Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers link jellyfish, other small sea creatures to large-scale ocean mixing

03.08.2009
New mechanism shows how swimming animals affect the marine environment

The ocean's smallest swimming animals, such as jellyfish, can have a huge impact on large-scale ocean mixing, researchers have discovered.

"The perspective we usually take is how the ocean--by its currents, temperature, and chemistry--is affecting animals," says John Dabiri, a Caltech bioengineer who, along with Caltech graduate student Kakani Katija, discovered the new mechanism. "But there have been increasing suggestions that the inverse is also important, how the animals themselves, via swimming, might impact the ocean environment."

Dabiri's and Katija's findings show this inverse to be true, and are published in the July 30 issue of the journal Nature.

"Results from this study will change some of our long-held conceptions about mixing processes in the oceans," says David Garrison, director of NSF's biological oceanography program, which funded the research.

Scientists have increasingly been thinking about how and whether the animals in the ocean might play a role in larger-scale ocean mixing, says Dabiri, the process by which various layers of water interact with one another to distribute heat, nutrients and gasses throughout the oceans.

He says that oceanographers had previously dismissed the idea that animals might have a significant effect on ocean mixing, believing that the viscosity of water would cancel out any turbulence created, especially by small planktonic, or drifting, animals.

But Dabiri and Katija thought there might be a mechanism that had been overlooked, a mechanism they call Darwinian mixing, because it was first discovered and described by Darwin's grandson.

"Darwin's grandson discovered a mechanism for mixing similar in principle to the idea of drafting in aerodynamics," Dabiri explains. "In this mechanism, an individual organism literally drags the surrounding water with it as it goes."

Using this idea as their basis, Dabiri and Katija performed mathematical simulations of what might happen if many small animals all moved at the same time, in the same direction.

Each day, for example, billions of tiny krill and copepods migrate hundreds of meters from the depths of the ocean toward the surface.

Darwin's mechanism would suggest that they drag some of the colder, heavier bottom water up with them toward warmer, lighter water at the top. This would create instability, and eventually, the water would flip, mixing itself as it went.

The researchers found that the water's viscosity enhances Darwin's mechanism, and that the effects are magnified with very small animals like krill and copepods.

"It's like a human swimming through honey," Dabiri explains. "What happens is that even more fluid ends up being carried by a copepod, relatively speaking, than would be carried by a whale."

To verify the findings from their simulations, the scientists traveled to the island of Palau, where they studied animal-led transport of water--otherwise known as induced drift--among jellyfish.

Their jellyfish experiments involved putting fluorescent dye in the water in front of the jellies, then watching what happened to that dye and to the water that took up the dye as the jellyfish swam.

Rather than being left behind the jellyfish, or dissipated in turbulent eddies, the dye travelled right along with them, following for long distances.

The findings verified that swimming animals are capable of carrying bottom water with them as they migrate upward, and that the movement indeed creates an inversion that results in ocean mixing.

After a series of calculations, Dabiri and Katija were able to estimate the impact of this biogenic ocean mixing.

"There are enough of these animals in the ocean," Dabiri says, "that the global power input from this process is as much as a trillion watts of energy, comparable to that of wind forcing and tidal forcing."

While these numbers are estimates, they are likely to be conservative estimates, Dabiri says. "They were based on the fluid transport induced by individual animals swimming in isolation."

In the ocean, these individual contributions to fluid transport may interact with one another, and amplify how far ocean waters can be pulled upward.

In addition, says Dabiri, scientists have yet to consider the effects of such factors as fecal pellets and marine snow (falling organic debris), which pull surface water along as they drift downward.

"This may have an impact on carbon sequestration on the ocean floor," says Dabiri. "It's something we need to look at."

Dabiri says the next major question is how these effects can be incorporated into computer models of global ocean circulation. Such models are important for simulations of global climate change scenarios.

The research was also supported by the Office of Naval Research, the Department of Defense's National Science and Engineering Graduate Fellowship, and the Charles Lee Powell Foundation.

Cheryl Dybas | EurekAlert!
Further information:
http://www.nsf.gov

More articles from Ecology, The Environment and Conservation:

nachricht How does the loss of species alter ecosystems?
18.05.2017 | Deutsches Zentrum für integrative Biodiversitätsforschung (iDiv) Halle-Jena-Leipzig

nachricht Excess diesel emissions bring global health & environmental impacts
16.05.2017 | International Institute for Applied Systems Analysis (IIASA)

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

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

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

Im Focus: Using graphene to create quantum bits

In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.

In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...

Im Focus: Bacteria harness the lotus effect to protect themselves

Biofilms: Researchers find the causes of water-repelling properties

Dental plaque and the viscous brown slime in drainpipes are two familiar examples of bacterial biofilms. Removing such bacterial depositions from surfaces is...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

Innovation 4.0: Shaping a humane fourth industrial revolution

17.05.2017 | Event News

 
Latest News

Scientists propose synestia, a new type of planetary object

23.05.2017 | Physics and Astronomy

Zap! Graphene is bad news for bacteria

23.05.2017 | Life Sciences

Medical gamma-ray camera is now palm-sized

23.05.2017 | Medical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>