Environmental degradation of the Mexican Caribbean reef lagoons.

Insufficient attention to the large volumes of wastewater produced by expansive tourism and urban development in the north of the Mexican Caribbean has increased concerns on the ecological and economic sustainability of this important tourist destination, which is currently threatened by massive arrivals of pelagic Sargassum. Comparing environmental descriptions for sites exposed to contrasting anthropogenic pressure and before and during massive Sargassum tides, uncovered significant shifts in the environmental conditions in the last 20 years, from oligotrophic to mesotrophic-eutrophic conditions. The most significant changes were observed in the north, for habitats exposed to high anthropogenic pressure. Accordingly, the severe threat that massive Sargassum beaching currently represents for the survival of Caribbean coral reefs cannot be considered the only driver of reef eutrophication in the Mexican Caribbean, as the habitat degradation documented here has an important contribution from anthropogenic fertilization.