Active mixing in reef corals

Do corals rely entirely on ocean currents to deliver nutrients for their survival? HFSP grantees Roman Stocker and Assaf Vardi set out to answer this question and made the stunning discovery showing that corals actually engineer their environment so as to improve the flow of water in the immediate vicinity.

HFSP grant awardees Roman Stocker and Assaf Vardi
authored on Mon, 15 September 2014

Contrary to the traditional view that corals passively depend on ocean currents to deliver sustenance, a team from the Massachusetts Institute of Technology (MIT) led by Prof. Roman Stocker and from the Weizmann Institute of Science (WIS) led by Prof. Assaf Vardi discovered that corals actually engineer their environment to sweep water into turbulent patterns and thereby greatly enhance their ability to exchange nutrients and dissolved gases. In a paper in the Proceedings of the National Academy of Sciences, the researchers report that cilia, the threadlike hairs that push water along the coral surface, produce strong swirls of water that draw nutrients toward the coral while driving away potentially toxic waste products such as excess oxygen. Knowing that the boundary between coral and water is a dynamic environment will be important for studying the interactions of marine microorganisms with coral colonies, an important subject due to a global increase in coral disease and reef degradation. Besides illuminating how coral reefs function, the authors suggest that this research could be of interest in studying other organisms with cilia, including inside human airways where cilia help to sweep away contaminants. The first authors of the paper are postdocs Orr H. Shapiro (WIS) and Vicente Fernandez (MIT). Read the full news story at


Figure caption:

Vortical ciliary flows enhance the exchange of oxygen and nutrients between corals and their environment. The paths of tracer particles are color-coded by fluid velocity, demonstrating that the coral surface is driving the flow. Credit: Orr Shapiro, Assaf Vardi, Weizmann Institute of Science, Israel; Vicente Fernandez, Roman Stocker, MIT, USA.

Full reference:

Vortical ciliary flows actively enhance mass transport in reef corals. Orr H. Shapiro, Vicente I. Fernandeza,1, Melissa Garrena, Jeffrey S. Guastoa, François P. Debaillon-Vesque, Esti Kramarsky-Winter, Assaf Vardi, and Roman Stocker.