Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Corals switch skeleton material as seawater changes

10.07.2006
Leopards may not be able to change their spots, but corals can change their skeletons, building them out of different minerals depending on the chemical composition of the seawater around them.

That's the startling conclusion drawn by a Johns Hopkins University marine geologist, writing in the July issue of the journal Geology.

Postdoctoral fellow Justin Ries and his collaborators say this is the first known case of an animal altering the composition of its skeleton in response to change in its physical environment. The aquatic animal's sensitivity to such changes poses questions about its evolutionary history, as well as the future of the ecologically important coral reefs that it builds, Ries said, especially at a time when seawater is changing in response to global warming and the buildup of carbon dioxide in the atmosphere.

A 2005 Ph.D. graduate of Johns Hopkins, Ries collaborated on the research with his dissertation advisors, Steven M. Stanley (now of the University of Hawaii) and Lawrence A. Hardie, professor in the Morton K. Blaustein Department of Earth and Planetary Sciences at Johns Hopkins.

Reefs are large underwater structures of coral skeletons, made from calcium carbonate secreted by generation after generation of tiny coral polyps over sometimes millions of years of coral growth in the same location. The team showed that corals can switch from using aragonite to another mineral, calcite, in making the calcium carbonate. They make that switch in response to decreases in the ratio of magnesium to calcium in seawater, Ries said. That ratio has changed dramatically over geologic time.

"This is intriguing because, until now, it was generally believed that the skeletal composition of corals was fixed," he said.

Ries spent two months growing three species of modern scleractinian corals (the major reef-building corals in today's seas) in seawater formulated at six different chemical ratios that have existed throughout the 480-million-year history of corals. He concocted this "artificial seawater" using "recipes" provided by Hardie, who several years ago discovered that the magnesium-calcium ratio in seawater has vacillated throughout geologic history between a low of 1.0 and today's 5.2, changing due to chemical reactions between seawater brine and rising magma along the ocean floor.

Ries placed his artificial seawaters in 10-gallon glass tanks, then added fragments of the three species of Caribbean reef-building corals. These were replete with colonies of polyps, which had spent the previous month in "equilibration tanks." Ries adjusted the chemistry of those tanks over 30 days, until their magnesium-to-calcium ratios were in line with the prescribed "ancient seawater" chemistries.

Two months later, Ries removed the coral skeletons and used X-ray diffraction to analyze their mineral composition. He was surprised to find that corals grown in the artificial seawater with a magnesium-to-calcium ratio less than 2-to-1 began producing a large portion of their skeleton with the calcite mineral, while those grown in unmodified modern seawater produced exclusively the aragonite mineral.

Though most scientists believed that corals were programmed to produce only the aragonitic form of calcium carbonate, he said, the team's work reveals that corals are far more flexible and able to vary at least a portion of their skeleton to growth favored by seawater chemistry. He postulates that this "mineralogical flexibility" provides corals with an "evolutionary advantage," as it would take more energy for corals to produce skeletons that are not favored by the chemistry of the seawater surrounding them.

The calcite-producing corals grown in artificial ancient water grew significantly slower than did the aragonite-producing corals grown in modern water.

"The reduction in the corals' rate of growth that accompanied their exposure to the chemically modified seawaters is further evidence of corals' extreme sensitivity to environmental change," Ries said.

"This is particularly significant given recently observed and predicted future changes in the temperature and acidity of our oceans ¬¬-- via global warming and rising atmospheric CO2 , respectively -- that will presumably have a significant impact on corals' ability to build their skeletons and construct their magnificent reefs," he said.

Corals are crucial to nearshore tropical ecosystems because the reefs they build are inhabited by tens of thousands of marine animals, plants, algae and bacteria that make up the coral reef ecosystem, which is one of the planet's most diverse, Ries said. But coral reefs also serve a more practical purpose: They absorb wave energy generated by hurricanes and other severe tropical storms.

"Ironically, the same factor that is likely causing such storms to increase in intensity – global warming – is also causing the corals to bleach (lose their symbiotic algae) and die, ultimately leading to the destruction of the coral reefs, which protect the coasts from these storms," Ries said. "All that being said, it is also important to note that the magnesium-calcium ratio of seawater changes only over millions of years and has no direct relationship to recent global warming and ocean acidification, which are believed to be at least partly human caused."

His team's experiments do, however, have significance with respect to global warming and ocean acidification, Ries said, because they reveal that although corals can adapt mineralogically to altered seawater chemistry, doing so slowed the corals' rate of growth by nearly 65 percent.

"This provides us with further evidence that corals are extremely sensitive to rapid environmental change, such as global warming," he said.

Lisa DeNike | EurekAlert!
Further information:
http://www.jhu.edu

More articles from Ecology, The Environment and Conservation:

nachricht Minimized water consumption in CSP plants - EU project MinWaterCSP is making good progress
05.12.2017 | Steinbeis-Europa-Zentrum

nachricht Jena Experiment: Loss of species destroys ecosystems
28.11.2017 | Technische Universität München

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: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

Im Focus: Virtual Reality for Bacteria

An interdisciplinary group of researchers interfaced individual bacteria with a computer to build a hybrid bio-digital circuit - Study published in Nature Communications

Scientists at the Institute of Science and Technology Austria (IST Austria) have managed to control the behavior of individual bacteria by connecting them to a...

Im Focus: A space-time sensor for light-matter interactions

Physicists in the Laboratory for Attosecond Physics (run jointly by LMU Munich and the Max Planck Institute for Quantum Optics) have developed an attosecond electron microscope that allows them to visualize the dispersion of light in time and space, and observe the motions of electrons in atoms.

The most basic of all physical interactions in nature is that between light and matter. This interaction takes place in attosecond times (i.e. billionths of a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Midwife and signpost for photons

11.12.2017 | Physics and Astronomy

How do megacities impact coastal seas? Searching for evidence in Chinese marginal seas

11.12.2017 | Earth Sciences

PhoxTroT: Optical Interconnect Technologies Revolutionized Data Centers and HPC Systems

11.12.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>