By Femi Akinola
The world sharks are facing gauntlet of threats from marine heat waves and cold waves which eventually disrupt their reproduction and development, study revealed.
The scientists said over the last couple of centuries, sharks have survived five mass extinctions, making them some of the oldest and sturdiest creatures still in existence today.
According to the experts, a six mass extinction that many scientists fear is underway could be too much for these fierce predators.
According to Kiley Price of the Inside Climate News, in recent years, overfishing and ocean degradation have pushed many shark species to the brink.
Now, a growing number of studies are unravelling some of the unique ways that ocean warmings , and in some cases, ocean cooling, fueled by human caused climate change could disrupt shark population and reproduction, if emissions continue to rise.
The study shows that around 40% of the more than 500 species of sharks swimming in the ocean lay eggs rather than given birth to live pups. The embryo within these eggs incubate in the condition that surround them, which could be a problem as the ocean gets hotter and acidifies.
To determine just how much of an issue this cloud be, a team of researchers tested eggs from the small-spotted – catshark (one of the most abundant shark species in Europe) under different temperatures and acidities based on various emissions scenarios.
While the researchers found that moderate emissions would likely have a small impact on egg development, the rapid expansion of fossil fuels around around the world could cause catastrophic declines.
When they tested water that was around 72degrees Fahrenheit (7.9 degrees hotter than in recent decades during the summer in western world and central Europe) just 11% of the embryo hatched.
”We were shocked,” Noemie Coulon, a doctoral student at the Labaoratoire de Biologie des Organismes et des Ecosystemes Aquatiques in France, said in a statement, ” The embryos of egg-laying species are especially sensitive to environmental conditions.”
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Digging deep, research found that hot ocean temperatures could cause some sharks to hatch early, resulting in smaller and less healthy pups in species like the epaulette (walking) shark, nicknamed for its ability to temporarily crawl on land. But the complex effects of ocean warming and acidification extend well beyond the beginning of sharks life.
Studies show that warmer ocean temperatures are speeding up shark’s metabolic rates, forcing them to use more energy just to swim and stay alive. Some species, like the shortfin mako shark, are diving deeper to find coller waters. Ocean warming is also creating newly suitable habitats for sharks in certain parts of the world, primarily northward.
In addition, it was found out that climate change also affect a shark’s ability to find prey, fish and squid migrate to new areas in response to warming waters.
Interestingly, when winds blow across the ocean surface, they can push warm water away from the coast, which is then replaced by cold water from greater depths through a process called upwelling.
Local upwelling events, essentially ocean cold snaps, have become increasingly common in certain parts of the world over the past 40 years as climate change alters wind patterns, current and surface ocean temperatures, according to recent research.
The study points to a ”coldwave” that spread across South Africa’s southeast coast in 2021, where temperatures dropped from 70 degrees to 53 degrees in under 24 hours. The researcher say the event killed hundreds of animals, including bull sharks.
By tracking bull sharks in South Africa and Australia, the researchers discovered that these predators are expanding their range as ocean waters warm, but frequently have to dodge chilly upwelling events that could kill them along the way, resulting in ”bait and switch situations.” according to the study.
This really shows the complexity of climate change, as tropical species would expand into higher – latitude areas as
overall warming continues, which then places them at risk of
exposure to sudden extreme cold events,” study authors Nicolas Benjamin Lubitz and David Schoeman wrote.
In this way, species such as bull sharks and whale sharks may very well be running in the gauntlet on their seasonal migrations.
