Effects of sedimentation on coral communities of southern Socorro Island, Revillagigedo Archipelago, Mexico

Abstract

This paper documents the disturbances suffered in 1994 by the coral communbities of Braithwaite, Vargas Lozano and Binners bays of southern Socorro Island, Revillagigedo Archipelago (18°N), after an event of excessive sedimentation caused by an input of terrigenous sediments from the island surface. This phenomenon probably occurred because of the severe erosion of the southern zone of Socorro, originated by the overgrazing and transit of the population of feral sheep (Ovis aries L.), whose activities have caused severe soil losses in the locality. The sediment primarily damaged the coral colonies at Braithwaite Bay, and conspicuously diminished the rocky areas suitable for use by other marine invertebrates. The noticeable differences in the development of coral communities from northern and southern Socorro Island may be due to the repeated occurrence of similar events in the past, as the sheep have lived on the island for more than one century. This paper presents the first record of sedimentation damages to marine communities in oceanic islands of the Mexican Pacific.