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Sharks lose their ability to hunt because of warming and acidification of oceans

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Posted November 17, 2015

We all heard about effects of the pollution in the atmosphere. However, it is not so often to hear about what rising CO2 levels do for ocean ecosystems. Now scientists at the University of Adelaide found that sharks are going to be affected by the increased CO2 levels and warmer oceans in a rather interesting way – in the future they may suffer from impaired hunting ability and growth issues.

Because of rising temperature and acidity of the ocean Port Jackson sharks, used in the research, lose their ability to rely on smell during hunting, which results in reduced growth rates. Image credit: Mark Norman / Museum Victoria via Wikimedia, CC-BY-3.0

Because of rising temperature and acidity of the ocean Port Jackson sharks, used in the research, lose their ability to rely on smell during hunting, which results in reduced growth rates. Image credit: Mark Norman / Museum Victoria via Wikimedia, CC-BY-3.0

Scientists performed long term experiments, which demonstrated that the effect on sharks comes from warming water and its acidification. Sharks will start struggling to meet their energy demands and scientists say that the effects are likely to be visible in entire ecosystem.

Experiments were conducted with Port Jackson sharks in large tanks with natural habitat and prey. They showed that embryonic development was faster under elevated temperatures. However, warmer water and high CO2 does a lot of damage – it increases shark’s energy demand, reduces metabolic efficiency and removes their ability to locate food through smelling.

All these effects translate into reductions in growth rates of these sharks. Ivan Nagelkerken, leader of the research team, explained: “In warmer water, sharks are hungrier but with increased CO2 they won’t be able to find their food. With a reduced ability to hunt, sharks will no longer be able to exert the same top-down control over the marine food webs, which is essential for maintaining healthy ocean ecosystems”. Port Jackson sharks are especially vulnerable for such changes in the environment as they are bottom feeders and rely on their ability to smell to find food. High CO2 levels mean that sharks take much longer to find food, which in the end results in smaller sharks.

This study is a response in the lack of researches of effects of rising CO2 levels on large, long-lived predators. Scientists say that it also provides strong support for the call to prevent global overfishing of sharks. Approximately one third of world population of sharks and rays are already threatened by overfishing. Warming temperatures and acidification of water are only going to accelerate these processes and push these species closer to extinction.

Source: adelaide.edu.au

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