INFLUENCE OF PHOSPHORUS CONCENTRATION AND TEMPERATURE ON GROWTH AND PHOSPHORUS UPTAKE BY THE MICROALGA SCENEDESMUS-OBLIQUUS

The growth of the freshwater microalga Scenedesmus obliquus has been s tudied in a mineral medium with P concentrations of between 0 and 372 mu M and temperatures of 20, 25, 30 and 35 degrees C. At all the tempe ratures, growth was inhibited by the P. The inhibition by P was highly dependent on temperature, detected at concentrations on the order of 1 mu M at 35 degrees C, 2 mu M at 20 and 25 degrees C, and 350 mu M at 30 degrees C. The greatest specific growth rate, 0.047 h(-1), was reg istered at 30 degrees C. The specific growth rates were adjusted to a semistructured model of inhibition by the substrate. The inhibition co nstants, K-1 (mu M), increased with rising temperatures from 20 to 25 and 30 degrees C, and decreased at higher temperatures. At 35 degrees C, the lowest value was recorded for K-1 1.20 mu M, and thus the inhib itory effect was the most pronounced. At 30 degrees C, within the inte rval of P concentrations of 0-300 mu M, it was possible for the variat ion in mu/S-0 to be fitted to a semistructured Monod kinetic model of limitation by the substrate. Yield of biomass varied with temperature. The highest yields were reached at 20 degrees C. The specific rates o f P consumption increased with S-0, tending towards a constant value. The highest values, obtained at 30 degrees C and 35 degrees C, were pr actically the same, and the lowest were obtained at 20 degrees C. (C) 1998 Elsevier Science Ltd. All rights reserved.