Climate change may pose a graver risk to shark populations than previously understood, according to new findings that show that increasingly acidic water prevents the oceangoing predators from sensing the odor of prey.
As Discovery News notes, two new studies predict that current shark populations could be reduced by as much as 44 percent by the year 2100, while those remaining will largely lose the ability to detect their prey. Rui Rosa, lead author of one of the studies, published in the journal Proceedings of the Royal Society B, worked with his team to expose shark embryos to water with a higher acidity level, which is predicted by 2100. Carbon dioxide that is released into the atmosphere can be absorbed by the ocean, lowering the pH of the water.
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Sharks that were exposed to higher temperatures and more acidic water saw a reduction in their survival rate of nearly 44 percent after the first month of the study, while the surviving sharks acted lethargically. Rosa’s team predicts that tropical sharks in particular, including species like the Hammerhead and Bull shark, along with the Whale and Tiger shark, will be more vulnerable to changes in climate as their evolution has taken place in a stable environment.
A second study, performed by another group of researchers, subjected sharks to the same lowered pH levels, yet focused on their ability to smell prey. When exposed to temperatures and pH consistent with end-of-century projections, the adult sharks used in the study significantly avoided the odor of prey, Phys.org notes. Lead author Danielle Dixson, an assistant professor in the School of Biology at the Georgia Institute of Technology, posited that while sharks can use other senses to hunt, olfactory perception is among their most important.
“The sharks’ tracking behavior and attacking behavior were significantly reduced…Sharks are like swimming noses, so chemical cues are really important for them in terms of finding food.”
A variety of dangers threaten to deplete shark populations worldwide. Aside from overfishing, the practice of shark finning, recently banned in Massachusetts (as The Inquisitr reported), contributes greatly to declining populations. Conservation efforts aimed at mitigating fishing have proven largely responsible for a surge in the number of Atlantic great white sharks, bringing the species back from decline in recent years.
Acidic waters affect sharks and other fish by interfering with a receptor in their nervous system, known as GABAA. Previous studies have indicated that fish living in carbon dioxide saturated environments lose interest in food, as well as their ability to detect odors, indicating that sharks are far from the only species at risk from increasingly acidic waters.
[Image via Discovery]