The muscular activity of the marginal sphincters of Oulactis muscosa ,Aulactinia marplatensis and Aulactinia reynaudi from the intertidal zones of two different ecosystems was compared. The study was made upon the quartzitic outcrop ecosystem of Punta Cantera and the sandbar ecosystem of Santa Clara del Mar from Mar del Plata (Argentina). The isolated marginal sphincters were stimulated at increasing KCl concentrations and analysed as a dose-response curve expressed in tension in grams (gr: grams force) vs. concentration. Sphincters of sea anemones from the outcrop ecosystem of Punta Cantera developed greater maximal tension than specimens from the sandbar ecosystem of Santa Clara del Mar. No significant differences were found between the species from Punta Cantera. The same result was observed for the species from Santa Clara del Mar. It was concluded that sphincters of sea anemones from Punta Cantera are adapted to resist the continuous dashing of waves. Hence, they developed higher isometric forces in their sphincters compared to those specimens from Santa Clara del Mar. These physiological responses are correlated with the different physiography of both ecosystems.