How Did Sharks Survive a Rapid Rise in Earth’s Temperature?

Sharks, the majestic predators of the oceans, have fascinated scientists for millions of years with their ability to survive in changing environmental conditions. In the face of dramatic climate changes that occurred around 93 million years ago, sharks had to adapt to new, extreme conditions. How did these ancient creatures manage to survive a rapid rise in Earth’s temperature? The answer lies in their remarkable evolution and adaptive abilities.

 

 

 

The Evolution of Sharks

Around 93 million years ago, massive volcanic lava outflows led to a sharp increase in carbon dioxide levels in the atmosphere. This phenomenon resulted in a greenhouse climate, in which ocean temperatures reached the highest levels in history. Scientists from the University of California, Riverside discovered that some sharks responded to these changes by elongating their pectoral fins.

 

Extraordinary Adaptive Abilities

Research published in the journal Current Biology showed that sharks which survived this period had elongated pectoral fins. Longer pectoral fins make shark movement much more efficient, allowing them to move more effectively in open waters.

Phillip Sternes, a doctoral student in biology at UCR and the first author of the paper, explains:
“Pectoral fins are a critical structure, comparable to our arms. After examining a massive dataset, we observed that these fins changed shape as sharks expanded their habitats from the seafloor to the open ocean.”

The Impact of Climate Change

Oxygen levels near the ocean floor during the Cretaceous period likely declined as temperatures rose. Modern sea surface temperatures average around 20 degrees Celsius, whereas during the Cretaceous they were much warmer, reaching an average of about 28 degrees Celsius. Global warming led to the evolution of some groups of animals, including sharks, while others became extinct. Sharks survived the rapid rise in Earth’s temperature thanks to their extraordinary ability to adapt. The elongation of pectoral fins and adjustment to new environmental conditions allowed them to move efficiently in open waters and survive extreme conditions.

4Sharks living in open waters are faster compared to bottom-dwelling sharks. Only about 13% of modern sharks are fast-swimming predators.

 

Biologists observe that some sharks, including tropical species such as the tiger shark and bull shark, are beginning to swim farther north. However, it is unclear whether threatened sharks will be able to adapt again to new habitats and survive rapidly increasing heat.

As one researcher noted: “Temperature is rising so quickly now that, in the geological record I know of, there is nothing we can use for a true comparison.”

This statement highlights the challenges scientists face in trying to predict the future of sharks in the context of a rapidly changing climate.

Sharks are fascinating creatures that have survived for millions of years thanks to their ability to adapt. However, the current pace of climate change presents them with a new challenge. How will these predators respond to changing environmental conditions?