Nav: Home

Coral reef symbiosis: Paying rent with sugar and fat

February 10, 2015

-Scientists have revealed how coral-dwelling microalgae harvest nutrients from the surrounding seawater and shuttle them out to their coral hosts, sustaining a fragile ecosystem that is under threat.

Coral reefs are the jungles of the oceans, home to some of the planet's most fertile fishing grounds, and hotspots of global tourism. Their survival depends on an intricate relationship with tiny coral-dwelling algae. The relationship is a fragile one, as the algae are all too easily driven away by changes in water temperature and pollution. Scientists are only now beginning to understand this symbiosis at a molecular level. Publishing in the journal mBio, researchers from EPFL, the University of Lausanne, as well as the Museum of Natural History and the Tropical Aquarium in Paris present new discoveries on how nutrients are harvested and shuttled between algae and corals.

Charles Darwin was the first to describe what has since become known as the Darwinian Paradox: coral reef ecosystems flourish in water that is almost devoid of nutrients. Today we know that this would be impossible without tiny coral-dwelling photosynthetic algae that use sunlight to produce the nutrients needed to support their coral hosts. The corals return the favor by sheltering the algae and providing them with other nutrients.

"In this study, we are looking at the real cellular engine behind coral reefs: the algae's capability to photosynthetically extract carbon from the surrounding water and store it as sugar and fat," says principle investigator Anders Meibom. For the first time, Christophe Kopp, a researcher in Meibom's Laboratory for Biological Geochemistry, was able to visualize at the cell level how the algae produce sugars and fats using photosynthesis and store them, before being shuttling them to their coral hosts.

Kopp found that, when exposed to sunlight, it only took minutes for the micro-algae to use photosynthesis to convert bicarbonate present in the surrounding seawater to sugar, then to fat. These fats, which are passed on to the corals within 2-3 hours, can be seen within the coral tissue as small lipid droplets, from which the corals can draw energy for many of their physiological processes.

He also discovered a second form of carbon storage, in the form of granules composed of glycogen. While the lipid droplets were found throughout the coral tissue, the glycogen, a readily available source of energy, was found predominantly in the coral's outer membrane, where little hair-like structures, cilia, swirl up the water that is in direct contact with the corals to promote the exchange of nutrients.

By studying samples of corals grown at the Tropical Aquarium in Paris, Kopp was able to observe firsthand the flow of nutrients from the surrounding water first into the algae, and then into their coral hosts. He did so using a combination of two imaging techniques, one with a nanometer spatial resolution (TEM), and the other with the capability of detecting the presence of minute concentrations of atomic markers (NanoSIMS).
These findings are important to understand the impact of coral bleaching on reef ecosystems. Coral bleaching is caused by the mass exodus of micro-algae from their coral hosts in response to environmental stresses such as changes in temperature and acidity. Left to themselves, the corals are unable to generate enough nutrients and eventually die off. In future studies, the researchers will use their imaging techniques to study the impact of such environmental changes the microalgae and their coral hosts.

Ecole Polytechnique Fédérale de Lausanne

Related Photosynthesis Articles:

Even bacteria need their space: Squished cells may shut down photosynthesis
Introverts take heart: When cells, like some people, get too squished, they can go into defense mode, even shutting down photosynthesis.
Marine cyanobacteria do not survive solely on photosynthesis
The University of Cordoba published a study in a journal from the Nature group that supports the idea that marine cyanobacteria also incorporate organic compounds from the environment.
Photosynthesis -- living laboratories
Ludwig-Maximilians-Universitaet (LMU) in Munich biologists Marcel Dann and Dario Leister have demonstrated for the first time that cyanobacteria and plants employ similar mechanisms and key proteins to regulate cyclic electron flow during photosynthesis.
Photosynthesis seen in a new light by rapid X-ray pulses
In a new study, led by Petra Fromme and Nadia Zatsepin at the Biodesign Center for Applied Structural Discovery, the School of Molecular Sciences and the Department of Physics at ASU, researchers investigated the structure of Photosystem I (PSI) with ultrashort X-ray pulses at the European X-ray Free Electron Laser (EuXFEL), located in Hamburg, Germany.
Photosynthesis olympics: can the best wheat varieties be even better?
Scientists have put elite wheat varieties through a sort of 'Photosynthesis Olympics' to find which varieties have the best performing photosynthesis.
Strange bacteria hint at ancient origin of photosynthesis
Structures inside rare bacteria are similar to those that power photosynthesis in plants today, suggesting the process is older than assumed.
Just how much does enhancing photosynthesis improve crop yield?
In the next two decades, crop yields need to increase dramatically to feed the growing global population.
Algal library lends insights into genes for photosynthesis
To identify genes involved in photosynthesis, researchers built a library containing thousands of single-celled algae, each with a different gene mutation.
New molecular blueprint advances our understanding of photosynthesis
Researchers at Lawrence Berkeley National Laboratory have used one of the most advanced microscopes in the world to reveal the structure of a large protein complex crucial to photosynthesis, the process by which plants convert sunlight into cellular energy.
Structure and function of photosynthesis protein explained in detail
An international team of researchers has solved the structure and elucidated the function of photosynthetic complex I.
More Photosynthesis News and Photosynthesis Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at