Community structure of shallow water Alcyonacea (Anthozoa: Octocorallia) from the southern Tropical Eastern Pacific

Contribution of metabolomics to the taxonomy and systematics of octocorals from the Tropical Eastern Pacific

Octocorals are sessile invertebrates that play a key role in marine habitats, with significant diversity in the Tropical Eastern Pacific, especially in Ecuador's shallow waters. This study focuses on the most representative octocorals within the Marine Protected Area El Pelado, Santa Elena, Ecuador, as a part of a marine biodiscovery project employing an integrative approach. While molecular techniques have advanced, challenges persist in distinguishing closely related species. Octocorals produce a wide range of compounds, characterized by unique chemical structures and diverse biological properties. Therefore, the main objective of this study was to assess the potential of metabolomics and advanced analytical techniques to analyze the metabolome of these organisms, aiming to refine species classification and improve understanding of octocoral systematics in this region. Untargeted metabolomics effectively discriminates 12 octocoral species across five genera: Muricea, Leptogorgia, Pacifigorgia, Psammogorgia, and Heterogorgia, with notable differentiation between species within the genus Muricea, reinforcing its utility as an additional data set for species characterization. Secondary metabolites such as sterols, steroids, and terpenes (furanocembranolides and sesquiterpenes), were identified in Leptogorgia and Muricea. Overall, this method enabled the identification of 11 known species and a potentially new one, Leptogorgia cf. alba, confirming the extreme diversity of this group in the Tropical Eastern Pacific and within the Ecuadorian marine ecosystem. The study highlights the value of metabolomics in octocoral systematics and encourages for its broader application in marine biodiversity research.

Octocoral populations and connectivity in continental Ecuador and Galápagos, Eastern Pacific

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.