Interspecific Interaction between Microcystis aeruginosa and Chlorella pyrenoidosa in Different Phosphate Media

ABSTRACT

The effects of pyrophosphate and polyphosphate on the growth of Microcystis aeruginosa and Chlorella pyrenoidosa were studied in unialgal cultures and in cultures separated by a dialysis membrane. M. aeruginosa and C. pyrenoidosa were able to similarly utilize pyrophosphate and polyphosphate, but their growth rates and cell densities were low in comparison with those in the orthophosphate controls. C. pyrenoidosa had a higher growth rate than M. aeruginosa in both unialgal and the separated cultures; moreover, C. pyrenoidosa had a greater ability to utilize phosphorus than M. qeruginosa. But because the C. pyrenoidosa population developed early but then declined, M. aeruginosa eventually became dominant in the separated cultures. Therefore, the interaction between M. aeruginosa and C. aeruginosa might be complex because of an allelopathy effect, and nutrient competition is not the only factor determining species dominance in the phytoplankton assemblage.