By Karthika Swamy Cohen
Soft corals of the Xeniidae family have an active pulsating motion. Image credit: Shilpa Khatri, joint AN/LS meeting.
Coral ecosystems are of interest for environmental
conservation due to the notable diversity exhibited by them. While coral reefs
are composed of hard corals with calcium carbonate skeletons, soft coral of the Xeniidae family have an active pulsating
motion, which is unusual among sessile organisms. While this behavior expends
energy, it has been shown to enhance photosynthesis rates in these
“Is the pulsating motion really
adding anything to the flow dynamics that's already exists and really
benefiting the animals?"
That’s the question Shilpa Khatri
(University of California, Merced) asked during her talk, “Modeling of Pulsating
Soft Corals” at the minisymposium celebrating Charles S. Peskin's 70th
Birthday, “Mathematical Modeling in Biological Fluid Dynamics and Systems
Khatri proceeded to answer the question
by describing a combination of mathematical models and experiments.
Three-dimensional simulations of red sea coral. Image credit: Shilpa Khatri, joint AN/LS meeting.
Preliminary data sets indicate that somehow the pulsating
motion is helping the coral: pulsating increases turbulence which may increase
mixing. Their data also shows that it's beneficial for photosynthesis. However,
the corals don't pulse only in the presence of light; they pulse 24 hours a day,
so open questions remain.
Her group is also studying the pulsing dynamics’ effect on
particle capture, nutrient exchange, and waste removal. Khatri presented direct numerical simulations of the coral pulsations, and
the consequent fluid flow by solving the Navier-Stokes equations coupled with
the immersed boundary method.
She described kinematics methods
used by her group to simulate the movement, six points along a tentacle are
tracked using image processing and tracking methods.
||Karthika Swamy Cohen is the managing editor of SIAM News.