Corals 'resilient' to climate change


Rebecca Pool

Friday, June 2, 2017 - 07:45
Scanning helium ion micrograph showing the crystal growth process in stony corals, [Viacheslav Manichev and Stanislas Von Euw, Rutgers].
Using a stunning array of high resolution imaging methods, US-based researchers have shed new light on how stony corals form skeletons and may be more resilient to ocean acidification than once thought.
Little has been known about how stony corals deposit calcium carbonate skeletons with two hypotheses suggesting the process is either chemically- or biologically-driven.
Given this, researchers from Rutgers University studied Stylophora pistillata - a common stony coral in the Indo-Pacific - using ultra-high-resolution 3D imaging and 2D nuclear magnetic resonance  spectroscopy.
Stylophora pistillata, a well-studied stony coral common in the Indo-Pacific. [Kevin Wyman/Rutgers University]
Imaging methods included scanning electron microscopy, polarized light microscopy, electron backscatter diffraction, confocal Raman microscopy, Raman spectroscopy profiles, scanning helium ion microscopy, transmission electron microscopy, cathodoluminescence microscopy, backscattered electron imaging and wavelength dispersive X-ray spectroscopy.
As Professor Paul Falkowski from the Environmental Biophysics and Molecular Ecology Laboratory at Rutgers University-New Brunswick highlights: "As far as I know, we were unique in the world in using a coordinated set of techniques to understand the ultrastructure of coral skeletons."
Scanning helium ion micrograph of a centre of calcification surrounded by skeletal inorganic fibers consisting of elongated aragonite crystals. [Viacheslav Manichev and Stanislas Von Euw, Rutgers].
Falkowski and colleagues discovered that these corals deposit minerals in a biologically-driven process, using acid-rich proteins to build rock-hard skeletons made of calcium carbonate minerals.
Random nanoparticles are deposited in coral microenvironments enriched in organic material, which accumulate and form stony structures made of calcium carbonate - known as aragonite - by growing crystals.
Scanning helium ion micrograph of a centre of calcification filled of nanosized amorphous particles, and surrounded by microsized aragonite crystals. [Viacheslav Manichev and Stanislas Von Euw, Rutgers].
NMR imaging results indicate that coral acid-rich proteins are the main drivers.
“What we’re showing is that the decades-old general model for how corals make rock is wrong,” highlights Falkowski. “This very careful study very precisely shows that corals will secrete proteins, and the proteins are what really forms the mineral and the proteins are very acidic, which will surprise a lot of people.”
High-resolution scanning helium ion micrograph of a biogenic coral aragonite crystal. [Viacheslav Manichev and Stanislas Von Euw, Rutgers].
According to Falkowski, the proteins function at a pH of about 8.5 to 7; the ocean normally has a pH of 8.1 or 8.2, which may drop to 7.8 in the coming century, sugggesting these stony corals will still be able form skeletons.
“For stony corals, we’re fairly confident that the acidification issue is exaggerated,” he says. “They’re more resilient than we give them credit for.”
“The bottom line is that corals will make rock even under adverse conditions...and will probably make rock even as the ocean becomes slightly acidic from the burning of fossil fuels,” he adds.
Research is published in Science.
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