Distribution and abundance of two species of Echinometra on coral reefs near Puerto Rico
Caribbean Journal of Science 28(3-4): 173-183
The distribution and habitat affinities of two species of sea urchins, Echinometra lucunter (Linnaeus) and E. viridis (Agassiz), were studied on seven coral reefs near the southwest coast of Puerto Rico. The distribution and abundance of the urchins, as well as degree of water motion and substrate particle sizes, varied significantly within and among the reefs. Within reefs, E. lucunter was most abundant on the shallow forereef, generally above 2-3 m depth. Among reefs, this species was more abundant on offshore reefs, which received greater exposure to wind and currents than nearshore reefs. In general, shallow forereefs and offshores reefs were characterized by a high degree of water movement and an abundance of boulder-size substrates. Echinometra viridis was more common on deep forereefs, below 2 m depth, and at nearshore reefs. Deep forereefs and nearshore reefs were characterized by low to moderate water motion and smaller sized substrates, particularly sand and pebble. These species of urchins occupied different habitats characterized by differences in water movement, depth, and substrate size.