Shark babies in one recent study were able to survive equally well in ocean acidification conditions thought to be like those in the year 2100 and in current ocean waters.
In other words, baby sharks are tiny, not-yet-toothy, survivors.
"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 study co-author Jodie Rummer of Australia's James Cook University.
That said, Rummer also urged caution. Because shark gills help maintain a balance for pH discrepancies, and infant sharks are still forming their gills, future projections are still a bit uncertain, she said. But the baby sharks that got past the early gill-formation stages in the study performed equally well in either type of water.
The research team was studying epaulette shark embryos as they formed.
Normally, this type of shark egg incubates for 3 to 4 months, then hatches. In the research, the scientists raised the shark eggs from 10 days after laying until 30 days following their hatch date. The sharks grew up in either of two groups: normal, current ocean conditions or those meant to simulate the acidification level of the year 2100.
The team monitored several factors: gill and tail movement counts for the embryos as they developed; how much yolk each embryo consumed; and rate of growth of the embryo. Later, they kept track of post-hatching survival and growth.
It's important to keep track of how well ocean predators, and the already vulnerable marine branch of elasmobranches (rays, skates and sharks), will survive. Also, "We know that sharks, even the small ones, play an important role in balancing ecosystems as predators," Rummer said. "Healthy ecosystems need healthy predators. But, what about when water quality becomes challenging, such as what is happening with climate change?"
Rummer's research group has seen in previous studies that adult epaulette sharks survive well in long-term exposure to high carbon dioxide in water that simulates ocean acidification. Their behavior - such as in seeking shelter and finding food - also remained the same in the studies. The team believes the adult sharks have adapted to carbon dioxide conditions and fluctuating oxygen in the tight spaces of coral reefs and other hiding places that they frequent.
"Therefore, if these sharks are able to tolerate challenging conditions as adults, they must also be able to early in life, and maybe even more so!" she said.
All that said, Rummer feels that we must keep in mind the importance of healthy coral reefs as habitat for these sharks and other creatures. "No matter how tough this species seems, if climate change takes away its shelter, it will be just as vulnerable as any other," she said.
The study was recently published in the journal Conservation Physiology.
Follow Catherine Arnold on Twitter at @TreesWhales.
