Physiological And Behavioural Effects Of Anemone Bleaching On Symbiont Anemonefish In The Wild

1. Climate change causes extreme heat waves that have induced worldwide mass coral bleaching. The impacts of temperature-induced bleaching events on the loss of algal endosymbionts in both corals and anemones are well documented. However, the cascading impacts of bleaching on animals that live in association with corals and anemones are understudied.2. We performed a field-based experiment to investigate how host anemone bleaching affected the metabolic rate, growth, behaviour and survival of wild juvenile orange-fin anemonefish Amphiprion chrysopterus over 1, 2 and (for survival) 9 months.3. We found that the standard metabolic rate of anemonefish residing in bleached anemones decreased over time but was unaffected in fish from healthy anemones. Despite the reduced metabolic cost, the growth rate of fish from bleached anemones was significantly lower compared to fish from healthy anemones, suggesting that animals residing in bleached hosts are at an energetic disadvantage. This was corroborated by our finding that fish from bleached anemones spent more time out of their anemones, suggestive of a greater need to forage in the water column. However, fish from bleached anemones were overall less active and used less space around the anemone, resulting in a negative correlation between space use and survival after 4 weeks.4. Our results provide insight into the physiological and behavioural effects of host bleaching on juvenile fish in the wild, and highlight how relatively short-term thermal anomalies can have long-lasting impacts beyond the bleached anemones or corals themselves.5. A free Plain Language Summary can be found within the Supporting Information of this article.