Ecología poblacional de Diadema mexicanum (Echinodermata: Echinoidea) en dos comunidades arrecifales de bahías de Huatulco, Oaxaca, México

Abstract

In 2009 there was a report on an event of mass mortality of Diadema mexicanum in La Entrega, Bahías de Huatulco, and partial mortality in adjacent reef communities. In this study we estimated population density of D. mexicanum, as well as natural mortality and spatial distribution in 2 affected localities (San Agustín and Isla Montosa) during a subsequent period (May 2009-October 2011). Additionally we evaluated the relation between population density and temperature, pH and pluvial precipitation. Mean density (± SD) was 0.64±0.42 ind.m–2 in San Agustín, and 1.29±1.24 ind.m–2 in Isla Montosa. Mortality rate was 0.219 in San Agustín, and 0.605 in Isla Montosa. For both localities spatial distribution was aggregated during the whole period except in 5 months when it was random. In San Agustín pluvial precipitation was significantly related to density, whereas in Isla Montosa there were not significant relations. Isla Montosa has a larger availability of resources and a more suitable substrate for D. mexicanum population than San Agustín, however, the sea urchin population in this locality showed more instability, probably because it is closer to La Entrega and the level of the die-off was higher.