Featured Research

from universities, journals, and other organizations

Shark teeth analysis provides detailed new look at Arctic climate change

Date:
July 9, 2014
Source:
University of Chicago
Summary:
A new study shows that some shark species may be able to cope with the rising salinity of Arctic waters that may come with rising temperatures. The Arctic is of special interest today because it is increasing in temperature at twice the global rate. According to researchers, past climate change in the Arctic can serve as a proxy to better understand our current climate change and aid future predictions. The Eocene epoch is like a "deep-time analogue for what's going to happen if we don't curb CO2 emissions today, and potentially what a runaway greenhouse effect looks like."

Both graceful and docile, this modern sandtiger shark swims through a school of round scad fish in the coastal waters off North Carolina. Modern sand tigers prefer waters of high salinity, though they tolerate brackish waters for short periods as well.
Credit: Erik Rebeck

A new study shows that some shark species may be able to cope with the rising salinity of Arctic waters that may come with rising temperatures.

The Arctic today is best known for its tundra and polar bear population, but it wasn't always like that. Roughly 53 to 38 million years ago during what is known as the Eocene epoch, the Arctic was more similar to a huge temperate forest with brackish water, home to a variety of animal life, including ancestors of tapirs, hippo-like creatures, crocodiles and giant tortoises. Much of what is known about the region during this period comes from well-documented terrestrial deposits. Marine records have been harder to come by.

A new study of shark teeth taken from a coastal Arctic Ocean site has expanded the understanding of Eocene marine life. Leading the study was Sora Kim, the T.C. Chamberlin Postdoctoral Fellow in Geophysical Sciences at the University of Chicago, in coordination with Jaelyn Eberle at the University of Colorado, Boulder, and their three co-authors. Their findings were published online June 30 by the journal Geology.

The Arctic is of special interest today because it is increasing in temperature at twice the global rate. According to Kim, past climate change in the Arctic can serve as a proxy to better understand our current climate change and aid future predictions. The Eocene epoch, she said, is like a "deep-time analogue for what's going to happen if we don't curb CO2 emissions today, and potentially what a runaway greenhouse effect looks like."

Before this study, marine records primarily came from deep-sea cores pulled from a central Arctic Ocean site, the Lomonosov Ridge. Kim and Eberle studied shark teeth from a new coastal site on Banks Island. This allowed them to better understand the changes in ocean water salinity across a broader geographic area during a time of elevated global temperatures. Shark teeth are one of the few available vertebrate marine fossils for this time period. They preserve well and are incredibly abundant.

To arrive at their results, Kim isolated and measured the mass ratio of oxygen isotopes 18 to 16 found in the prepared enameloid (somewhat different from human tooth enamel) of the shark teeth. Sharks constantly exchange water with their environment, so the isotopic oxygen ratio found in the teeth is directly regulated by water temperature and salinity. With assumptions made about temperatures, the group was able to focus on extrapolating salinity levels of the water.

The results were surprising. "The numbers I got back were really weird," Kim said. "They looked like fresh water." The sand tiger sharks she was studying are part of a group called lamniform sharks, which prefer to stay in areas of high salinity.

"As more freshwater flows into the Arctic Ocean due to global warming, I think we are going to see it become more brackish," said Eberle, associate professor of geological sciences at CU-Boulder. "Maybe the fossil record can shed some light on how the groups of sharks that are with us today may fare in a warming world."

Because the teeth are 40 to 50 million years old, many tests were run to eliminate any possible contaminates, but the results were still the same. These findings suggest that sharks may be able to cope with rises in temperature and the subsequent decrease of water salinity. It has long been known that sharks are hardy creatures. They have fossil records dating back some 400 million years, surviving multiple mass extinctions, and have shown great ecological plasticity thus far.

Additionally, these results provide supporting evidence for the idea that the Arctic Ocean was most likely isolated from global waters.

"Through an analysis of fossil sand tiger shark teeth from the western Arctic Ocean, this study offers new evidence for a less salty Arctic Ocean during an ancient 'greenhouse period,'" said Yusheng (Chris) Liu, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which co-funded the research with NSF's Division of Polar Programs. "The results also confirm that the Arctic Ocean was isolated during that long-ago time."

While Kim has hopes to expand her research both geographically and in geologic time in an effort to better understand the ecology and evolution of sharks, she remarked that "working with fossils is tricky because you have to work within the localities that are preserved. "You can't always design the perfect experiment."


Story Source:

The above story is based on materials provided by University of Chicago. Note: Materials may be edited for content and length.


Cite This Page:

University of Chicago. "Shark teeth analysis provides detailed new look at Arctic climate change." ScienceDaily. ScienceDaily, 9 July 2014. <www.sciencedaily.com/releases/2014/07/140709115501.htm>.
University of Chicago. (2014, July 9). Shark teeth analysis provides detailed new look at Arctic climate change. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2014/07/140709115501.htm
University of Chicago. "Shark teeth analysis provides detailed new look at Arctic climate change." ScienceDaily. www.sciencedaily.com/releases/2014/07/140709115501.htm (accessed July 31, 2014).

Share This




More Plants & Animals News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Visitors Feel Part of the Pack at Wolf Preserve

Visitors Feel Part of the Pack at Wolf Preserve

AP (July 31, 2014) — Seacrest Wolf Preserve on the northern Florida panhandle allows more than 10,000 visitors each year to get up close and personal with Arctic and British Columbian Wolves. (July 31) Video provided by AP
Powered by NewsLook.com
Florida Panther Rebound Upsets Ranchers

Florida Panther Rebound Upsets Ranchers

AP (July 31, 2014) — With Florida's panther population rebounding, some ranchers complain the protected predators are once again killing their calves. (July 31) Video provided by AP
Powered by NewsLook.com
Dangerous Bacteria Kills One in Florida

Dangerous Bacteria Kills One in Florida

AP (July 31, 2014) — Sarasota County, Florida health officials have issued a warning against eating raw oysters and exposing open wounds to coastal and inland waters after a dangerous bacteria killed one person and made another sick. (July 31) Video provided by AP
Powered by NewsLook.com
Raw: Thousands Flocking to German Crop Circle

Raw: Thousands Flocking to German Crop Circle

AP (July 30, 2014) — Thousands of people are trekking to a Bavarian farmer's field to check out a mysterious set of crop circles. (July 30) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

    Environment News

    Technology News



      Save/Print:
      Share:  

      Free Subscriptions


      Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

      Get Social & Mobile


      Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

      Have Feedback?


      Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
      Mobile iPhone Android Web
      Follow Facebook Twitter Google+
      Subscribe RSS Feeds Email Newsletters
      Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins