A team of researchers from University of Adelaide warned that by 2050, the oceans and carbon dioxide levels will have increased and the temperature will rise. In Scientific Reports, marine ecologists stated that long-term tests showed that sharks will be unable to meet their energy needs due to rising water temperatures and acidification. They predicted that these negative effects will have an adverse effect on entire ecosystems. Port Jackson sharks rely on their sense of smell for food. What will the shark do if CO2 levels keep rising while it is unable to smell food? Researchers conducted lab experiments with Port Jackson sharks in the Environment Institute at University of Adelaide. They observed that the embryonic growth of these animals was quicker in high-temperature environments with prey and natural habitat. High levels of CO2 are bad for the sense of smell of sharks. However, sharks were unable to find food by olfaction due to higher levels of carbon dioxide (CO2) and warm water. The effects had a significant impact on the growth rate of sharks. Associate Professor Ivan Nagelkerken (ARC Future Fellow), led the study. He stated that while sharks become more hungry in warmer waters, they will not be able find food due to increased levels of CO2. Sharks won’t be able exert top-down control of the ocean food webs due to reduced hunting ability. Jennifer Pistevos (a doctoral student) explained that Port Jackson, a bottom-feeding shark, relies on olfaction for food. Higher CO2 environments resulted in sharks that were less efficient in finding food. They often didn’t bother to try, leading to significantly smaller animals. Most studies investigating the impacts of climate change and ocean acidification on fish behavior in general focused on small fish prey. The authors noted that there are few studies that examine the behaviour and physiological changes in large-sized, long-lasting predators. Prof. Sean Connell (marine biologist) says that the findings of the study strongly support the need to end global shark overfishing. Professor Connel stated that overfishing has already caused the extinction of a third of all shark and ray species. The combination of climate change and ocean acidification will add stress to the situation and increase the extinction rate. These results indicate a complex reality in predators. Ocean acidification decreases their ability to hunt effectively and exert strong top down control over food webs. Scientific Reports. 12 November, 2015. DOI: 10. 1038/srep16293.
