Australian researchers claim rising CO2 levels impairs sharks’ ability to smell, hunt for food

Sharks are dramatically losing the ability to hunt and to grow in the oceans of Australia due to the impact of increasing CO2 levels and warmer oceans, according to marine ecologists from the University of Adelaide. The study warns that the effects of climate change to sharks would significantly influence the health of ocean ecosystems.

Researchers have found that sharks tend to take much longer time to find their food due to the exposure to climate change, and most species didn't even bother to try to hunt for food. The effect may result to much smaller sharks.

In long-term experiments, researchers analysed the activities of Port Jackson sharks, which primarily rely on its ability to smell to find food, in warmer waters. The findings show that these sharks tend to experience major detrimental effects from warmer waters and ocean acidification.

The combination of warmer water and high carbon levels increased the energy requirement of the sharks but reduced their metabolic efficiency. The warm environment also removed the ability of the species to locate food through olfaction or smelling.

"In warmer water, sharks are hungrier but with increased CO2 they won't be able to find their food," lead researcher Ivan Nagelkerken, from the Australian Research Council (ARC) Future Fellow, said in a press release. The impact of CO2 to the animals led to marked reductions in their growth rates.

The reduced ability to hunt would lead sharks to lose their ability to exert the same top-down control over the marine food webs, important to maintain healthy ocean ecosystems, he added.

The findings strongly support the call for the prevention of global overfishing of sharks, according to Professor Sean Connell, a marine ecologist at the University of Adelaide. The study was recently published in the journal Scientific Reports.

"One-third of shark and ray species are already threatened worldwide because of overfishing," Connell said. "Climate change and ocean acidification are going to add another layer of stress and accelerate those extinction rates."

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