Comparison of ecological diversity and species composition of macroalgae, benthic macroinvertebrates, and fish assemblages between two tropical rocky reefs

Within the marine environment, the rocky shores are recognized for their high species diversity and particularly transitional zones represent areas of biotic mix, promoted by historical and ecological natural variations that allow the presence of taxa from different regions and which present dissimilar biological traits. An extensive survey describes the benthic macroalgae, macroinvertebrates (molluscs, crustaceans, and echinoderms), and fish assemblages at two rocky reefs, Islas Marietas and near Tehuamixtle, in a tropical-temperate transitional zone in the Pacific waters of central Mexico using traditional ecological indices (richness, diversity, and evenness) and complementary taxonomic distinctness indices. Biological material inside each of ten randomly-chosen quadrants (25 x 25 cm) placed along two 50 m transects oriented parallel to the coastline, between 6 and 2 m depth was collected. From field collections, 204 species were identified: macroalgae (22), molluscs (55), crustaceans (78), echinoderms (11), and fish (38). The structure of macroalgae, macroinvertebrates and fishes was similar between sites. Species of macroalgae, molluscs, and fishes were more diverse in summer; crustaceans and echinoderms were more diverse in winter. Our results and the literature suggest a latitudinal pattern of lower seasonal changes in echinoderms and crustaceans at high latitudes, as compared to southern regions of the Mexican tropical Pacific.