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Pacific kelp forests existed 32 million years ago

A study led by researchers at the University of California, Berkeley and the Swedish Museum of Natural History has uncovered that Pacific Coast kelp forests have much older origins than previously thought. 

The study reveals that these underwater forests existed more than 32 million years ago, predating the emergence of the modern marine ecosystem that currently inhabits them.

Ancient food source

Cindy Looy, a paleobotanist and professor of integrative biology at UC Berkeley, and Steffen Kiel, a senior curator at the Swedish Museum of Natural History, spearheaded the research.

The team found that the kelp forests provided a primary food source for an ancient mammal called a desmostylian, a relative of today’s sea cows and elephants.

Initially, it was believed that kelp forests emerged around 14 million years ago, aligning with the appearance of modern marine animals.

However, as Looy explains, “Now, we show the kelps were there, it’s just that all the organisms that you expect to be associated with them were not.”

This new understanding suggests a more complex evolutionary history of these ecosystems.

Fossilized kelp forest holdfasts

The discovery was made possible through fossilized kelp holdfasts – the root-like structures anchoring kelp to the seafloor – dated back to 32.1 million years ago.

These holdfasts, containing clams, barnacles, and snails, provide insight into the ancient kelp’s ecosystem. 

Prior to this, the oldest known kelp fossil was an air bladder and blade similar to today’s bull kelp, dating back to 14 million years ago, held by the University of California Museum of Paleontology (UCMP).

“Our holdfasts provide good evidence for kelp being the food source for an enigmatic group of marine mammals, the desmostylia,” Kiel said.

These findings challenge previous assumptions and highlight the complex evolution of kelp forests over millions of years.

The research team’s innovative approach included the use of Synchrotron Radiation X-ray Tomographic Microscopy (SRXTM) to obtain detailed 3D X-ray scans of the fossilized holdfasts.

The scans revealed a diverse range of marine life, including barnacles, snails, mussels, and foraminifera, within the holdfasts, indicating a vibrant but less complex ecosystem compared to today’s kelp forests.

Study implications for kelp forests

The study also emphasizes the critical role of amateur fossil hunters in advancing scientific understanding. The fossils were initially discovered by James Goedert, an amateur collector, along the beach near Jansen Creek on the Olympic Peninsula in Washington.

Looy and Kiel plan to continue their research to further understand the evolution of the North Pacific kelp ecosystem and its relationship with ocean-climate changes.

This research not only sheds light on the ancient history of these vital marine habitats but also underscores the importance of fossil records in unraveling the complexities of Earth’s ecological past.

The study is published in the Proceedings of the National Academy of Sciences

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