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Lost ecosystem found buried in mud of southern California coastal waters

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Paleontologists investigating the sea bed off the coast of southern California have discovered a lost ecosystem that for thousands of years had nurtured communities of scallops and shelled marine organisms called brachiopods.

These brachiopods and scallops had thrived along a section of coast stretching approximately 250 miles from San Diego to Santa Barbara for at least 4,000 years. But they had died off by the early 20th century, replaced by the mud-dwellling burrowing clams that inhabit this seabed today. Paleontologists Adam Tomašových of the Slovak Academy of Sciences and Susan Kidwell of the University of Chicago examine the lost ecosystem in a study published online June 7 in the Royal Society Proceedings B.

Paleontologists investigating the sea bed off the coast of southern California have discovered a lost ecosystem that for thousands of years had nurtured communities of scallops and shelled marine organisms called brachiopods.

These brachiopods and scallops had thrived along a section of coast stretching approximately 250 miles from San Diego to Santa Barbara for at least 4,000 years. But they had died off by the early 20th century, replaced by the mud-dwellling burrowing clams that inhabit this seabed today. Paleontologists Adam Tomašových of the Slovak Academy of Sciences and Susan Kidwell of the University of Chicago examine the lost ecosystem in a study published online June 7 in the Royal Society Proceedings B.

Evidence indicates that the brachiopod and scallop die-off occurred in less than a century. Because this community disappeared before biologists started sampling the seafloor, its existence was unknown and unsuspected. Only dead shells remain, permitting analysis by paleontologists.

“This loss unfolded during the 19th century, thus well before urbanization and climate warming,” said Kidwell, the William Rainey Harper Professor in Geophysical Sciences. “The disappearance of these abundant filter-feeding animals coincided with the rise of lifestock and cultivation in coastal lands, which increased silt deposition on the continental shelf, far beyond the lake and nearshore settings where we would expect this stress to have an impact.”

Continue reading at University of Chicago

Image: Shells from muddy sediment collected on the western Palos Verdes shelf off the coast of southern California. The shells are from the scallop Chlamys hastata.

Credit: Courtesy of Prof. Susan Kidwell