What do modern oceans reveal about the ancient fossil record?
STRI/DICYT Scientists sometimes aggressively test the theories of their peers. Recently, Seth Finnegan preferred to put his own hypotheses to a stress test. Finnegan wants to examine how energy flows through Panama’s modern marine ecosystems to test ideas about the causes of diversification and extinction in marine ecosystems hundreds of millions of years ago.
“I want to know about energy flow because that’s what an ecosystem is: it’s an energy-exchange network and a nutrientexchange network,” said Finnegan, a professor of paleobiology at University of California, Berkeley, who specializes in the Ordovician Period (488 to 444 million years ago), which was characterized by both a boom in biodiversity and a mass extinction. “It’s obvious why people haven’t taken this approach very much in the fossil record — it’s really hard.”
Finnegan chose to study Panama’s two oceans because they have strikingly different energetic environments due to the rise of the isthmus about 3 million years ago. Productivity — the conversion of sunlight into organic carbon, the basic currency of the food chain —is much higher in the Gulf of Panama (Pacific) than in the Caribbean. Finnegan’s first step was to sample and compare the shells accumulating on the seafloor in the Gulf of Panama and, on the Caribbean side of the isthmus, in Bocas del Toro.
Finnegan hopes to quantify how the productivity differences between these oceans are recorded by the size, type, and abundance of shells on the seafloor. These shells dominate the long fossil record of marine ecosystems, so the results could shed light on unanswered questions about what drove change in ancient ecosystems.