Navigation Links
Decline of carbon-dioxide-gobbling plankton coincided with ancient global cooling
Date:1/8/2009

ITHACA, N.Y. The evolutionary history of diatoms -- abundant oceanic plankton that remove billions of tons of carbon dioxide from the air each year -- needs to be rewritten, according to a new Cornell study. The findings suggest that after a sudden rise in species numbers, diatoms abruptly declined about 33 million years ago -- trends that coincided with severe global cooling.

The study is published in the Jan. 8 issue of the journal Nature.

The research casts doubt on the long-held theory that diatoms' success was tied to an influx of nutrients into the oceans from the rise of grasslands about 18 million years ago. New evidence from a study led by graduate student Dan Rabosky of the Department of Ecology and Evolutionary Biology takes into account a widespread problem in paleontology: that younger fossils are easier to find than older ones.

"We just tried to address the simple fact that the number of available fossils is colossally greater from recent time periods than from earlier time periods," Rabosky said. "It's a pretty standard correction in some fields, but it hasn't been applied to planktonic paleontology up till now."

More than 90 percent of known diatom fossils are younger than 18 million years. So an unadjusted survey of diatom fossils suggests that more diatom species were alive in the recent past than 18 million years ago.

The dearth of early fossils is understandable. Sampling for diatom fossils requires immense drill ships to bore into seafloor sediment. To find an ancient fossil, scientists first have to find ancient sediment -- and that's no easy task because plate tectonics constantly shift the ocean floor, fossils and all. Much of the seafloor is simply too young to sample.

So Rabosky and co-author Ulf Sorhannus of Edinboro University of Pennsylvania controlled for how many samples had been taken from each million-year period of the Earth's history, going back 40 million years. After reanalysis, the long-accepted boom in diatoms over the last 18 million years disappeared. In its place was a slow recent rise, with a much more dramatic increase and decline at the end of the Eocene epoch, about 33 million years ago.

With the new timeline, diatoms achieved their peak diversity at least 10 million years before grasslands became commonplace.

"If there was a truly significant change in diatom diversity at all, it happened 30 million years ago," Rabosky said. "The shallow, gradual increase we see is totally different from the kind of exponential increase you would expect if grasslands were the cause."

As an example of that kind of increase, Rabosky turned to another fossil record: horse teeth. Before grasslands, horses had small teeth suited for chewing soft leaves. But as grasslands appeared, much hardier teeth appeared adapted to a lifetime of chewing tough, silica-studded grass leaves. Diatoms ought to show a similar evolutionary response to the sudden availability of silica, Rabosky said, but they don't.

Although the new results don't explain the current prevalence of diatoms in the ocean, Rabosky said that whatever led to diatoms' rise at the end of the Eocene, the tiny organisms may have contributed to the global cooling that followed.

"Why diatom diversity peaked for 4 to 5 million years and then dropped is a big mystery," Rabosky said. "But it corresponds with a period when the global climate swung from hothouse to icehouse. It's tempting to speculate that these tiny plankton, by taking carbon dioxide out of the air, might have helped trigger the most severe global cooling event in the past 100 million years."


'/>"/>

Contact: Blaine Friedlander
bpf2@cornell.edu
607-254-8093
Cornell University Communications
Source:Eurekalert

Related biology news :

1. Global warming link to amphibian declines in doubt
2. Pollinator decline not reducing crop yields just yet
3. Wildflower declines in Thoreaus Concord woods are due to climate changes
4. Vitamin K does not stem BMD decline in postmenopausal women with osteopenia
5. In a last stronghold for endangered chimpanzees, survey finds drastic decline
6. Decline in Alaskan sea otters affects bald eagles diet
7. In scientific first, Einstein researchers correct decline in organ function associated with old age
8. River damming leads to dramatic decline in native fish numbers
9. Great Ape Trusts Wich lead author of Oryx paper on continuing orangutan population declines
10. Understanding autumn rain decline in SE Australia
11. NOAA reports coastal waters show decline in contaminants
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:1/26/2017)... CITY , Jan. 26, 2017  Crossmatch, a ... unveiled a new solution aimed at combatting fraud, waste ... solution was introduced at the Action on Disaster Relief ... key meeting point for UN agencies and foreign assistance ... Fraud, waste and abuse are a largely unacknowledged ...
(Date:1/23/2017)...  The latest mobile market research from Acuity Market ... The quarterly average price of a biometric smartphone decreased ... 2016.  There are now 120 sub-$150 models on the ... just 28 a year ago at an average price ... Most , Acuity Market Intelligence Principal, "Biometric Smartphones are ...
(Date:1/18/2017)... MedNet Solutions , an innovative ... spectrum of clinical research, is proud to announce ... the organization in terms of corporate growth, outside ... and services. The company,s exceptional achievements can be ... iMedNet ™ – MedNet,s ...
Breaking Biology News(10 mins):
(Date:2/17/2017)... ... February 17, 2017 , ... ... and DJI, the world’s leading maker of unmanned aircraft systems (UAS), are launching ... officers to use drones effectively, and support educational outreach efforts. , AMA and ...
(Date:2/16/2017)... Calif. and GREENWICH, Conn. ... a private investment firm focused on venture growth ... the promotion of Josh Richardson , M.D. ... on investments in biotechnology companies.  He is a ... played important roles in Longitude,s investments in Aimmune ...
(Date:2/16/2017)...   Biostage, Inc. (Nasdaq: BSTG ... bioengineered organ implants to treat cancers and other life-threatening ... the closing on February 15, 2017 of its previously ... and warrants to purchase 20,000,000 shares of common stock, ... was priced at $0.40 per share of common stock, ...
(Date:2/16/2017)... (PRWEB) , ... February 16, 2017 , ... ... cervical case. Dr. Kingsley Chin, professor and Harvard trained surgeon, completed the procedure ... was performed on a 55-year-old practicing female physician suffering from degenerative disc disease ...
Breaking Biology Technology: