A former UC Riverside researcher is the lead author on a study showing that the world's oceans became toxic about 500 million years ago, resulting in mass extinctions of the planet's burgeoning early life.
Scientists have been debating for more than 50 years why the huge die-off followed what's known as the Cambrian explosion, a period marked by a sudden increase in the diversity of animal life.
UCR: Ancient waters could predict future changes
That explosion is believed to have been the result of oxygen in the ocean reaching levels similar to those seen today. Scientists have long believed that a subsequent drop in oxygen was responsible for the extinction of such primitive animals as trilobites and brachiopods. But the oxygen loss had never been explained..
Ben Gill, 28, his UCR adviser Tim Lyons and researchers from four other universities showed that elevated levels of sulfur sucked up much of the ocean's oxygen about 499 million years ago, and conditions remained that way for 2 million to 4 million years. The study, funded by a National Science Foundation grant, appears in the most recent issue of the journal Science News. Gill is now a post-doctoral researcher at Harvard University.
The team analyzed rocks from that period found in several locations around the globe, including Nevada, Utah, Missouri, Australia and Sweden. Using samples from such diverse locations creates a bigger picture, Gill said.
"In the past, you've usually gone to one place (for samples)," he said. Traveling to wide-ranging places, he added, "takes a lot of money. But it's one of the sure ways to make sure that what you're seeing is a global event."
It was a step-by-step process, he said. First they looked at rocks in Nevada from the period in question, testing them for certain elements.
"We went to one place and saw something interesting," he said. "Then we went to the next place."
Gathering the data took four years, he said. Once the samples were in the lab, it took only about a month to perform the analysis. New techniques in testing for the sulfur, carbon and molybdenum -- the elements they were looking for -- made the process possible, he said.
No one knows yet why the sulfur levels rose.
"The cause is wide open," Gill said. Similar toxic events in more recent geologic time periods, he said, "have been linked to volcanic eruptions. In those conditions, you have more greenhouse gases. The oceans are warmer, and water that is warmer cannot handle as much oxygen."
There is no evidence that happened during the period Gill and his associates studied. But, he said, "people haven't been looking yet."