The effect of small-scale fluid motion on the green alga Scenedesmus quadricauda

The effect of shear flow on the green alga Scenedesmus quadricauda grown in Bristol's medium wastested. The shear flow was generated using a Couettetype rotating cylinder apparatus. Growth of Scenedesmus quadricauda, measured in terms ofchlorophyll a concentration, was inhibited underdifferent fluid motions. Inhibition was mostpronounced at high Reynolds number (Re) and thecorresponding mean rate of energy dissipation(e). Algal growth was maximum during thestagnant fluid flow experiment. The flocs comprised of dead and living cells of algae formed as a resultof shear flow. Cell morphometry did not changeconsistently under different flow conditions but celldestruction was evident. A two step model isproposed, relating algal growth as a function of Re,and e. The attenuation factor, φF for growth limiting conditions underdifferent fluid motions, was defined as the ratio of the algal growth rate constant to the maximum algalgrowth constant under stagnant fluid flowconditions.