How soft corals defy their environment

Aug 16, 2011

Many marine organisms, including corals, build skeletons from calcium carbonate -- in the form of calcite or aragonite. The current composition of seawater favors the formation of aragonite -- but soft corals have a specific protein that allows them to form calcite skeletons instead.

Calcium carbonate is a salt for all seasons. It turns up not only in marble, but also in biogenic sediments such as limestone and – and even in pearls. The compound exists in two major crystalline forms, as calcite or aragonite. However, it is not clear what determines which variant an organism will exploit under conditions in which both forms can precipitate.

A team of researchers led by LMU geobiologist Dr. Azizur Rahman, who is also a Research Fellow of the Alexander von Humboldt Foundation, has now answered this question, in collaboration with colleagues based at the University of the Ryukyu Islands in Japan. Together, the scientists have shown that, in the soft coral species Lobophytum crissum, a secreted, extracellular protein known as ECMP-67 is the decisive factor that results in the precipitation of calcite, irrespective of the chemical conditions prevailing in the surrounding seawater.

"Over the course of Earth's history, and most probably depending on the relative amounts of dissolved magnesium and calcium ions, either calcite or aragonite has dominated in the world's oceans," says Professor Gert Wörheide, one of the authors of the new study. Current conditions favor the formation of aragonite, and many stony corals build their skeletons exclusively from this material. However, thanks to ECMP-67, Lobophytum crassum can still produce calcite in an aragonite sea.

"We have also been able to show how the extracellular ECMP-67 contributes to the production of calcite at the molecular level," says Rahman. "These findings should also allow us to elucidate the crystal structure of in natural environments." The study was funded by the Alexander von Humboldt Foundation and the Japanese Society for the Promotion of Sciences.

Explore further: New technique reveals immune cell motion through variety of tissues

More information: Calcite formation in soft coral sclerites is determined by a single reactive extracellular protein, Azizur Rahman, Tamotsu Oomori and Gert Wörheide, Journal of Biological Chemistry 286: 31638-31649, 2. September 2011. Doi 10.1074/jbc.M109.070185

Provided by Ludwig-Maximilians-Universitat Munchen

not rated yet
add to favorites email to friend print save as pdf

Related Stories

Study: Corals can switch skeletal material

Jul 06, 2006

U.S. marine geologists say they've determined corals can change their skeletons, using different minerals depending on the seawater's chemical composition.

Ocean acidification threatens cold-water coral ecosystems

Apr 03, 2006

Corals don't only occur in warm, sun-drenched, tropical seas; some species are found at depths of three miles or more in cold, dark waters throughout the world's oceans. Some cold-water coral reefs are home to more than 1,300 ...

Calcium carbonate and climate change

Aug 30, 2010

(PhysOrg.com) -- What links sea urchins, limestone and climate change? The common thread is calcium carbonate, one of the most widespread minerals on Earth. UC Davis researchers have now measured the energy changes among ...

Soft coral builds strong reefs

Aug 16, 2011

Scientists have long believed soft corals, one of the many endangered elements of marine life, are only minor contributors to the structure of coral reefs. But that's not true, says new research from Tel Aviv ...

Recommended for you

'Global positioning' for molecules

Dec 19, 2014

In everyday life, the global positioning system (GPS) can be employed to reliably determine the momentary location of one en route to the desired destination. Scientists from the Institute of Physical and ...

Cells build 'cupboards' to store metals

Dec 17, 2014

Lawrence Livermore researchers in conjunction with collaborators at University of California (link is external), Los Angeles have found that some cells build intracellular compartments that allow the cell ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.