Triops Longicaudatus
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Triops Longicaudatus
Triops Longicaudatus Red
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Earth’s history: How the Mediterranean became a salt desert and then recovered
The Mediterranean was once almost completely dry, which is almost unimaginable today. It turned into a deadly hot salt desert in which marine life could barely survive. The seawater became extremely salty, which led to the extinction of numerous animal and plant species. Only around eleven per cent of endemic species survived this crisis, as reported by a research team in the journal Science. It took at least 1.7 million years for biodiversity to recover when the basin was refilled with water. New species were also added.
The recovery of the ecosystem took a surprisingly long time
Without inflow from the Atlantic, the water in the Mediterranean largely evaporated. Tributaries such as the Nile or the Ebro were not enough to fill the basin between Africa, Europe and the Near East. Today, there is only one connection to the Atlantic: the Strait of Gibraltar. This passage, which is only a few kilometres wide, allows fresh water from the Atlantic to flow into the saltier Mediterranean. Movements in the Earth’s upper mantle around six million years ago closed this passage, which led to strong fluctuations in the salinity and temperature of the Mediterranean.
A kilometre-thick layer of salt under the sea still bears witness to conditions 5.5 million years ago. Around one million cubic kilometres of salt accumulated, as the team led by Konstantina Agiadi from the University of Vienna reports. In order to investigate the effects of these extreme changes on life in the Mediterranean, the researchers analysed fossils that are 12 to 3.6 million years old from the coastal states and from sediment cores in the deep sea.
Two thirds of the species in the Mediterranean disappeared after the so-called Messinian salinity crisis. Tropical reef-building corals became extinct. Of the 779 species originally found only in the Mediterranean, only 86 survived, although it remains unclear how and where these species were able to survive. After the Atlantic Ocean flowed back into the basin around 5.33 million years ago, earlier and new species colonised the habitat, including white sharks and dolphins.
Throughout the earth’s history, movements in the earth’s crust have repeatedly led to the isolation of regional sea areas from the oceans and to massive salt accumulations. Such salt giants have also been found in Australia, Siberia, the Middle East and other regions and have been used for salt extraction since ancient times, for example in the Hallstatt mine in Austria and the Khewra salt mine in Pakistan.
Overall, the recovery of the ecosystem took a surprisingly long time, as Agiadi’s team discovered. The current pattern of decreasing biodiversity from west to east emerged. Despite the small size of the basin, the biodiversity in the Mediterranean is disproportionately high due to the many endemic species.
- Earth’s history: How the Mediterranean became a salt desert and then recovered - 5. September 2024
- Palaeontology: New predatory dinosaur discovered in Kyrgyzstan - 23. August 2024
- History of prehistoric crustaceans: Fascinating survival over millions of years - 20. August 2024
