Clown fish metabolism slows when coral homes damaged by climate change – study

Climate change damage to the homes of clown fish can have a negative impact on their physiology, according to new research.

Scientists studied what happens to clown fish, known from the film Finding Nemo, living in bleached coral reefs.

Mass coral bleaching is the result of extreme heatwaves caused by worldwide climate change.

The study found that the fish, also known as anemone fish, living in bleached anemones for longer than a month progressively decreased their metabolism, had less growth and modified their behaviour to become less active.

The research was led by an international team of scientists from the University of Glasgow and researchers from France, Chile and Denmark, and was carried out at Criobe (Centre for Island Research and Environmental Observatory) in French Polynesia.

Dr Shaun Killen, from the University of Glasgow’s Institute of Biodiversity, Animal Health and Comparative Medicine, said: “So far scientists have mainly focused their attention on the direct effects of bleaching on corals and on the effects of bleaching-induced coral mortality on the coral reef community.

“However, our results suggest that, even if corals survive and recover from a bleaching event, this doesn’t occur without costs for their associated communities that structure coral reef ecosystems.

“Overall, our findings highlight the gravity of bleaching events and emphasise the need to regulate human actions that contribute to climate change-related events, such as bleaching.”

For the study, the international team exposed 47 wild juvenile anemone fish to thermally-induced bleached anemones, as well as healthy anemones, for several months in Moorea Lagoon.

The team measured fish behaviour, metabolism and growth after one month of living within healthy or bleached white homes.

Each measure was repeated after two months of exposure and juvenile anemone fish survival was monitored over nine months.

Suzanne Mills, Associate Professor at Ecole Pratique des Hautes Etudes (EPHE) PSL Universite Paris, Criobe, France, said: “Although fish in bleached anemones spent more time out of their anemone, they were less active and moved around the anemone less, suggesting an inability to adjust their feeding rate to cope with the lower amount of food available.

“Our finding that bleached anemone hosts lower the growth of associated fish is therefore likely to have cascading and life-long consequences for individual anemone fish, but also for other fish species associated with hosts that bleach.”

Daphne Cortese, PhD student with EPHE, Criobe and the University of Glasgow, said: “In food-limited environments, it can be advantageous to down-regulate metabolism, but there is a limit to how much it can be decreased, and we didn’t obverse any stabilisation over time.

“This finding, together with lower growth and modified behaviour, suggests that fish in bleached anemones are at an energetic disadvantage and that there is an increasingly negative impact of anemone bleaching on anemone fish over time rather than an acclimation to the new condition.”

– The study is published in Functional Ecology.