Spatial Distribution and Community Structure of Echinoderms in the Tropical Marine Ecosystem of East Nusa Tenggara, Indonesia: A Comparative Analysis of Species Diversity and Abundance Patterns

This study examines the spatial distribution and community structure of echinoderms in East Nusa Tenggara, Indonesia, a region within the Coral Triangle biodiversity hotspot. Sampling was conducted at eight sites across three islands (Timor, Rote, and Alor) using a quadrat transect method, with a total of 120 sample plots. Data were analyzed using the Shannon-Wiener diversity index, evenness, dominance index, Importance Value Index (IVI), and Principal Component Analysis (PCA). A total of 22 echinoderm species across four classes were identified, of which 13 species (59%) exhibited cosmopolitan distributions across all sites. Two new species records (Thelenota ananas and Paracaudina australis) were documented exclusively at Onan Ana Beach, which served as the primary biodiversity hotspot with 19 species (86% of total). Species diversity was highest at Onan Ana (H’ = 2.89, E = 0.87) and lowest at the sand mining-degraded Mali Utara (H’ = 1.45, E = 0.52, 13 species), demonstrating that anthropogenic disturbance intensity is a primary driver of community structure variation. The dominant generalist species Ophiocoma scolopendrina (IVI 18.5%) and Diadema setosum (IVI 15.2%) persisted across all disturbance levels, while specialist species were progressively excluded from degraded sites, reflecting ecological filtering. PCA revealed that PC1 (79.31% of variance) separated sites along an anthropogenic disturbance gradient, with habitat heterogeneity and substrate diversity as key determinants of echinoderm community composition. These findings highlight the need for integrated conservation strategies that combine strict protection of high-biodiversity sites with sustainable management of human activities to maintain habitat heterogeneity and ecosystem function in East Nusa Tenggara.