Several studies have shown that within the Florida Coastal Everglades, periphyton mat properties, (incuding biomass, nutrient and organic content, and community composition) vary predictably in response to water quality.The Florida Coastal Everglades (FCE) wetland system is very similar with respect to climate, geology, hydrology and vegetation, to wetlands found in Jamaica, the Yucatan region of Mexico and parts of Belize. This study was therefore conducted to ascertain (i) the level of similarity between the periphyton diatom communities from karstic wetland sites in Belize, Mexico, Jamaica and comparable sites within the FCE, (ii) the relationship between periphyton biomass, TP levels and diatom community composition at these sites, and (iii) the feasibility of employing diatoms as indicators of water quality at these sites, using models relating diatom community composition to water quality from comparable sites within the FCE. Multiple wetland sites in Jamaica, the Yucatan region of Mexico and parts of Belize were visited between 2006 and 2008, during wet and dry seasons. At each site physico-chemical data were collected along with periphyton samples. The periphyton samples were processed in accordance with standard methods to obtain biomass, organic content and TP measures, and to identify and enumerate diatom and soft algae species. Various aspects of the diatom communities were then compared to previously compiled data on diatom communities from various parts of the FCE. SIMI analysis was used to determine the level of similarity between the systems and Non-Metric Multidimensional Scaling was used to identify relationships between diatom communities and water quality.