Assessment of factors limiting growth rate of Oscillatoria agardhii in hypertrophic Lake Wolderwijd, 1978, by use of physiological indicators1

Abstract

Physiological information from chemostat‐cultured Oscillatoria agardhii Gomont has been used to assess the nature of factors limiting growth rate in a natural population of this cyanobacterium, which dominates the phytoplankton in Lake Wolderwijd. Phosphorus, light (E), and nitrogen limited the growth rate of the population at different times of year: E and P limitation, alternately during January, February, and March; P limitation during April and May; N followed by E limitation in June; N limitation in July until mid‐August, followed by P limitation until October; E limitation in October, November, and December. In winter, however, an effect of temperature on the phytoplankton growth could not be excluded. Internal nutrient and pigment contents cannot be used as physiological indicators without prior knowledge of the growth rates and light conditions in nature. Similarly, N:P ratios (internal or external) are not reliable indicators of N‐ or P‐limited phytoplankton growth. On the other hand, nutrient uptake capacity values (Vmax) are useful in assessing factors that limit growth rates in nature.