Sharks more resilient than expected.
Some baby sharks are able to cope with the level of ocean acidification predicted for the end of this century, according to a recently published Australian study.
Dr Jodie Rummer from the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University and her co-authors arrived at this conclusion after conducting some research into the development of epaulette shark embryos.
“Overall, there were no differences between growth and survival in sharks reared under current day conditions versus those reared under ocean acidification conditions predicted for the year 2100,” said Dr Rummer.
However, the researcher added a word of caution: The gills of sharks were important in correcting pH balances. Under ocean acidification conditions, the team concluded that the epaulette shark's risk of death might be the highest before the gills were fully developed. Once developed, the level of risk became as per normal.
The eggs of the epaulette shark usually incubate for three to four months before they hatch. For the study, the eggs were raised ten days after they were laid until 30 days after they hatched. They were divided into two groups: one which was exposed to current oceanic conditions, and the other group which was exposed to oceanic conditions projected for 2100, when the acidification of the oceans is expected to increase by 150 percent when compared to the pre-industrial era.
Then they counted the gill and tail movements of the embryos, how much yolk the embryo consumed, and how much the embryo grew. After hatching, they continued to monitor the sharks’ growth.
“We know that sharks, even the little ones, play an important role in balancing ecosystems as predators,” said Dr Rummer. “Healthy ecosystems need healthy predators. But, what about when water quality becomes challenging, such as what is happening with climate change?”
While some marine creatures are able to move to another location in their environment, others may not be able to do so due to their size, and thus may end up being eaten. In such cases, they may seek shelter in places like coral reefs. Unfortunately, the water quality of such places may prove to be more challenging. As for eggs, they cannot move from the place at which they were laid if the environmental conditions are unfavourable.
In short, ocean acidification is expected to pose a serious threat for reef-building corals that serve as the habitat and shelter for this shark species.
“No matter how tough this species seems, if climate change takes away its shelter, it will be just as vulnerable as any other,” concluded Dr Rummer.
Link to Study: conphys.oxfordjournals.org/.../cow003.full