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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 1195

James H. Reynolds, E.J. Middlebrooks, D.B. Porcella, and W.J. Grenney; Effects of temperature on growth constants of Selenastrum capricornutum. WPCF 47(10):2420-2436, 1975

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The alga Selenastrum capricornutum (Printz) has been specified for use in eutrophication bioassays by the Environmental Protection Agency (EPA). The organism was selected because it is unicellular, generally does not clump or attach to surfaces, divides uniformly, has a broad nutrient response, is an obligate autotroph, and is generally found in oligotrophic waters. The growth kinetics and nutrient response of the organism have been widely studied. In general, previous investigations have been conducted at a single temperature (24 degrees C), however. Therefore, little is known concerning the effect of temperature on the Michaelis-Menten (Monod) kinetic growth constants (µ and Ks) of this organism. In addition, the growth response and the mode of nutrient uptake by this organism in an ammonium-nitrogen-limited environment have not been investigated previously. The general objective of this study was to determine the effect of various temperatures (20 to 33 degrees C) on the Michaelis-Menten (Monod) kinetic growth constants and the mode of nutrient uptake of S. capricornutum in an ammonium-nitrogen-limited environment. To achieve this general objective, the following specific objectives were accomplished: 1. Determination of an acceptable temperature range for conducting the experiment. 2. Determination of the maximum specific growth rates, µ, and the half-saturation constants, Ks, in an ammonium-nitrogen-limited environment over the temperature range selected for study. 3. Application of the luxury uptake function developed by Toerien et al, to an ammonium-nitrogen-limited environment. 4. Determination of the nutrient utilization constants, Ka and Kb over the temperature range selected for study.