Skip to content

News Center | Georgia Institute of Technology Georgia Institute of Technology

Search

Search form

  • Facebook
  • Twitter
  • YouTube
  • LinkedIn
  • News Home
  • Campus Map
  • Directory
  • Offices

News Center

Menu
Close
  • Calendar
  • Categories
    • Business and Economic Development
    • Campus and Community
    • Earth and Environment
    • Health and Medicine
    • Science and Technology
    • Society and Culture
    • Feature Stories
  • Media Contacts
  • Experts
    • Find an Expert
    • Featured Expert
  • Daily Digest
  • The Whistle
    • Home
    • Classifieds
    • Archives
  • Social Media
  • Subscribe
  • You are here:
  • GT Home
  • Georgia Tech NewsCenter
  • Home
  • Sharks in Acidic Waters Avoid Smell of Food

Earth and Environment

Sharks in Acidic Waters Avoid Smell of Food

September 9, 2014 • Atlanta, GA

Credit: Jayne M. Gardiner, J Exp Biol, 2007

The increasing acidification of ocean waters caused by rising atmospheric carbon dioxide levels could rob sharks of their ability to sense the smell of food, a new study suggests.

Elevated carbon dioxide levels impaired the odor-tracking behavior of the smooth dogfish, a shark whose range includes the Atlantic Ocean off the eastern United States. Adult sharks significantly avoided squid odor after swimming in a pool of water treated with carbon dioxide. The carbon dioxide concentrations tested are consistent with climate forecasts for midcentury and 2100. The study suggests that predator-prey interactions in nature could be influenced by elevated carbon dioxide concentrations of ocean waters.

“The sharks’ tracking behavior and attacking behavior were significantly reduced,” said Danielle Dixson, an assistant professor in the School of Biology at the Georgia Institute of Technology in Atlanta. “Sharks are like swimming noses, so chemical cues are really important for them in terms of finding food.”

The study is the first time that sharks’ ability to sense the odor of their food has been tested under conditions that simulate the acidity levels expected in the oceans by the turn of the century. The work supports recent research from Dixson and other research groups showing that ocean acidification impairs sensory functions and alters the behavior of aquatic organisms.

The study was published August 11 the journal Global Change Biology and was sponsored by the National Science Foundation (NSF).

Carbon dioxide released into the atmosphere is absorbed into ocean waters, where it dissolves and lowers the pH of the water. Acidic waters affect fish behavior by disrupting a specific receptor in the nervous system, called GABAA, which is present in most marine organisms with a nervous system. When GABAA stops working, neurons stop firing properly.

Dixson’s previous research has shown that fish living on coral reefs where carbon dioxide seeps from the ocean floor were less able to detect predator odor than fish from normal coral reefs. Study co-author Philip Munday, from James Cook University in Australia, has shown in previous work that a tiny coral reef predator fish, the dottyback,also loses interest in food in waters that simulate ocean acidification conditions forecast for the future.

In the experimental part of the new study, conducted at Woods Hole Oceanographic Institute in Cape Cod, Massachusetts, 24 sharks from local waters were studied in a 10-meter-long flume. The flume resembled two lanes of a swimming pool. Odor from a squid was pumped down one lane of the flume, while normal seawater was pumped down the other side.

Sharks tend to prefer one side of a tank over the other, so researchers first assessed each sharks’ side preference. Then the research team ran control experiments under normal ocean conditions to ensure that the sharks were tracking the food cue. Under present-day water conditions, sharks adjusted their position in the flume to spend a greater amount of time on the side containing the squid odor plume, regardless of the individual shark’s natural side preference.

Next, sharks spent five days in holding pools of three different carbon dioxide concentrations: local water concentration today (405 ± 26microatmospheres (µatms) CO2), projected midcentury concentration (741 ± 22 µatms CO2),projected concentration for 2100 (1,064 ± 17 µatms CO2). Sharks were not fed while in the holding pools to ensure they were motivated to track a food odor. The sharks were then released into the flume and their tracking behavior was observed.

Sharks from the normal seawater pool and mid-level carbon dioxide pool spent more than 60 percent of their time in the water stream containing the food stimulus. Sharks from the high carbon dioxide pool spent less than 15 percent of their time in the water stream containing the food stimulus. These sharks avoided the odor plume even when it was on the side of the flume that the sharks’ naturally prefer.

The food odor stream was pumped through bricks to make the plume flow better and to give the sharks a target to attack. Sharks treated under mid and high CO2 conditions also reduced their attack behavior.

“They significantly reduced their bumps and bites on the bricks compared to the control group,” Dixson said. “It’s like they’re uninterested in their food.”

Exposure to carbon dioxide did not significantly affect the sharks’ overall activity levels. The gill rate of the sharks – an indicator of heart rate – held in different water conditions was not significantly different, suggesting that differences in stress to the sharks was not likely affecting the experimental results.

Dixson noted that the study was carried out under laboratory conditions and thus does not allow for the full evaluation of the potential effects of ocean acidification on predatory abilities of the smooth dogfish.

Live food was not used as the odor cue because sharks can detect prey with their other senses, such as hearing and their ability to detect electrical impulses. By using an odor cue, the researchers were focusing on only the chemical sensing of sharks. Dixson’s future work will explore how sharks’ other senses might be affected by ocean acidification.

