Next, they assembled a timeline of how the nitrogen is processed by the corals and their resident algae by lining up the images of the samples extracted at different times. A combination of electron microscopy and mass spectrometry allowed them to study with unprecedented precision into which cellular compartments the heavier nitrogen isotopes had been incorporated.
Crystal food banks
The research revealed that the corals depend strongly on the algae to extract sufficient nutrients from the water. This was particularly true when the corals were exposed to nitrate, a compound that they are unable to process and assimilate on their own.
But most interestingly, the scientists observed that the algae act as tiny food banks. Their images revealed that the algae temporarily store the nitrogen in the form of uric acid crystals a fact they later confirmed using crystallographic analysis. This way, the algae can stock up on nutrients when supply is abundant and draw on them when supply drops, leaching some out to their coral host.
Because coral reefs are at the foundation of immense economic activity, both as tourist magnets and as the habitats of some of the most productive fish populations, understanding their fate as the environment they inhabit changes is not only of ecological, but also of economic importance.
|Contact: Anders Meibom|
Ecole Polytechnique Fdrale de Lausanne