Octocorals are important zoobenthic organisms, contributing to structural heterogeneity and species diversity on hardgrounds. Their persistence amidst global coral reef degradation and ocean acidification, has prompted renewed interest in this taxon. Octocoral assemblages at 52 sites in continental Ecuador and Galápagos (23 species, 3742 colonies) were examined for composition, size distributions within and among populations, and connectivity patterns based on ocean current models. Species richness varied from 1 to 14 species per site, with the richest sites on the continent. Three assemblage clusters were recognised based on species richness and population size, one with a mix of sites from the mainland and Galápagos (defined by Muricea fruticosa and Leptogorgia alba, Muricea plantaginea and Pacifigorgia darwinii), the second from Santa Elena in southern Ecuador (defined by M. plantaginea and L. alba) and the third from the northernmost sites on the continent, in Esmeraldas (defined by Muricea fruticosa, Heterogorgia hickmani, Leptogorgia manabiensis). Based on biophysical larval flow models with 30, 60, 90-day Pelagic Larval Duration, good connectivity existed along the South American mainland, and from the continent to Galápagos. Connectivity between Galápagos, Cocos, Malpelo and the Colombian mainland may explain the wide distribution of L. alba. Muricea plantaginea had the densest populations with the largest colonies and therewith was an important habitat provider both in continental Ecuador and Galápagos. Continental Ecuador harbours the most speciose populations of octocorals so far recorded in the southern Eastern Tropical Pacific (ETP). Most species were uncommon and possibly vulnerable to local extirpation. The present study may serve as a base line to determine local and regional impacts of future disturbances on ETP octocorals.
Keywords: Assemblage pattern; Connectivity; Ecuador; Galápagos; Octocorals; Population density.
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