Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Nature's tiny engineers


Coral organisms use minuscule appendages to control their environment, stirring up water eddies to bring nutrients

Conventional wisdom has long held that corals — whose calcium-carbonate skeletons form the foundation of coral reefs — are passive organisms that rely entirely on ocean currents to deliver dissolved substances, such as nutrients and oxygen.

But now scientists at MIT and the Weizmann Institute of Science (WIS) in Israel have found that they are far from passive, engineering their environment to sweep water into turbulent patterns that greatly enhance their ability to exchange nutrients and dissolved gases with their environment.

"These microenvironmental processes are not only important, but also unexpected," says Roman Stocker, an associate professor of civil and environmental engineering at MIT and senior author of a paper describing the results in the Proceedings of the National Academy of Sciences.

When the team set up their experiment with living coral in tanks in the lab, "I was expecting that this would be a smooth microworld, there would be not much action except the external flow," Stocker says. Instead, what the researchers found, by zooming in on the coral surface with powerful microscopes and high-speed video cameras, was the opposite: Within the millimeter closest to the coral surface, "it's very violent," he says.

It's long been known that corals have cilia, small threadlike appendages that can push water along the coral surface. However, these currents were previously assumed to move parallel to the coral surface, in a conveyor-belt fashion. Such smooth motion may help corals remove sediments, but would have little effect on the exchange of dissolved nutrients.

Now Stocker and his colleagues show that the cilia on the coral's surface are arranged in such a way as to produce strong swirls of water that draw nutrients toward the coral, while driving away potentially toxic waste products, such as excess oxygen.

Not just passive

"The general thinking has been that corals are completely dependent upon ambient flow, from tides and turbulence, to enable them to overcome diffusion limitation and facilitate the efficient supply of nutrients and the disposal of dissolved waste products," says Orr Shapiro, a postdoc from WIS and co-first author on the paper, who spent a year in Stocker's lab making these observations.

Under such a scenario, colonies in sheltered parts of a reef or at slack tide would see little water movement and might experience severe nutrient limitation or a buildup of toxic waste, to the point of jeopardizing their survival. "Even the shape of the coral can be problematic" under that passive scenario, says Vicente Fernandez, an MIT postdoc and co-first author of the paper. Coral structures are often "treelike, with a deeply branched structure that blocks a lot of the external flow, so the amount of new water going through to the center is very low."

The team's approach of looking at corals with video microscopy and advanced image analysis changed this paradigm. They showed that corals use their cilia to actively enhance the exchange of dissolved molecules, which allows them to maintain increased rates of photosynthesis and respiration even under near-zero ambient flow.

The researchers tested six different species of reef corals, demonstrating that all share the ability to induce complex turbulent flows around them. "While that doesn't yet prove that all reef corals do the same," Shapiro says, "it appears that most if not all have the cilia that create these flows. The retention of cilia through 400 million years of evolution suggests that reef corals derive a substantial evolutionary advantage" from these flows.

Corals need to stir it up

The reported findings transform the way we perceive the surface of reef corals; the existing view of a stagnant boundary layer has been replaced by one of a dynamic, actively stirred environment. This will be important not only to questions of mass transport, but also to the interactions of marine microorganisms with coral colonies, a subject that attracts much attention due to a global increase in coral disease and reef degradation over the past decades.

Besides illuminating how coral reefs function, which could help better predict their health in the face of climate change, this research could have implications in other fields, Stocker suggests: Cilia are ubiquitous in more complex organisms — such as inside human airways, where they help to sweep away contaminants.

But such processes are difficult to study because cilia are internal. "It's rare that you have a situation in which you see cilia on the outside of an animal," Stocker says — so corals could provide a general model for understanding ciliary processes related to mass transport and disease.


In addition to Stocker, Shapiro, and Fernandez, the research team included Assaf Vardi, faculty at WIS; postdoc Melissa Garren; former MIT postdoc Jeffrey Guasto, now an assistant professor at Tufts University; undergraduate François Debaillon-Vesque from MIT and the École Polytechnique in Paris; and Esti Kramarski-Winter from WIS. The work was supported by the Human Frontiers in Science Program, the National Science Foundation, the National Institutes of Health, and the Gordon and Betty Moore Foundation.

Written by David Chandler, MIT News Office

Andrew Carleen | Eurek Alert!
Further information:

Further reports about: MIT Oxygen Photosynthesis Technology WIS colonies corals nutrients processes tiny toxic waste turbulent

More articles from Ecology, The Environment and Conservation:

nachricht Invasive Insects Cost the World Billions Per Year
04.10.2016 | University of Adelaide

nachricht Malaysia's unique freshwater mussels in danger
27.09.2016 | The University of Nottingham Malaysia Campus

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: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>