Photosynthetic differences between Microcystis aeruginosa and Oscillatoria simplicissima in relation to species succession in the Vaal River, South Africa

  • A Venter
  • S du Plessis
  • PDR van Heerden
  • AJ Strauss
  • J Bezuidenhout

Abstract

In 1991 Oscillatoria simplicissima replaced Microcystis aeruginosa in the Vaal River, South Africa. This study explored the reason for this succession by looking at the photosynthetic  performance of these two cyanoprokaryotes at different temperatures, light intensities and N:P  ratios. Microcystis aeruginosa showed higher growth rates and chlorophyll a concentrations than O. simplicissima for most treatments,  except the N-deficient treatments. It seems that M. aeruginosa can maintain growth under a range  of different conditions and can keep forming mass occurrences, but has high light requirements for photosynthesis and maintenance and can tolerate a much higher light intensity without experiencing photo-inhibition. Oscillatoria simplicissima, on the other hand, is able to harvest available light more efficiently at 25 °C and 15 µmol m–2 s–1, experiences less damage or loss at antenna level and retains more of its electron transport capabilities than Microcystis, giving it a competitive edge over M. aeruginosa under these environmental conditions.

Keywords: fluorescence; light; N:P ratio; photosystem II; temperature

African Journal of Aquatic Science 2009, 34(2): 159–168

Author Biographies

A Venter
School of Environmental Sciences and Development (Botany Division), North-West University, Private Bag X6001, Potchefstroom 2520, South Africa
S du Plessis
School of Environmental Sciences and Development (Botany Division), North-West University, Private Bag X6001, Potchefstroom 2520, South Africa
PDR van Heerden
School of Environmental Sciences and Development (Botany Division), North-West University, Private Bag X6001, Potchefstroom 2520, South Africa
AJ Strauss
School of Environmental Sciences and Development (Botany Division), North-West University, Private Bag X6001, Potchefstroom 2520, South Africa
J Bezuidenhout
School of Environmental Sciences and Development (Botany Division), North-West University, Private Bag X6001, Potchefstroom 2520, South Africa
Section
Articles

Journal Identifiers


eISSN: 1727-9364
print ISSN: 1608-5914