Physiological and behavioural effects of anemone bleaching on symbiont anemonefish in the wild

Shaun S Killen,Daphne Cortese,Tommy Norin,Suzanne C Mills,Amélie Crespel,Ricardo Beldade,Diego Barneche

doi:10.1111/1365-2435.13729

Abstract

Abstract 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. 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. 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. 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. A free Plain Language Summary can be found within the Supporting Information of this article.

Highlights

Anthropogenic climate change and extreme weather events are global phenomena that impact terrestrial and aquatic organisms
We found that the standard metabolic rate of anemonefish residing in bleached anemones decreased over time but was unaffected in fish from healthy anemones
Our field-based experiment allowed us to test the indirect effects of climate change and warming-induced bleaching on wild coral reef fish in the absence of elevated temperature, while exposing fish and anemones to natural variability arising from selection and environmental variables, including water current, food availability, solar radiation and inter- and intra-specific interactions

Summary

| INTRODUCTION

Anthropogenic climate change and extreme weather events are global phenomena that impact terrestrial and aquatic organisms. Short-term climatic stressors such as transient heat waves lasting from days to weeks (Glynn, 1996; Oliver et al, 2018) are outlived by the ensuing longer-term bleaching episodes The impacts of these bleaching events may cascade onto other animals associated with corals and anemones for either shelter, foraging, or recruitment (Graham et al, 2007; Jones & Syms, 1998; Wilson et al, 2006). We compared standard (resting) metabolic rate (SMR), behaviour (activity and space use) and growth rate of anemonefish after 4 and 8 weeks of living with unbleached or bleached anemones, and tracked the fish's survival for 9 months These exposure durations are ecologically relevant both to bleaching and anemone recovery (Jones, 1997; Lang et al, 1992), and sufficient to observe the potential for acclimation (Fangue et al, 2014; Sandblom et al, 2014). We explored correlations among the measured traits, as environmental disturbances are known to alter the relationship between physiological and behavioural traits (Killen et al, 2013)

| MATERIALS AND METHODS

Findings

| DISCUSSION