A reconstruction of the Burgess Shale site during the Cambrian explosion. Painting by D. W. Miller
My UNC colleague Justin Ries and his collaborators just published a paper in Geology that offers an important new clue about the cause of the Cambrian explosion, the rapid radiation and appearance of new life forms on earth just over half a billion years ago. One theory has been that suddenly increased oxygen levels made this rapid diversification of animal life possible. But many geologists dismissed this argument because they thought that oxygen concentration had already increased in the earth’s atmosphere by then. Justin and his team traveled to the desert of namibia to sample the Nama group carbonate rocks from which they measured the sulfur isotopic signature. Sulfur is used as a proxy for oxygen concentration. The teams findings indicate that oxygen concentration in shallow seas was indeed very low just before the Cambrian explosion.
Justin is a relatively new faculty in my department and UNC. He is a carbonate geochemist and also is doing some cutting edge work on the effects of ocean acidification on calcifying organisms.
UNC marine geologist Justin Ries in the Zebra River Valley, southern Namibia. The Nama Group carbonates, which contain sulfur isotopic signatures suggesting that low marine sulfate and low atmospheric oxygen conditions persisted up until the Cambrian Explosion, loom in the background. (Credit: Gordon Love)
Read the full story on Futurity here. Excerpted below:
“This period was a game-changer in terms of the evolutionary structure of life,” Ries says. “Our findings are consistent with the idea that it occurred because of major changes in the composition of the ocean and atmosphere at that time.”
Scientists have maintained that relatively high oxygen levels existed on the planet long before the Cambrian period, Ries says, but if that was the case and oxygen was key to the evolutionary event, why did it take until then for the few initial stems of animal life to expand into the thousands of lineages that emerged?
The new research appears to answer that puzzle. The team examined the chemical signature of limestone rocks in southern Namibia, Africa, that were deposited in the oceans between 553 million and 543 million years ago, just before the Cambrian Explosion and found that at that time, sulfate levels in the ancient ocean—and by implication, oxygen levels in the atmosphere—were much lower than previously thought.
Scientists are able to use sulfate—a molecule that is dissolved in seawater—as a proxy for the amount of oxygen that existed, because their respective levels vary in proportion with one another (marine sulfate is primarily derived from the oxidation of terrestrial sulfide).
“This implies that the subsequent alleviation of these low sulfate and low oxygen conditions may have led to the intense diversification of animals in early Cambrian time,” Ries concludes.
Earlier research has already established that fish have shifted their geographic ranges and their migratory and breeding patters in response to rising water temperatures. It has also been established that warmer regions tend to be inhabited by smaller fish. Mr Daufresne and his colleagues examined long-term surveys of fish populations in rivers, streams and the Baltic and North Seas and also performed experiments on bacteria and plankton. They found the individual species lost an average of 50 per cent of their body mass over the past 20 to 30 years while the average size of the overall fishing stock had shrunk by 60 per cent. This was a result of a decrease in the average size-at-age and an increase in the proportion of juveniles and small-sized species, Daufresne said. (
Researchers from the University of Connecticut have created a new light-emitting material by doping spun strands of salmon DNA with fluorescent dyes. The material, which is robust because DNA is such a strong polymer, absorbs energy from ultraviolet light and gives off different colors depending on the amounts of dye it contains. A team led by chemistry professor Gregory Sotzing created the new material by mixing salmon DNA with two types of dye, then pumping the solution from a fine needle while a voltage is applied between the needle tip and a grounded copper plate covered with a glass slide. As the liquid jet comes out, it dries and forms long nanofibers that are deposited on the glass slide as a mat. The researchers then spin this nanofiber mat directly on the surface of an ultraviolet LED to make a white-light emitter. The color-tunable DNA material relies on an energy-transfer mechanism between two different fluorescent dyes, and the DNA keeps the dye molecules separated at a distance of 2 to 10 nanometers from each other. (
A male sea lion on has died of exhaustion after a marathon mating session at an zoo in Germany. The mammal, named Mike who was originally from California, was already a father of 12. He passed away yesterday after an extended session with the females at the park in Nuremberg proved too much for his heart. Mike – described as ‘good-natured’ by the zoo – had mated repeatedly with females Farah, Tiffy and Soda. The park said in a statement that the 550lb mammal began showing tiredness around midday: ‘Mike could no longer get out of the pool and was brought ashore by staff. ‘The extremely weakened animal was treated by a vet but died from acute heart failure around 3:30 pm. ‘Mating season is a common time for fatalities when bulls often stop eating for days to devote themselves fully to mating. ‘For sea lion bulls with a harem this is the most exhausting time. ‘He will be remembered fondly by visitors of the animal park for his appearances during shows in the dolphinarium where he had close contact with the dolphins,’ added the statement. Mike’s 12 children can be found in zoos all over Europe, from Berlin to Spain to the Netherlands, the zoo said. (
Scientists in Nevada are reporting development of a new and environmentally friendly process for producing biodiesel fuel from “chicken feather meal,” made from the 11 billion pounds of poultry industry waste that accumulate annually in the United States alone. The researchers describe a new process for extracting fat from chicken feather meal using boiling water and processing it into biodiesel. Given the amount of feather meal generated by the poultry industry each year, they estimate this process could create 153 million gallons of biodiesel annually in the U.S. and 593 million gallons worldwide. In addition, they note that removal of fat content from feather meal results in both a higher-grade animal feed and a better nitrogen source for fertilizer applications. (
Something big and strange is floating through the Chukchi Sea between Wainwright and Barrow. Hunters from Wainwright first started noticing the stuff sometime probably early last week. It’s thick and dark and “gooey” and is drifting for miles in the cold Arctic waters, according to Gordon Brower with the North Slope Borough’s Planning and Community Services Department. Brower and other borough officials, joined by the U.S. Coast Guard, flew out to Wainwright to investigate. The agencies found “globs” of the stuff floating miles offshore Friday and collected samples for testing. Later, Brower said, the North Slope team in a borough helicopter spotted a long strand of the stuff and followed it for about 15 miles, shooting video from the air. The next day the floating substance arrived offshore from Barrow, about 90 miles east of Wainwright, and borough officials went out in boats, collected more samples and sent them off for testing too. Nobody knows for sure what the gunk is, but Petty Officer 1st Class Terry Hasenauer says the Coast Guard is sure what it is not. (
“Based on the stories I had heard, I was expecting them to be very aggressive, so I was surprised at how timid they were. As soon as we turned on the lights, they were gone,” he said. “I didn’t get the sense that they saw the entire diver as a food item, but they were definitely going after pieces of our equipment.”
