Marine Heatwaves, Ocean Warming and Acidification Reshape Reef Fish Gut Microbiomes

Area of Science:

• Marine biology
• Microbiome research
• Climate change ecology

Background:

• Climate change, including ocean warming, acidification, and marine heatwaves, is reshaping marine ecosystems.
• The effects of these stressors on host-associated microbial communities and their role in host adaptation are not well understood.

Purpose of the Study:

• To assess shifts in gut microbiome communities of two reef fish species exposed to simulated climate change conditions.
• To investigate the association between microbiome changes and physiological performance in reef fish under climate change.
• To examine the impact of marine heatwaves on fish gut microbiomes.

Main Methods:

• Compared gut microbiome communities and physiological performance of tropical (Abudefduf vaigiensis) and subtropical (Microcanthus strigatus) reef fish across three temperate reefs: cool, warm, and extreme (warming + acidification).
• Analyzed gut microbiome changes in A. vaigiensis before and during a severe marine heatwave.
• Assessed physiological parameters including protein content, oxidative stress, antioxidant capacity, and body condition.

Main Results:

• A. vaigiensis exhibited decreased gut microbiome evenness and diversity at warm and extreme reefs, with a significant increase in opportunistic Vibrio bacteria at the extreme reef.
• During a marine heatwave, A. vaigiensis showed reduced gut microbiome richness compared to pre-heatwave individuals.
• M. strigatus displayed increased microbiome evenness and diversity at the warm reef, but these returned to baseline levels at the extreme reef.
• Microbiome alterations were generally not linked to significant changes in the physiological performance of either fish species.

Conclusions:

• Marine heatwaves, ocean warming, and acidification significantly alter reef fish gut microbiomes, leading to simplification in A. vaigiensis and distinct restructuring in M. strigatus.
• Climate-driven microbiome reshuffling can impact host-microbiome relationships and functions in fish populations facing future ocean conditions.
• Reef fish exhibit species-specific responses to climate change stressors affecting their gut microbial communities.