Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Sea change: Skeletons of ancient corals different from today’s

10.11.2004


A Johns Hopkins University graduate student may have solved a problem that has been baffling marine biologists and paleontologists for years: Why do coral reefs disappear from the fossil record during the beginning of the Cretaceous period -- 120 million years ago -- only to reappear after its end 35 million years ago?



The possible answer: Ancient seawater’s low magnesium-to-calcium ratio during this interval made it difficult for the marine animals -- which build their skeletons from a mineral called aragonite calcium carbonate -- to grow and flourish into vast reefs. That left few to end up in the fossil record, posits doctoral candidate Justin Ries and his advisor Steven Stanley, professor in the Morton K. Blaustein Department of Earth and Planetary Sciences at the university’s Zanvyl Krieger School of Arts and Sciences.

"Scientists have grappled with this question for years, and my research shows that the answer is that the chemistry of Cretaceous seawater did not support the secretion of the aragonite mineral from which corals construct their skeleton," said Ries, who will present his research on Nov. 10 at the 116th annual meeting of The Geological Society in Denver. "What’s more, my experiments suggest that corals from the Cretaceous period almost certainly built at least part of their skeletons from calcite. This is groundbreaking, because it was previously believed that organisms do not generally change their skeletal mineralogy over time. Now we know that they do."


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 geologic history of corals. He created this seawater "from scratch" according to recipes provided by earth and planetary sciences Professor Lawrence Hardie, who recently discovered that the magnesium-to-calcium molecular ratio of seawater has oscillated between 1.0 and 5.2 over the past 540 million years due to chemical reaction between rising magma and seawater brine along various parts of the ocean floor.

"The artificial seawaters were created by adding different concentrations of salts as calculated by Lawrence Hardie," Ries said. "I specifically wanted to test how modern corals respond to the ancient levels of magnesium and calcium because these chemicals, along with carbon and oxygen, are the building blocks of their skeletons. More important, however, is that the ratio of these two chemicals determines whether the aragonite or calcite mineral will form."

Into 10-gallon tanks filled with these mixtures went coral fragments replete with colonies of polyps -- tiny animals, a few millimeters in size, from which larger corals and, eventually, reefs grow. Ries prepared the polyps for the experiment by having them spend a one-month "adjustment period" in tanks filled with modern seawater. Gradually, Ries adjusted the tanks’ chemistry until their contents were in line with the prescribed "ancient" seawater chemistries.

"To prevent the corals from experiencing chemical shock in the unfamiliar seawaters, I learned that they must be acclimated gradually, in stages," Ries said. "This was actually one of the most challenging aspects of the project. There were many failed attempts before I was able to keep the corals alive, so that I could observe their growth and calcification in the ancient seawaters."

The corals were grown under special lights called "PowerCompacts" which simulated true daylight by emitting a wavelength commensurate to sunrise and sunset in the morning and evening, as well as normal sunlight during the rest of the day. Ries fed the growing corals with plankton particles, and monitored each tank’s pH level -- and level of chemicals such as strontium, iodine and manganese, as well as vitamins -- several times a week. Ries credits his experiments with leading to "two very important discoveries about corals."

First, the skeletons of the corals cultivated in the ancient seawaters had a different mineral composition from those grown in modern seawater. Those in the so-called Cretaceous seawater began building skeletons of 35 percent calcite mineral, as opposed to modern corals, which built them from 100 percent aragonite. This suggests that the skeletons of corals have been changing along with seawater throughout the geologic past. "This is astounding, given that most scientists have long believed that the mineral composition of a group of organisms’ skeletons is fixed over time," Ries said.

Secondly, the experiment was important because it proved corals cultivated in Cretaceous seawater grew more slowly than their counterparts raised in modern seawater. "This solves, experimentally, the longstanding question of why the Scleratinian corals stopped making reefs during the Cretaceous: because the low magnesium/calcium ratios in the oceans at that time inhibited the growth of the aragonite mineral that they used to build their skeletons," Ries said.

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

More articles from Earth Sciences:

nachricht The Wadden Sea and the Elbe Studied with Zeppelin, Drones and Research Ships
19.09.2017 | Helmholtz-Zentrum Geesthacht - Zentrum für Material- und Küstenforschung

nachricht FotoQuest GO: Citizen science campaign targets land-use change in Austria
19.09.2017 | International Institute for Applied Systems Analysis (IIASA)

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

Im Focus: Fast, convenient & standardized: New lab innovation for automated tissue engineering & drug

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...

Im Focus: Silencing bacteria

HZI researchers pave the way for new agents that render hospital pathogens mute

Pathogenic bacteria are becoming resistant to common antibiotics to an ever increasing degree. One of the most difficult germs is Pseudomonas aeruginosa, a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Molecular Force Sensors

20.09.2017 | Life Sciences

Producing electricity during flight

20.09.2017 | Power and Electrical Engineering

Tiny lasers from a gallery of whispers

20.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>