Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Sharks in Acidic Waters Avoid Smell of Food

11.09.2014

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.


Danielle Dixson

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.

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 online in a recent edition of 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 ± 26 microatmospheres (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

Brett Israel | newswise

Further reports about: Biology CO2 Food GABAA Waters concentration concentrations conditions dioxide levels odor sharks

More articles from Studies and Analyses:

nachricht Win-win strategies for climate and food security
02.10.2017 | International Institute for Applied Systems Analysis (IIASA)

nachricht The personality factor: How to foster the sharing of research data
06.09.2017 | ZBW – Leibniz-Informationszentrum Wirtschaft

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>