<p><strong>Background: </strong>Cozumel island, Mexico has one of the best preserved and threatened coastal vegetation in the Mexican Caribbean. Increasing the ecological knowledge about these communities can help to establish conservation priorities.<strong></strong></p><p><strong>Question: </strong>How are the structure and composition of well-preserved coastal vegetation communities in the Island of Cozumel?<strong></strong></p><p><strong>Study site and dates: </strong>The study was conducted in the northeastern coast of the island of Cozumel, at the Municipality of Cozumel, Quintana Roo, Mexico, from July 2014 to November 2014.<strong></strong></p><p><strong>Methods: </strong>Five interception lines of 80 m were randomly established along environmental gradient, perpendicular to the coastal line, in each three different environments: rocky beaches, sandy beaches, and coastal dunes. Species richness, diversity, and importance value index of the species in the community were computed, and floristic composition recorded.<strong></strong></p><p><strong>Results: </strong>We recorded 23 families, 35 genera and 37 species. The most representative families are Poaceae with four species, Rubiaceae and Asteraceae with three species each; <em>Sideroxylon</em> and <em>Euphorbia</em> were the richest genera, with two species each. The three coastal environments presented no statistical differences in its relative density, coverage and diversity, but differed in species composition and richness (higher in rocky beaches and coastal dunes).<strong></strong></p><strong>Conclusions: </strong>Two dissimilar coastal plant communities can be recognized into the halophilous vegetation type, which are established in sandy and rocky environments respectively. The floristic composition and the species association of the rocky beaches reveal the relationship between the Island of Cozumel coastal vegetation and plant communities in other Caribbean islands.

The Mexican Caribbean coast has great scenic beauty both on the surface and underwater, which is why it has been a developing area for tourism since the 1970s, establishing sites such as Cancun and Playa del Carmen and empowering others such as Cozumel and Tulum. Their biological richness is enormous, especially in the Mesoamerican Reef of which they are a part. However, this richness and scenic beauty are not possible without the ecological assemblages that exist within these regions’ adjacent ecosystems, mainly the surrounding seasonally dry tropical forest and the coastal wetlands that, together with the oceanographic characteristics of the Caribbean Sea, potentiate it, turning the region into the most visited in Latin America. To this end, groundwater plays a very important role in the assemblages of biotic and abiotic elements that are shared with the Caribbean Sea; thus, its constant monitoring allows us to identify how the changes that occur in the tropical forest are producing various changes in the composition and abundance of coastal reef elements. Here, we present results of our study of groundwater conditions (temp, pH, oxygen dissolved, and salinity) in nineteen cenotes and underground rivers of the Riviera Maya and six cenotes of Cozumel. We also profiled the predominant vegetation on the surface of this region, which is a seasonally dry tropical forest, to understand the components and functioning of these subterranean ecosystems to assess their vulnerability and identify their threats from human development (population growth, tourism development, mobility capacity). These threats not only affect the cave and coastal organisms but also the tropical karstic landscapes that are characteristic of these systems.

La calidad visual de los paisajes de playa de Cozumel evaluada a través de los ojos del observador