Featured Research

from universities, journals, and other organizations

Stirred not mixed: How seawater turbulence affects marine food webs

Date:
November 5, 2012
Source:
National Science Foundation
Summary:
New research shows that ocean turbulence directly affects the ability of microscopic marine organisms to recycle organic material back into the food web.

Larval fish are dependent on zooplankton (pictured) as their food source.
Credit: NOAA

New research shows that ocean turbulence directly affects the ability of microscopic marine organisms to recycle organic material back into the food web.

Results of the study are published in this week's issue of the journal Science.

Scientists John Taylor of Cambridge University and Roman Stocker at MIT found that there's a relationship between the natural movement of water in the ocean and the ability of marine bacteria to act as recyclers.

"The research provides a unique insight into how small organisms, such as bacteria, interact with their environment," says biological oceanographer David Garrison of the National Science Foundation's Division of Ocean Sciences, which funded the research.

"The results will lead to a better understanding of microbial dynamics and nutrient cycling in nature."

The movement of seawater--including small whirls and eddies--affects how marine bacteria absorb organic material, such as that produced by phytoplankton.

In the process of generating oxygen, phytoplankton produce waste matter in the form of organic material, some of which becomes dissolved in seawater.

This dissolved organic material is then absorbed by marine bacteria foraging for food. Bacteria are then consumed by larger organisms.

The organic waste material excreted by phytoplankton becomes part of the microbial loop -- and contributes to the functioning of the marine food web.

Taylor's and Stocker's research revealed that a delicate balance exists between the extent of water turbulence and the recycling activity of bacteria--with high and low levels of turbulence linked to lower recycling rates.

Their study also looked at how the physical environment of the ocean might help to select the most successful types of marine bacteria, which compete for nutrients.

Some marine bacteria have evolved the ability to swim. Swimming bacteria, known as motile bacteria, have advantages over non-swimming species in foraging for food.

However, swimming is energy-intensive so motile bacteria swim only when it is worth the effort in terms of pay-back.

Some bacteria can also detect and respond to chemicals dissolved in the surrounding water, an ability known as chemotaxis.

The researchers compared the activity of motile and non-motile bacteria across environments that differed in levels of water movement and nutrient availability.

All water moves, but the extent of its turbulence varies widely in the ocean.

Wind and waves strongly churn the water near the surface, while the level of turbulence is much lower in the deep ocean, says Stocker.

The results show that the organic matter excreted by phytoplankton is patchy in the ocean, and is not as uniform as had been thought.

Organic matter enters water in bursts, after which a natural mixing and stirring action comes into play and the organic matter is dispersed.

The patterns of dispersal depend on the strength of turbulence and the extent of stirring and mixing.

"When you pour cream into coffee and stir it carefully, you get swirls of cream," says Taylor.

"Something similar happens when bursts of organic matter enter gently moving water. The swirls of organic matter are easily accessed by swimming bacteria which surround and absorb it.

"If you mix cream into your coffee vigorously, it quickly becomes evenly dispersed. When this happens in the ocean, the swimming bacteria have less to gain in seeking out the thinly-dispersed organic matter."

Bacteria get energy from organic matter--but they also expend energy in swimming.

"Our research suggests that the optimum environment is one of intermediate turbulence intensity--when bursts of organic matter are stirred into thin filaments that can be exploited by large numbers of bacteria," says Taylor.

"The best environment for motile bacteria is one in which the organic matter is lightly stirred into the water rather than vigorously mixed."


Story Source:

The above story is based on materials provided by National Science Foundation. Note: Materials may be edited for content and length.


Journal Reference:

  1. J. R. Taylor, R. Stocker. Trade-Offs of Chemotactic Foraging in Turbulent Water. Science, 2012; 338 (6107): 675 DOI: 10.1126/science.1219417

Cite This Page:

National Science Foundation. "Stirred not mixed: How seawater turbulence affects marine food webs." ScienceDaily. ScienceDaily, 5 November 2012. <www.sciencedaily.com/releases/2012/11/121105200056.htm>.
National Science Foundation. (2012, November 5). Stirred not mixed: How seawater turbulence affects marine food webs. ScienceDaily. Retrieved July 29, 2014 from www.sciencedaily.com/releases/2012/11/121105200056.htm
National Science Foundation. "Stirred not mixed: How seawater turbulence affects marine food webs." ScienceDaily. www.sciencedaily.com/releases/2012/11/121105200056.htm (accessed July 29, 2014).

Share This




More Plants & Animals News

Tuesday, July 29, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Deadly Ebola Virus Threatens West Africa

Deadly Ebola Virus Threatens West Africa

AP (July 28, 2014) West African nations and international health organizations are working to contain the largest Ebola outbreak in history. It's one of the deadliest diseases known to man, but the CDC says it's unlikely to spread in the U.S. (July 28) Video provided by AP
Powered by NewsLook.com
Traditional African Dishes Teach Healthy Eating

Traditional African Dishes Teach Healthy Eating

AP (July 28, 2014) Classes are being offered nationwide to encourage African Americans to learn about cooking fresh foods based on traditional African cuisine. The program is trying to combat obesity, heart disease and other ailments often linked to diet. (July 28) Video provided by AP
Powered by NewsLook.com
Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Newsy (July 28, 2014) The asteroid that killed the dinosaurs struck at the worst time for them. A new study says that if it hit earlier or later, they might've survived. Video provided by Newsy
Powered by NewsLook.com
Raw: Sea Turtle Hatchlings Emerge from Nest

Raw: Sea Turtle Hatchlings Emerge from Nest

AP (July 27, 2014) A live-streaming webcam catches loggerhead sea turtle hatchlings emerging from a nest in the Florida Keys. (July 27) 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:

More Coverage


Staying Still or Going Hunting: Which Works Better for a Hungry Ocean Microbe?

Nov. 1, 2012 For the kinds of animals that are most familiar to us -- ones that are big enough to see -- it's a no-brainer: Is it better to sit around and wait for food to come to you, or to move around and ... read more
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