News in Science

Cold climate animals may suffer as world heats up

Mosquitofish study Animals that live in cold, stable environments may suffer more as the climate changes, suggests new research on the ability of mosquitofish to deal with temperature increases.

The study, published today in the journal Royal Society Open Science, showed that mosquitofish acclimatised to live in colder water did worse when temperatures were raised.

"Our research shows that some animals that live in colder climates now will suffer as temperatures becomes more variable due to climate change," says Dr Frank Seebacher from the University of Sydney.

"We now have evidence that even mosquitofish, which are really good at acclimating, none the less pay a price if they move from cold to warm environments. They do worse. So if the climate becomes more variable, they won't do as well as a population."

Two species of gambusia, commonly known as mosquitofish, were introduced to northeast Australia in 1925 in an unsuccessful bid to control mosquito lava. These small but resilient fish have since spread to waterways in every state and territory, apart from the Northern Territory.

These noxious pests breed rapidly, eat the eggs and fry of native fish and compete with them for food. They can even increase populations of mosquito larvae by preying on the insects that feed on them.

But it's their ability to thrive in varying environments and temperatures that make mosquitofish perfect candidates for research into acclimatisation, Dr Seebacher says.

The study involved collecting mosquitofish from Sydney's Manly Dam and gradually acclimatising them to a water temperature of 20 degrees centigrade, the lowest temperature this cohort of fish would experience in the wild.

Three weeks later the team measured the swimming performance of the fish by exposing them to increasing strengths of water currents at different temperatures. The experiment stopped when the fish appeared visibly exhausted.

The scientists measured swimming performance at temperatures of 20 degrees, 28 degrees and 32 degrees.

The same fish were then acclimatised to 28 degrees, the highest water temperature they would experience at manly Dam, and the experiment was repeated.

The results showed that when the fish were acclimatised to a water temperature of 28 degrees they swam for longer at all three test temperatures than when they were acclimatised to 20 degrees. They also performed at their optimum at higher temperatures than when they were acclimatised to living in cooler water.

There was a pronounced difference in performance between individual fish, however, with some performing better at higher temperatures than they would have experienced in Manly Dam.

"This indicates that there are genetic constraints among individuals, which could mean that some individuals are better at reacting to temperature shocks than others and probably explains why they do so well in different environments," Dr Seebacher explains.

"However, while they are good at remodeling their biochemical processes depending on what temperatures they experience, there is still this trade off and they pay a price. So, if they are really good at compensating for a cold environment, like in winter, they do worse when it gets warm again. It's called a generalist-specialist tradeoff."

Climate change

As for climate change, mammals and birds might be able to cope quite well with changing temperatures by remodelling themselves and doing just as well in warmer or colder climates, he suggests.

"But cold-blooded animals, like fish, reptiles and insects that live in relatively stable temperatures now, may not do as well when there are bigger fluctuations in temperature. Those that do well in colder temperatures may not do as well in warmer ones."

He suggests that if we want to predict what some of the future impacts are of climate change then we need to understand the physiological capacity of animals to respond to it.

"This may allow us to manage some particular populations better than others, perhaps by allocating resources to those populations that we know will do better than others, based on their physiological capacities. It could be a really important management tool."