Earth’s oceans underwent a dramatic transformation after the most devastating catastrophe in the planet’s history. Around 252 million years ago, a mass extinction event wiped out marine organisms, virtually erasing familiar ecosystems from the planet. As a result, most marine species disappeared, and the survivors were able to spread across the globe, occupying the newly vacant habitats.
Researchers from Spain and Argentina analyzed how marine life recovered after this catastrophe. Their study focused on bivalves—relatives of modern mussels and mollusks—whose fossils preserve traces of ancient changes. The research revealed that, following the catastrophe, the seas became strikingly similar to each other, with many species being found across vast distances.
Loss of diversity
The mass extinction led to a sharp decline in biological diversity. Oceans that were once filled with unique communities became almost identical in composition. Only a few species managed to survive the crisis and spread throughout the globe. This resulted in the same organisms being found in different parts of the world, while local features of marine ecosystems vanished.
Scientists note that such catastrophes not only wipe out species, but also completely reshape the structure of life. After the extinction, recovery was slow: it took millions of years for distinct marine communities to reappear. During this period, the oceans were almost empty, and their inhabitants were generalists with little diversity.
New ecosystems
Gradually, as life recovered, new biological regions began to form. In the Middle Triassic, distinct zones emerged, such as the ancient Tethys Ocean (the ancestor of today’s Mediterranean Sea) and the Pacific Ocean. Each of these areas developed its own unique fauna, marking the beginning of today’s marine ecosystems.
By the end of the Triassic period, these regions were clearly defined and their inhabitants were markedly different from one another. It was at this time that the foundations were laid for the marine communities that still exist today. Scientists emphasize that similar processes occur after every major catastrophe, but the event 252 million years ago was the largest and most significant for the evolution of marine life.
Cosmopolitan phase
After the catastrophe, the so-called phase of cosmopolitanism began. During this period, the surviving species spread across the globe, and differences between the seas virtually disappeared. The oceans were poor in life, and it took millions of years before biodiversity began to recover. This process was marked by the emergence of new species and the formation of unique ecosystems in different parts of the planet.
To analyze these changes, scientists used modern methods, including network analysis of connections between organisms. Such approaches help to understand how life recovered and how new communities formed after the catastrophe. Thanks to this data, researchers were able to reconstruct the picture of ancient oceans and trace how their structure changed over millions of years.
Impact on evolution
The mass extinction not only destroyed old ecosystems but also triggered the emergence of new forms of life. Recovery was slow, but it was during this period that many modern groups of marine organisms appeared. The study showed that such catastrophes can completely reshape the biosphere and set a new course for evolution.
Scientists note that studying ancient catastrophes helps us understand how modern ecosystems respond to change and what consequences global crises can have for life on the planet. This knowledge is especially relevant today, as humanity faces new environmental challenges.
, the University of Valencia (Universidad de Valencia) is one of the oldest and largest universities in Spain, founded in 1499. It actively participates in international scientific projects and collaborates with leading research centers around the world. In recent years, the university has focused particularly on research in biology, geology, and ecology, and also supports major interdisciplinary initiatives. Among its partners is the National Scientific and Technical Research Council of Argentina (CONICET), recognized as a leading scientific organization in Latin America.
