Density Distribution and Factors Influencing Sea Stars in Selected Islands of Lakshadweep India

Abstract

Coral reefs are the most fragile, complex and diverse ecosystem on earth. But recently, they arc under severe threat due to both natural (climate change, storms and disease outbreaks) and anthropogenic factors (overexploitation, coastal developmental activities and pollution). As evident from earlier studies, a major factor causing degradation of coral reefs is due to an asteroid species belonging to phylum Echinodermata which is considered second to storm damage. Thus to analyze the condition in Lakshadweep Islands I assessed the density of asteroids in four Islands of Lakshadweep. It was found that the five species detected belonging to three families (Oreasteridae, Linckiidae and Acanthasteridae) were having varied density across the four islands. Overall density estimates of the asteroids ranged from 0.05(S.E = 0.02) to 0.80(S.E = 0.09) per 250 square meter. The asteroid density was highest in the uninhabited Island named Bangaram. Correspondence Analysis (CCA) showed that major gradients in environmental variables influenced asteroid species distribution. Sample scores on ordination ' axis 1 were strongly correlated with water pH, water depth and dead coral. Out of the three strongly correlated environmental variables pH was found to be the most ecologically important variable that affects the asteroid distribution. Corallivorous asteroid population outbreaks are becoming a boon to the coral reef ecosystem all over the world and contribution of water pH variation of this outbreaks are being studied well. Thus management strategies in Lakshadweep Islands that 'accounts the variation of water pH are required to conserve the coral reef ecosystem.