Background.

The macroalgae of the tropical Mexican Pacific have been studied and results published in numerous texts since the 1940s. Nevertheless, there is no compilation of records of macroalgae from reef communities, nor have specific inventories of reef macroalgae been prepared.

Objective.

To integrate the knowledge generated on the tropical Mexican Pacific coral reef macroalgae. Carry out an integration of the knowledge generated on reef macroalgae and make inventories of these macroalgae in the reefs of Guerrero and Oaxaca in the Mexican tropical Pacific.

Methods.

Sørensen›s similarity analysis and Non-Metric Multidimensional Scaling (NDMS) analysis were applied to data of algal composition from different coral reefs to determine their distribution patterns. The ANOSIM analysis method was applied to demonstrate the significant differences between groups. Results. The total number of macroalgal species was 144, 100 Rhodophyta, 32 Chlorophyta and 12 Ochrophyta-Phaeopyceae; 75 were exclusive to Guerrero, 24 to Oaxaca, and the number of shared species was 45. El Zacatoso, Guerrero, had 92 species and was the locality with the greatest specific richness. The Sørensen Index indicated a similarity of more than 50% among most localities, but with a clear separation between the communities of Guerrero and Oaxaca. Four groups were formed by localities’ species with the NMDS analysis without seasonal effect (rainy and dry), ANOSIM shows significant differences among the localities of each group.

Conclusion.

This work represents the first inventory of the reef-inhabiting macroalgae of Guerrero and Oaxaca, the only states in the Mexican tropical Pacific with specific systematic reports on this type of coral reef algae. This study provides baseline information to develop a regional monitoring program, a diagnosis of the degree of disturbance of coral reefs and generate conservation strategies and plans for these ecosystems.