The interaction between the proliferating macroalga Asparagopsis taxiformis and the coral Astroides calycularis induces changes in microbiome and metabolomic fingerprints

Stéphane Greff,Olivier P Thomas,Ester A Serrão,Aschwin H Engelen,Tânia Aires,Thierry Pérez

doi:10.1038/srep42625

Abstract

Mediterranean Sea ecosystems are considered as hotspots of biological introductions, exposed to possible negative effects of non–indigenous species. In such temperate marine ecosystems, macroalgae may be dominant, with a great percentage of their diversity represented by introduced species. Their interaction with temperate indigenous benthic organisms have been poorly investigated. To provide new insights, we performed an experimental study on the interaction between the introduced proliferative red alga Asparagopsis taxiformis and the indigenous Mediterranean coral Astroides calycularis. The biological response measurements included meta–barcoding of the associated microbial communities and metabolomic fingerprinting of both species. Significant changes were detected among both associated microbial communities, the interspecific differences decreasing with stronger host interaction. No short term effects of the macroalga on the coral health, neither on its polyp activity or its metabolism, were detected. In contrast, the contact interaction with the coral induced a change in the macroalgal metabolomic fingerprint with a significant increase of its bioactivity against the marine bacteria Aliivibrio fischeri. This induction was related to the expression of bioactive metabolites located on the macroalgal surface, a phenomenon which might represent an immediate defensive response of the macroalga or an allelopathic offense against coral.

Highlights

Macroalga–coral interactions received a great attention during the last decades in tropical marine ecosystems, leading to the general assumption that coral reef degradation is at least partly linked to macroalgal proliferation[1,2]
128 introduced macroalgal species have been reported in the Mediterranean Sea, which represent more than 10% of the known marine flora[8]
In a second set of experiments dedicated to the study of the longer term interaction, the metabolomic fingerprints were obtained from coral and macroalga specimens sampled in the Alboran Sea, from an area where A. taxiformis is well–established and outcompeting A. calycularis for several years

Summary

Introduction

Macroalga–coral interactions received a great attention during the last decades in tropical marine ecosystems, leading to the general assumption that coral reef degradation is at least partly linked to macroalgal proliferation[1,2]. Macroalgal overgrowth may represent physical barriers to larval settlement, acting as abrasive or shading factors, and as a source of bioactive metabolites or pathogens that could affect coral health[4]. These processes of competition are mainly studied in tropical rather than in temperate ecosystems[5,6,7]. In a second set of experiments dedicated to the study of the longer term interaction, the metabolomic fingerprints were obtained from coral and macroalga specimens sampled in the Alboran Sea, from an area where A. taxiformis is well–established and outcompeting A. calycularis for several years (personal observations)

Methods

Results

Conclusion