Increasing water temperatures and pollution cause hormone changes that make coral reef fish more vulnerable to predators, according to a study in the latest edition of the Nature Communications scientific magazine.
Fish are affected by a host of stress factors induced by human activity, particularly increasing water temperatures caused by climate change and pollution by farm pesticides, noted the study, published on Friday.
According to the researchers, this first study shows that stress disrupts the way coral reef fish secrete the various hormones that are supposed to regulate their bodies and enable their sensory structures, such as retinas, nostrils and lateral lines to develop. Normally, these structures make fish better able to detect movement, and therefore dangers and threats, in nearby waters.
“This matters because animals use their sensory systems to inform ecologically important behaviours, such as their ability to identify and respond to predators,” said study co-author William Feeney of the Griffiths University’s Environmental Futures Research Institute in Australia.
The study shows that a temperature variation of three degrees, as predicted between now and 2100 due to global warming, and pollution both diminish the quantity of thyroid hormones in fish.
Aquatic animals exposed to different types of stress all showed changes in sensory development and increased vulnerability to predators. However, when they received an additional thyroid hormone, that enabled such effects to be reversed, the study showed.
“This means even exposure to low amounts of temperature change or pollution, which on their own have little or no detectable effect, may be worse in the developmental stage of coral fish than exposure to a single stressor alone,” Feeney explained.