About 5.5 million years ago, a dramatic event known as the Messinian Salinity Crisis drastically altered the Mediterranean Sea.
This event, caused by the Mediterranean’s temporary disconnection from the Atlantic Ocean, led to the formation of a giant layer of salt beneath the sea and had a profound impact on the marine life that once thrived there.
A new study, led by Konstantina Agiadi from the University of Vienna, has revealed just how severely this crisis affected marine biodiversity and how long it took for the ecosystem to recover.
The Mediterranean salt giant, discovered in the early 1970s, is a massive, kilometer-thick layer of salt that formed due to the isolation of the Mediterranean from the Atlantic Ocean.
This disconnection caused the sea to evaporate significantly, leaving behind vast amounts of salt.
While these salt formations have been valuable resources throughout history, they also had devastating effects on the marine life that lived in the Mediterranean during that time.
A team of 29 scientists from 25 institutes across Europe, led by Agiadi, conducted extensive research on fossils dating from 12 to 3.6 million years ago, found both on land around the Mediterranean and in deep-sea sediment cores.
Their findings, published in the journal Science, revealed that the Messinian Salinity Crisis wiped out a significant portion of marine species in the Mediterranean.
In fact, about 67% of the marine species that existed before the crisis were completely different after it ended. Out of 779 endemic species—those that lived exclusively in the Mediterranean before the crisis—only 86 survived the harsh changes brought on by the crisis.
The crisis not only caused extreme fluctuations in salinity and temperature but also disrupted crucial ecological processes, such as the migration of marine organisms and the flow of larvae and plankton.
These disruptions led to the extinction of many species, including tropical reef-building corals that were once abundant in the Mediterranean.
Once the Mediterranean reconnected with the Atlantic Ocean, new species like the Great White shark and oceanic dolphins began to move into the region.
However, the biodiversity that had once characterized the Mediterranean was forever changed. The number of species in the Mediterranean decreased from west to east, a pattern that continues to this day.
What surprised scientists the most was how long it took for the Mediterranean ecosystem to recover from this crisis. The study found that it took over 1.7 million years for the number of species in the Mediterranean to return to pre-crisis levels. This recovery period was much longer than anyone had expected.
This research not only provides the first statistical analysis of a major ecological crisis but also offers a new way to understand the impact of such events on marine life. The methods used in the study could be applied to other regions of the world where similar salt formations have occurred throughout geological history.
The findings also raise new questions for scientists to explore. For example, how did the 11% of species that survived the crisis manage to do so? What impacts did other large salt formations have on ecosystems and the Earth as a whole?
These questions will be the focus of future research, including a new initiative called the “SaltAges” Cost Action Network, which will investigate the social, biological, and climatic impacts of these ancient salt ages.
This study not only sheds light on a pivotal moment in the history of the Mediterranean but also opens the door to understanding how life on Earth responds to massive environmental changes, both in the past and potentially in the future.
Source: University Of Vienna.