Sharks are an ancient species, and in the past have adapted to ocean acidification conditions projected for the future. But they’ve never had to adapt to changes happening as quickly as they are today.

“It’s the rate of change that’s happening that’s concerning. Sharks have never had to deal with it this fast,” Dixson said.

This research is supported by the National Science Foundation (NSF) under award number NSF-IOS-0843440. Any conclusions or opinions are those of the authors and do not necessarily represent the official views of the sponsoring agency.

CITATION: Danielle L. Dixson, et al., “Odor tracking in sharks is reduced under future ocean acidification conditions.” (Global Change Biology, August 2014) http://onlinelibrary.wiley.com/doi/10.1111/gcb.12678/full

Research News
Georgia Institute of Technology
177 North Avenue
Atlanta, Georgia  30332-0181  USA
@GTResearchNews

Media Relations Contacts: Brett Israel (@btiatl) (404-385-1933) (brett.israel@comm.gatech.edu) or John Toon (404-894-6986) (jtoon@gatech.edu)

Writer: Brett Israel 

Additional Photos

  • Smooth dogfish shark
     

    Smooth dogfish shark

    The smooth dogfish, a shark whose range includes the Atlantic Ocean off the eastern United States, could lose their ability to sense the smell of food if climate change if ocean acidification continues its current pace. Credit: Danielle Dixson

    Download Image
  • Shark mouth
     

    Shark mouth

    The new study is the first time that sharks’ ability to sense the odor of their food has been tested under conditions that simulate the acidity levels expected in the oceans by the turn of the century. Credit: Danielle Dixson

    Download Image
  • Shark flume
     

    Shark flume

    A smooth dogfish swims in a flume at Woods Hole Oceanographic Institute in Massachusetts. Arrows point to the brick baffles and the source of the food odor plume. The start box holding area is also labeled. Dashed lines indicate the flume quadrants used to determine activity level through number of lines crossed. Credit: Danielle Dixson

    Download Image

Contact Information

Brett Israel

404-385-1933

@btiatl

Categories

Earth and Environment

News Categories

  • Business and Economic Development
  • Campus and Community
  • Earth and Environment
  • Health and Medicine
  • Science and Technology
  • Society and Culture

Expert Voices

Mariel Borowitz

Photo by Rob Felt

Half of Earth’s satellites restrict use of climate data
Mariel Borowitz
Sam Nunn School of Int'l Affairs

Professor Marilyn Brown on the green/solar roof of the Cough Building. (Photo Rob Felt)

Would a Green New Deal Add or Kill Jobs?
Marilyn Brown
School of Public Policy

Featured Videos

Seth Osekre, a custodian in Facilities Management, follows safety protocols when cleaning. (Video by Allison Carter)

2020 graduate TJ Weiler talks about his journey to earning a Georgia Tech degree.

Georgia Tech Resources

  • Offices & Departments
  • News Center
  • Campus Calendar
  • Special Events
  • GreenBuzz
  • Institute Communications
  • Visitor Resources
  • Campus Visits
  • Directions to Campus
  • Visitor Parking Information
  • GTvisitor Wireless Network Information
  • Georgia Tech Global Learning Center
  • Georgia Tech Hotel & Conference Center
  • Barnes & Noble at Georgia Tech
  • Ferst Center for the Arts
  • Robert C. Williams Paper Museum

Colleges, Instructional Sites & Research

  • Colleges
  • College of Computing
  • College of Design
  • College of Engineering
  • College of Sciences
  • Ivan Allen College of Liberal Arts
  • Scheller College of Business
  • Instructional Sites
  • Georgia Tech-Lorraine
  • Georgia Tech-Savannah
  • Georgia Tech-Shenzhen
  • Georgia Tech Online
  • Professional Education
  • The Language Institute
  • Global Footprint
  • Global Engagement
  • Research
  • Georgia Tech Research Institute
  • Research at Georgia Tech
  • Executive Vice President for Research

Student & Parent Resources

  • Student Resources
  • Apply
  • BuzzPort
  • Buzzcard
  • Career Center
  • Co-ops & Internships
  • Commencement
  • Library
  • Student Life
  • Student Entrepreneurship
  • Study Abroad
  • T-Square
  • Parent Resources
  • Parent and Family Programs
  • Dean of Students
  • Scholarships & Financial Aid

Employee, Alumni, & Other Resources

  • Employees
  • Administration and Finance
  • Advising & Teaching
  • Faculty Affairs
  • Faculty Hiring
  • Human Resources
  • Office of the Provost
  • TechWorks
  • Alumni
  • Alumni Association
  • Alumni Career Services
  • Giving Back to Tech
  • Outreach
  • Startup Companies
  • Economic Development
  • Industry Engagement
  • Government & Community Partners
  • Professional Education
Map of News Center | Georgia Institute of Technology

Georgia Institute of Technology
North Avenue, Atlanta, GA 30332
Phone: (404) 894-2000

  • Contact Us
  • Site Feedback
  • Tech Lingo
  • Emergency Information
  • Legal & Privacy Information
  • Human Trafficking Notice
  • Accessibility
  • Accountability
  • Accreditation
  • Employment
Georgia Tech

© Georgia Institute of Technology