, such as tilcampo, crocodiles, iguanas and turtles, which are vulnerable to ecosystem loss; crabs, ocelots and tigrillos, which are in danger of extinction; and also flounder, bass, yellowfin crappie and striped crappie, which are valuable commercial species for the local fishermen [18]. Mangrove is also an ecosystem that acts as an ecological membrane. Martínez et al. [49] analyzed the accumulation of heavy metals in La Mancha, noting that it was greater in mangrove leaves than in nearby sediments, noting the ability of this ecosystem to protect and regulate the balance and mitigate the effects of these substances in the environment, thus decreasing marine pollution.

Psuty et al. [15] pointed out that the germination of seedlings may eventually become more limited, depending on the opening and closing of the inlet, as some species, such as *Avicennia* seedlings, are dispersed by the water currents at the end of the rainy season (September–October), and they germinate when the sandbar closes the inlet.
