Researchers at EPFL present new evidence for the crucial role of algae in the survival of their coral hosts. Ultra-high resolution images reveal that the algae temporarily store nutrients as crystals, building up reserves for when supplies run low.
The relationship between corals and the microscopic algae they harbor is a classic example of biological symbiosis - the mutually beneficial interaction of two species. But crucial details regarding their relationship have remained elusive until now. Using state-of-the-art imaging techniques, Anders Meibom and his team of researchers in the Laboratory for Biological Geochemistry have found new evidence on the vital role algae play in helping corals survive in environments where nutrients are scarce. Their findings were published in the journal mBio on May 16, 2013.
"Coral reefs are the jungles of our oceans - hotspots of biodiversity that easily outcompete all other marine ecosystems," says Christophe Kopp, first-author of the publication. Coral bleaching occurs when the colorful algae abandon their coral host because of environmental strains like rising sea temperatures. On their own, corals struggle to survive in tropical waters where nutrients are scarce, and persistent starvation can have irreversible effects. While it is well known that algae help corals to assimilate certain nutrients, such as nitrogen from seawater, how this occurs, and to what extent the corals can get by on their own, are less clear.
To study how nitrogen-rich nutrients are taken up and processed by the corals and the algae that inhabit them, Meibom's research group teamed up with the Aquarium Tropicale Porte Dore in Paris to run a series of experiments. There, they fed the corals nitrogen-rich compounds labeled with a heavy nitrogen isotope that they could later trace in the lab. Every few minutes, they extracted bits of coral, which they fixed and analyzed with a state-of-the-art isotopic imaging instr
|Contact: Anders Meibom|
Ecole Polytechnique Fdrale de Lausanne