Three-dimensional swimming characteristics of dunaliella primolecta in a moving fluid

Microscopic algae are often mediated by various environmental factors in the field, yet its response is not well studied. Experiments are conducted in an in-house developed microfluidic channel to study the effects of fluid motion on the swimming responses of halophilic microalga Dunaliella primolecta. Digital holographic microscopy allows us instantaneous three-dimensional (3D) measurements of swimming characteristics of microscopic organisms in a dense suspension, and microfluidics provides exquisite control over fluid flow. The swimming behavior of Dunaliella primolecta is characterized by 3D velocities, velocity auto-correlation functions, kinetic power spectral densities and swimming induced cellular dispersion. To investigate the shear induced response, the algal culture is injected into a 20mm channel with cross section of 3.5×0.4mm (latter being height) at several fluid flow rates, generating flow shear rates that are consistent with the energy dissipation levels in estuaries, coastal waters, and lakes. Preliminary measurements indicate that swimming velocities and dispersion were strongly mediated by local fluid shear rates. Ongoing analysis is to reveal scaling parameters and functional relationships among small-scale fluid motion and microorganism motility characteristics.