Oral Presentation Australian Society for Fish Biology & Australian Freshwater Sciences Society Conference 2026

Molecular, Physiological, and Behavioral Responses of a Coral Reef Fish to Ocean Warming and Acidification (143502)

Joseph L Proietti 1 , Davide Spatafora 2 3 4 , Shannon McMahon 1 , Roger Huerlimann 1 5 , Yasuhito Hayashi 3 , Chengze Li 1 , Jeffrey Jolly 1 , Michael Izumiyama 1 4 6 , Marina L Gerton 7 , Guinther Mitushasi 3 , Joshua M Heitzman 4 8 , Lucia Porzio 3 , Carlo Cattano 2 4 , Ben P Harvey 3 4 , Shigeki Wada 4 8 , Marco Milazzo 4 9 , Sylvain Agostini 4 10 , Timothy Ravasi 1 4 5
  1. Marine Climate Change Unit, Okinawa Institute of Science and Technology, Onna, Okinawa, Japan
  2. Department of Integrative Marine Ecology, Stazione Zoologica Anton Dohrn, Palermo, Sicily, Italy
  3. Shimoda Marine Research Centre, University of Tsukuba, Shimoda, Shizuoka, Japan
  4. Labex ICONA International CO2 Natural Analogues Network, Shimoda, Shizuoka, Japan
  5. College of Science and Engineering, James Cook University, Townsville, Queensland, Australia
  6. University of the Ryukyus, Nishihara, Okinawa, Japan
  7. School of Geosciences, University of Edinburgh, Edinburgh, Scotland, United Kingdom
  8. Seto Inland Sea Carbon-neutral Research Center, Hiroshima University, Higashi-Hiroshima, Hiroshima, Japan
  9. Department of Earth and Marine Sciences, University of Palermo, Palermo, Sicily, Italy
  10. UMR Entropie, IRD, Noumea, New Caledonia, France

Ocean warming and acidification can profoundly affect marine organisms. To understand how coral reef fish are affected by changing environments, we used a manipulative aquaria-based experiment to assess the response to warming and ocean acidification in the Neon Damselfish (Pomacentrus coelestis) in Shimoda, Japan. Fish were exposed to one of four treatments: elevated temperature, elevated pCO2, combined elevated temperature and elevated pCO2, and ambient conditions (control). Respirometry, behavioral assays, and brain transcriptomics were used to assess physiological performance, behavioral changes, and molecular responses, respectively.

Both warming and elevated pCO2 decreased factorial aerobic scope, and warming alone decreased activity levels. In the combined stressor treatment, there was an increase in activity level relative to the warming treatment, leading to activity levels which were comparable to the ambient temperature treatments. Transcriptomic analysis revealed enrichment of pathways associated with immune response, neuronal activity, metabolic activity, and vision, indicating that these fish may be equipped to acclimate to elevated pCO2 and temperature with a robust transcriptomic response. The highest number of enriched pathways was found in the pCO2 treatment, followed by the combined stressor treatment, with the lowest number in the warming treatment. 

Reduced activity level in the warming treatment indicates that reduced factorial aerobic scope may force these fish to downregulate activity under warming conditions to conserve energy. However, this compensatory response is disrupted in the multiple stressor treatment, eliminating the behavioral changes seen in the warming treatment. The combined stressor treatment also reduces the number of enriched pathways relative to the pCO2 treatment. These results imply that multiple stressors may dilute the response seen in a single stressor treatment, leading to a maladaptive synergistic effect. This study highlights the value of multiple stressor experiments by demonstrating the complexity of coral reef fish response to environmental change.