How a starfish could help us understand climate change

How a starfish could help us understand climate change

Scientist Pierre Thibault observes these organisms through X-rays in search of alterations. A new possibility to measure the impact of climate change on ecosystems which will be discussed at Trieste Next

(photo: Pierre Thibault, University of Trieste) The sea has always been the inspiration for many stories. But one in particular, that on the future of the planet, could somehow already be written in its inhabitants, even in the smallest and most unnoticed ones. Deciphering this hidden trace is today one of the great challenges for scientists, with explorers, biologists, environmental and technology experts working side by side to study the impact that climate change has on ecosystems. The goal is to build increasingly accurate predictive models of what will happen in the next few years.

We talked about this for Wired with Pierre Thibault, professor of applied physics at the University of Trieste and X-ray expert, with whom he is now investigating in particular an organism of the Northern seas, a small starfish , looking for signs attributable to climate change, which as we know affects temperatures, acidity and other characteristics of the planet's waters. A project that makes use of an international team of scientists, conducted in collaboration with Elettra synchrotron and which will be told during the tenth edition of Trieste Next, a scientific research festival and a real "showcase of innovation" scheduled for Friday 24 to Sunday 26 September in the Julian capital.

Why a starfish?

The animal in the center of the "crosshair", just a few centimeters large, is called Ctenodiscus crispatus, a very widespread species throughout the Norwegian Arctic, which comprises over 3% of the biomass of this region and which populates the muddy bottoms, which is why it is nicknamed mud star - where mud in English means precisely mud. "The choice fell precisely on this organism for its widespread use, which makes it a good candidate as a representative of environmental conditions - explains Thibault - but also for the specific functions it performs: in fact it has an important role in cleaning the seabed, where it contributes to mixing the materials that continually settle there, feeding on organic debris ".

Like all organisms, even Ctenodiscus crispatus must be able to adapt to the changes triggered by climate change on its habitat and the idea is to investigate what mechanisms this creature is putting in place at the level of the digestive organs and reproductive to cope with these alterations and ensure survival. An idea born, the scientist tells us, from the meeting in February last year between the marine biologist Christina Woods of the National Oceanography Center of the University of Southampton and Irene Zanette, researcher in the field of X-ray imaging at the Elettra synchrotron of Trieste, both part of the team that carries on the work today.

The role of the synchrotron

On the reason for X-rays and precisely those of a large and complex machine like a synchrotron, let's take a step back. We are used to hearing mention of this technology in medical contexts, where it is used for diagnostic purposes especially for osteoarticular problems and chest assessments (it has also found use for Covid-19). The meaning is to look "beyond the surface" and build an image of the inside of the organism based on the different absorption of radiation by tissues and organs.

X-rays are traditionally produced by generating a large potential difference in the space between two metal entities, the cathode and the anode, a condition that once the vacuum is applied causes the electrons included there to undergo a acceleration that determines the emission of X-rays. However, these are X-rays that scientists define as “dirty”, ie where different wavelengths are present and which are not suitable for measurements that require very high precision. In short, the final quality of the image strictly depends on the type of tool used.

The Trieste synchrotron is quite different from the laboratory machinery that we are used to seeing in hospital clinics. It is a dedicated ring-shaped infrastructure with a diameter of about 300 meters, along which dozens of laboratory stations dedicated to data collection are located. "In synchrotrons, electrons travel at enormous speeds and with the ability to work with specific wavelengths, directing the beam very precisely - explains Thibault - with a quality comparable to that of a laser". It would be unthinkable to obtain detailed information such as that required by this type of investigation with a plant other than this one.

"Woods has provided us with suitable starfish samples" the professor goes on "and in this way we here in Trieste were able, in December 2020, to take action with the first data collection at our synchrotron ". The samples, prepared from organisms recovered from the Norwegian research vessel G.O. Sars, otherwise, would have been simply dissected to be observed with respect to their internal anatomy, without the possibility of being reused for subsequent analysis or of being investigated for more than a single characteristic for each individual. X-rays, on the other hand, have the potential, in addition to providing structural information with an unparalleled degree of detail, of penetrating objects of a different nature without degrading them and with the possibility of re-facing investigations over time, as the techniques of study are refined.

How it exploits X-rays

This is precisely the phase in which the project is currently: refine the techniques, that is, find the best way to exploit the power of X-rays to find fragility of the organisms in question and the traces left by the evolution of the climate. "After months we are still analyzing the data collected during the first measurement session, and this already gives the pulse of how complex the work is", explains the expert: "The first scientific publication on this project is still in preparation and it will not yet deal with strictly biological issues: for those it will be necessary to subject the samples to X-rays further times. If anything, it will concern methodological issues, that is, we will discuss X-ray imaging and tomography techniques for studying the properties of these organisms ”.

(photo: Pierre Thibault, University of Trieste) Having an original idea, good samples and a highly respectable tool is not a guarantee of immediate results and being able to easily recognize the "signature" of climate change on living beings: “This will take time: even just gaining the opportunity to use synchrotron light again presupposes a process for evaluating the project that is not at all obvious. Furthermore - continues Thibault - analyzing the internal organs of these starfish is a very delicate process, so much so that it is likely that it will not be left in the hands of the machine, but that a real-life scientist will need to follow the experiments in real time and detect , almost 'drawing them by hand', the fabrics that are interesting for the project ”.

This is because, unlike the animal's exoskeleton, the soft parts inside it are much more difficult to visualize and measure and because there are no algorithms (yet) capable of performing these operations automatically. “Once we have reached this point, after what we call volume segmentation, we will finally be able to compare the relative size of digestive and reproductive organs of specimens collected in more or less cold waters”, the professor anticipates.

The other candidates

During the project, funded with a grant from the European Research Council, other key organisms of the health of our seas will also be examined. The sea urchin, a species very present in the Mediterranean, for example, but also some varieties of sponges, sensitive to changes in temperature and acidity of the water and which can also open our gaze to another problem of the planet's waters: pollution from microplastics, invisible but potentially harmful as they can even block the internal channels of these creatures. In addition, researchers plan comparisons with past species from dated samples or even fossils, collaborating with natural history museums and trying to "rewind the tape" centuries and centuries ago.

Beyond marine biology and paleontology, the development of X-ray diffraction techniques that Thibault's team is dealing with also meets the materials sciences, with the study of the properties of composite ones in carbon fiber, "increasingly widespread in the industrial field, but extremely complex to study", the scientist goes on. He adds: “Another of my dreams has instead to do with history: to be able to interpret through X-rays the papyri of Herculaneum, charred by the famous eruption of Vesuvius, very well preserved but which for obvious reasons we cannot unroll. Developing a sufficiently powerful and precise method could mean being able to read words from two thousand years ago verbatim on the computer ”.

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