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When atmospheric carbon dioxide dissolves in the oceans it forms carbonic acid, which in turn has a negative impact on marine life. Laboratory studies show that as seawater acidity increases, the calcium carbonate shells and skeletons of many marine species, such as hard corals, sea urchins, and stony seaweeds, begin to corrode. Since 2000, scientists have measured the acidity of seawater around Tatoosh Island off the coast of Washington state. The acidity increased ten times quicker than climate models predicted.
The organisms most directly affected are those that build hard shells or other mineral structures of calcium carbonate. But it has not become clear, that sharks will also be victims of this process in the bear future. By year 2100, shark populations could undergo steep declines — by up to 44 percent — and remaining sharks may lose much of their ability to sense the odor of food, predict two new studies.
The first experimental investigation on the effects of climate change and ocean acidification on sharks is published in the journal Proceedings of the Royal Society B.
“Besides habitat degradation and overfishing, ocean acidification also directly affects shark fitness and survival,” added Rosa, a senior research fellow and the University of Lisbon’s Center for Oceanography.
For the study, Rosa and his team incubated 60 shark embryos at the Tropical Marine Center in the U.K. The embryos previously were collected from waters around Lungsod Ng Cebu, in the Philippines. Some of the embryos were exposed to the slightly higher temperatures and lower pH levels predicted by the year 2100.
Thirty days after the shark embryos hatched, survival rapidly declined by up to 44 percent for those exposed to the warming and acidification conditions that are expected by 2100. Those that did survive “became more lethargic,” Rosa said.
He and his team predict that tropical sharks may be more vulnerable to the expected changes “because they have evolved in a relatively more stable environment,” he explained. Such sharks include the bamboo shark, zebra shark, scalloped hammerhead shark, whitetip reef shark, whale shark, great hammerhead shark, nurse shark, tiger shark, bull shark and many more.
Dutch Shark Society, 17 September 2014. Article.
