What types of plants and animals lived in the Mediterranean area when the sea dried up millions of years ago?

Context

The Messinian salinity crisis was a geological event during which the Mediterranean Sea went through a cycle of near-complete desiccation throughout the Messinian age of the Miocene epoch, from 5.96 to 5.33 million years ago. It ended with the Zanclean flood, when the Atlantic Ocean rapidly refilled the basin. Understanding the flora and fauna that adapted to the extreme conditions during this period provides insights into ecological resilience and evolutionary adaptations to harsh environments.

Simple Answer

• Lots of salt-loving plants, like the ones you see near salty lakes.
• Animals that could handle dry, desert-like conditions, similar to those in North Africa.
• Some creatures probably evolved quickly to deal with the super salty environment.
• Rivers still flowed into the valley, so there were probably plants and animals living near those rivers.
• Scientists are still figuring out exactly what lived there, but it was probably a mix of hardy species.

Detailed Answer

The desiccation of the Mediterranean Sea during the Messinian salinity crisis created a drastically altered environment. Instead of a deep sea, a vast, dry valley punctuated by hypersaline lakes and river systems emerged. This transformation fundamentally changed the types of flora and fauna that could survive in the region. The formerly marine ecosystem was replaced by terrestrial and brackish water habitats. The plants that thrived were likely halophytes, which are salt-tolerant species similar to those found in modern-day salt marshes and deserts. These plants developed mechanisms to extract water from the saline soil and excrete excess salt. Alongside these, there would have been drought-resistant species adapted to the arid climate that prevailed during this period. The extent of vegetation cover would have varied, with denser growth along riverbanks and around freshwater sources, and sparser vegetation in the more arid and saline areas.

The animal life during the Messinian salinity crisis also underwent a significant shift. Marine species that couldn't adapt to the increasing salinity and eventual desiccation either perished or migrated to other oceans. In their place, terrestrial animals from surrounding regions, particularly North Africa and Europe, would have colonized the exposed Mediterranean basin. These would have included various species of mammals, reptiles, and birds adapted to dry and semi-arid conditions. Smaller animals, such as insects and rodents, would have been particularly well-suited to the harsh environment. The presence of freshwater sources, such as rivers and oases, would have supported a more diverse range of animal life in localized areas. Furthermore, some aquatic species may have evolved unique adaptations to survive in the hypersaline lakes, potentially leading to the development of endemic species found nowhere else.

Fossil evidence from the Messinian period suggests a complex interplay of species migrating into the region and adapting to the new conditions. While the fossil record is incomplete, paleontologists have uncovered remains of various mammals, including rodents, ungulates, and carnivores, indicating the presence of a terrestrial ecosystem. Fossil pollen and plant remains provide clues about the types of vegetation that existed. However, the precise composition of the flora and fauna remains a subject of ongoing research. The extreme conditions during the Messinian salinity crisis likely resulted in a relatively low biodiversity compared to the pre-crisis marine ecosystem. The species that managed to survive and thrive were those that possessed traits allowing them to tolerate high salinity, aridity, and limited resources.

One important aspect to consider is the role of river systems in supporting life during the Messinian salinity crisis. Major rivers, such as the Nile and the Rhone, continued to flow into the Mediterranean basin, carving deep canyons and creating freshwater corridors. These rivers would have provided essential water and nutrients, supporting localized ecosystems along their banks. The fauna and flora inhabiting these riverine environments would have differed from those in the surrounding arid landscapes. It's also possible that some marine species adapted to live in the brackish water conditions near the river mouths. The presence of these river systems created a mosaic of habitats, each supporting its unique assemblage of plants and animals, contributing to the overall ecological complexity of the Messinian Mediterranean.

The end of the Messinian salinity crisis with the Zanclean flood dramatically altered the environment once again. The rapid refilling of the Mediterranean Sea with water from the Atlantic Ocean led to the extinction of many of the species that had adapted to the dry, hypersaline conditions. The influx of marine water created a new marine ecosystem, allowing marine species to recolonize the basin. The terrestrial animals that had established themselves during the Messinian period were forced to retreat or adapt to the changing environment. The Zanclean flood represents a major turning point in the ecological history of the Mediterranean, marking the transition from a terrestrial or brackish environment back to a marine one. The few terrestrial species that were able to survive the ecological change are seen as some of the most adaptable and resilient flora and fauna on the planet.