Physics and coral skeletons at the nanoscale

Given that today, Oct. 31, 2013, is Hallowe’en, it seems thematically appropriate to be talking about skeletons, in this case, coral skieleton. An Oct. 29, 2013, news item on Nanowerk profiles the research (Note: A link has been removed),

An international team of scientists, led by physicists from the University of York, has shed important new light on coral skeleton formation.

Their investigations (“Microstructural evolution and nanoscale crystallography in scleractinian coral spherulites”), carried out at the nanoscale, provide valuable new information for scientists and environmentalists working to protect and conserve coral from the threats of acidification and rising water temperatures.

The Oct. 29, 2013 University of York (UK) news release, which originated the news item, describes coral and what the scientists were looking for,

As corals grow, they produce limestone – calcium carbonate – skeletons which build up over time into vast reefs. The skeleton’s role is to help the coral’s upper living biofilm to move towards the light and nutrients.

Understanding the calcification mechanism by which these skeletons are formed is becoming increasingly important due to the potential impact of climate change on this process.

The scientists looked at the smallest building blocks that can be identified – a microstructure called spherulites – by making a thin cross-section less than 100 nanometres in thickness of a skeleton crystal. They then used Transmission Electron Microscopy (TEM) to analyse the crystals in minute detail.

The TEM micrographs revealed three distinct regions: randomly orientated granular, porous nanocrystals; partly oriented nanocrystals which were also granular and porous; and densely packed aligned large needle-like crystals.

These different regions could be directly correlated to times of the day – at sunset, granular and porous crystals are formed, but as night falls, the calcification process slows down and there is a switch to long aligned needles.

“It has been suspected for some time that the contrast bands seen in crystals in optical images were daily bands. Through our research we have been able to show what the crystals actually contain and the differences between day and night crystals.” [said corresponding author Renée van de Locht,]

I know coral is important but I didn’t know why (from the news release),

Corresponding author Renée van de Locht, a final-year PhD student with the Department of Physics at the University of York, says, “Coral plays a vital role in a variety of eco-systems and supports around 25 per cent of all marine species. In addition, it protects coastlines from wave erosion and plays a key role in the fisheries and tourism industries. However, the fundamental principles of coral’s skeleton formation are still not fully understood.

While the researchers are concerned about climate change and ocean acidification, there are other agendas being pursued as well (from the news release),

The York researchers are now turning their attention to looking directly at the effects of acidification. Their latest research is looking at five-day old coral larvae and compares a population from a normal seawater environment with another in an acidic environment.

The aim is to investigate the nanoscale impacts of the different environments at an early growth stage to assess how these could affect the whole colony and the bigger reef.

The coral research at York is also part of a much larger project looking at the hard and soft matter interface called the MIB – Interface between Materials and Biology – project. Nature has created materials that combine mineral (hard) and organic (soft) components in a way that provides properties that are extremely well suited to function – for example in bone, egg or mollusc shells. The collaborative project aims to develop a working understanding of how this control is worked out in natural systems, so that the same techniques can be used to develop new materials with specially tailored properties.

Here’s a citation for and a link to the published research paper,

Microstructural evolution and nanoscale crystallography in scleractinian coral spherulites by Renée van de Locht, Andreas Verch, Martin Saunders, Delphine Dissard, Tim Rixen, Aurélie Moya, and Roland Kröger. Journal of Structural Biology, Volume 183, Issue 1, July 2013, Pages 57–65 DOI:10.1016/j.jsb.2013.05.005

The paper is behind a paywall which includes a rental option, as well as, the option of paying for the paper outright. You can also try accessing the paper here at ResearchGate which requires that you register for a free account.

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