Marine metagenome Targeted loci environmental. marine metagenome strain:Bacteria

Coralline algae are a crucial component of reef systems, stabilising reef substrate, providing habitat and contributing to accretion. They and their microbiomes are also important as settlement cues for marine invertebrates yet few studies address the impact of future environmental conditions on interactions between coralline algae, reef microbes and settlement by larvae of marine invertebrates. We exposed the temperate coralline algal species Amphiroa gracilis to future climate change scenarios for 21 days. Algae became bleached but their photosynthetic capabilities were not measurably impacted. Settlement by larvae of the abundant sea urchin Heliocidaris erythrogramma was reduced and the structure of the microbial community associated with A. gracilis changed. Coralline algae in ambient conditions were dominated by Alphaproteobacteria from the Rhodobacteraceae including Loktonella; those exposed to increased temperature had high abundances of Bacteroidetes and Verrucomicrobia; algae in increased acidification had less Loktonella and more Planctomycetes; and a combination of increased temperature and acidification caused increases in Bacteroidetes, Verrucomicrobia and the Alphaproteobacteria family Hyphomonadaceae. These experiments indicate that predicted future environmental change will reduce the ability of temperate reef coralline algae and associated reef microbes to facilitate settlement of invertebrate larvae as well as having a direct impact to algae via bleaching.