How marine heatwaves and warming change kelp microbes and affect food chain relationships

The microbiota of the kelp Ecklonia radiata was enriched with microorganisms linked to disease and tissue degradation under warming conditions.

• Ocean warming may alter the interactions between tropical herbivores and temperate seaweed communities.
• The kelp Ecklonia radiata showed significant changes in its microbiota when exposed to sustained warming and marine heatwaves.
• Increased grazing by the tropical sea urchin Tripneustes gratilla occurred on Ecklonia radiata with altered microbiota, suggesting a link between microbiota changes and herbivore behavior.
• The fucoid seaweed Sargassum linearifolium's microbiota remained stable under temperature changes.
• Elemental traits, chemical defenses, and tissue bleaching of both seaweed species did not show significant changes due to temperature variations.

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