The Ocean's Tiny Engineers
Researcher believe corals are not just sitting there waiting for the oceans currents to sweep food to them but actively engineer their environment to improve the gathering of nutrients.
A study by scientists at MIT and the Weizmann Institute of Science (WIS) in Israel has established that corals engineer their environment to sweep water into turbulent patterns that greatly enhance their ability to exchange nutrients and dissolved gases with their environment.
'These microenvironmental processes are not only important, but also unexpected,' says Roman Stocker, an associate professor of civil and environmental engineering at MIT and senior author of a paper describing the results in the Proceedings of the National Academy of Sciences.
When the team set up their experiment with living coral in tanks in the lab, 'I was expecting that this would be a smooth microworld, there would be not much action except the external flow,' Stocker says. Instead, what the researchers found, by zooming in on the coral surface with powerful microscopes and high-speed video cameras, was the opposite.
It's long been known that corals have cilia, small threadlike appendages that can push water along the coral surface. However, these currents were previously assumed to move parallel to the coral surface, in a conveyor-belt fashion. Such smooth motion may help corals remove sediments, but would have little effect on the exchange of dissolved nutrients. Now Stocker and his colleagues show that the cilia on the coral's surface are arranged in such a way as to produce strong swirls of water that draw nutrients toward the coral, while driving away potentially toxic waste products, such as excess oxygen.