Nature's Tiny Engineers: How Corals Stir Things Up [VIDEO]

Corals, once thought to be merely passive organisms in the world's oceans, are actually nature's tiny engineers, according to a new study, effectively stirring up currents to bring in nutrients and oxygen.

"These microenvironmental processes are not only important, but also unexpected," senior author Roman Stocker, an associate professor of civil and environmental engineering at MIT, said in a statement.

It was once thought that corals - whose calcium-carbonate skeletons form the foundation of coral reefs - were passive organisms that relied entirely on ocean currents to deliver dissolved substances, such as nutrients and oxygen. However, new research brings their true nature to light. These creatures are not passive it all, it turns out. In fact, they are rather violent, sweeping water into turbulent patterns that greatly enhance their ability to exchange nutrients and dissolved gases with their environment.

Researchers determined this surprising finding by studying living corals in a tank in a lab. They zoomed in on the coral surface with powerful microscopes and high-speed video cameras, exposing this turbulent phenomenon.

"The general thinking has been that corals are completely dependent upon ambient flow, from tides and turbulence, to enable them to overcome diffusion limitation and facilitate the efficient supply of nutrients and the disposal of dissolved waste products," added co-author Orr Shapiro.

Corals have cilia, small threadlike appendages that can push water along the coral surface. They 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.

While they only found that six different species of coral reefs possess this ability, it's most likely that most or all coral reefs use their cilia in this way.

"The retention of cilia through 400 million years of evolution suggests that reef corals derive a substantial evolutionary advantage" from these flows said Shapiro.

The findings were published in the journal Proceedings of the National Academy of Sciences.

[Credit: Massachusetts Institute of Technology]