The metabolome of crustose coralline algae is driven by phylogeny and environmental conditions

Metabolomics is a powerful approach to investigate the effect of environmental conditions on metabolite variations in marine algae. Here, we focused on crustose coralline algae (CCA), a group of calcifying, red algae which play an important role on coral reefs through their interactions with corals and contribution to coral reef formation. Despite their ecological importance, little is known about their metabolome and how it varies with environmental conditions and phylogeny. Using an untargeted metabolomic approach, we explored the metabolomic fingerprints of seven CCA species (order: Corallinales) commonly found on the coral reefs of Moorea, French Polynesia. We developed an extraction method to characterize the CCA metabolome on two sample types (whole fragment and surface only) and explored the chemical variations of CCA across species, reef habitat and microhabitat. The extraction method successfully characterized the CCA metabolome, as demonstrated by a technical variability lower than the biological variability for both sample types. The CCA metabolome was species-specific and a correlation was found between phylogenetic taxonomy and metabolomic profiles of the different species. Moreover, the metabolomic composition of certain species differed between the back and fore reef habitats and between exposed and cryptic microhabitats. These results highlight a high variability in the CCA metabolome mediated by phylogeny and environmental conditions. This study provides valuable insights into the sources of metabolomic variation in CCA. It lays the groundwork for exploring the ecological functions of the CCA metabolome and its potential use as a tool to assess organismal and ecosystem health.