The effect of hydrodynamic stress derived from gas bubble dispersion and broth mixing on Dunaliella growth was examined by growing the algae in two different vessels; a Roux bottle and a miniloop reactor. It was found that Dunaliella cells were increasingly sensitive to high specific bubble rates at modified orifice Reynolds numbers between 9 . 9~1 P to 18-8XlP and liquid motion with Reynolds numbers between 712 and 1293. The addition of carboxymethylcellulose and agar to the cultures served to protect the microorganisms from the effects of shear stress.