How the Asteroid That Wiped Out Dinosaurs Sparked an Unexpected Ocean Renaissance

Around 66 million years ago, a massive asteroid hit Earth, leading to a major extinction that wiped out about 70% of life. It’s well-known for ending the reign of dinosaurs, but the oceans faced their own dramatic changes. Marine ecosystems were deeply affected. Species like mosasaurs and ammonites vanished, but surprisingly, some bivalves—like clams and oysters—managed to survive.

Many bivalves thrive in different roles within ocean environments. Interestingly, even though around three-quarters of them disappeared, almost every type of bivalve lifestyle persisted in some form. Researchers analyzed thousands of bivalve fossils in a recent study published in Science Advances. They found that despite the dramatic loss, diverse ecological roles continued to exist among the surviving bivalves. This was unexpected, as the data suggested such continuity shouldn’t have happened.

What enabled this unexpected survival? Bivalves employ unique strategies to adapt. Some form symbiotic relationships with bacteria and algae, allowing them to produce nutrients in diverse conditions. Others, like mussels, latch onto rocks with strong silk threads, making them more resilient during environmental changes. In contrast, many species dependent on sunlight struggled due to dust and debris blocking the sun after the asteroid impact. The survival of bivalves with specialized diets suggests that life on Earth can bounce back even without sunlight.

The aftermath didn’t mean an instant return to normalcy for marine life. Even though some bivalves thrived, others, like the rudists—huge reef-building bivalves—were completely wiped out. They held significant ecological roles in shallow seas, later replaced by giant clams and other species, which, however, lacked the same diversity. Meanwhile, trigoniid bivalves, known for their tough shells, survived but didn’t flourish. Today, very few can be found, mainly around Australia. This indicates that surviving an extinction doesn’t always guarantee a successful comeback.

Marine ecosystems have evolved since that time. Current bivalve species showcase a mix of resilience and vulnerability. Understanding their past helps explain the complex nature of survival and ecological change, reminding us that survival is just one part of the equation.

For more on marine ecology and extinction events, check out resources from NOAA.

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